High-voltage switchgear generally includes high-voltage circuit breakers, disconnectors, load switches, fuses, and high-voltage switchgear.
High-voltage circuit breakers: During normal operation, high-voltage circuit breakers are mainly used to connect or disconnect load current. In the event of equipment failure or severe overload, high-voltage circuit breakers can automatically and quickly disconnect fault current (with the aid of relay protection devices) to prevent accidents. High-voltage circuit breakers mainly consist of conductive circuits, arc-extinguishing chambers, casings, insulating supports, operating and transmission mechanisms, etc.
High-voltage disconnectors: The main purpose of high-voltage disconnectors is to isolate high-voltage power supplies and create a clearly visible separation to ensure safe maintenance of other electrical equipment. However, because disconnectors lack arc-extinguishing mechanisms, they cannot connect or disconnect load current; they can only connect or disconnect smaller currents.
Disconnect switches can be categorized by installation location into indoor and outdoor types (no indoor type for voltages of 60 kV and above); by number of poles into single-pole and three-pole types; by construction into double-pole, three-pole, and V-type types; by insulation into ordinary and reinforced insulation types; and by grounding into types with and without grounding switches. Disconnect switches are generally open-type, but can be customized as enclosed disconnect switches under specific conditions.
High-Voltage Load Switches
Applications
In high-voltage power distribution systems, load switches are electrical devices specifically designed to connect and disconnect load currents; when equipped with a trip unit, they can automatically trip under overload conditions. However, they only have a simple arc-extinguishing device and therefore cannot interrupt short-circuit currents. In most cases, load switches are connected in series with high-voltage fuses (generally RN type) to interrupt short-circuit currents.
Types
High-voltage load switches are available in indoor and outdoor types and operate with a manual operating mechanism. They have a clear breaking gap and can also function as ordinary high-voltage disconnect switches.
High-Voltage Fuses
Applications: High-voltage fuses are commonly used protective electrical appliances. They have a simple structure and are widely used in power distribution equipment, commonly used to protect lines, transformers, and voltage transformers. A high-voltage fuse consists of three parts: a fusible element, contacts supporting a metal body, and a protective casing, connected in series in the circuit. If an overload or short-circuit fault occurs in the circuit, when the fault current exceeds the rated current of the fusible element, the fusible element will be rapidly heated and melted, thereby cutting off the current and preventing the fault from spreading.
Types: High-voltage fuses can be divided into indoor and outdoor types according to their application location. Indoor types are generally manufactured in a standard configuration, while outdoor types are all made as drop-out fuses (the fusible element tube automatically disconnects after the fuse wire melts).
High-Voltage Switchgear
Applications: 6–35 kV high-voltage switchgear is generally suitable for AC 50 Hz, 3–35 kV power systems, used for power reception, distribution, switching, and monitoring protection. It is a complete set of equipment supplied to users, assembled by the manufacturer according to a specific wiring method, including switchgear, busbars, measuring instruments, protective devices, and auxiliary equipment for the same circuit, all housed in a closed metal cabinet. This equipment is characterized by its compact structure and ease of use, and is therefore widely used in the control and protection of transformers, high-voltage lines, and high-voltage motors.
Types: High-voltage switchgear mainly includes two types: Fixed and truck-mounted. Based on structure, it can be divided into open, enclosed, and semi-enclosed types; based on the operating environment, it can be divided into indoor and outdoor types; based on the operating method, it can be divided into electromagnetic operating mechanisms, spring operating mechanisms, and manual operating mechanisms.