Technological map for the installation of a transformer in Belarus. We repair power transformers. Terms of work

TYPICAL TECHNOLOGICAL CARD

INSTALLATION OF POWER TRANSFORMERS WITH NATURAL OIL COOLING, VOLTAGE UP TO 35 kV, CAPACITY 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 guidelines for technical instructions "Power transformers, transportation , unloading, storage, installation and commissioning ".

The power transformer arriving from the equipment supplier (manufacturer, intermediate base) is subjected to external inspection. When inspecting, 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 assemblies (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 stamps 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 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 lining is 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 trolley rollers. 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 loading platform that allows the transformer to be freely installed 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 to exclude the subsequent reversal before installation at the substation.

Dismantled units and parts can be transported together with the transformer, if the lifting 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.

Fig. 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 are stored for a long time in on-site warehouses. Storage should be organized and carried out in such a way as to exclude the possibility of mechanical damage to transformers and wetting of the 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 duration 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 oil topped up as soon as possible. short term, but no later than after 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, topped up and filled with oil as soon as possible, but no later than 3 months from the date of the transformer arrival. 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 operations in sequence:

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 further work, the whole range of issues related to transportation and storage, the condition of transformers by external examination 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;

The scheme of unloading and transportation 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 filled or topped up oil, results of 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 the 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 the transformers transported with the 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 an ambient temperature of 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 inspection 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 the lifting of the removable part. The decision to install transformers without revision of 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 execution of the corresponding protocols. If the requirements of the instructions are not followed 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 leak 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.

The 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 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 up to 6300 kVA inclusive.

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 subsequent 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.

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. General technical conditions.

PPB 01-03. rules fire safety v 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

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 thermosiphon filters and, if necessary, replacing the sorbent,
• checking the condition of the breakdown fuse, circulation pipes, welds, flange seals,
• verification of protection,
• sampling and checking oil samples,
• carrying out preventive tests and measurements.

The scope of the overhaul includes all the work provided for the current repair, as well as the repair of windings, magnetic circuit, checking the condition of the contact connections of the windings to the voltage switch and terminals, checking the switching devices, repairing their contacts and switching mechanism, checking the condition of the transformer tank, expanders and pipelines, repair of inputs.

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 lowering of 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.

Malfunction in the form of "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 a ground break, in which electrical discharges from the winding or its taps to the case can occur.

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 repairs, 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.

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 of the transformer, in addition to the listed works, if necessary, the yoke of the magnetic circuit is loosened with the unpressurization 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 - axes 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 plates of the rods 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 bandage 10 of insulating material or steel tape with an insulating material spacer instead of pins. The upper and lower yokes are pulled together with vertical tie rods 2 by means of nuts, under which Belleville springs are placed 13. Insulating gaskets 14 are used to isolate the pins from the yoke, and insulating tubes 11 are used 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 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 at the extreme packages. The plates are folded in the same sequence in which they are removed from the yoke, and bundled into 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. It is possible to use glyphtal 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. For large volumes of work, special machines are used for varnishing the plates, and special ovens for baking and drying them.

When replacing worn-out plates, new steel plates made from samples or templates are used. In this case, the cutting of the sheets is performed so that the tire side of the plates is along the rolling direction of the steel. 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 by hammering on 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. They 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, different winding designs are used in transformers. So, in power transformers with a capacity of up to 630 kV A 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 gaskets made of electrical cardboard, which form vertical channels along the inner surface of the winding, as well as between its turns. The screw windings have great 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 work 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 tightness 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 the gaskets 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 core 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).

The unloading of the plates of the upper yoke of the magnetic circuit begins simultaneously from the HV and LV side, taking out 2 - 3 plates alternately from the extreme packages. The plates are laid 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 with a width of 15 - 25 mm 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 way the windings are made depends on their type and construction. 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.

The diagram of the algorithm and the flow chart for the manufacture of a multilayer winding of the HV transformer with a capacity of 160 kVA and a voltage of 10/04 kV are given below.

The winding is dried at a temperature of about 100 ° C for 15 - 20 hours, depending on the coil volume, the degree of insulation moisture, drying temperature, etc. Then it is pressed, impregnated at a temperature of 60 - 80 ° C with TF-95 varnish 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 - turn counter; 5 - clutch; 6 - spindle; 7 - textolite disc; 8 - nut; 9 - template; 10 - control pedal.

Various machines are used for the manufacture of windings. A cantilever machine for winding windings of small and medium power transformers (up to 630 kVA) (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 a spindle 6, which rotates from an electric motor 1 through a belt drive 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) during the installation of 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 studs, 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 transformers of low power, 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 frequently used method in practice is the method of drying in its own heated tank: when alternating current passes through a special winding superimposed on the heat-insulated surface of the tank, a strong magnetic field is formed, which is closed 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 maintain 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 turns of the winding, while preventing the temperature of the windings from increasing 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 rinsed with used transformer oil. The dents are heated with a gas burner flame and straightened 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, through holes with a diameter of several millimeters are drilled at its ends. 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 oil gauge glass tube is replaced. The rubber gaskets and seals that have lost their elasticity 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 prepared 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; the inside of the pipe is 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 with an area of ​​up to 3 cm² 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 a temperature of 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 is destroyed 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 nitro enamel 624C.

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

Switch repair consists in eliminating defects in contact connections, cylinder insulating tubes 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. Switches 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 sequential operation of the moving contacts a and b switch and contactors K1 and K2. Failure to operate these elements in the switching device can result in 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 (a) 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 leakage from the joints and seams.

Routine repair of transformers with a capacity of 10,000 - 63,000 kV-A 1. Composition of executors

Electromechanic- 1

Terms of work

The work is being done:

2.1. With stress relief

2.2. Alongside

Preparatory work and admission to work

4.1. On the eve of the work, apply for a withdrawal for repair trans
formator.

4.2. Check the serviceability and shelf life of protective equipment,
ditch, prepare tools, mounting accessories and materials.

4.3. After the release of the order, the manufacturer of the work should receive instructions from
the person who issued the outfit.

4.4. Operational personnel to prepare the workplace.
The manufacturer of the works to check the implementation of technical measures for
preparation of the workplace.

4.5. Carry out the admission of the brigade to work.

4.6. The contractor should instruct the team members and clearly
distribute responsibilities between them.

End of technological art no. 2.2.

Note. All operations with oil filled and 110-220 kV bushings must be performed in conjunction with a RRU specialist.

Completion of work

Technological map No. 2.3. Current repair of autotransformers for voltage 110-220 kV

Cast

Electromechanic - 1

Electrician of traction substation 4 category - 1

Electrician of traction substation 3 category - 1

Terms of work

The work is being done:

2.1. With stress relief

2.2. 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

Technological map No. 2.4. Current repair of transformers with a capacity of 40 - 630 kV-A

Cast

Electromechanic - 1

Electrician of traction substation 3 category - 1

Terms of work

The work is being done:

2.1. With stress relief

2.2. 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, zeolite, transformer oil, CIATIM grease, white spirit, moisture-oil-resistant varnish or enamel, spare oil indicator glasses, rubber gaskets, cleaning material, rags

Oil switches

Continuation of technological map No. 3.1.

Cast

Electromechanic - 1

Electrician of traction substation 4 categories - 1 Electrician of traction substation 3 categories - 1

Terms of work

The work is being done:

2.1. With stress relief

2.2. 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, electric stopwatch, wrenches, combination pliers, screwdrivers, scraper, brushes, glass containers with a ground stopper for oil sampling, silica gel indicator, silica gel, transformer oil, CIATIM grease, white spirit, insulating varnish, spare oil indicator glasses, rubber gaskets, cleaning material, rags

Cast

Electromechanic - 1

Electrician of traction substation 3 category - 1

Terms of work

The work is being done:

2.1. With stress relief

2.2. 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, testing device type LVI-100, electric stopwatch, wrenches, combination pliers, screwdrivers, scraper, brushes, transformer oil, CIATIM grease, white spirit, insulating varnish, spare oil indicating glasses, rubber gaskets, cleaning material, rags

Completion of work

6.1. Collect devices, tools, fixtures and materials.

6.2. Return to the control room of the traction substation.

6.3. Pass workplace admitting and close the outfit

6.4. Record the results of the measurements in a protocol.

Cast

Electromechanic - 1

Electrician of traction substation 3 category - 1

Terms of work

The work is being done:

2.1. With stress relief

2.2. Alongside

3. Protective equipment, devices, tools, fixtures and materials:

Protective helmets, grounding, short circuits, dielectric gloves, a megohmmeter for voltages of 1000 and 2500 V, an electric stopwatch, wrenches, combination pliers, screwdrivers, a scraper, transformer oil, TsIA-TIM grease, white spirit, insulating varnish, spare oil indicating glasses, rubber gaskets, cleaning material, rags

Completion of work

6.1. Collect devices, tools, fixtures and materials.

6.2. Return to the control room of the traction substation.

6.3. Hand over the workplace to the admitting person and close the outfit

6.4. Record the results of the measurements in a protocol.

Cast

Electromechanic - 1

Electrician of traction substation 4 category - 1

Terms of work

The work is being done:

2.1. With stress relief

2.2 Alongside

3. Protective equipment, devices, tools, fixtures and materials:

Megohmmeter for voltage 500 and 2500 V, tester, electric soldering iron, vacuum cleaner, calibration wrench, wrenches, combination pliers, screwdrivers, files, scraper, control lamp, hair brush, wooden ladder, stepladder, white spirit, wiping material, CIATIM lubricant

Completion of work

6.1. Collect devices, tools, fixtures and materials.

6.2. Return to the control room of the traction substation.

6.3. Hand over the workplace to the admitting person and close the outfit

6.4. Record the results of the measurements in a protocol.

Cast

Electromechanic - 1

Electrician of traction substation 4 category - 1

Terms of work

The work is being done:

2.1. With stress relief

2.2 Alongside

3. Protective equipment, devices, tools, fixtures and materials:

Ohmmeter, portable lamp, vacuum cleaner, wrenches and socket wrenches, screwdrivers, ruler, vernier caliper, files, scraper, wire brush, set of probes, files for cleaning switch contacts, wooden stick, sandpaper, white and carbon paper, white spirit, grease CIATIM, rags, cleaning material

Cast

Electromechanic - 1

Electrician of traction substation 4 category - 1

Terms of work

The work is being done:

2.1. With stress relief

2.2 Alongside

3. Protective equipment, devices, tools, fixtures and materials:

Stopwatch, portable lamp, vacuum cleaner, wrenches and socket wrenches, screwdrivers, ruler, caliper, files, scraper, wire brush, set of probes, files for cleaning switch contacts, glass sheet, wooden stick, sandpaper, white and carbon paper, white spirit, CIA-TIM grease, rags, cleaning material

Transformers Technological map № 2.1.

Including reconstruction (change of structural elements) and modernization (change of nominal voltages and powers).

We always fulfill our obligations, so our Customers can count on a decent level of service and quality work.