Classification and Abnormal Handling of High-Voltage Disconnect Switches
1. Primary Uses of High-Voltage Disconnector Switches
1. Used to isolate the power supply, ensuring safety during maintenance by providing a clear disconnection point between the electrical equipment under repair and the power source;
2. Perform switching operations to alter the system operating mode, such as transferring equipment or lines from one busbar set to another in a double-busbar circuit using disconnect switches;
3. Under certain conditions, it can be used to connect and disconnect small current circuits. For example, isolating switches can perform the following operations:
1)Disconnect and connect the Voltage Transformer and lightning arrester circuits.
2) Charging current of busbars during closing and opening.
3) No-load transformers with excitation current not exceeding 2A and no-load lines with capacitive current not exceeding 5A.
II. Classification of High-Voltage Disconnector Switches
1. Classified by installation location: indoor and outdoor types;
2. According to the number of poles, it is divided into two types: single-pole and three-pole;
3. According to the number of insulating pillars, it is divided into three types: single-column, double-column, and triple-column;
4. Based on structural characteristics, they are divided into three types: knife-type, spiral-type, and insert-type;
5. They are categorized into two types based on function: those with a grounding knife switch and those without;
6. According to the type of control mechanism used, they are classified into manual, electric, and pneumatic operation mechanisms, among others.
3、 Abnormal phenomena and handling of high-voltage isolating switches
High Voltage Isolating Switches should have sufficient insulation strength when single-phase grounding occurs in the system; When operating at full load, it should be able to meet the requirements of thermal stability; In the event of a short circuit fault in the system, it should be possible to ensure that thermal and dynamic stability are not compromised under the impact of short-circuit current. The abnormal phenomena during the operation of high-voltage isolating switches include:
1. The contact part of the isolation switch is overheated
Under normal circumstances, the isolation switch should not experience overheating, and the temperature should generally not exceed 70 ℃. If the contact part reaches 80 ℃, the load should be reduced or stopped. The cause of overheating in the contact area is the loosening of compressed springs and bolts, as well as surface oxidation. Under the influence of heat, the surface of the contact part is more prone to oxidation, causing an increase in resistance and temperature, which may lead to the formation of an arc if it continues to develop. When the isolation switch overheats during operation, the following measures should be taken:
1) In a dual busbar system, when one set of busbar isolation switches heats up, it should be switched to another set of busbars; When the isolation switch of a single busbar system heats up, efforts should be made to reduce the load. If conditions permit, it is best to disable the isolation switch. If a power outage is possible, immediate maintenance should be carried out, otherwise monitoring should be strengthened. If the heat is severe, the corresponding Circuit Breaker should be disconnected according to the regulations.
2) When the contact part of the line isolation switch overheats, the handling method is the same as that of the single busbar isolation switch, but due to the protection of the series connected circuit breaker, the isolation switch can continue to operate, but monitoring needs to be strengthened until the power can be cut off for maintenance.
2. Wrong pulling or closing of isolation switch with load
The isolation switch does not have arc extinguishing capability, and it is strictly prohibited to pull or close the isolation switch with load. Once this phenomenon occurs, it should be handled according to the following methods:
1) Accidentally pulling the isolation switch
If the blade has just left the blade edge (arc has started but not yet broken), the unopened isolation switch should be immediately closed to avoid arc short circuit; If the isolation switch has already been opened, it is not allowed to close it. The isolation switch should be kept in the open position, and the circuit should be disconnected with a circuit breaker before closing the isolation switch.
2) Misclosing isolation switch
After accidentally closing the isolation switch with load, it is not allowed to open it again. It must be opened after the circuit breaker cuts off the circuit.
3. Isolation switch refuses to open or close
1) Refuse to close the switch
When the isolating switch refuses to close due to mechanical failure, an insulating rod can be used for operation, or the rotating shaft of the isolating switch can be turned with a wrench while ensuring personal safety.
2) Refuse to open the switch
When the isolation switch cannot be turned on, if the operating mechanism is frozen, you can gently shake it to find the obstacle point. If the obstacle point is at the contact part of the switch, it cannot be forcibly pulled open, otherwise the supporting porcelain bottle may be damaged.
4. The ceramic components of the isolation switch are damaged
If it is a flashover discharge, monitoring should be strengthened and cleaning should be carried out after applying for a power outage; If the supporting porcelain bottle is damaged or broken, a circuit breaker should be used to disconnect the circuit and the damaged isolation switch should be removed for repair.