What are the characteristics of the 35kV high-voltage switchgear?

The following is a detailed analysis of the characteristics, application scope, and key parameters of the 35kV

 high-voltage switchgear:

 I. Definition of 35kV High-voltage Switchgear

The **35kV high-voltage switchgear** is an indoor power distribution device used in the **35kV power system**, 

mainly for controlling, protecting, and monitoring high-voltage circuits. It has functions such as **electric energy 

distribution, fault protection, and electrical isolation**. Its design complies with the national standards **GB 3906*

* (AC metal-enclosed switchgear) and **DL/T 404** (Indoor AC high-voltage switchgear).

 II. Core Characteristics

 1. Structural Design

- **Types**:

  - **Armored type (KYN type)**: It has a metal armored layered structure, with the circuit breaker, busbar, and

 cable chamber isolated from each other, and a high protection level (IP4X/IP54).

  - **Compartment type (JYN type)**: It has a modular compartment design, which is convenient for maintenance

 and has a lower cost.

  - **Box type (XGN type)**: It has a compact box structure, occupying a small space and is suitable for small 

substations.

- **Handcart Function**: It supports the three-position switching of the circuit breaker handcart ("working/

testing/maintenance") to achieve live maintenance.

2. Insulation Performance

- **Main Insulation Materials**:

  - Air insulation (clearance ≥ 300mm) + Epoxy resin bushing

  - Optional **composite insulation** (vacuum circuit breaker + solid insulation encapsulation), with strong

 pollution resistance.

- **Rated Voltage**: 35kV, with a maximum operating voltage of **40.5kV**.

 3. Protection and Control Functions

- **Standard Protection Devices**:

  - Overcurrent protection, zero-sequence protection, overvoltage/undervoltage protection, differential protection

  - Equipped with a **microcomputer integrated protection device (relay protection instrument)**, supporting

 remote monitoring and fault diagnosis.

- **Operation Mode**: Electric/manual opening and closing, supporting **intelligent control** 

(can be connected to the SCADA system).

 4. Short-circuit Breaking Capacity

- **Rated Short-circuit Breaking Current**: 25kA, 31.5kA, 40kA (depending on the model)

- **Dynamic and Thermal Stability Performance**: It meets the instantaneous withstand requirements of 

short-circuit faults in the power system.

 5. Reliability and Safety

- **Five-prevention Functions**:

  - Prevent misoperation of opening/closing the circuit breaker, prevent opening/closing the isolating switch

 with load, prevent hanging the grounding wire when live, prevent closing the switch with the grounding wire, 

and prevent entering the live compartment by mistake.

- **Materials**: The cabinet body is made of **cold-rolled steel plate with a thickness of more than 2mm**, 

and the surface is sprayed with plastic for anti-corrosion treatment, with a service life of ≥ 30 years.

III. Application Scope

1. Power System Scenarios

- **Substations**:

  - Inlet, outlet, and main transformer power distribution circuits of 35kV substations.

  - As a **medium-voltage power distribution hub**, it connects the 110kV/35kV main transformer with the 

10kV power distribution system.

- **Urban Power Grid**:

  - Control of the high-voltage side of regional power distribution centers and cable branching boxes.

2. Industrial and Commercial Fields

- **Large Industrial Enterprises**:

  - Direct starting and protection of high-voltage motors (such as 35kV motors) in steel, chemical, mining, etc.

  - The internal high-voltage power distribution system of the factory (such as the 35kV busbar to the workshop

 transformer).

- **Data Centers/Hospitals**:

  - Switching control between the backup power supply (diesel generator) and the utility power to ensure the 

continuity of power supply.

3. New Energy Projects

- **Photovoltaic/Wind Power Step-up Stations**:

  - Collect 35kV collector lines and connect to the main transformer to step up the voltage to 110kV/220kV

 for grid connection.

- **Energy Storage Systems**:

  - Connection and protection of 35kV energy storage converters (PCS).

4. Special Environments

- **Wet/Polluted Areas**:

  - Optional moisture-proof heaters and anti-pollution insulators are available, suitable for scenarios such as 

coastal areas and chemical industrial parks.

- **High-altitude Areas**:

  - Customized enhanced insulation switchgear (altitude ≤ 4000m).

V. Precautions for Selection

1. **Load Matching**:

   - Select the rated current according to the loop current (for example, for a 35kV motor, a current above 2500A

 should be selected).

   - The short-circuit current needs to be coordinated with the protection of the superior substation.

2. **Environmental Conditions**:

   - Altitude, temperature, humidity, pollution grade (for example, for pollution grade II, the creepage distance

 ratio should be ≥ 31mm/kV).

3. **Intelligent Requirements**:

   - Whether it is necessary to configure an **intelligent operation and control device** and condition monitoring 

sensors (partial discharge, temperature).

4. **Standard Compliance**:

   - It needs to pass the **type test** (including temperature rise test, insulation test, short-circuit test).

Conclusion

The 35kV high-voltage switchgear is a **core device in the medium-high voltage power distribution system**, 

combining reliability and economy, and is suitable for scenarios such as substations, industrial enterprises, and

 new energy projects. When selecting, key attention should be paid to the **short-circuit breaking capacity, 

environmental adaptability**, and **intelligent configuration** to meet the long-term safe operation requirements.