Components of the PT Cabinet

   The PT cabinet, also known as the potential transformer cabinet, is a key device in the power system used 

for monitoring the bus voltage and providing voltage signals for protection and metering devices. Its components

 mainly include the following categories:

### I. Core Electrical Components

1. **Potential Transformer (PT)**

    - **Function**: It converts the high voltage of the power grid into a standard secondary voltage of 100V or

 lower at a certain ratio, thus providing voltage signals for measuring, protecting, and metering devices.

    - **Types**: It can be divided into single-phase and three-phase types, and may have multiple secondary 

windings (such as measuring windings, metering windings, and auxiliary windings). The auxiliary winding is 

mainly used for insulation monitoring (open delta connection).

2. **Fuse**

    - **Function**: When the potential transformer experiences overload or short-circuit faults, the fuse will 

blow to protect the potential transformer and the primary circuit.

    - **Configuration**: High-voltage fuses are generally installed on the high-voltage side (for example, the 

RN2 type is commonly used in the 10kV system), and miniature circuit breakers may be configured on the

 low-voltage side.

3. **Lightning Arrester (Overvoltage Protector)**

    - **Function**: It protects the bus and the potential transformer from damage caused by lightning strikes 

or switching overvoltages.

    - **Types**: Commonly seen are zinc oxide lightning arresters (MOA), which can quickly release overvoltage 

energy and maintain the stability of the system voltage.

### II. Switch and Isolation Equipment

4. **Isolating Switch (or Isolating Knife)**

    - **Function**: When the equipment is under maintenance, it provides a clear disconnection point to ensure

 the safety of personnel and can also achieve live operation (such as the draw-out type structure).

    - **Configuration**: Draw-out type isolation structures are usually adopted for draw-out cabinets, while GN

 series isolating switches are used for fixed cabinets.

5. **Grounding Switch**

    - **Function**: It grounds the primary circuit during maintenance to prevent mis-energization and ensure 

the safety of personnel.

### III. Auxiliary Equipment

6. **Primary Resonant Suppressor**

    - **Function**: It suppresses the ferromagnetic resonance overvoltage caused by electromagnetic potential

 transformers in the ungrounded neutral system.

    - **Configuration**: The neutral point is grounded through a primary resonant suppressor (commonly seen

 in the 10kV system).

7. **Live Line Indicator**

    - **Function**: It shows whether the bus is live and is used for safety warning. It is usually used in conjunction

 with an electromagnetic lock to achieve the five-prevention function.

### IV. Cabinet Structure

8. **Withdrawable Metal-Clad Structure**

    - Adopting a draw-out type design, each potential transformer is equipped with an independent trolley, 

enabling live withdrawal for maintenance.

    - The primary chamber and the secondary chamber are separated from each other to ensure the safety of

 operation.

9. **Observation Window**

    - A large-area observation window is provided on the panel, which is convenient for real-time monitoring of 

the operating status of the equipment in the cabinet (such as the heating condition of the potential transformer, 

whether the fuse is blown, etc.).

### V. Secondary Circuit Components

10. **Low-Voltage Relay and Protection Device**

    - It is used to monitor abnormal voltages (such as overvoltage and undervoltage) and trigger alarms or 

protection actions.

11. **Terminal Block and Terminal Connector**

    - It realizes the wiring of the secondary circuit and transmits the voltage signal to the instrument, relay 

protection device, or metering device.

### Conclusion

The core components of the PT cabinet are **potential transformers, fuses, lightning arresters, and isolating 

switches**, and the auxiliary equipment includes resonant suppressors, live line indicators, etc. The cabinet body 

adopts a modular structure, supporting flexible configuration and maintenance. Different application scenarios

 (such as draw-out cabinets or fixed cabinets, neutral grounding methods) may lead to differences in specific 

components, but the basic functions are the same, that is, to provide reliable voltage signals and overvoltage

 protection.