Detailed Basics of High Voltage Switchgear
Apr 29, 2026| High-voltage switchgears are familiar to most electrical professionals. High-voltage switchgears are mainly applied to power grids with a voltage above 1 kilovolt.It guarantees stable circuit operation under normal working conditions, while enabling effective current regulation and circuit isolation.
Specifically, high-voltage switchgears serve power grids exceeding 1kV, with stringent requirements for reliability and safety. They are generally equipped with three-phase disconnectors, circuit breakers and other components to control and protect high-voltage circuits.This article will elaborate on the core knowledge of high-voltage switchgears in detail.
Functions of High-Voltage Switchgear
High-voltage switchgear is a generic term for metal-enclosed switching equipment. It denotes a fully integrated power distribution assembly, where various electrical components are arranged and installed within a sealed metal housing in strict accordance with predefined circuit layouts.
Widely used in power distribution systems, high-voltage switchgear serves to receive and distribute electric energy. On one hand, it can put part of power equipment or lines into or out of operation according to the grid operation requirements; on the other hand, when a fault occurs in power equipment or lines, it can quickly isolate the faulty section from the power grid. This ensures the normal operation of the fault-free part of the grid, as well as the safety of equipment and operation and maintenance personnel. Therefore, high-voltage switchgear is a critical piece of power distribution equipment, and its safe and reliable operation is of great significance to the entire power system.
Widely deployed throughout power distribution networks, high-voltage switchgear is primarily responsible for power reception and distribution. It allows operators to energize or de-energize specific power equipment and transmission lines in response to grid operational needs. In the event of electrical faults on equipment or lines, it can rapidly isolate the faulty sections from the main grid.
This ensures stable operation of unaffected grid sections, while protecting power facilities and safeguarding the safety of operation and maintenance personnel.As a core piece of power distribution infrastructure, high-voltage switchgear plays an indispensable role, and its stable, reliable performance is fundamental to the secure operation of the entire power system.
Classification of High-Voltage Switchgear
High-voltage switchgear can be classified into various types based on different criteria.
By Structural Type：
Armored Type: Each functional compartment inside the cabinet is separated by grounded metal plates, featuring extremely high protection grade and safety performance.
Compartmental Type: Compartments are isolated by one or more non-metallic partition boards.
Box Type: Equipped with an integral closed metal enclosure, but has fewer independent internal compartments compared with armored and compartmental types.
By Circuit breaker Installation Mode：
Floor-standing Type:The entire breaker trolley rests directly on the floor, and can be smoothly pushed into the cabinet body as a whole, enabling intuitive and convenient maintenance and operation.
Middle-mounted Type:The circuit breaker trolley is securely installed in the middle compartment of the switchgear. Dedicated trolleys are required for the loading, unloading and transportation of the breaker unit. This design is currently the mainstream solution for indoor high-voltage switchgear applications.
By Insulation Type:
Air-insulated Metal-enclosed Switchgear: Uses atmospheric air as the main internal insulating medium. It boasts mature technology, easy maintenance and the widest range of application scenarios.
SF₆ Gas-insulated Metal-enclosed Switchgear (Gas Insulated Cabinet): Adopts sulfur hexafluoride (SF₆) gas as both insulating and arc-extinguishing medium. It features compact cabinet size, low environmental susceptibility and superior reliability, and is mainly applied in special scenarios such as limited installation space, high humidity environments or occasions requiring ultra-high operational reliability.
Structure Composition of KYN High-Voltage Switchgear
This switchgear is composed of two major parts: a stationary cabinet body and a withdrawable unit, commonly known as the breaker trolley.
(1) Cabinet Body
The enclosure and partitions of the switchgear are made of aluminum-zinc coated steel plates. The whole cabinet features high manufacturing precision, excellent corrosion and oxidation resistance, high mechanical strength and aesthetic appearance. The switchgear adopts an assembled configuration fastened by rivet nuts and high-strength bolts, enabling outstanding overall dimensional uniformity.
The internal space of the switchgear is divided by partitions into four independent compartments: breaker trolley compartment, busbar compartment, cable compartment and relay instrument compartment, with each unit reliably grounded.
A - Busbar Compartment
The busbar compartment is arranged at the upper rear of the switchgear, designed to accommodate three-phase high voltage AC busbars, which connect to fixed contacts through branch busbars. All busbars are fully enclosed and sleeved with insulating sheaths. Busbar bushings are adopted to fasten busbars at positions where they penetrate cabinet partitions. In case of an internal arc fault, this structural design effectively restricts fault propagation to adjacent cabinets and preserves the structural integrity of the busbars.
B - Breaker Trolley (Circuit Breaker) Compartment
Special guide rails are fitted inside the breaker compartment to support the sliding movement and operation of the circuit breaker trolley. The trolley can travel freely between the working position and the test position.
A partition shutter for fixed contacts is installed on the rear wall of the trolley compartment. The shutter opens automatically as the trolley moves from the test position to the working position. When the trolley retracts to the test position, the shutter fully closes and resets. This interlock mechanism effectively avoids accidental contact with live components, thereby protecting operating personnel and ensuring operational safety.
C - Cable Compartment
The cable compartment accommodates auxiliary devices including current transformers, earthing switches, surge arresters (overvoltage protection devices) and power cables.A slotted, detachable aluminum plate is fitted at the compartment bottom, significantly simplifying on-site installation and wiring operations.
D - Relay and Instrument Compartment
The front panel of the relay compartment is fitted with microcomputer protection devices, operating handles, measuring meters, and status indicator lamps (or status displays). The compartment interior accommodates terminal blocks, DC switches and working DC power supplies for microcomputer protection control circuits, as well as power switches for DC/AC energy storage motors. It also reserves space for secondary equipment configured to meet special customized requirements.
Live Indication Device
This device comprises two core units: a high voltage sensor and a live display indicator. It is capable of indicating the live state of high voltage circuits and achieving forced interlocking in coordination with the electromagnetic lock. This mechanism prevents the earthing switch from closing when the circuit is energized and avoids accidental access of personnel to live compartments, effectively enhancing the anti misoperation capability of the entire switchgear assembly.
Anti-Condensation and Anti-Corrosion Measures
To eliminate potential safety hazards arising from condensation in high-humidity and drastically fluctuating climatic conditions, independent heaters are installed in both the breaker and cable compartments. This ensures reliable and safe equipment operation under harsh ambient conditions and effectively prevents cabinet corrosion.