Generally, a set of disconnectors are installed on the front and back of the circuit breaker. The purpose is to isolate the circuit breaker from the power supply to form a clear disconnection point. Because the original circuit breaker was an oil circuit breaker, the oil circuit breaker needs to be repaired frequently. Therefore, there must be obvious disconnection points on the two sides to facilitate maintenance. In general, the outlet cabinet supplies power from the busbar above through the switch cabinet. A group of disconnectors are required in front of the circuit breaker to isolate the power supply, but sometimes, There is also the possibility of incoming calls behind the circuit breaker, such as through the other loops, capacitors and other devices, so a set of disconnectors are also required behind the circuit breaker.
Isolation switch is mainly used to reliably isolate the part of the high-voltage power distribution device that needs to be powered off from the live part to ensure the safety of maintenance work. The contacts of the disconnector are all exposed in the air and have obvious disconnection points. The disconnector does not have an arc extinguishing device, so it cannot be used to cut off the load current or short-circuit current. Otherwise, a strong arc will occur at the disconnection point under the action of high voltage. It is difficult to extinguish by itself, and may even cause arcing (short to ground or phase-to-phase), burn equipment, and endanger personal safety. This is a serious accident called "pulling isolating switch with load". Isolation switches can also be used to switch certain circuits to change the way the system operates. For example: In a double-bus circuit, an isolating switch can be used to switch the running circuit from one bus to another. At the same time, it can also be used to operate some small current circuits.
1. When servicing electrical equipment, provide an electrical interval and a clearly visible disconnect point to protect the personal safety of maintenance personnel.
2. Isolation switch can not be operated with load: it can not be operated with rated load or large load, can not be divided, combined load current and short-circuit current, but those with arc extinguishing chamber can be operated with small load and no-load line.
3. In general power-on operation: close the disconnector first, then close the circuit breaker or load switch; in power-off operation: first disconnect the circuit breaker or load switch, and then disconnect the disconnector.
4. When selected, it is the same as other electrical equipment, and its rated voltage, rated current, dynamic stable current, and thermal stable current must meet the needs of the application.
The function of the disconnector is to disconnect the circuit with no load current. The equipment to be repaired has a clear disconnection point with the power supply to ensure the safety of the maintenance personnel. Therefore, the disconnect switch must be operated only when the circuit breaker opens the circuit.
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