Current repairs of transformers are carried out in the following terms:
- transformers of central distribution substations - according to local instructions, but at least once a year;
- all others - as needed, but at least once every 3 years.
The first overhaul of substation transformers is carried out no later than 6 years after commissioning, and subsequent repairs are carried out as necessary, depending on the measurement results and the condition of the transformer.
The scope of the current repair includes the following works:
- external examination and elimination of damage,
- cleaning of insulators and tank,
- drainage of mud from the expander,
- topping up oil and checking the oil indicator,
- checking thermosyphon filters and, if necessary, replacing the sorbent,
- checking the condition of the breakdown fuse, circulation pipes, welds, flange seals,
- verification of protection,
- taking and checking oil samples,
- carrying out preventive tests and measurements.
In volume overhaul includes all the work provided for current repair, as well as repair of windings, magnetic circuit, checking the condition of the contact connections of the windings to the voltage switch and outputs, checking switching devices, repairing their contacts and switching mechanism, checking the condition of the transformer tank, expanders and pipelines, repairing bushings.
The transformer is taken out of service for repair in an emergency under the following conditions:
- severe internal crackling, characteristic of electrical discharge, or uneven noise,
- abnormal and constantly increasing heating during normal load and cooling,
- ejection of oil from the expander or destruction of the diaphragm of the exhaust pipe,
- oil leaks and a decrease in its level below the permissible limit,
- when receiving unsatisfactory results of the chemical analysis of the oil.
Aging of the winding insulation and wetting of the oil can lead to a short to the frame and phase-to-phase faults in the transformer windings, resulting in abnormal operating noise of the transformer.
A malfunction in the form of a "steel fire", which occurs due to a violation of the inter-sheet insulation of the core or the insulation of the tie bolts, leads to an increase in the heating of the case and oil under normal load, hum and characteristic crackling inside the transformer.
Increased "hum" in the transformer can occur due to the weakening of the magnetic conductor pressing, significant phase load unbalance and when the transformer operates at increased voltage. Crackling inside the transformer indicates an overlap (but not a breakdown) between the winding or taps to the case, or an open ground, in which electrical discharges can occur from the winding or its taps to the case.
| Loosening of the bolts securing the transformer cover and other parts (expander, exhaust pipe, etc.) | Check and tighten all bolts |
| The transformer operates at overvoltage | Set the voltage switch to the appropriate position. |
| The pressing of the joints in the magnetic circuit is broken | The tightening of the vertical studs tightening the rods with the yokes has been loosened. Repress the magnetic circuit, replacing the gaskets in the upper and lower joints of the magnetic circuit |
| Loosening of the compaction of the laminated magnetic circuit | Check all pressing bolts and studs and tighten loose |
| Vibration of the outer sheets of the magnetic circuit | To wedge the sheets of the magnetic circuit |
| Overload transformer | Reduce load | Reduce load unbalance |
| Short circuits between phases, between turns of windings | Repair or replace the winding |
Breaks in the windings are a consequence of the poor quality of the contact connections in the windings.
An open in the primary winding of a delta-star, delta-delta and star-star transformer leads to a change in the secondary voltage.
To determine the scope of the upcoming repair, the transformer is diagnosed, which is a set of works to identify the nature and extent of damage to its parts. Based on the fault detection, the reasons, the size of the damage and the required amount of repair of the transformer are determined. At the same time, the need for materials, tools, fixtures for the production of repairs is determined.
| Malfunction symptoms | Possible causes of the malfunction | Troubleshooting |
| Overheating of transformers | Transformer overloaded | Establish an overload by instruments or by removing the daily current graph. Eliminate overload by switching on another transformer or disconnect less critical consumers |
| High room temperature of the transformer | If the air temperature rises by 8 - 10 ° C at a distance of 1.5 - 2 m from the transformer in the middle of its height, improve the ventilation of the room | |
| The oil level in the transformer has dropped | Top up oil to normal level | |
| Damage inside the transformer (turn circuit, short-circuited circuits due to damage to the insulation of tie bolts and studs, etc.) | With the rapid development of these damages, an increase in the oil temperature, the evolution of gases and the operation of the gas protection for a signal or shutdown will occur. | Eliminate overload or reduce load phase unbalance |
| Breakdown of windings on the case, between HV and LV windings or between phases | Deterioration of oil quality or a decrease in its level | Insulation is tested with a megohmmeter or overvoltage |
| Deterioration of the quality of insulation due to its aging | If necessary, the winding is repaired, and the oil is topped up or changed completely | |
| Crackle inside the transformer | Overlapping between windings or body taps | Open the transformer and repair the winding and grounding taps |
| Ground break | ||
| Breakage in windings | Poorly soldered windings | Often a break occurs at the bend of the wire ring under the bolt |
| Damage in taps from windings to terminals | Replaced with flexible damper connection | |
| The contact surfaces of the switching device are melted or burned out | Switch poorly assembled or short circuited | Repair or replace the switch |
| Oil leaks from taps, flanges, welds | The valve plug is badly lapped, the gaskets of the flange joints are damaged, the tightness of the weld seam of the transformer tank is broken | Grind the tap, replace the gaskets or tighten the bolts on the flanges, weld the seams with acetylene welding. After welding, test the tank with water for 1 - 2 hours with a water column pressure of 1.5 m above the oil level in the expander |
Disassembly of transformers
Disassembly of the transformer during overhaul is carried out in the following order. The oil is drained from the expander, the gas relay, the safety pipe and the expander are removed; put plugs on the holes in the tank lid. With the help of lifting mechanisms, the lid with the active part of the transformer is lifted with slings by the lifting rings. Raising it by 10-15 cm, inspect the condition and position of the sealing gasket, separate it from the tank frame with a knife and, if possible, save it for reuse. After that, the active part is removed from the tank in sections convenient for removing oil sludge, washing the windings and core with a stream of heated oil and defect detection. Then the active part is installed on a previously prepared platform with a pallet. Raising the active part of the transformer 20 cm above the level of the tank, move the tank to the side, and for the convenience of inspection and repair, the active part is installed on a solid platform. The windings are cleaned of dirt and washed with a stream of transformer oil heated to 35 - 40 ° C.
If the transformer bushings are located on the tank walls, then first remove the lid, drain the oil from the tank 10 cm below the bushing insulators and, having disconnected the bushings, remove the insulators, and then remove the active part from the tank.
Disassembly, inspection and repair of the transformer is carried out in a dry, closed room adapted for the production of these works.
After removing the active part, the state of the magnetic circuit is checked - the density of the assembly and the quality of the mixture, the strength of the fastenings of the yoke beams, the condition of the insulating sleeves, washers and gaskets, the degree of tightening of nuts, studs, tie bolts, and the state of grounding. Pay special attention to the condition of the windings - wedging on the rods of the magnetic conductor and the strength of the winding fit, the absence of traces of damage, the condition of the insulating parts, the strength of the connections of the terminals, dampers.
During the overhaul period of the transformer, in addition to the listed works, if necessary, the yoke of the magnetic circuit is loosened with the pressing of the iron and the removal of the winding coils.
Repair of the magnetic circuit of the transformer
The most common type of magnetic circuit of power transformers is flat (rod) (Fig. 123, a). The cross-section of the yoke 6 and 7 is rectangular, and the rod is in the form of a multistage figure 3, close to a circle. The magnetic core is pulled together with yoke beams 5 n 8 using through pins 4 and tie-down vertical pins 2.
Rice. 123. Flat (a) and spatial (b) magnetic circuits of the transformer:
1 - axis of rods; 2 - vertical tie rods: 3 - multi-stage bar shape; 4 - through pins; 5, 8 - yoke beams; 6, 7 - cross-sections of the yoke; 9 - support beam; 10 - bandage; 11 - insulating tube; 12 - insulating gasket; 13 - Belleville spring, 14 - insulating gasket.
Transformers with a capacity of 250 - 630 kVA are produced with pinless magnetic cores. The pressing of the rod plates in these transformers is carried out by means of strips and wedges driven between the magnetic circuit and the cylinder. Recently, the industry has been manufacturing transformers with a capacity of 160 - 630 kV A with a spatial magnetic circuit (Fig. 123, b). The magnetic circuit of such a transformer is a rigid structure, the vertical axes of the rods 1 of which have a spatial arrangement. The steel sheets of the rod are compressed by a band 10 of insulating material or a steel tape with a spacer of insulating material instead of pins. The upper and lower yokes are pulled together by vertical tie rods 2 by means of nuts, under which Belleville springs are placed 13. To isolate the pins from the yoke, insulating gaskets 14 are used, and insulating tubes 11 from the rods. The entire structure of the magnetic circuit is attached with studs to the support beams 9.
The spatial magnetic circuit is manufactured as a butt magnetic circuit instead of a laminated one, since the yoke and the rods are connected into a magnetic circuit by docking. To avoid shorting between the steel of the yoke and the rod, an insulating gasket 12 is laid between them.
In previously produced transformers, the magnetic cores were pulled together by horizontal pins, isolated from the steel of the magnetic core and passing through the holes in the plates.
The disassembly of the magnetic circuit is as follows: the upper nuts of the vertical studs and the nuts of the horizontal studs are unscrewed, they are removed from the holes in the yoke, the yoke beams are removed and the upper yoke of the magnetic circuit is removed, starting with two or three plates in each of the outer packages. The plates are folded in the same sequence in which they are removed from the yoke, and tied in bags.
In magnetic circuits tightened by horizontal pins, the insulation of the pins is often damaged, which leads to short circuits of the steel plates and causes strong heating of iron by eddy currents. During the repair of the magnetic circuit of such a design, the insulating sleeve is replaced with a new one. In the absence of spare, the sleeve is made of bakelite paper, winding it on a hairpin, impregnated with bakelite varnish and baked. Insulating tubes for studs with a diameter of 12 - 25, 25 - 50 and 50 - 70 mm are made with a wall thickness of 2 - 3, 3 - 4 and 5 - 6 mm, respectively. Press-on insulating washers and spacers for studs are made of electrical cardboard with a thickness of 2 mm or more.
Restoration of the damaged insulation of the magnetic core plates begins with boiling the sheets in a 10% sodium hydroxide solution or in a 20% trisodium phosphate solution, followed by washing the sheets in hot (50-60 ° C) running water. After that, a mixture of 90% hot-drying varnish No. 202 and 10% pure filtered kerosene is carefully applied to a steel sheet heated to 120 ° C with a spray gun. You can use glyphthal varnish No. 1154 and benzene and gasoline solvents to insulate the plates. After applying a layer of insulation, the plates are dried at 25 C for 7 hours. special machines, and for baking and drying them - special ovens.
When replacing worn-out plates, new steel plates made from samples or templates are used. In this case, the sheets are cut so that the tire side of the plates is along the rolling direction of the steel - | and Holes for tie rods in the plates are made by stamping, not drilling. After making the plate, I cover it! insulation in one of the above ways.
Mixing begins with the central package of the middle rod, laying the plates with the insulated side inside the yoke. Then carry out the blending of the extreme packages, starting with long plates and avoiding overlapping narrow plates of rods and gaps in the joints. The holes in the yoke plates must match exactly with the holes in the rod plates. The plates are aligned with a hammer blow against a copper or aluminum busbar. A well-stitched yoke has no gaps between the layers of the plates, gaps, and damage to the insulation between the plates at the junction.
After aligning the upper yoke, the upper yoke beams are installed and the magnetoproiod and windings are pressed using them. Yoke beams in transformers are isolated from the plates with a ring-shaped washer made of electrocardboard with a thickness of 2-3 mm with pads attached on both sides.
On both sides of the upper yoke, yoke beams are installed into the holes of the beams, four vertical tie rods with insulating tubes are introduced, cardboard and steel washers are put on the ends of the studs and tightened with nuts, The earthing of the vertical yoke beams is carried out with several tinned copper tapes.
On the tie rods, tighten the nuts, pressing the upper yoke, and evenly tighten the nuts of the vertical pressing pins; the winding is pressed, and then the upper yoke is finally pressed. Measure the insulation resistance on the studs with a megohmmeter, cut the nuts on the studs so that they do not self-unscrew during the operation of the transformer.
Repair of transformer windings
Power transformer windings are the main element of the active part. In practice, the windings are damaged much more often than other elements of the transformer.
Depending on the power and rated voltage, transformers are used various designs windings. So, in power transformers with a capacity of up to 630 kVA at low voltage, mainly single and two-layer cylindrical windings are used; with power up to 630 kV -A at the highest voltage of 6, 10 and 35 kV, multilayer cylindrical windings are used; with a capacity of 1000 kV A and more, screw windings are used as LV windings. In the case of a helical winding, the rows of wound turns are arranged so that channels for oil are formed between them. This improves the cooling conditions of the winding due to the cooling oil flows. The wires of the helical winding are wound on paper-bakelite cylinders or cut templates using strips and spacers made of electrical cardboard, which form vertical channels along inner surface winding, as well as between its turns. The screw windings have high mechanical strength. Repair of windings of power transformers can be carried out without stripping or with stripping of magnetic cores.
Insignificant deformation of individual turns, damage to small sections of wire insulation, loosening of the pressing of windings, etc., are eliminated without dismantling the active part of the transformer.
When repairing the windings without removing them, the deformed turns of the windings are straightened with hammer blows on a wooden gasket applied to the turn. When repairing coil insulation without dismantling the windings, use oil-resistant varnish cloth (LHSM brand), which is applied to the bare conductor of the coil. The conductor is pre-squeezed with a wooden wedge for the convenience of working on the insulation of the coil. A tape of varnished cloth is wound with an overlap with the overlap of the previous turn of the tape by V2 part of its width. A common bandage made of cotton tape is applied to a loop insulated with varnished cloth.
Loose windings, the design of which does not provide for pressing rings, are pressed using additional insulating gaskets made of electrical cardboard or getinax. For this, a wooden wedge is temporarily driven into adjacent rows of winding to weaken the density of the spacers, thus allowing the insertion of the driven press spacer in the weakened place. Hammer the pressing pad and move on to the next location. This work is carried out along the entire circumference of the winding, hammering in spacers between the yoke and additional insulation.
Significant damage to the windings (turn short circuits, breakdown of the insulation of the windings to the steel of the magnetic circuit or between the HV and LV windings, etc.) is eliminated after removing the windings.
To dismantle the windings, the magnetic circuit of the transformer is removed. Work begins by unscrewing the upper nuts of the vertical studs. Then the nuts of the horizontal studs are unscrewed, the horizontal pressing studs are removed from the hole in the yoke and the yoke beams are removed. One of the yoke beams is pre-marked with a conventional designation (VN or NN).
De-alignment of the plates of the upper yoke of the magnetic circuit begins simultaneously from the HV and LV sides, taking out 2 - 3 plates alternately from the extreme packages. The plates are stacked in the same order in which they were removed from the yoke. and bundled into packages. To protect the plates of the cores of the magnetic circuit from damage to the insulation and spillage, they are tied by passing a piece of wire through the hole for the stud.
Dismantling of windings of low-power transformers is carried out manually, and with a power of 630 kVA and above - using removable devices. Before lifting, the winding is firmly tied with a rope along its entire length and the grips of the device are carefully inserted under the winding.
Replace damaged coils with new ones. If a new coil could get moistened during storage, then it is dried in a drying chamber or infrared rays.
The copper wire of the failed coil is reused. To do this, wire insulation is fired in a furnace, washed in water to remove insulation residues, straightened and new insulation is wound. For insulation, cable or telephone paper 15 - 25 mm wide is used, wound on a wire in two or three layers. The lower layer is applied end-to-end, and the upper overlap with the overlap of the previous turn of the tape by ½ or ¼ of its width. The strips of insulating tape are glued together with bakelite varnish.
Often a new one is made to replace a failed coil. The method of making windings depends on their type and design. The most advanced design is continuous winding, produced without breaks. In the manufacture of continuous winding, the wires are wound on a template wrapped in a sheet of electrical cardboard with a thickness of 0.5 mm. On the cylinder, installed on the winding machine, rails with spacers are laid to form channels and the end of the winding wire is fixed with cotton tape. Continuous winding can be wound clockwise (right-handed) and counterclockwise (left-handed). Turn on the machine and guide the winding wire evenly over the cylinder. The transitions from one coil to another during winding are determined by the settlement note and are performed in the interval between the same two rails. The wire junctions are additionally insulated with boxes made of electrical cardboard, secured with cotton tape. After the end of the winding, bends are made (external and internal), placing them in accordance with the drawings, and isolating them. Insulating support rings are installed at the ends of the coil and removed from the machine. The coil is pulled together with metal plates by means of tie rods and sent to the drying chamber for drying.
Algorithm diagram and routing for the manufacture of a multilayer winding of a high voltage transformer with a capacity of 160 kVA and a voltage of 10/04 kV are given below.
| P / p No. | The procedure for making a winding | Tool, material |
| 1. | Prepare a bakelite cylinder, for which check its condition and dimensions, and fix it on the machine. In the absence of a finished one, make a cylinder of electrical cardboard with a length of 32 mm longer than the length of the winding | Yardstick Electrocardboard EMC 1.5 - 2 mm thick |
| 2. | Prepare insulating material for interlayer insulation. For the manufacture of post-layer insulation, an electrical cardboard is used with a thickness equal to the diameter of the wire (or the thickness of the coil); the finished insulation is wrapped with telephone paper. | Scissors, cable paper (0.1 m), electrocardboard EMC (0.5 mm) telephone paper (0.05 mm) |
| 3. | Place the wire spool on the turntable, adjust the wire tension. | Pinwheel, PB winding wire with a diameter of 1.45 / 1.75. |
| 4. | Place the end equalizing collar on the cylinder close to the cheek of the template. Bend the wire lead at a right angle. | Tapes (keeper, varnished cloth). |
| Isolate the lead and secure. | ||
| Thread the bend through the cutout in the template and secure the template to the winding machine faceplate. | Hammer, fiber wedge. | |
| Wind one layer of the coil, sealing its turns in the axial direction with a wedge. | Cable paper 0.1 mm. | |
| Wrap the first layer of wrapping in layers of cable paper. | ||
| 5. | Wind up the layers of the winding one by one. Each transition from layer to layer should lag one third of the circle. At the end of each layer (2 - 3 turns before the end), an equalizing belt is installed (as in 4). Beech strips are installed between the layers in accordance with the calculation note. | Manual scissors for metal. Beech planks with cardboard boxes. |
| When making bends on beech strips, according to the calculation note, the points of exit of the bends are marked. | ||
| 6. | Perform bends in accordance with the settlement note. The cross-section of the branches should be at least 1.5 - 2 sections of the winding wire with a diameter of up to 1 mm and 1.2-1.25 - with a diameter of more than 1 mm. | |
| Insulate the end of the coil with half-layer tape. | ||
| Thread the end of the spool through the loop and tighten. Cut off the end of the tape. | ||
| Apply cable paper in half overlapping layers to the top layer of the winding. | ||
| Strip the insulation at the ends of the winding. | ||
| 7. | Remove the winding from the machine. | Hammer. |
| Tie the winding axially in 3-4 places with tape. | ||
| Anchor in related locations electrical cardboard gaskets. | ||
| 8. | Soak the winding in varnish for at least 15 minutes and let the varnish drain (15 - 20 minutes). | Installation for impregnation and drying. Glyftel varnish GF-95. one |
| Dry the winding at a temperature of 100 ° C for 5 - 6 hours. | ||
| Bake the winding varnish at a temperature of 85 - 90 ° С for 18 - 20 hours with hot air blowing. | ||
| Remove the winding from the oven and cool. |
The winding is dried at a temperature of about 100 ° C for 15 - 20 hours, depending on the volume of the coil, the degree of moisture insulation, drying temperature, etc. Then it is pressed, impregnated at a temperature of 60 - 80 ° C with varnish of the TF-95 brand and baked at a temperature of 100 ° C for 10-12 hours. The winding is baked in two stages - first, the impregnated winding is dried at a slightly lower temperature to remove the solvents remaining in the insulation, and then the temperature is increased to bake the winding. Drying and baking the winding increase the dielectric strength of the insulation and the mechanical strength of the coil, giving it the necessary solidity.
Rice. 124. Machine for winding transformer windings:
1 - electric motor; 2 - case; 3 - belt drive; 4 - turns counter; 5 - clutch; 6 - spindle; 7 - textolite disc; 8 - nut; 9 - template; 10 - control pedal.
Various machines are used for the manufacture of windings. Console machine for winding transformer windings of small and medium power (up to 630 kV A) (Fig. 124) consists of a template with two wooden counter wedges 9, clamped by textolite discs 7 and fixed nuts 8. The template is installed on the spindle 6, which rotates from the electric motor 1 through belt transmission 3. To account for the number of turns of the wire, the machine has a turn counter 4. The finished winding is removed from the template after unscrewing the nut 8, removing the right disk and spreading the wedges 9 of the template. The machine is controlled by a pedal 10 connected to the clutch 5.
Rice. 125. Insulation of the magnetic circuit (a) and wedging of the windings (c) when installing the transformer windings:
1 - yoke insulation; 2 - electric cardboard cylinder; 3 - round rods; 4 - strips; 5 - extension.
The windings are pushed onto the cores of the magnetic circuit, previously tightly tightened with keeper tape (Fig. 125). The windings mounted on the magnetic circuit are wedged using beech strips and rods, having previously laid two layers of electric cardboard between the HV and LV windings. Beech strips rubbed with paraffin are first inserted between the wrappers to a depth of 30-40 mm, and then hammered in alternately opposite pairs (Fig. 125, b). To preserve the cylindrical shape of the windings, first, round rods 3 are hammered, and then strips 4 with a hammer using a wooden extension 5, avoiding splitting the ends of the rods or strips.
In the same way, the LV winding is wedged on the rod with round wooden pins, hammering them along the entire circumference of the winding between the cylinder and the steps of the magnetic core.
After the end of the wedging of the windings, the upper yoke insulation is installed and the upper yoke of the magnetic circuit is charged.
In low-power transformers, to connect the windings with the switch contacts and the bushing rods, the ends of the wires are carefully stripped at a length of 15 - 30 mm (depending on their cross section), superimposed on each other, connected with a brace of tinned copper tape 0.25 - 0 thick, 4 mm or a bandage of tinned copper wire 0.5 mm thick and soldered with POS-30 solder using rosin or borax as a flux.
In high-power transformers, copper-phosphorus solder with a melting temperature of 715 ° C is used to connect the ends of the windings and connect them to the taps. The place of soldering is cleaned, insulated with paper and varnished cloth up to 25 mm wide and covered with varnish GF-95. The winding taps are made with a damper at the end to protect the wire from breakage. The HV winding taps along the entire length are covered with GF-95 varnish.
The insulating parts of the transformer core are made of cardboard, paper, wood. These materials are hygroscopic and absorb moisture from the surrounding air, reducing their electrical insulating properties. For high dielectric strength of the core insulation, it is dried in ovens in special cabinets, with an air blower, etc.
The most commonly used in practice is the drying method in its own heated tank: when passing alternating current a special winding applied to the heat-insulated surface of the tank generates a strong magnetic field, which closes through the steel of the tank and heats it up.
Dry transformers in a tank without oil (to speed up the drying process of the active part and preserve the quality of the oil and insulation of the windings). A magnetizing coil placed on the tank heats the tank. The winding turns are placed on the tank in such a way that at least 60% of the winding is in the lower part of the tank. During warming up, the tank lid is also insulated. The increase in temperature is regulated by changing the number of winding turns, while preventing an increase in the temperature of the windings above 100 ° C, and of the tank above 110-120 ° C.
The indicator of the end of drying is the steady-state value of the insulation resistance of the windings for 6 hours at a constant temperature of at least 80 ° C. After finishing drying and reducing the temperature of the windings to 75 -80 ° C, the transformer tank is filled with dry oil.
Transformer tank repair
The inner surface of the tank is cleaned with a metal scraper and washed with used transformer oil. Dents are heated with a flame gas burner and straighten with hammer blows. Cracks on the rib and wall of the body are welded by gas welding, and in the pipe - by electric welding. To check the quality of welding, the outer side of the seam is cleaned and covered with chalk, and the inside is moistened with kerosene (in the presence of cracks, the chalk is moistened with kerosene and darkens). The tightness of the body is checked by filling the tank with used oil for 1 hour at a temperature not lower than 10 ° C.
Before welding, cracks at its ends are drilled through holes a few millimeters in diameter. Chamfer the edges of the crack and weld it with electric welding. The tightness of the seam is controlled with kerosene. Loose seams are cut out and welded again.
Expander repair
When repairing the expander, check the integrity of the glass tube of the oil gauge, the condition of the gaskets. Defective flat glass or glass tube oil gauges are replaced. Lost elasticity rubber gaskets and the seals are replaced with new ones made of oil-resistant rubber. Remove sediment from the bottom of the expander and wash it with clean oil. The cork is rubbed in with a fine abrasive powder. The stuffing box packing is replaced with a new one, which is made from asbestos cord impregnated in a mixture of fat, paraffin and graphite powder.
Check the strength and tightness of the fastening of the glass diaphragm at the safety pipe; interior the pipes are cleaned of dirt and washed with clean transformer oil.
When repairing transformers, special attention is paid to the safety of the insulators and the reinforcement of the bushings. Chips up to 3 cm² in area or scratches up to 0.5 mm deep are washed with acetone and covered with two layers of bakelite varnish, drying each layer in an oven at 50 -60 ° C.
Repair of reinforcement joints
Reinforcement seams are repaired as follows: the damaged section of the seam is cleared with a chisel and filled with a new cementitious compound. If the reinforcement seam breaks down more than 30%, the bushing is completely replaced. The cementing composition per portion of one input is prepared from a mixture consisting (by weight) of 140 parts of magnesite, 70 parts of porcelain powder and 170 parts of a solution of magnesium chloride. This composition is used within 20 minutes. After the putty has hardened, the seam is cleaned and covered with 624C nitro enamel.
Cleaning the thermosiphon filter
The thermosiphon filter is cleaned of the old sorbent, the inner cavity is washed with transformer oil, filled with a new absorbing substance and attached to the transformer tank on the flanges.
Switch repair
Repair of the switch consists in the elimination of defects in contact connections, insulating tubes of cylinders and sealing devices. The contacts are cleaned, washed with acetone and transformer oil. The burned and melted contacts are filed with a file. Broken and burnt out contacts are replaced with new ones. Minor damage to the insulation of the tube or cylinder is repaired with two layers of bakelite varnish. The weakened points of attachment of the winding taps are sealed with POS-30 solder.
The repaired switch is assembled, the installation site is wiped with a rag, the stuffing box is inspected, the switch handle is put in place and the studs are tightened. The quality of the switch is checked by switching its positions. Shifts must be clear, and the locking pins in all positions must fully engage in their sockets.
Checking the operation of the switching device for voltage regulation under load consists in determining the correct consistent work movable contacts a and b switch and contactors K1 and K2. Failure to operate these elements of the switching device in the sequence can lead to serious damage to the transformer and an accident in the electrical network.
Assembling the transformer
The assembly of the transformer without an expander, the inputs of which are located on the walls of the tank, begin with lowering the active part into the tank, then install the inputs, connect the taps from the windings to them and the switch, and install the tank cover. Covers of low-power transformers are installed on the lifting pins of the active part, equipped with the necessary parts, and in more powerful ones, assembled, they are installed separately. During assembly, make sure that the gaskets are correctly installed and the fastening nuts are tightened. The length of the lifting pins is adjusted so that the removable part of the magnetic circuit and the cover are correctly positioned in their places. The required length of the lifting pins is pre-determined with a wooden lath. The length of the studs is adjusted by moving the nut.
The active part of the transformer using lifting devices is lowered into the tank with a sealing gasket made of oil-resistant sheet rubber (Fig. 126).
Rice. 126. The joint of the gasket (s) and methods of installing the gasket (s) when sealing the tank with an oil-resistant rubber gasket:
1 - tank wall; 2 - limiter; 3 - tank cover; 4 - gasket; 5 - tank frame.
Brackets for attaching an expander with an oil indicator, a safety pipe, a switch drive, a gas relay and a breakdown fuse are installed on the tank lid.
The transformer is filled with dry transformer oil to the required level according to the expander oil indicator, check the tightness of the fittings and parts, as well as the absence of oil leaks from the joints and seams.
The results of the analysis of the organization of work and measures to improve it.
Technological maps provide a detailed technically sound description of operations for the current repair of equipment of traction substations, substations and substations and must be strictly observed during the performance of work. They define the categories of work in relation to safety measures, the composition of the performers and their qualifications, set out the basic requirements to ensure the safety of personnel. The number of performers and safety measures in the preparation of the workplace are specified by the order (order) issued for the production of work.
The name of the position of an electromechanical in this collection is adopted in accordance with the Qualification characteristics and grades of remuneration for the positions of managers, specialists and employees according to the industry wage scale (approved by the Ministry of Railways of the Ministry of Railways No. labor positions of managers, specialists and employees according to the industry wage scale (Moscow, PVTs Ministry of Railways of the Russian Federation, 1999). The name of the profession and the qualification category of a traction substation electrician - according to the Unified Tariff and Qualification Reference Book of Work and Occupations of Workers (ETKS), issue 56 and the Collection of tariff and qualification characteristics of the professions of workers employed in railway transport (Moscow, PVTs Ministry of Railways of the Russian Federation, 1999).
When performing the works provided for in the collection, devices, tools and devices manufactured by the electrical industry and designed specifically for work in electrical installations of traction substations are used. Their recommended lists are given in each technological map. In addition to the recommended ones, other types of devices with similar or close characteristics can be used.
The performers must be provided with the necessary tools, devices and fixtures that meet the specifications. They are cared for by the personnel performing the main work.
All service personnel involved in technological processes must have sufficient experience and pass the safety test.
Given in the collection of the limits of numerical indicators, which indicate "to", should be understood inclusive, "not less" - are the smallest.
When this collection is published, the collection "Maps of technological processes of capital, current repairs and preventive tests of specific equipment of traction substations of electrified railways", approved on January 14, 1994, by the Ministry of Railways of the Russian Federation, No. TSEE-2, becomes invalid.
2. Transformers Technological map № 2.1.
Current repair of transformers with capacity10000 - 63000 kV-A1. Cast
Electromechanic- 1
Electrician of traction substation 4 category - 1
Electrician of traction substation 3 category - 1
2. Terms of work
The work is being done:
With stress relief
Alongside
3. Protective equipment, devices, tools, fixtures and materials:
Protective helmets, safety belt, ladder, grounding, short-circuits, dielectric gloves, megohmmeter for voltages of 1000 and 2500 V, stopwatch, thermometer, level, pump with manometer and hose, wrenches, combination pliers, screwdrivers, scraper, brushes, container for draining sediment, glass containers with a ground-in stopper for oil sampling, indicator silica gel, silica gel, transformer oil, CIA-TIM grease, white spirit, moisture-oil-resistant varnish or enamel, spare oil-indicating glasses, rubber gaskets, cleaning material, rags
4. Preparatory work and admission to work
On the eve of the work, submit an application for the withdrawal of the transformer for repair.
Check the serviceability and shelf life of protective equipment, devices, prepare tools, mounting devices and materials.
After the release of the order, the manufacturer of the work should receive instructions from the person who issued the order.
4.4. Operational personnel to prepare the workplace. The contractor should check the implementation of technical measures to prepare the workplace.
To make the admission of the brigade to work.
The contractor should instruct the team members and clearly assign responsibilities between them.
End of technological ^ art№ 2.2.
|
Changing the oil in the hydraulic seals of the oil-filled bushings a silica gel in absorbent cartridges (see pH 2.1.1., Fig. 2.1.3.) |
The state of the silica gel in desiccant cartridges is determined by the color of the indicator silica gel. When changing the color from blue to pink, replace the silica gel in the cartridges and the oil in the water seal. Replace siliga gel in dry weather, taking the desiccant out of service for no more than one hour. Check the oil level in the water seal. Replacing silica gel is performed as follows: disconnect the cartridge from the inlet, replace the silica gel, after cleaning the cartridge from contamination, replace the oil in the hydraulic seal, connect the cartridge to the inlet |
|
|
Checking the operating condition of the valves and transformer dampers |
Check the compliance with the working position of devices, taps, dampers. Carry out an inspection with checking the oil level in the bushings and tanks of the transformer. Record the readings of thermal alarms, oil level indicators, air temperature, the position of the switches of all windings |
Note. All operations with oil filled and 110-220 kV bushings must be performed in conjunction with a switchgear specialist.
Including reconstruction (change structural elements) and modernization (change of rated voltages and powers).
produced by the Khmelnitsky plant PJSC ("Ukrelectroapparat") with a guarantee of the manufacturers.
Supply voltage: 6 kV, 10 kV, 35 kV, non-standard.
Output voltage: 0.23 kV, 0.4 kV, 0.5 kV, 0.66 kV, non-standard.
We always fulfill our obligations, so our Customers can count on a decent level of service and quality work.
TYPICAL TECHNOLOGICAL CARD
INSTALLATION OF POWER TRANSFORMERS WITH NATURAL OIL COOLING, VOLTAGE UP TO 35 kV, POWER UP TO 2500 kVA
1 AREA OF USE
A typical technological map is developed for the installation of power transformers.
General information
Requirements for transportation, storage, as well as for installation and commissioning of power transformers are determined by the instruction "Transportation, storage, installation and commissioning of power transformers with voltage up to 35 kV inclusive without revision of their active parts" and the guiding technical instructions "Power transformers, transportation , unloading, storage, installation and commissioning ".
A power transformer arriving from an equipment supplier (manufacturer, intermediate base) is subjected to external inspection. During the inspection, they check the presence of all places on the railway bill, the condition of the packaging, the absence of oil leaks at the joints of the radiators with the tank and in the places of seals, the integrity of the seals, etc.
The packaging of dry transformers must ensure their safety from mechanical damage and direct exposure to moisture.
If a malfunction or damage is found, an act is drawn up, which is sent to the plant or intermediate base.
After the inspection and acceptance of the transformer, they begin to unload it.
It is recommended to unload the transformer with an overhead or mobile crane or a stationary winch of appropriate lifting capacity. If no lifting means are available, it is permitted to unload the transformer onto the sleeper cage using hydraulic jacks. Unloading of transformer units (coolers, radiators, filters, etc.) is carried out by a crane with a lifting capacity of 3 to 5 tons. When unloading transformers with lifting devices (crane, etc.), it is necessary to use inventory slings of the appropriate lifting capacity, which have factory brands and have passed tests ...
For lifting the transformer, special hooks are provided on the walls of its tank, and on the roof of the tank there are eyelets (lifting rings). The slinging of cables for large transformers is carried out only for hooks, for small and medium-sized ones - for hooks or eyelets. Tie ropes and hoisting ropes used for hoisting must be made of steel rope of a certain diameter, corresponding to the mass of the transformer. To avoid cable breaks, wooden pads are placed under all sharp edges of the bends.
The disassembled heavy transformer is unloaded using a heavy-duty railroad crane. In the absence of such a crane, unloading is carried out using winches and jacks. For this, the transformer tank, installed on the railway platform, is first raised with two jacks by the lifting lugs welded to the bottom and walls of the tank, then a trolley supplied separately from the tank is brought under the tank, and the tank is rolled from the platform onto a specially prepared sleeper cage with the help of winches. Rolling is carried out on steel strips placed under the rollers of the trolley. The rest of the components of the transformer (expansion tank, outlets, etc.) are unloaded with conventional cranes.
The unloaded transformer is transported to the installation site or workshop for inspection. Depending on the weight of the transformer, transportation is carried out by car or on a heavy-duty trailer. Carriage by drag or on a steel sheet is prohibited.
Vehicles used for the transport of transformers must have a horizontal cargo platform that allows free installation there is a transformer on it. When positioning the transformer on the vehicle, the major axis of the transformer must coincide with the direction of travel. When installing a transformer on a vehicle, it is necessary to take into account the location of the inputs on the transformer in order to exclude the subsequent reversal before installation at the substation.
Dismantled units and parts can be transported together with the transformer, if the carrying capacity allows vehicle and if this does not violate the requirements for the transportation of the transformer itself and its units.
The carrying capacity of the vehicle must be at least the mass of the transformer and its elements in the case of their transportation together with the transformer. It is not allowed to apply traction, braking or any other types of forces to the elements of the transformer structure during their transportation.
Figure 1 shows a diagram of the installation of a transformer on a car.
Fig. 1. Installation and fastening diagram of the transformer on the car
In some cases, prior to installation, transformers long time are stored in on-site warehouses. Storage should be organized and carried out in such a way as to exclude the possibility of mechanical damage transformers and moisture insulation of their windings. The fulfillment of these requirements is ensured by certain storage conditions. Storage conditions will vary depending on the design and method of shipping transformers. In all cases, it is necessary that the storage time of the transformers does not exceed the maximum permissible time established by the instructions mentioned above.
The storage conditions for power transformers with natural oil cooling are taken according to the group of storage conditions for the OZhZ, i.e. in open areas.
Storage conditions for dry unsealed transformers must comply with the conditions of group L, for transformers with a non-combustible liquid dielectric - group OZH4. The storage conditions for spare parts (relays, fasteners, etc.) for all types of transformers must comply with condition group C.
Dry transformers should be stored in their own casings or original packaging and should be protected from direct atmospheric precipitation. Oil-immersed transformers and transformers with a liquid non-combustible dielectric must be stored in their own tanks, hermetically sealed with temporary (during transportation and storage) plugs and filled with oil or liquid dielectric.
When storing transformers up to 35 kV inclusive, transported with oil without conservators, the expander must be installed and the oil topped up as soon as possible, but no later than 6 months. When storing transformers with a voltage of 110 kV and above, transported without an expander with oil and without oil, the expander should be installed, topping up and filling with oil as soon as possible, but no later than 3 months from the day the transformer arrives. The oil must meet the requirements of the PUE. The oil level should be checked periodically (when the level drops, it is necessary to add oil), at least once every 3 months it is necessary to take an oil sample for an abbreviated analysis. The absence of oil leakage from the transformer tank is periodically checked following the marks on the tank and fittings. Sealed oil transformers and transformers with a non-combustible liquid dielectric must be stored in the manufacturer's packaging and protected from direct atmospheric precipitation.
2. ORGANIZATION AND TECHNOLOGY OF WORK PERFORMANCE
INSTALLATION OF NATURALLY OIL-COOLED POWER TRANSFORMERS
The facilities mainly use power transformers with natural oil cooling, voltage up to 35 kV, power up to 2500 kVA. The scope of work on the installation of a power transformer with natural oil cooling depends on whether it comes from the factory - assembled or partially disassembled. Regardless of the type of delivery, the sequence of assembly operations will be the same.
When installing a power transformer, it is necessary to perform the following steps:
Accept a room (assembly site) and a transformer for assembly;
Carry out an audit of the transformer;
Dry the windings (if necessary);
Assemble and reinstall the transformer.
Acceptance for installation of a room (assembly site) and a transformer
The room (open area) for the installation of the transformer must be completely finished with construction. Lifting devices or gantries must be installed and tested prior to installation of the transformer.
As you know, the supply of power transformers and their delivery to the installation area must be performed by the customer. When accepting transformers for installation and determining the possibility of carrying out further work the whole range of issues related to transportation and storage, the condition of transformers according to external inspection and determination of insulation characteristics, the readiness and equipment of the premises or the installation site are considered.
The customer must provide the following required information and documents:
The date of dispatch of the transformers from the manufacturer;
Transportation conditions from the manufacturer (by rail or other transport, with or without oil, with or without an expander);
The act of acceptance of the transformer and component parts from railroad;
Unloading and transportation scheme from the railway to the installation site;
Storage conditions for transformers and component parts (oil level in the transformer, oil filling and topping-up period, characteristics of the filled or topped up oil, the results of the transformer insulation assessment, oil sample tests, tightness tests, etc.).
At the same time, the state of the transformer is assessed by external inspection, the results of checking the tightness of the transformer and the state of indicator silica gel.
During an external examination, they check for dents, the safety of seals on the taps and transformer plugs.
The tightness of the transformer is checked before installation, before topping up or filling with oil. Do not tighten the seals before checking the tightness. The tightness of transformers transported with an expander is determined within the oil indicator marks.
Checking the tightness of transformers transported with oil and a dismantled expander is carried out by the pressure of a column of oil 1.5 m high from the level of the cover for 3 hours. transformer. It is allowed to check the tightness of the transformer by creating an overpressure of 0.15 kgf / cm (15 kPa) in the tank. The transformer is considered hermetically sealed if, after 3 hours, the pressure drops to no more than 0.13 kgf / cm (13 kPa). Checking the tightness of transformers transported without oil, filled with dry air or inert gas, is carried out by creating an overpressure of 0.25 kgf / cm (25 kPa) in the tank. The transformer is considered hermetic if the pressure drops after 6 hours to no more than 0.21 kgf / cm (21 kPa) at a temperature environment 10-15 ° C. Overpressure in the transformer tank is produced by pumping dry air through a silica gel dryer with a compressor or by supplying dry inert gas (nitrogen) to the tank from cylinders.
Acceptance of transformers for installation is formalized by an act of the established form. The acceptance is attended by representatives of the customer, installation and commissioning (for transformers of IV gauge and above) organizations.
Revision
Revision of power transformers is carried out before installation in order to check their condition, identify and timely eliminate possible defects and damages. An audit can be carried out without examining the removable (active) part or with examining it. All transformers to be installed are subject to revisions without inspecting the removable part. An audit with inspection of the removable part is carried out in cases of damage to the transformer, which give rise to assumptions about the presence of internal faults.
Currently manufactured transformers have additional devices that protect their removable part from damage during transportation. This makes it possible, subject to certain storage and transportation conditions, not to carry out a laborious and expensive operation - revision with lifting the removable part. The decision to install transformers without revising the removable part should be made on the basis of the requirements of the instructions "Transportation, storage, installation and commissioning of power transformers for voltages up to 35 kV inclusive without revision of their active parts" and "Power transformers. Transportation, unloading, storage, installation and commissioning ". At the same time, a comprehensive assessment of the fulfillment of the requirements of the instructions is carried out with the design of the corresponding protocols. If the requirements of the instructions are not complied with or if faults are detected during external inspection that cannot be eliminated without opening the tank, the transformer is revised with an inspection of the removable part.
When conducting an audit without inspecting the removable part, a thorough external inspection of the transformer is performed, an oil sample is taken for electric strength testing and chemical analysis; measure the insulation resistance of the windings.
During the inspection, they check the condition of the insulators, make sure that there is no oil leakage at the seals and through the welds, and that the required oil level in the conservator is present.
The electrical strength of the oil, determined in a standard vessel, should not be less than 25 kV for devices with a higher voltage up to 15 kV inclusive, 30 kV for devices up to 35 kV and 40 kV for devices with voltages from 110 to 220 kV inclusive.
Chemical analysis of transformer oil is carried out in a special laboratory, while determining the compliance of the chemical composition of the oil with the requirements of GOST.
The insulation resistance of the windings is measured with a megohmmeter for a voltage of 2500 V. The insulation resistance is measured between the high and low voltage windings, between each of the windings and the case. For oil transformers with a higher voltage up to 35 kV inclusive and with a power up to 6300 kVA inclusive, the values of insulation resistances measured at the sixtieth second () must be at least 450 MΩ at a temperature of +10 ° C, 300 MΩ at +20 ° C, 200 MΩ at +30 ° C, 130 MΩ at +40 ° C. The value of the absorption coefficient must be at least 1.3 for transformers with a capacity of up to 6300 kVA.
The physical essence of the absorption coefficient is as follows. The nature of the change in the measured value of the insulation resistance of the winding over time depends on its condition, in particular on the degree of moisture. To understand the essence of this phenomenon, we will use the winding insulation replacement circuit.
Figure 2 shows the circuit for measuring the insulation resistance and the equivalent circuit. In the process of measuring the insulation resistance using a megohmmeter, a DC voltage is applied to the winding insulation. The drier the winding insulation, the greater the capacitance of the capacitor formed by the winding conductors and the transformer case, and therefore the greater the charge current of this capacitor will flow in the initial measurement period (at the fifteenth second from the moment the voltage is applied) and the megohmmeter readings will be lower ( ).
In the next measurement period (at the sixtieth second), the capacitor charge ends, the charge current decreases, and the megohmmeter reading increases () .
The drier the insulation of the windings, the greater the difference in the readings of the megohmmeter in the initial () and final () periods of measurement, and, conversely, the more humid the insulation of the transformer windings, the smaller the difference in these readings will be. 
6. TECHNICAL AND ECONOMIC INDICATORS
State estimated standards.
Federal unit prices for equipment installation.
Part 8. Electrical installations
FERm 81-03-08-2001
Order of the Ministry of Regional Development of Russia dated 04.08.2009 N 321
Table 08-01-001. Power transformers and autotransformers
Meter: pcs.
| Price code | Name and technical specifications equipment or types of assembly | Direct costs, rub. | Including rub. | Labor costs of workers installers, man-h |
|||
| Remuneration for workers installers | machine operation | mat- rials | |||||
| Total | incl. wages of workers who control the machine | ||||||
| Three-phase transformer: |
|||||||
| 08-01-001-06 | 35 kV with a capacity of 2500 kVA | 7018,51 | 2635,88 | 3748,71 | 360,72 | 633,92 | 274 |
BIBLIOGRAPHY
SNiP 3.03.01-87. Bearing and enclosing structures.
SNiP 12-03-2001. Labor safety in construction. Part 1. General requirements.
SNiP 12-04-2002. Labor safety in construction. Part 2. Construction production.
GOST 12.2.003-91. SSBT. Manufacturing equipment. General safety requirements.
GOST 12.3.009-76. SSBT. Loading and unloading works. General safety requirements.
GOST 12.3.033-84. SSBT. Construction machines... General safety requirements for operation.
GOST 24258-88. Scaffolding tools. Are common technical conditions.
PPB 01-03. Fire safety rules in the Russian Federation.
The electronic text of the document was prepared by Kodeks CJSC
and verified against the author's material.
Author: Demyanov A.A. - Ph.D., teacher
Military Engineering and Technical University,
Saint Petersburg, 2009
TYPICAL TECHNOLOGICAL CARD (TTK)
ORGANIZATION OF LABOR TO REPLACE KTP 6-10 / 0.4 KV
1 AREA OF USE
A typical technological map is developed for the organization of labor for the replacement of 6-10 / 0.4 kV transformer substations.
COMPLETE TRANSFORMER SUBSTATIONS
ELECTRICAL CONNECTION DIAGRAMS FOR 6-10 / 0.38 kV SUBSTATION
A complete transformer substation (KTP) is a substation consisting of transformers and blocks supplied assembled or fully prepared for assembly.
Transformer substations 6-10 / 0, 38 kV are made of one- and two-transformer, dead-end and through-type. At dead-end substations on the high voltage side, a disconnector with grounding knives and fuses are provided (Fig. 1 and 2).
Fig. 1. Scheme of electrical connections of KTP 10 / 0.4 kV with a power of 25 and 40 kVA:
1 - line disconnecting point 10 kV (LRP); 2 - valve arrester RVO-10; 3 - transformer TM-25/10 - TM-40/10;
4 - fuse PC-1; 5 - RP-313 switch; 6 - arrester RVN-1U1; 7 - current transformer TK-20U3; 8 - automatic switch A3700; 9 - automatic circuit breaker AP50-2MZTO; 10 - magnetic starter PME-211; 11 - photo relay FR-2
Fig. 2. Scheme of electrical connections for KTP 10 / 0.4 kV with a power of 63-160 kVA:
1 - LRP 10 kV; 2 - valve arrester RVO-10; 3 - transformer TM-63/10 - TM-160/10; 4 - fuse PC-1; 5 - RP-313 breaker;
6 - arresters RVN-1U1; 7 - current transformer TK-20; 8 - automatic switch A3700; 9 - magnetic starter PME-211;
10 - photo relay FR-2
Load break switches are installed at walk-through substations in the circuits of 6-10 kV lines (Fig. 3 and 4).
Fig. 3. Electrical connection diagrams of 10 / 0.4 kV KTP of through-type with a capacity of 250-630 kV-A (KTPP-V-630-2, KTPP-K-630-2).
Automatic switches are installed on outgoing lines 0.38 kV:
1 - transformer TM-250/10 - TM-630/10; 2 - 4 - circuit breaker VN-11 with drives PR-17, PR-10; 5 - valve arrester RVO-10; 6 - valve arrester RVN-1U1, 7 - block-switch BV;
8 - current transformer TK-20; 9 - active energy counter SACHU-I672M; 10 12 - resistor PE-75; 13 - fuse Ts27PP-6-2; 14 - fuse Ts27PP-15-2; 15 - packet switch; 16 - magnetic starter PME-211;
17 - photo relay FR-2; eighteen, 19 - automatic switches A3700; 20 - packet switch; 21 - thermal relay TRN-10;
22 - maximum current relay RE-571T; 23 - intermediate relay RP-41; 24 - lamp NB-27
Fig. 4. Scheme of electrical connections of KTP 10 / 0.4 kV through-type with a capacity of 250-630 kVA (KTPP-V-630-2, KTPP-K-630-2).
Fuses are installed on outgoing lines 0.38 kV
1 - transformer TM-250/10 - TM-630/10; 2 - PK-10N fuse; 3 - RVZ-10/400 disconnector with PR-10 drive; 4 - circuit breaker VN-11 with drives PR-17, PR-10; 5 - valve arrester RVO-10; 6 - valve arrester RVN-1U1; 7 - block-switch БВ;
8 - Stock transformer TK-20; 9 - active energy meter SACHU-I672M; 10 - batch switch; 11 - voltmeter E-378;
12 - resistor PE-75; 13 - fuse Ts27PP-6-2; 14 - fuse Ts27PP-15-2; 15 - packet switch; 16 - magnetic starter PME-211; 17 - photo relay FR-2; 18 - fuse block - switch BPV; 19 - batch switch; 20 - NB-27 lamp;
21 - plug socket ШР
The power transformer is connected to the 6-10 kV busbars through a disconnector with earthing knives and fuses. Input from the power transformer to 0.38 kV busbars is carried out through a switch. From the buses through air circuit breakers or fuses, there are three to five (depending on the power of the transformer) 0.38 kV lines for powering electrical receivers and a street lighting line equipped with a magnetic starter, which is switched on and off automatically from the photo relay.
PROTECTION OF SUBSTATIONS 6-10 / 0.38 kV AGAINST SHORT-CIRCUIT CURRENTS AND OVERVOLTAGE.
ELECTRICITY ACCOUNTING
Protection of power transformers against short-circuit currents(SC) from the high voltage side is provided by PK-10 fuses. The rated current of fuse-links, depending on the power of the power transformer, is:
Air circuit breakers are installed on the outgoing lines of 0.38 kV, which perform the functions of both protective and operational devices, or a switch-fuse block.
At substations with 25 and 40 kVA transformers, automatic switches AP50 are installed, having a maximum permissible maximum short-circuit current of 1500 A. At substations with 63-630 kVA transformers, automatic switches of the A3700, AE2000 series are installed. The circuit breakers are equipped with combined releases with both thermal and electromagnetic elements. Short-circuit currents in rural distribution networks have small values (commensurate with the maximum currents of the lines), especially with single-phase short-circuits. This is due to the large length of the lines and the small cross-sections of the wires. In this regard, current protection is used, installed in the neutral wire of the line,
Automatic switches of the AP50 type have a special release in the neutral wire, and the A3700 and AE2000 circuit breakers have a remote release operating from a current relay of the RE-571T type installed in the neutral wire or an attachment of the ZT-0.4 type. Two-transformer substations are produced without ATS on the 0.38 kV side, and on special order delivery with ATS is possible (Fig. 5). On the street lighting line, different phases of which are laid in different directions, fuses of the Ts-27PP type are installed.
|
|
|
Fig. 5. Scheme of electrical connections of two-transformer KTP 10 / 0.4 kV pass-through type
with a power of 2 x (250 - 630) kVA (KTPP-V-2 x 630-4KTPP-K-2 x 630-4):
1 - transformer TM-250/10 - TM-630/10; 2 - fuse PK-10N; 3 - RVZ-10/400 disconnector with PR-10 drive; 4 - circuit breaker BH-11 with drives PR-17, PR-10; 5 - valve arrester RVO-10; 6 - valve arrester RVN-1U1; 7 - block-switch БВ;
8 - current transformer TK-20; 9 - active energy meter SACHU-I672M; 10 - packet switch; 11 - voltmeter E-378; 12 - resistor PE-75; 13 - fuse Ts27PP-6-2; 14 - fuse Ts27PP-15-2; 15 - packet switch; 16 - magnetic starter PME-211;
17 - photo relay FR-2; 18 - fuse block - switch BPV; 19 - fuse block; 20 - batch switch; 21 - NB-27 lamp; 22 - plug socket ШР
The number of lines, types of circuit breakers installed on them, rated currents of circuit breakers releases and rated currents of fuse links, depending on the power of the substation and the manufacturer, are given in Table 1.1-1.3.
Table 1.1
|
AP50-2MZTO, 16 |
AP50-2MZTO, 25 |
AP50-2MZTO, 25 |
||
|
AP50-2MZTO, 16 |
AP50-2MZTO, 25 |
AP50-2MZTO, 40 |
||
Table 1.2
Outgoing circuit breakers
|
Transformer power, kVA |
A type circuit breaker, rated current of the release, A, for numbers of outgoing lines |
||||
|
AP50-2MZTO, 16 |
AP50-2MZTO, 25 |
AP50-2MZTO, 25 |
|||
|
AP50-2MZTO, 16 |
AP50-2MZTO, 25 |
AP50-2MZTO, 40 |
|||
Table 1.3
Rated currents of fuse-links of type PN2 fuses installed on outgoing lines
|
Transformer power, kVA |
Type of circuit breaker, rated current of the release, A, for numbers of outgoing lines |
||||
Overvoltage protection of substation equipment is carried out by valve arresters RVO-10 from the side of the higher voltage and RVN-1 from the side of 0.38 kV.
The metering of active electricity at the substation is carried out by a three-phase meter of the SACHU-I672 type, connected to the network through current transformers. At the substation, grounded: the neutral of the transformer on the low voltage side, all metal parts of structures, apparatus and equipment.
CONSTRUCTIONS OF SUBSTATIONS 6-10 / 0.38 kV
Complete transformer substation of dead-end type with a capacity of 25-160 kVA consists of three main parts: switchgear 0.38 kV, fuse box high voltage and a power transformer (Fig. 6). The power transformer is located at the back of the substation, under the high voltage fuse box. Power transformer insulators are covered with a special casing, which is attached to the rear wall of the cabinet. 6-10 kV input is carried out through bushings. A bracket is provided for fixing low voltage insulators.
Fig. 6. General view of 10 / 0.4 kV KTP of dead-end type with a capacity of 25-160 kVA
The substations are mounted on two reinforced concrete racks, installed in drilled pits (Fig. 7). The following can be taken as foundations: racks of the USO-ZA type (length 3.6 m), attachments of the PT-2.2-4.25 type (length 4.25) and T-shaped foundations.
A 10 kV disconnector with a drive is installed on the end support of a 10 kV overhead line. Removing the disconnector to the end support allows all necessary work at the substation with de-energized.
In accordance with the PUE, unenclosed KTPs must have a distance from the ground to the high voltage input (6-10 kV) of at least 4.5 m. Such KTPs are installed on foundations, the height of which must be at least 1.8 m from the ground level.
Fig. 7. Installation of KTP 10 / 0.4 kV with a capacity of 25-160 kVA
KTPs with a capacity of 250 kVA are produced, which differ from KTPs 25-160 kVA in dimensions of a switchgear of 0.38 kV and a frame for installing a KTP.
Complete transformer substation of through passage type with a capacity of 250-630 kV· A is a single block 3330x2250x4300 mm in size and consists of three units: low voltage, high voltage and a power transformer. High voltage inputs and low voltage outputs can be overhead (fig. 8) or cable (fig. 10). The substation is installed on four reinforced concrete racks fixed in drilled pits. It is possible to install the KTP on two racks laid horizontally on a sandy base. This option is allowed on rocky soils with large pebbles and boulders.
|
|
|
Fig. 8. General view of KTP 10 / 0.4 kV through-type with air inputs up to 630 kVA
A complete transformer substation of a pass-through type with a capacity of 250-630 kVA is a single block 4300x2320x1900 mm in size and consists of three nodes: low, high voltage and a power transformer (Fig. 9). High voltage bushings - air.
Fig. 9. General view of KTP 10 / 0.4 kV through-type with air inputs up to 630 kVA
|
|
|
Fig. 10. General view of 10 / 0.4 kV KTP of dead-end type with cable entry up to 630 kVA
A two-transformer complete transformer substation of a pass-through type with a capacity of 2x (250-630) kVA consists of two blocks measuring 3300x2250x4300 mm, each of which includes three nodes: low and high voltage and a power transformer. The blocks are interconnected by two boxes (fig. 11 and 12).
|
|
|
Fig. 11. Two-transformer KTP 10 / 0.4 kV pass-through type with cable entries up to 2x630 kVA
Fig. 12. Two-transformer KTP 10 / 0.4 kV bushing type with air inputs up to 2x630 kVA
2. ORGANIZATION AND TECHNOLOGY OF WORK PERFORMANCE
Table 2.1
|
COMPOSITION OF THE TEAM |
EB qualification group |
Accepted designation |
Number of persons |
|||
|
Electrician for repair of overhead lines - manufacturer of works |
5 people |
|||||
|
Electrician for repair of overhead lines |
||||||
|
Truck crane driver |
||||||
|
Responsible work manager |
1. All work should be carried out alongside, on a disconnected and grounded electrical installation, under the guidance of the responsible work manager. In the outfit, indicate the type and registration number crane. In the line "Separate instructions", make a record of the appointment of an employee responsible for the safe production of work by cranes.
2. Arriving at the place of work, check the line and the diagram with the inscriptions on the KTP about the conformity of the place of arrival.
3. Before starting work, check the condition of grounding, the base of the package transformer substation, racks, fastening of the stairs, the platform.
4. Carry out lifting work under the guidance and commands of the responsible work manager.
5. The package transformer substation was prepared on the basis of the enterprise.
Workplace preparation scheme
Fig. 13. Workplace preparation scheme
Table 2.2
|
Work technology |
||
|
Pr, E2, E2, M1 |
Receive and issue an admission order. Receive targeted briefing. Prepare devices, tools, protective equipment and a truck crane, check their serviceability. Receive components, re-preserve if necessary. Load tools, devices, means into the car |
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Arrive at the workplace. Obtain permission to prepare a workplace. Prepare the workplace by completing all the necessary safety measures in accordance with the POT RM and local instructions. Check the condition of the grounding, the base of the transformer substation, racks, supports, fastening of the stairs, the platform. Strengthen the supports if necessary. Disconnect the load (outgoing lines) in the low voltage cabinet with automatic switches (switches), turn off the main switch. Open the 10 kV disconnector, make sure that the disconnector blades are in the off position, block the disconnector drive with a mechanical lock. Check the serviceability of the low voltage indicator. Check the absence of voltage on the outgoing buses of 0.4 kV, apply portable grounding according to the scheme. Check that the high voltage indicator is working properly. Check the absence of voltage on all phases, starting from the near phase of 10 kV, apply portable grounding according to the scheme. Hang out portable posters according to the scheme. |
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Obtain a permit for admission to work. Obtain permission. Conduct targeted safety training in the workplace. Allow the brigade to work. Conduct a briefing on the technology of work. |
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Pr, E2, E2, M1 |
Install the truck crane in a place prepared if necessary and a position convenient for work, ground it. If necessary, fence off the workplace, limit the sector of movement of the crane boom with flags. Unload and unfold fixtures and fittings. Unload the new package transformer substation. Install the ladder, disconnect the 10 kV and 0.4 kV loops from the old KTP, dismantle the transformer. Dismantle 10 kV valve arresters (or surge arresters) and jumpers between bushings and arresters. Disconnecting the grounding conductor from the ground loop of the KTP. Remove the 10 kV fuses. Dismantle the KTP using a truck crane. |
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Pr, E2, E2, M1 |
Install and secure a new KTP. Install a transformer, valve arresters (or surge arresters), jumpers between arresters and bushings in the HV cabinet. Connect 10 kV and 0.4 kV loops to the KTP. Install 10 kV fuses according to the tables. Restore the grounding of the KTP. Check the integrity of the ground loop. |
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Load the old KTP onto the vehicle. Collect materials, tools, fixtures and protective equipment. Tidy up the workplace. Move the crane to transport position. Remove the team and equipment from the place of work. Close the outfit. Remove portable grounding. |
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Remove the brigade. Complete the completion of the work in the outfit. Report to the dispatcher on completion of work. |
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Turn on the 10 kV disconnector, turn on the main switch of the 10 / 0.4 kV KTP, open the door of the low-voltage cabinet, turn on the circuit breakers of the outgoing lines. Listen to the operation of the transformer for extraneous noise. Check the voltage on the 0.4 kV side in all phases and the direction of rotation of the motors at the consumer. Lock the door of the low-voltage cabinet. Remove the stairs. |
Fig. 14. Truck crane installation diagram
3. REQUIREMENTS FOR THE QUALITY OF PERFORMANCE OF WORKS
Table 2.3
Technical characteristics of KTP outdoor installation
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Indicator |
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|
KTP25- (10) /0.4 KTP40- (10) / 0.4 KTP63-6 (10) /0.4 |
KTP100-6 (10) /0.4 KTP160-6 (10) /0.4 |
KTP250-6 (10) /0.4 |
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|
Rated power, kVA |
|||||
|
Power transformer type |
TMF-400/6 (10) |
TMZ-630/6 (10); TMZ-1000/6 (10) |
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Type of switching device on the HV side |
RV-10-250; PK-6 (10) |
RV-10-250; PK-6 (10) |
RV-10-250; PK-6 (10) |
VNPz-17 with PRA-17 drive (in a VVN-1 type cabinet); PK-6 (10) |
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|
Switching device type on the LV side: |
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|
A3124 (40 and 60 A) |
AVM-YUSV (in a cabinet of KBN-1 type); 2 pcs. BGTV-2 |
AVM-20SV (in a KNN-1 or KNN-2 type cabinet) |
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|
on the lines |
AP50-2M; A3124 (30, 40 and 60 A) |
A3134 (200A); A3124 (100A) |
4 things. BPV-1 (in the KBN-1 cabinet) |
AVM-4V, AVM-10V or AVM-20V (in the KNN-4 or KNN-5 type cabinets), AVM-20SV (in the KNN-3 type cabinet) |
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|
Number of outgoing lines |
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Dimensions, mm: |
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|
width Length) |
Determined by order |
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1185; 1255; 2000 |
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Weight, kg |
Determined by order |
4. MATERIAL AND TECHNICAL RESOURCES
Technical equipment of works
ACCESSORIES AND MATERIALS
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KTP 10 / 0.4 kV, assembled, pcs. |
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Welding electrode, kg |
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Mechanisms |
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Truck crane, pcs. |
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Welding machine, pcs. |
Fixtures, tools, inventory
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Plumber's set, set |
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Set of wrenches, set |
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Megohmmeter, pcs. |
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Hemp rope 20 m, pcs. |
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Sledge hammer 3 kg, pcs. |
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Mechanical lock, pcs. |
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Device for determining the health of the voltage indicator, pcs. |
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Metal brush, pcs. |
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Device for measuring the ground loop M-416, pcs. |
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Scrap 30 mm, pcs. |
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Ladder, pcs. |
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Release device, set |
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Signal flags, set |
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Laundry soap, cous. |
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Thermos, mug to-t |
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Personal towel, pcs. |
5. ENVIRONMENTAL PROTECTION AND SAFETY RULES
Safety regulations and instructions
1. Cross-sectoral rules for labor protection during the operation of electrical installations. POT R N M-016-2001
2. Cross-sectoral rules on labor protection when working at height POT R N M-012-2000.
3. Instructions for the use and testing of protective equipment used in electrical installations.
4. Rules for electrical installations.
5. Rules for the design and safe operation of cranes. PB 10-382-00.
6. Intersectoral rules on labor protection during loading and unloading operations and placement of goods POT R N M-007-98.
7. Interindustry rules on labor protection during the operation of industrial transport POT R N M-008-99.
8. Rules for the use of tools and devices, during the repair and installation of power equipment.
Means of protection
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High voltage indicator UVN-10 |
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Portable grounding 10 kV |
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Inventory earthing switch |
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Grounding rod |
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Portable grounding 0.4 kV |
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Dielectric gloves |
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Protective helmet GOST 12.4.087-84 |
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Safety belt GOST 12.4.184-95 |
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Tarpaulin mittens |
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Portable medical kit |
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Safety posters |
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Low voltage indicator UNN-0.4 |
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Individual voltage signaling device |
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Protective mask for the welder |
Special conditions for work
1. Work to carry out alongside, on a disconnected and grounded overhead line.
2. Post insulators for replacement at the disconnector must pass an acoustic emission test.
SAFETY
Labor safety is part of the overall set of labor protection measures that ensure healthy, rational and safe working conditions in production.
Full safety of workers is ensured by the rules of electrical safety and fire-fighting measures.
Workers entering a repair facility must be instructed on general labor safety rules, electrical safety rules, behavior in the workplace when repairing electrical equipment, and internal regulations.
Measures to ensure electrical safety
Electrical installations and devices must be in full working order, for which, in accordance with the rules of operation, they must be periodically checked. Non-conductive parts that could be energized as a result of insulation breakdown must be reliably grounded.
It is forbidden to work or test live electrical equipment and equipment in the absence or malfunction of protective equipment, blocking of guards or grounding circuits. For local portable lighting, special lamps with lamps for a voltage of 12 V should be used. It is prohibited to use a faulty or untested power tool (electric drills, soldering irons, welding and other transformers). In rooms with an increased risk of electric shock (damp, with conductive floors, dusty) work must be performed with special precautions. Protective equipment is of great importance.
Safety guidelines should be PTE and PTB, as well as local or departmental instructions.
Safety measures in the production of locksmith and machine tools
When working with a hammer and chisel, when sharpening a tool on an emery wheel, you need to use only a serviceable tool. Do not lengthen wrenches, hit the wrench, or loosen nuts and bolts with a chisel and hammer. The chisel must be at least 150 mm long and its striking part must not be broken. The tool must be sharpened with protective goggles.
Handles of hammers, sledge hammers, files, screwdrivers must be of a certain length, securely fastened, smoothly processed and made of dry hard wood (birch, beech). Wrenches may only be used for the size of the nuts and bolt heads; when tightening nuts and bolts, do not install spacers between the edges of the key and nut, the latter may break out and injure.
Only qualified workers who have undergone special instructions are allowed to work independently on machines. To ensure safety, all rotating parts of the machine (gear wheels, pulleys) must be protected with special guards, covers or nets. Working sleeves should be tightly tied at the hands to avoid getting them into the rotating parts of the machine. Wear protective goggles when working on metal-cutting machines.
When making windings or bands, care must be taken not to get your fingers caught under the wire being wound. It is forbidden to align the wires on the templates of the winding machines during the work of the latter. When installing the rotor at the centers of the machine, banding, balancing or in order to cut off the winding head, it is necessary to securely fix the tailstock of the machine so that during rotation the rotor does not break out of the centers and does not fall on the legs of the worker.
Safety measures at repair sites
In the winding-insulating section, special attention should be paid to working with insulation containing glass. There is a risk of small glass particles coming into contact with the skin and causing severe skin irritation. To avoid this, wires with fiberglass insulation are pre-impregnated in a liquid-diluted varnish, and then dried to a semi-moist state. In this state, the wire is used to wind the coil sections.
Welding or soldering the ends of the windings should only be done with protective goggles, as occasional drops of solder can get into the eyes.
At the impregnation and drying areas, special attention is paid to working with paints and varnishes and their solvents. They are flammable, highly flammable, and their vapors are explosive! Store these substances separately from other materials in rooms with reliable ventilation and well-closed metal doors. A small amount of paints and varnishes can be stored in a lockable iron box at a temperature not lower than +8 and not higher than +25 ° C. Containers for storing varnishes and paints must be tightly closed, marked and in good condition. Do not leave open containers. The released containers are immediately handed over to the warehouse.
In workplaces, flammable and combustible materials can be present in daily consumption quantities, provided that fire safety is observed.
For long-term storage of varnishes, enamels and especially solvents, it is recommended to fill the corks of bottles, tanks and can lids with cable mass MB-70 MB-90 or bitumen with the addition of 10% transformer oil.
It is forbidden to open containers with paints and varnishes with steel tools in order to avoid sparking and ignition!
Some solvents are harmful to human skin. When working with them, thin rubber (medical) gloves are put on your hands. If the solvent comes into contact with the skin, wash your hands immediately with soap and water.
When immersing products in an impregnating bath, do not allow them to fall in order to avoid splashing the impregnating solution. When rolling the trolley with parts into the drying oven, push the trolley away from you. It is forbidden to drive the cart with you! Turning on the drying chamber is allowed only after the chamber doors are tightly closed. Drying of windings by induction may only be performed by two workers in fenced areas with warning signs posted. The circuit must be connected when the breaker contacts are visible.
In the drying and impregnation rooms, all equipment must be explosion-proof.
All workers dealing with paints and varnishes must undergo special training on labor safety.
Rigging safety measures
All operations for the movement and lifting of goods, starting from unloading at storage sites and ending with installation at the installation sites, refer to rigging. Rigging work requires special care and is carried out by specially trained rigging workers who know the rules for handling cargo.
It is completely unacceptable to disregard any requirement of safety rules, even insignificant ones! Do not start rigging work in poorly fitted, unbuttoned clothing. It can catch on cables, hooks or protruding parts of the load and cause an accident.
To protect your hands from injury, you need to work in gloves. The workplace must be free of any foreign objects and debris, the floors must be dry to prevent workers from falling. Passages to the cargo must be cleared.
The placement of equipment in the installation area should correspond to the sequence of its arrival to the installation site. The platforms must be equipped with a guardrail at least 1 m high. Loads weighing more than 20 kg may only be lifted with lifting mechanisms. The lifting of the load should be carried out only vertically and in two steps: first, the load should be lifted to a height of no more than 0.5 m, make sure that it is securely fastened, and then it should be lifted or moved further. Steel and hemp ropes are widely used for lifting loads. Steel ropes must be supplied with the manufacturer's passport, which indicates the breaking strength. Ropes must be kept in good condition on drums. When unwinding and winding ropes, the formation of loops and spirals is not allowed.
The manufacture of slings and the braiding of the ends of the rope is allowed only by qualified workers. All slings must be tagged with the lifting capacity, test date and suitability for service.
When lifting electrical equipment (for example, the stator of machines, windings, the active part of the transformer, panels or consoles), special devices are used to protect it from damage by slings. These devices eliminate the pressure of the slings on the equipment being lifted.
Work on lifting and moving loads should be supervised by a foreman. There must be no people under or near the raised load. Do not leave the tool on the equipment to be lifted.
When performing rigging work, special attention should be paid to the serviceability of slings and lifting mechanisms, which include: blocks, pulley blocks, hoists, telphers, jacks, winches, all kinds of goats and tripods. The operation of these mechanisms and devices is not allowed if they have not passed a periodic check, do not have the appropriate passports authorizing their operation, or if they are made fragilely, without appropriate calculation.
Safety measures when working at height
Work performed at height, are called those in which the worker is above 1 and up to 5 m from the surface of the ground, overlap or on the table. Work performed at a height of more than 5 and is called steeplejack. Such works may include work on the repair of lamps, cable wires, overhead lines, etc. Persons who are at least 18 years of age and who have passed a special medical examination for suitability for work at height or climbers are allowed to these works.
Work using ladders and stepladders, specially adapted and provided with stops, should be carried out by two workers, one of whom is on the floor and holds the ladder. Do not work with random objects such as boxes, stools, untested or unusable scaffolds. Installation and removal of lighting fixtures, panels and devices weighing more than 10 kg is carried out by two persons or one, using special mechanisms or devices.
Fire-fighting measures
As a rule, the causes of fire are: working with an open fire, malfunctioning electrical devices and wiring, smoking and non-observance of fire safety rules.
When working with a blowtorch, the following requirements must be met:
the lamp reservoir must be filled with fuel no more than 3/4 of its capacity;
wrap the filling plug tightly;
do not work with the lamp near fire;
do not light the lamp by supplying fuel to the burner;
do not pump over the lamp to avoid explosion;
do not remove the burners until the pressure has dropped;
use only the fuel for which the lamp is intended;
do not reduce the air pressure from the lamp reservoir through the filler plug;
work only with a working lamp.
All workshops and sections must be provided with fire-fighting equipment and fire extinguishers. Workers must be able to use them. Smoking is allowed only in designated areas. It is forbidden to wash work clothes with gasoline, acetone and other flammable liquids. Spilled flammable liquid must be cleaned up immediately. Used cleaning materials should be stored in special metal boxes with tight-fitting lids.
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