What is a high-voltage disconnector, and what are its functions and classifications?

A high-voltage disconnector (also called a disconnector or knife switch) is a switching device used to isolate electrical equipment in a power system. It is mainly used for no-load operation (i.e. when the circuit does not carry current) to cut off or connect the circuit to ensure the safety of equipment during overhaul and maintenance. In high-voltage power systems, high-voltage disconnectors are usually installed in substations and power lines to separate different electrical circuits.

Function

The main functions of high-voltage disconnectors include:

1. Safety isolation: Isolate electrical equipment from high-voltage power supplies to ensure the safety of personnel during equipment maintenance. By physically disconnecting the power supply, maintenance personnel can avoid the risk of electric shock.

2. Electrical segmentation: Segmented control of circuits in power systems. When electrical equipment or lines need to be overhauled, the faulty or overhauled part can be isolated from the power grid through an isolating switch.

3. Indication of circuit status: Since the isolating switch has a visible disconnection point, it can intuitively display whether the circuit is energized or de-energized.

Classification

According to different structures, operation methods and installation environments, high-voltage disconnectors can be divided into the following categories:

1. Classification by installation location:

- Outdoor disconnectors: used in outdoor substations or power line systems, and can withstand severe weather conditions.

- Indoor disconnectors: used for indoor equipment, usually used in internal power equipment such as high-voltage switchgear.

2. Classification by number of poles:

- Single-pole disconnectors: only control one power line, often used in high-voltage DC systems.

- Bipolar disconnectors: control two power lines at the same time, mostly used in AC systems.

3. Classification by operation method:

- Manual disconnectors: opened and closed by manual operating levers, often used in smaller power systems.

- Electric disconnectors: remotely or automatically operated by electric devices, often used in larger or frequently operated power systems.

4. Classification by structure:

- Horizontal rotary disconnectors: open and close contacts by horizontal rotation, commonly used in power grids with voltage levels of 110kV and above.

- Vertical break disconnector: It opens or closes by vertical movement, has a compact structure, and is often used in substations.

Notes

High-voltage disconnectors are usually used under no-load or light-load conditions and cannot be used to cut off load current or short-circuit current because they do not have an arc extinguishing device.