Installation Methods of Circuit Breakers in High-Voltage Switchgear

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1. **Fixed Installation**
- **Features**:
- The circuit breaker is fixedly installed at a specific position in the switchgear, and this installation method has a simple structure. The connection mode between the circuit breaker and the busbars, cables, etc. in the switchgear is relatively fixed, and the position basically remains unchanged after installation.
- For example, in some small substations or places where operational flexibility is not highly required, 10kV fixed high-voltage switchgear is widely used. Its circuit breaker is connected to the busbars and outgoing lines through copper bars or cables. During the installation process, the circuit breaker is firmly fixed within the framework of the switchgear, and generally, the base of the circuit breaker is fixed to the mounting bracket of the switchgear by bolt connection.
- **Advantages**:
- Low cost. Because its structure is relatively simple, without complex moving and connecting mechanisms, the manufacturing cost and installation cost of the equipment are relatively low.
- High stability. As the position of the circuit breaker is fixed, its connection with other electrical components is relatively stable, and during normal operation, it is less affected by external factors (such as vibration, etc.), which can ensure the reliability of electrical connections.
- **Disadvantages**:
- Inconvenient for maintenance and repair. When the circuit breaker needs maintenance or replacement, due to its fixed installation, some surrounding connecting parts and protective devices may need to be disassembled, and the limited operating space will increase the difficulty and time of maintenance.
- Poor flexibility. It is not possible to flexibly adjust the position of the circuit breaker or perform replacement operations according to operational requirements. For example, during system expansion or modification, certain limitations may be encountered.

2. **Removable (Trolley-Type) Installation**
- **Features**:
- The circuit breaker is installed on a movable trolley, and the trolley can move on the tracks inside the switchgear. When the circuit breaker needs maintenance or replacement, the trolley can be moved from the working position (connected position) to the test position or maintenance position. At the test position, electrical tests can be performed on the circuit breaker; at the maintenance position, the circuit breaker can be conveniently maintained and repaired.
- For example, in most modern substations of 35kV and below, removable high-voltage switchgear is widely used. The circuit breaker on the trolley is connected to the busbars and outgoing lines in the switchgear through plum blossom contacts. When the trolley moves on the track, the plum blossom contacts can achieve reliable connection or disconnection with the busbars and outgoing lines.
- **Advantages**:
- Convenient for maintenance. The trolley can be easily moved out of the switchgear, and there is sufficient space outside the switchgear to conduct comprehensive maintenance, repair, and testing on the circuit breaker, which greatly improves maintenance efficiency and reduces power outage time.
- High interchangeability. In the same type of switchgear, different trolleys (with circuit breakers of the same specifications) can be replaced with each other. When a circuit breaker fails, a spare trolley can be quickly replaced to restore power supply, improving the reliability and flexibility of the system.
- **Disadvantages**:
- High cost. Due to the complex structure of removable switchgear, including trolleys, tracks, interlocking devices, etc., its manufacturing cost and installation cost are higher than those of fixed switchgear.
- High operational requirements. When moving the trolley, it must be operated strictly in accordance with the operating procedures; otherwise, it may damage the equipment or cause safety accidents. For example, if the trolley is not aligned with the track during movement or if the interlocking device fails, it may cause damage to contacts or short circuits, etc.