Analysis of Common Faults of On-Load Transformer Switch of Transformer
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On-load tap-changer operation or fault handling
1. When the regulator switch refuses to operate, check the following:
(1) Operation is correct Incorrect operation:
1 Operation mode selection switch (such as remote or local operation selection switch, manual or automatic selection switch, etc.) The position is incorrect, they should be placed in the correct position;
2 If the operation exceeds the limit position (has been increased continuously at the highest position or has been reduced at the lowest position), the report shall be issued to correct the mistake.
(2) Whether the operation circuit DC power supply is normal or not should recover the power supply.
(3) Is the operating mechanism's AC power normal?
Abnormal conditions may include:
1 The power source of the mechanism is three-phase or two-phase without voltage (the circuit breaker is not engaged or the fuse is disconnected), and the motor cannot start;
2 operation power supply has a phase without voltage, motor two-phase power caused by overcurrent to make the power contactor trip;
3 institutions exchange control power supply without voltage, the control circuit can not operate;
4 Operation The three-phase sequence of the AC power supply is incorrect, causing the motor to rotate in the reverse direction. The related protection action trips the power contactor. If this is the case, replace the two phases in the three-phase power supply and rectify the phase sequence of the power supply. In the case of 123, power failure should be ruled out, and then start regulating;
5 The control loop is locked.
Possible causes of latch-up: Loss of AC voltage, three-phase out-of-step, long adjustment times or other, depending on the design of the DC control loop. The cause of the blockage should be identified and eliminated based on the design loop diagram and the signals that appear.
2. On-load tap-changer mechanical failure
The mechanical failure of the on-load tap-changer, including the malfunction of the change-over switch or split selector, and the mechanical failure of the operating mechanism, is a serious failure and may result in the following conditions:
(1) Split selector with load conversion. This situation is similar to the load-disconnecting isolation switch, which will trip the main gas relay of the transformer body.
(2) The changeover switch refused to move or switch was not in place. If the switch is stopped at a middle position for a long time during the middle of switching, the transition resistance will be overheated due to long-term power on, which may cause the gas switch of the switch to act and trip the transformer.
(3) Poor contact in the switch or tap selector contact.
When the above situation occurs, the transformer shall be promptly applied for exit from operation and maintenance.
3, on-load tap-changer out of step
The on-load tap-changer of the transformer corresponds to the three positions in the same position. The so-called "out-of-step" refers to the inconsistency of the three-phase split position due to some reason in the pressure regulation. In this state, the zero-sequence voltage and the zero-sequence current are generated due to the unbalanced three-phase secondary voltage. In the process of transformer voltage regulation, short-term inconsistency is possible. If it is not consistent for a long time, it may cause the transformer to overheat or trip.
The reason why the on-load tap-changer is out of step may be that one or both of the phases has been refused due to an electrical or mechanical failure (for reasons shown in the above analysis), or stopped halfway after startup. When on-load tap-changer out-of-step occurs, the operator should immediately go to the site to check the actual position of the transformer three-phase tap-changer, find out the cause of the refusal, and handle it so that the three phases can be resynchronized. In order to avoid long-term operation of the transformer in an out-of-step condition, the phase that has been actuated can be returned to the original position (electrical or manual on site), and then the reason for the rejection of the operation is checked. If the transformer cannot be synchronized due to mechanical failure, the transformer shall be used to exit the operation in accordance with the provisions of the site regulations.
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Product name: On-load tap-changer tester, transformer on-load tap-changer tester, transformer on-load switch tester, transformer on-load tap-changer tester BYKC2000 transformer on-load switch tester for measuring transformers The parameters of the on-load tap-changer, which mainly measure the transition pattern of the switch, calculate the transition time, transition resistance, synchronization, etc. It is an indispensable device for transformer on-load switch detection.
The main performance indicators:
Transition time measurement: Measurement accuracy 0.1 ms transition resistance: 0.1 ohm accuracy
Three identical phases: Accuracy is 0.1ms Three-phase waveform is displayed: Accuracy is 0.1ms
Printable Waveform Range: 60ms/120ms Transition Resistance Measurement Range: ≤20Ω
Transition time measurement range: ≤400ms Working environment temperature: -10°C～50°C
Instrument weight: 6kg
Charge current: 0.6A (0.2A per phase)
Operating supply voltage: AC220±10%; 50Hz±10%