Operation and maintenance of on load tap changer for 110kV and below transformers

In recent years, the application of 110kV and transformer on load tap changer is more and more, mostly for domestic. The tap changer adopts the resistance type combination, and the overall structure can be divided into three parts: the control part, the transmission part and the switch part. On load tap changer plays an important role in improving the voltage qualification rate of power supply system. At present, the voltage regulating method of county power grid, which is powered by large power grid, is mainly realized by on load voltage regulating transformer. This puts the operation and maintenance of on load tap changer and tap changer into an important position.

Maintain content and requirements

(1) the oil conservator shall be checked before the load tap changer is put into operation, the oil level should be normal, no seepage oil leakage, and the control box should be damp proof. Manual operation of a cycle (that is, lifting a cycle), gear indicators and counters should be correct action, the limit position of the lock should be reliable, manual and electric control of the interlocking should also be reliable.

(2) gas protection for on load tap changer, heavy gas input trip, light gas signal. This is the same as the transformer gas protection requirements. We usually call the gas relay ontology as "gas", said the OLTC gas relay as small gas?". Gas relay should be installed in operation to facilitate the safety of bleeding position. When the new installed tap changer gas relay is installed, the operator shall release the gas in time when necessary.

(3) the electrical control of the load tap changer should be correct, the power supply is reliable, and the terminals are in good contact. The drive motor is in normal rotation and the steering is correct. The current rating of the fuse is 2 to 2.5 times the rated current of the motor.

(4) load power control circuit is connected with the switch, installed in the control panel on the electric button operation, and installed in the transformer on load tap switch control box button on the condition, the power indicator and gear indicator should be intact, electrical locking limit position should be reliable.

(5) an electric current locking device shall be provided for the electric control circuit of the load tap changer, whose setting value is mainly, and the current rating of the transformer is 1.2 times, and the return coefficient of the current relay is greater than or equal to 0.9. When using automatic voltage regulation, the main transformer control panel must have action counter, automatic voltage regulator voltage transformer two times disconnection, locking should be correct and reliable.

(6) new or after overhaul OLTC, should be in the transformer no-load running, in the main control room remote electric operation button and manual equipment in transformer field trial operation, a cycle, gear and voltage the correct instructions, electrical locking limit position can be adjusted by scheduling the tap stalls to run with load, and strengthen monitoring.

(7) the attendant will automatically adjust the voltage according to the voltage curve and voltage signal issued by dispatching. Each operation shall carefully check the operation of the tap, voltage and current changes (each transfer of one meter), and make a record.

(8) when two on load tap changing transformers are in parallel operation, the transformer shall be operated on the transformer under 85% rated load current. However, two tap changer operations can not be carried out continuously on a single transformer. After a sub transformer switching operation of one transformer is completed, another tap changer operation of another transformer is performed. A transformer and a load voltage regulating transformer parallel operation, must put the OLTC tap switch and no load tap changer in the same or similar position, even if the secondary voltage of two main transformers of the same or similar. When the on load tap changer and the no-load voltage regulating transformer are in parallel operation, the tap changer is strictly prohibited.

(9) when the personnel on duty carry out the tap changer control, they should follow the requirements of the inspection and inspection. Before and after the operation, attention should be paid to and observed whether or not the gas relay has bubbles.

(10) when the gas relay in the load tap changer sends out the signal or the tapping switch, the oil tank is forbidden to operate when the oil is changed, and the power isolating switch is pulled out.

(11) the operation of OLTC gas relay heavy gas protection should be tripping. When the light gas frequently moves, the duty personnel should make a good record and report the dispatch, stop the operation, analyze the reason and deal with it in time.

(12) the oil quality supervision and inspection cycle of on load tap changer:

Every 6 months during operation, oil samples shall be taken to withstand pressure test once, and the oil pressure resistance shall not be less than 30kV/2.5mm. When oil pressure is between (25 ~ 30kV) /2.5mm, automatic voltage regulation controller should be stopped. If the oil pressure is lower than 25kV/2.5mm, the pressure adjustment operation should be stopped and oil change is arranged in time. Oil shall be changed when running 2~4 years or 5000 times of transformation operation.

Inspection of suspension core of on load tap changer