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Date：07-13-2021
First. The operating principle of isolating switch
1. It is forbidden to use an isolating switch to pull in load equipment or load lines.
2 . It is forbidden to open and close the no-load main transformer with an isolating switch.
3 . The following operations are allowed using the isolating switch:
a) Open and close the voltage transformer and lightning arrester without fault;
b) When there is no fault in the system, open and close the neutral point grounding switch of the transformer;
c) Open and close the loop current without impedance;
d) The open and close voltage can be 10KV and below with the outdoor triple disconnect switch,
Load current below 9A; when it exceeds the above range, it must pass
Calculations, tests, and approval by the chief engineer of the unit in charge.
Second. Principles of Transformer Operation
1. Conditions for parallel operation of transformers:
a) The voltage ratio is the same;
b) The impedance voltage is the same;
c) The wiring group is the same.
2. Transformers with different impedance voltages must be accounted for and can be operated in parallel under the condition that none of them are overloaded.
3. Transformer power-off operation:
a) For power-off operation, the low-voltage side should be stopped first, the medium-voltage side should be stopped, and the high-voltage side should be stopped last;
b) When switching the transformer, it should be confirmed that the transformer to be stopped can be stopped only after the incorporated transformer is loaded.
4. Transformer neutral point grounding switch operation:
a) In the 110KV and above neutral point directly grounded system, when the transformer stops, transmits power and charges the bus through the transformer, the neutral point grounding switch must be closed before operation, and after the operation is completed, it is determined whether to open according to the system requirements. ；
b) When the neutral point grounding switch of the transformer in parallel operation needs to be switched from one to another operating transformer, the neutral point grounding switch of the other transformer should be closed first, and the original neutral point grounding switch should be opened. ；
c) If the neutral point of the transformer is running with an arc suppression coil, when the transformer is out of power, the neutral point isolation switch should be opened first. When the transformer is operated, the power-off sequence is one phase; it is forbidden to send the transformer with a neutral point isolation switch. Turn off the neutral point isolation switch after powering off the transformer first.
Third, the principle of electrical inspection grounding
1. Before testing the power-off equipment, in addition to confirming that the electroscope is intact and effective, the correct alarm should be checked on the live equipment of the corresponding voltage level before the electrical test can be performed on the equipment that needs to be grounded. It is forbidden to use electroscopes that do not correspond to the voltage level for electrical testing.
2. When the electrical equipment needs to be grounded, the electricity must be checked first, and the grounding switch can be turned on or the grounding wire can be installed only after it is confirmed that there is no voltage.
3. There should be a clear location for the electrical inspection and installation of the grounding wire, and the location of the installation of the grounding wire or the grounding switch must be consistent with the electrical inspection position.
4. When installing the grounding wire, ground it on the dedicated grounding pile first, and remove it in the reverse order at the conductor end. It is forbidden to install the grounding wire by winding method. When it is necessary to use a ladder, it is forbidden to use a metal material ladder.
5. When checking the electricity on the capacitor bank, it should be carried out after the discharge is completed.
