metal enclosed switchgear

Metal enclosed switchgear is a kind of power distribution device that integrates electrical equipment such as circuit breakers, disconnectors, instrument transformers, and busbars within a metal enclosure. It is mainly used in medium and high voltage power systems (usually 3kV to 35kV) and has the characteristics of safety, compactness, and reliability. The following is the collation of its core information:

 I. Main Characteristics

1. **Fully Enclosed Design**

   - The metal enclosure provides a protection level of IP20 to IP54, preventing electric shock, dust, and liquid intrusion, and is suitable for complex indoor and outdoor environments.

   - It complies with safety standards (such as IEC 62271-200 and ANSI C37.20.2).

2. **Modular Structure**

   - Adopting an interval design, functional units such as circuit breakers, busbars, and cable compartments are independently separated, making it easy for maintenance and expansion.

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   - Common types:

     - **Armored Type (K-type)**: The main circuit and the control circuit are completely isolated by metal.

     - **Compartment Type (C-type)**: Some functional units are isolated, with a relatively low cost.

     - **Box Type (MCCB-type)**: Integrates molded case circuit breakers and is used for low-voltage power distribution.

3. **Intelligent Control**

   - It supports electric operation and remote monitoring (such as through the SCADA system), and some models have built-in relay protection devices.

 II. Core Functions and Components

1. **Core Components**

   - **Circuit Breaker**: Interrupts fault current (such as vacuum circuit breakers, SF6 circuit breakers).

   - **Disconnector**: Provides a clear disconnection point for maintenance safety.

   - **Current/Voltage Transformer**: Monitors current and voltage signals.

   - **Busbar System**: Copper or aluminum busbars carry the main current.

2. **Functional Types**

   - **Incoming Line Cabinet**: Connects to the power supply side and is equipped with arresters and main circuit breakers.

   - **Feeder Cabinet**: Distributes power to loads and is equipped with protection devices.

   - **Bus Coupler Cabinet**: Connects two sections of busbars to achieve dual-power supply switching.

   - **PT Cabinet**: Installs voltage transformers to provide measurement and protection voltages.

 III. Application Scenarios

- **Substations**: Core equipment of 10kV/35kV power distribution systems.

- **Industrial Factories**: Motor control and power supply for large equipment.

- **High-rise Buildings**: Power distribution centers and emergency power supply systems.

- **Rail Transit**: Traction power supply systems of subways and airports.

 IV. Key Points for Model Selection

1. **Voltage Level**

   - Commonly used: 10kV, 20kV, 35kV (selected according to system requirements).

2. **Rated Current and Breaking Capacity**

   - **Rated Current**: Calculated according to the load, such as 1250A, 2500A, 4000A.

   - **Breaking Capacity**: Needs to match the system short-circuit current (such as 25kA, 31.5kA, 40kA).

3. **Operation Mode**

   - Manual operation (for simple scenarios) or electric operation (required for remote control).

4. **Protection Level**

   - IP20: Protects against finger touch; IP54: Protects against water spray (suitable for outdoor use).

5. **Environmental Conditions**

   - Altitude (affecting insulation design), temperature range (-25°C to +40°C), humidity.

 V. Installation and Maintenance

1. **Installation Requirements**

   - The error of the foundation levelness is ≤ 2mm/m, and the grounding resistance is ≤ 4Ω.

   - The cable connection needs to meet the requirements of current-carrying capacity and bending radius.

2. **Daily Maintenance**

   - **Cleaning**: Blow off the internal dust with dry compressed air every year.

   - **Mechanical Inspection**: The flexibility of the operating mechanism and the wear condition of the contacts (the contact wear amount ≤ 3mm).

   - **Insulation Test**: Use a 2500V megohmmeter, and the insulation resistance ≥ 100MΩ (between phases and to the ground).

3. **Fault Handling**

   - **Circuit Breaker Refusal to Open/Close**: Check the voltage of the control circuit and the jamming of the operating mechanism.

   - **Abnormal Temperature Rise**: Use an infrared thermometer to detect the contacts or the connection points of the busbars. If the temperature difference > 15°C, maintenance is required.

   - **Unusual Noise or Odor**: It may be due to insulation aging or partial discharge, and a power outage inspection should be carried out immediately.

 VI. Safety Precautions

1. **Five-prevention Functions**

   - Prevent misoperation of opening/closing the circuit breaker, misoperation of the disconnector, and entering the live compartment by mistake, etc.

2. **Grounding Protection**

   - The enclosure is reliably connected to the grounding system, and the cross-sectional area of the grounding wire ≥ 50mm².

3. **Maintenance Process**

   - Power outage → Voltage testing → Hanging of grounding wires → Hanging of warning signs, strictly following the electrical safety regulations.

 Summary

Metal enclosed switchgear is a key component of modern power distribution systems. When selecting a model, factors such as voltage level, breaking capacity, and environmental conditions need to be comprehensively considered. Regular maintenance should be carried out during operation to ensure reliability. Common brands include ABB (UniGear ZS1), Schneider (RM6), Siemens (8DJH), etc., and specific models need to be customized according to project requirements.