Supervision and maintenance of transformers

High-quality and reliable power supply to consumers can only be ensured if the equipment works properly, including power transformers. One of the prerequisites for ensuring the normal operation of transformers is periodic monitoring of their operation, as well as timely and proper maintenance.

The main goal is to ensure trouble-free operation, long service life, timely detection and elimination of deviations from normal operation and prevention of the development of a larger emergency situation.

Supervision and maintenance of transformers

Supervision of the operation of transformers

Supervision of transformers is carried out during periodic inspections of equipment in an electrical installation. If electrical installations have permanent maintenance personnel, checks are carried out daily.

Electrical installations serviced by the field team are checked at least once every 30 days. Transformers in distribution points are checked every six months.In case of emergency situations in the electrical installation or in case of possible unfavorable conditions for the operation of the equipment, additional inspections are organized.

Consider what you should pay attention to when inspecting a power transformer:

The magnitude of the load and the voltage for each of the windings

In this case, the current value should not exceed the nominal value for a particular coil. In emergency situations, if necessary, a short-term overload of one of the transformer windings is allowed. The operating instructions for each type of transformer separately show the possible value of overloading the windings in percentages and the corresponding time during which the winding can be overloaded without a negative impact on the equipment.

The voltage in each of the windings must be within the permissible values ​​for a certain voltage class. Continuous operation is allowed oil power transformer with an overload of one of the windings no more than 5%, provided that the winding voltage corresponds to the nominal value. It is also possible for the transformer to operate indefinitely at a voltage greater than 10% of the nominal value of one of the windings, and overloading the windings is unacceptable.

In case of overload, it is necessary to take measures to eliminate it (reduction of load of consumers, transfer of consumers to another power source). The voltage can be adjusted by switching ready-made devices or Transformer load switch in a given electrical installation, and if the problem is observed in several objects powered by one source, then voltage regulation is carried out on transformers (autotransformers) of the power substation.

Power transformer design

Position of switching devices, lack of triggering signals of protective and automation devices

The position of the switching devices must correspond to the operating mode of the equipment. In the case of operation of protection, automation (overload, ground fault, overheating, internal damage protection, undervoltage protection, automatic transfer switch, automatic reclosing, etc.), it is necessary to determine the cause of the operation and to take appropriate measures for the situation — to locate and disconnect from the network the emergency section of the electrical installation, to supply disabled consumers from backup power, etc.

Oil level in power transformer tank conservator and in load switching tank conservator (if structurally separated)

The oil level must be within the permissible limits between the minimum and maximum value of the manometer scale. The normal level is considered to be approximately corresponding to the average daily ambient temperature, taking into account the load of the transformer. The oil level is checked at each equipment check and additional checks may be arranged during periods of excessively high or low ambient temperatures.

The readings of the temperature sensors of the upper layers of the oil.The temperature of the upper layers of the oil must not exceed the permissible values ​​in accordance with the requirements for a certain cooling system of the transformer.

In oil transformers equipped with cooling systems, as well as in dry transformers, temperature sensors are used with a function to signal that the set temperature has been reached. The signal from the temperature sensor can be fed to the central alarm panel and, if necessary, to the automatic switching on of the cooling system of the transformer.

Substation transformer

Operation of the transformer cooling system

During the period of the year when additional cooling of the transformer is required, it is necessary to check the functionality cooling systems… When the oil temperature is reached at which the cooling should be turned on, it is necessary to check its operation or turn it on manually if there is no automatic mode for turning on the cooling. If the transformer is installed in a room equipped with forced supply and exhaust ventilation, it is necessary to check its operability and, if necessary, turn it on.

No oil leakage from the tank, from sealed oil filling bushings (if equipped)

For SF6 transformers — SF6 gas pressure in tank

The pressure value must correspond to the operating values ​​over the entire ambient temperature range.

Absence of unusual noises, crackling in the tank

The integrity of the grounding loop, conformity of the position of the zero short circuit (switch for zero grounding of the transformer) with the mode of operation of the neutral grounding of the electrical network

No contamination of the insulators, no visible signs of heating of the contact connections

Excessive pollution of the insulation can lead to its overlap and as a result of an emergency situation at the place of the electrical installation. Signs of overheating of the contact joints are a change in the color of the live parts, destruction of the outer coating (insulation or painting), visible melting of metal.

For timely detection of overheating of the contact connections, special alarms can be installed, which must be checked at each inspection of the transformer. In order to check the temperature of live parts, infrared pyrometers can be used, which enable remote recording of the surface temperature value.

Availability and suitability of fire extinguishers

When checking the transformer, it is necessary to check the presence fire extinguishing equipment in accordance with the diagram of their location in the electrical installation.

Maintenance of transformers

Maintenance of transformers

A long and trouble-free service life of a power transformer is ensured, provided that the maintenance of the transformer is carried out properly and in a timely manner.

Transformer maintenance involves regular maintenance and overhaul. Their frequency is determined based on the manufacturer's requirements and regulatory documents and equipment operating instructions in the enterprise that operates and maintains the electrical installation.

Planned repairs are carried out in accordance with previously drawn up schemes of the work process or production projects for work.These documents indicate the sequence of work and the requirements that must be followed when performing work and checking certain characteristics.

When carrying out maintenance activities on the transformer, the operation of the cooling devices is checked, oil leaks are eliminated, the reliability of the contact connections is checked, traces of corrosion on the structural elements of the transformer are eliminated, the oil level in the tank is corrected by draining or topping up the required amount transformer oil… For SF6 transformers, if necessary, SF6 gas is introduced to normalize the pressure in the transformer tank.

One of the most important stages of power transformer maintenance is checking the operation of relay protection and automation devices. These devices provide protection to the transformer from unwanted operating modes, ensuring their operation within the permissible nominal values ​​of current and voltage.

In case of emergency situations in which the transformer is disconnected from the action of protections, it is checked, physico-chemical analysis of transformer oil, insulation tests with increased voltage, based on which a conclusion is made about the possibility of further operation of this equipment. If necessary, the malfunctions that have occurred are eliminated.

The testing of the windings of a transformer excluded from the action of protection against internal damage is carried out regardless of the presence or absence of visible signs of damage.

The analysis of transformer oil is carried out in a specialized laboratory.In addition to emergency situations, oil samples are taken, as a rule, during the period of planned maintenance in order to promptly identify signs of deviations from the normal operation of the transformer. If necessary, the silica gel in the adsorption and thermosiphon filters is replaced.

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