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Section 2. Electrical equipment and electrical installations for general purposes

Chapter 2.1. Power transformers and reactors

Encyclopedia of radio electronics and electrical engineering / Rules for the technical operation of consumer electrical installations (PTE)

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1.1. The installation of transformers and reactors must be carried out in accordance with the rules for the installation of electrical installations and the norms for the technological design of substations.

Transportation, unloading, storage, installation and commissioning of transformers and reactors must be carried out in accordance with the governing documents (instructions) of the manufacturers.

2.1.2. When operating power transformers (autotransformers) and shunt oil reactors, their reliable operation must be ensured. Loads, voltage level, temperature, oil characteristics and insulation parameters must be within the established norms; cooling devices, voltage regulation, protection, oil facilities and other elements must be kept in good condition.

2.1.3. Transformers (reactors) equipped with gas protection devices must be installed so that the cover (removable part of the tank) has a rise of at least 1% towards the gas relay. In this case, the oil pipeline to the expander must have a slope of at least 2%.

2.1.4. The oil level in the expander of a non-working transformer (reactor) should be at a level corresponding to the oil temperature of the transformer (reactor) at the moment.

The maintenance personnel must monitor the temperature of the upper layers of oil using thermal alarms and thermometers, which are equipped with transformers with an expander, as well as the readings of pressure and vacuum meters for sealed transformers, for which, when the pressure in the tank rises above 50 kPa (0,5 kgf / cm2), the load should be reduced.

2.1.5. The air cavity of the safety tube of the transformer (reactor) must be connected to the air cavity of the expander.

The level of the diaphragm of the safety pipe must be higher than the level of the expander.

The exhaust pipe membrane, if damaged, can only be replaced with an identical factory one.

2.1.6. Stationary fire extinguishing installations must be in a state of readiness for use in emergency situations and be subject to inspections according to the approved schedule.

2.1.7. Gravel filling of oil receivers of transformers (reactors) must be kept clean and washed at least once a year.

If the gravel backfill is contaminated (dust, sand, etc.) or the gravel is oiled, it should be washed, as a rule, in spring and autumn.

If solid deposits from oil products with a thickness of more than 3 mm form on the gravel backfill, vegetation appears or it is impossible to wash it, the gravel should be replaced.

2.1.8. Substation numbers must be indicated on the tanks of three-phase outdoor transformers. On groups of single-phase transformers and reactors, the substation number is indicated on the middle phase. Phase colors are applied to the tanks of a group of single-phase transformers and reactors.

Outdoor transformers and reactors are painted in light colors with paint that is resistant to weathering and transformer oil.

2.1.9. Substation numbers of transformers must be indicated on the doors of transformer points and chambers on the outside and inside, and warning signs must be on the outside. Doors must be locked at all times.

2.1.10. Inspection and maintenance of high-lying elements of transformers and reactors (more than 3 m) should be carried out from stationary stairs with railings and platforms at the top in compliance with safety rules.

2.1.11. The inclusion of a transformer (reactor) in the network must be carried out by a push to full voltage. Transformers operating in a block with a generator can be put into operation together with the generator by raising the voltage from zero.

2.1.12. For each electrical installation, depending on the load schedule, taking into account the reliability of consumer power supply and the minimum of losses, the number of simultaneously operating transformers should be determined.

In distribution electrical networks with voltage up to 20 kV inclusive, measurements of loads and voltages of transformers are carried out in the first year of operation at least 2 times during the period of maximum and minimum loads, in the future - if necessary.

2.1.13. Reserve transformers must be kept in a state of constant readiness for inclusion in operation.

2.1.14. Neutral windings with a voltage of 110 kV of transformers and reactors should, as a rule, operate in the dead ground mode. A different mode of operation of the neutrals of transformers with a voltage of 110 kV and methods for their protection are established by the power supply organization.

2.1.15. In case of automatic shutdown of the transformer (reactor) by the action of protection against internal damage, the transformer (reactor) can be put into operation only after inspection, testing, analysis of gas, oil and elimination of identified defects (damages).

If the transformer (reactor) is disconnected from protections, the action of which is not associated with its internal damage, it can be switched on again without checks.

2.1.16. When the gas relay is triggered by a signal, an external inspection of the transformer (reactor) and gas sampling from the relay for analysis and testing for flammability must be carried out.

To ensure the safety of personnel when taking gas from the gas relay and identifying the cause of its operation, the transformer (reactor) must be unloaded and turned off as soon as possible.

If the gas in the relay is non-flammable and there are no signs of damage to the transformer, and its shutdown caused an undersupply of electricity, it can be put into operation until the cause of the gas relay's response to the signal is clarified. The duration of the transformer operation in this case is set by the consumer responsible for the electrical equipment. Based on the results of gas analysis from the gas relay, oil analysis and other measurements and tests, it is necessary to establish the cause of the gas relay triggering on the signal, determine the technical condition of the transformer (reactor) and the possibility of its normal operation.

2.1.17. The oil in the expander of transformers (reactors), as well as in the tank or expander of the on-load voltage regulation device (hereinafter - on-load tap-changer) must be protected from contact with air. For transformers and reactors equipped with special devices that prevent oil moistening, these devices must be constantly turned on, regardless of the operating mode of the transformer (reactor). These devices must be operated in accordance with the manufacturer's instructions.

Transformers with a capacity of 1000 kVA and more must be operated with a continuous oil regeneration system in thermosyphon and adsorption filters.

The oil of non-pressurized oil-filled bushings must be protected from oxidation and moisture.

2.1.18. If it is necessary to disconnect the open circuit current disconnector (separator) of an unloaded transformer equipped with an on-load tap-changer, after removing the load on the Consumer side, the switch must be set to the position corresponding to the rated voltage.

2.1.19. Parallel operation of transformers (autotransformers) is allowed, provided that none of the windings is loaded with a current exceeding the allowable current for this winding.

Parallel operation of transformers is permitted under the following conditions:

To equalize the load between transformers operating in parallel with different short circuit voltages, it is allowed to change the transformation ratio within a small range by switching taps, provided that none of the transformers is overloaded.

2.1.20. For oil transformers and transformers with non-combustible liquid dielectric, continuous loading of any winding with a current exceeding 5% of the rated current of the branch is allowed, if the voltage does not exceed the rated voltage of the corresponding branch. In an autotransformer, the current in the common winding must be no higher than the maximum continuous current of this winding.

Continuous permissible loads of dry-type transformers are established in the standards and specifications of specific groups and types of transformers.

For oil and dry transformers, as well as transformers with a liquid non-combustible dielectric, systematic overloads are allowed, the value and duration of which are regulated by the instructions of the manufacturers.

2.1.21. In emergency modes, a short-term overload of transformers in excess of the rated current is allowed for all cooling systems, regardless of the duration and value of the previous load and the temperature of the cooling medium within the following limits:

Oil transformers:

Dry transformers:

2.1.22. Continuous operation of transformers is allowed (at a load not exceeding the rated power) with an increase in voltage on any branch of any winding by 10% above the rated voltage of this branch. In this case, the voltage on any of the windings should not be higher than the highest operating voltage.

2.1.23. At the rated load of the transformer, the temperature of the upper layers of oil should not be higher (unless other temperatures are specified by the manufacturers in the factory instructions): for transformers with an oil cooling system with blast and forced oil circulation (hereinafter referred to as DC) - 75 ° C, with systems oil cooling (hereinafter - M) and oil cooling with blast (hereinafter - D) - 95 ° C; for transformers with an oil cooling system with forced circulation of oil through the water cooler (hereinafter referred to as C), the oil temperature at the inlet to the oil cooler should not exceed 70 °C.

2.1.24. On transformers and reactors with oil cooling systems DC, directional oil circulation in the windings (hereinafter - NDC), C, directional oil circulation in the windings and forced - through a water cooler (hereinafter - NC), the cooling devices should automatically turn on (turn off) simultaneously with turning on ( shutdown) of the transformer (reactor).

For rated load, the inclusion of transformers is allowed:

In emergency conditions, it is allowed to turn on transformers at full load, regardless of the ambient temperature (transformers with cooling systems NDC, NC - in accordance with factory instructions).

2.1.25. Forced circulation of oil in cooling systems must be continuous regardless of the load of the transformer.

2.1.26. The number of switched on and off coolers of the main and backup cooling systems of the DC (NDC), C (NC), the operating conditions of transformers with the cooling system blast turned off D are determined by the factory instructions.

2.1.27. The operation of transformers and reactors with forced oil circulation is allowed only when the signaling system is turned on to stop the circulation of oil, cooling water and the operation of the cooler fans.

2.1.28. When turning on the oil-water cooling system of the C and NC, the oil pump must be started first. Then, when the temperature of the upper layers of oil is above 15 ° C, the water pump is turned on. The water pump is switched off when the temperature of the upper oil layers drops to 10 °C, unless otherwise provided by the factory documentation.

The oil pressure in the oil coolers must exceed the pressure of the circulating water by at least 10 kPa (0,1 kgf/cm2) with a minimum oil level in the transformer expander.

Measures must be taken to prevent freezing of oil coolers, pumps, water lines.

2.1.29. For transformers with cooling systems D, in case of emergency shutdown of all fans, it is allowed to work with a rated load depending on the ambient temperature for the following time:

For transformers with DC and C cooling systems, it is allowed:

a) upon termination of artificial cooling, work with a rated load for 10 minutes. or idle mode for 30 minutes; if after the specified time the temperature of the upper layers of the oil has not reached 80 ° C; for transformers with a power of over 250 MV×A, it is allowed to work with a rated load until the specified temperature is reached, but not more than 1 hour;

b) when the fans are completely or partially turned off or the water circulation is stopped while maintaining the oil circulation, continuous operation with a reduced load at a temperature of the upper oil layers not higher than 45 °C.

The requirements of this paragraph are valid unless otherwise specified in the manufacturer's instructions.

Transformers with directional oil circulation in the windings (NC cooling system) are operated in accordance with the factory instructions.

2.1.30. On transformers with a cooling system D, the fan motors should automatically turn on at an oil temperature of 55 ° C or a current equal to the rated current, regardless of the oil temperature. The fan motors are switched off when the temperature of the upper oil layers drops to 50 °C, if the load current is less than the nominal one.

2.1.31. Voltage regulation devices under load should be in operation, as a rule, in automatic mode. Their work should be controlled according to the indications of counters of the number of operations.

By decision of the Consumer responsible for the electrical economy, remote switching of the on-load tap changer from the control panel is allowed if the voltage fluctuations in the network are within the limits that satisfy the requirements of the Consumers. Switching under voltage manually (by means of a handle) is not permitted.

The Customer's personnel servicing the transformers is obliged to maintain a correspondence between the mains voltage and the voltage set on the control branch.

2.1.32. Transformer on-load tap-changers may be put into operation at a temperature of the upper oil layers above -20 °C (for external resistor tap-changers) and above -45 °C - for tap-changers with current-limiting reactors, as well as for changeover devices with a contactor located on the base insulator outside the transformer tank and equipped with an artificial heating device. The operation of the on-load tap-changers must be organized in accordance with the factory instructions.

2.1.33. On transformers equipped with winding tap changers without excitation (hereinafter referred to as PBV), the correct choice of the transformation ratio must be checked at least 2 times a year - before the winter maximum and summer minimum load.

2.1.34. Inspection of transformers (reactors) without shutting them down should be carried out within the following periods:

Depending on local conditions and the condition of transformers (reactors), the indicated terms can be changed by the technical manager (responsible for electrical facilities) of the Consumer.

Unscheduled inspections of transformers (reactors) are carried out:

2.1.35. Current repairs of transformers (reagents) are made as needed. The frequency of current repairs is established by the technical manager of the Consumer.

2.1.36. Capital repairs (scheduled preventive maintenance - according to the standard range of works) should be carried out:

2.1.37. Unscheduled repairs of transformers (reactors) must be carried out if a defect in any of their elements can lead to failure. The decision to withdraw the transformer (reactor) for repair is made by the head of the Consumer or the person responsible for the electrical facilities.

2.1.38. A consumer who has oil-filled equipment on his balance sheet must store an irreducible supply of insulating oil of at least 110% of the volume of the most capacious apparatus.

2.1.39. Testing of transformers and reactors and their elements in operation must be carried out in accordance with the standards for testing electrical equipment (Appendix 3) and factory instructions. The test results are documented in acts or protocols and are stored together with the documents for this equipment.

2.1.40. The frequency of oil sampling of transformers and reactors with a voltage of 110 and 220 kV for chromatographic analysis of gases dissolved in oil must comply with the guidelines for diagnosing developing defects based on the results of chromatographic analysis of gases dissolved in oil of transformer equipment.

2.1.41. The transformer (reactor) must be emergency decommissioned when:

Transformers are taken out of service also if an immediate oil change is required based on the results of laboratory tests.

2.1.42. At each transformer substation (hereinafter - TS) 10 / 0,4 kV, located outside the territory of the Consumer, its name, address and telephone number of the owner must be applied.

See other articles Section Rules for the technical operation of consumer electrical installations (PTE).

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