What components does a high-voltage switchgear cabinet contain?

The high-voltage switchgear cabinet is a core device in the power system used for controlling, protecting, 

and monitoring high-voltage circuits. Its components can be classified into the following six categories 

according to their functions:

### I. Core Electrical Components

#### 1. Circuit Breaker (Core Component)

   - **Function**: It normally switches on and off the load current, and quickly breaks the short-circuit 

current in case of a fault.

   - **Types**:

     - **Vacuum Circuit Breaker** (commonly used in 10kV - 35kV systems): It uses vacuum for arc extinction, 

with a small volume and a long service life.

     - **SF₆ Circuit Breaker**: Suitable for higher voltage levels (such as 110kV), with strong arc-extinguishing

 capability.

#### 2. Isolating Switch

   - **Function**: It provides a clear electrical disconnection point and is used to isolate the power source

 during maintenance.

   - **Characteristics**: It **cannot be operated under load** and needs to be used in conjunction with a

 circuit breaker.

### II. Protection and Measurement Devices

#### 3. Instrument Transformer

   - **Current Transformer (CT)**: It converts large currents into 5A/1A for protection and metering purposes.

   - **Potential Transformer (PT)**: It converts high voltages into 100V for voltage monitoring (commonly

 found in PT cabinets or instrument rooms).

#### 4. Lightning Arrester (Overvoltage Protector)

   - **Function**: It suppresses lightning strikes or switching overvoltages and protects the insulation of 

equipment.

   - **Types**: Zinc oxide lightning arresters (MOA) are the mainstream, with a fast response speed.

#### 5. Fuse

   - **High-voltage Fuse**: It protects instrument transformers or small-capacity circuits (such as the RN2

 type used in PT cabinets).

   - **Low-voltage Fuse**: It protects the secondary circuit.

### III. Switch Operation and Control Equipment

#### 6. Operating Mechanism

   - **Function**: It drives the circuit breaker to open and close.

   - **Types**: Spring operating mechanism (common), electromagnetic operating mechanism, permanent 

magnet operating mechanism.

#### 7. Control Buttons and Indication Devices

   - Opening and closing buttons, status indicator lights (red/green), mechanical position indicators (such 

as "open" and "closed" marks).

### IV. Auxiliary Equipment and Safety Devices

#### 8. Grounding Switch

   - **Function**: It grounds the circuit during maintenance, releases residual charges, and prevents mis-energization.

   - **Configuration**: It is interlocked with the isolating switch and supports the "five-prevention" interlocking.

#### 9. Live Line Indicator

   - **Function**: It shows the live status of the busbar/line and is often used in conjunction with an electromagnetic

 lock to achieve the **"five-prevention"** (preventing entry into live compartments by mistake).

#### 10. Primary Resonance Suppressor

   - **Function**: It suppresses ferromagnetic resonance in an ungrounded neutral system (commonly found in 

10kV PT cabinets).

### V. Cabinet Structure and Busbar System

#### 11. Metal-Clad Cabinet

   - **Structure**:

     - **Draw-out Type**: Components such as the circuit breaker are installed on a movable trolley, supporting

 live maintenance.

     - **Fixed Type**: Components are fixedly installed, with a low cost, but maintenance requires a power outage.

   - **Zoning**: The primary compartment (busbar, circuit breaker), secondary compartment (instruments, 

protection devices), and cable compartment are designed separately to ensure safety.

#### 12. Busbar and Cable

   - **Busbar**: Copper or aluminum busbars are used to connect the power source to each circuit.

   - **Cable Interface**: It connects external cables and supports top or bottom cable entry.

### VI. Secondary Circuit and Intelligent Devices

#### 13. Relay Protection Device

   - **Function**: It monitors parameters such as current and voltage and triggers the circuit breaker to trip 

in case of a fault.

   - **Types**: Microcomputer protection devices (such as overcurrent protection, zero-sequence protection), 

traditional relays.

#### 14. Terminal Block and Instruments

   - Terminal block: It connects the wires of the secondary circuit.

   - Instruments: Ammeters, voltmeters, watt-hour meters, etc., which display operating data in real-time.

### Schematic Diagram of Components of a Typical High-voltage Switchgear Cabinet (Taking a 10kV Draw-out 

Cabinet as an Example)

┌───────────────┐

│     Busbar Compartment      │ （Upper part, connecting the power source busbar）

├───────────────┤

│   Circuit Breaker Trolley    │ （Middle part, can be withdrawn for maintenance）

│   （Including vacuum circuit breaker, CT）│

├───────────────┤

│     Cable Compartment      │ （Lower part, connecting the outgoing cables）

│   （Including grounding switch, lightning arrester）│

├───────────────┤

│     Secondary Compartment      │ （Front side, including protection devices, terminal block, instruments）

└───────────────┘

### Conclusion: Functional Integration of High-voltage Switchgear Cabinets

Through modular design, high-voltage switchgear cabinets integrate the functions of power distribution,

 protection, and monitoring. They are widely used in substations, switchgear rooms, and the industrial field 

and are key devices for ensuring the safe operation of the power system.