There are many types and models of electrical disconnect switches; the most common types are high-voltage disconnect switches and low-voltage disconnect switches, as shown in the figure below.
The image above shows a low-voltage disconnect switch, mainly used in low-voltage power distribution cabinets and power cabinets; the image below shows a high-voltage disconnect switch.
High-voltage disconnect switches are mainly used in high-voltage power distribution systems of 10KV and above.
Disconnect switches can be manually or electrically operated using a lever principle or a speed reducer.
The main characteristics and functions of an electrical disconnect switch are: it has a clear breaking gap (disconnection point), therefore it is mainly used to isolate power supply, ensure the safety of maintenance work, and interrupt current in the circuit. Furthermore, because it lacks a dedicated arc-extinguishing device, it cannot be used to interrupt load current when the load is not completely disconnected, and it cannot be used to interrupt short-circuit current. The main functions of a disconnect switch are as follows.
1. When maintaining high and low voltage electrical equipment, use disconnect switches to separate the energized and de-energized parts, forming a clear disconnection point to separate the equipment under maintenance from the large power input from the power system, ensuring the safety of maintenance personnel and electrical equipment.
2. The disconnecting switch and the circuit breaker work together to perform switching operations to change the operating mode.
① For double busbars with bypass connections, when a circuit breaker of a certain outgoing unit is locked due to other reasons, and the bypass circuit breaker is used to power other circuits, a disconnecting switch can be used to connect the circuit in parallel.
② For a half-open connection, when a circuit breaker in series is locked in the open or closed position, a disconnecting switch can be used to break the loop (but note that all other circuit breakers in series must be in the closed position).
③ For a double busbar single-section wiring method, when one of the two busbar circuit breakers and the section circuit breaker experiences a blocking of opening or closing, the circuit can be disconnected using a disconnecting switch.
3. Used to interrupt relatively small current loops and bypass/loop currents;
① Connecting and disconnecting voltage transformers;
② Capacitive current of the busbars and equipment directly connected to them;
③ Excitation current of unloaded transformers with an A rating of 2A or less;
④Inrush current of unloaded lines below 5A.
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