Functions and Roles of 6 Common Low-Voltage Electrical Components

Low-voltage disconnect switch
The isolating switch we are referring to is generally a high-voltage isolating switch, that is, an isolating switch with a rated voltage of 1 kilovolt or above. It is the most commonly used electrical appliance in high-voltage switchgear, serving to isolate the circuit. Its working principle and structure are relatively simple.
When performing maintenance on low-voltage electrical equipment, the power supply must be cut off to separate the maintenance part from the live part and maintain an effective isolation distance. It is required that the withstand voltage level between the breaking points can withstand overvoltage. Circuit breakers are used as switchgear for isolating the power supply. Circuit breakers for isolating the power supply are also called disconnectors. Disconnecting circuit breakers for isolation are generally load-independent switching devices and can only connect or disconnect “ignorable currents” (referring to the voltage of the busbar, the capacitance current of the short cable, or the current of the voltage transformer). Some circuit breakers have certain switching capabilities. When their switching capabilities are compatible with the required switching current, they can connect or disconnect part of the electrical equipment or a part of an integrated equipment under non-fault conditions.
The main features of the disconnect switch
2. It has no arc-extinguishing capability and can only open or close the circuit when there is no load current.
2. During normal power-on operations: First close the disconnect switch, then close the circuit breaker or load-type switch.
3. During power-off operation: First disconnect the circuit breaker or load-type switch, then disconnect the isolating switch.
The function and role of the disconnect switch
It is used to isolate the power supply, disconnecting the high-voltage maintenance equipment from the live equipment, so that there is a clearly visible disconnected point between them.
2. The isolating switch is coordinated with the circuit breaker to perform switching operations as required by the system’s operating mode, thereby changing the system’s operating wiring configuration.
3. Used to connect or disconnect circuits with small currents
Parameters of the isolating switch
Rated voltage = Nominal voltage of the circuit * 1.2/1.1 times;
Rated current standard value > 150% of the maximum load current
The differences between disconnectors, load switches and circuit breakers
The isolating switch serves as a distinct break point in the circuit, ensuring the safety of personnel during maintenance. It can only cut off the no-load current of the line, but cannot cut off the load current or short-circuit current.
2. The load switch also serves as an isolator and is capable of cutting off the load current.
3. Circuit breakers can cut off both the load current and the short-circuit (fault) current. During a fault, they can automatically trip. Additionally, some models of circuit breakers also have an isolation function and can be used as an isolation device for electricity.