High-Voltage Switchgear, also known as switchgear assemblies or distribution equipment, is a critical component in power systems. It serves as a device for receiving and distributing electrical energy, assembled according to specific circuit designs. This article aims to provide a comprehensive overview of high-voltage switchgear, covering its basic concepts, classifications, functions, operational procedures, and safety features.
Basic Concepts
High-voltage switchgear encloses high and low-voltage electrical appliances, including control, protection, and measurement devices, along with busbars, current-carrying conductors, and insulators, within a metal enclosure. These components are assembled based on the primary electrical wiring diagram, forming a key unit for electrical energy distribution in power systems. It is primarily used in transmission, transformation, and distribution systems for energy allocation, measurement, protection, control, and adjustment.
Classifications
High-voltage switchgear can be categorized in various ways:
- By Cabinet Structure: It can be divided into open and enclosed types. Open-type switchgear has exposed high-voltage busbars and unseparated components, making it simpler and less costly. Enclosed switchgear, on the other hand, separates circuit breakers, busbars, cable heads, and measurement instruments for enhanced safety, suitable for harsh working conditions.
- By Installation Method: Fixed and movable (handcart) types exist. Fixed switchgear has all electrical equipment fixed within the cabinet, while movable switchgear allows the circuit breaker and its operating mechanism to be mounted on a cart that can be moved in and out for easier maintenance and component replacement.
- By Number of Busbars: Single-bus and double-bus configurations are common, with single-bus systems typically used in distribution installations below 35KV.
Functions
Switchgear is equipped with primary and secondary schemes, ensuring electrical energy collection, distribution, measurement, and protection. Each switchgear has a main circuit and auxiliary circuit to maintain stable power system operation. Safety features, such as operational procedures and mechanical or electrical interlocks, are essential, with the “Five Protections” being key to preventing electrical accidents.
Operational Procedures
Operating high-voltage switchgear involves a series of steps. Initially, the rear cover is installed and sealed, followed by closing the front lower door. The grounding switch spindle is then operated to open. Using a transfer cart, the handcart (in the open position) is pushed into the cabinet to the test position. Ensure the secondary plug is correctly inserted into the static socket. The test position indicator should light up, and the front middle door is closed. The handle is then used to push the handcart from the test position to the working position. Once in place, the working position indicator lights up, and the test position indicator turns off. Finally, the circuit breaker handcart is closed to complete the operation. For power outages or maintenance, the reverse steps are followed.
Safety and Maintenance
Safety is paramount when dealing with high-voltage switchgear. Operators must wear insulating footwear and gloves, ensuring swift and decisive actions. After operations, it is crucial to check if the mechanism is correctly engaged. Regular maintenance includes observing the condition of switchgear components for overheating, discoloration, abnormal sounds, or poor contacts. Insulators should be clean and free from damage. All metal parts should be protected against rust, moving parts lubricated, and screws checked for looseness. The switchgear room should be protected against moisture, dust, and small animal intrusion.
For vacuum circuit breakers, periodic checks for vacuum levels and the condition of the arc extinguishing chamber are necessary. When replacing arc extinguishing chambers, ensure the conductive rod is securely clamped to prevent the bellows from bearing torsional moments. For isolating switches, attention should be given to the alignment of contacts and the closing position, with an adequate opening distance when in the open position.
Conclusion
High-voltage switchgear is a fundamental component in power systems, ensuring the safe and efficient distribution of electrical energy. Understanding its classifications, operational procedures, and safety measures is crucial for maintaining power system stability and operator safety. Regular maintenance and adherence to operational guidelines are essential to prevent accidents and ensure continuous power supply.
