Primary equipment of distribution network - switches and ring main units

Typical switchgear
The following introduces several circuit breakers, load switches and disconnectors from three well-known companies and their performance.
1. ABB Company
(1) Sectos NXA load disconnector (ANSI/IEC)
Sectos NXA load disconnector (ANSI/IEC) is shown in the figure below. It has a rated voltage of 24kV or 36kV and a rated current of 630A. It is an SF6 gas-insulated load disconnector for overhead lines with a maximum voltage of 36kV. The switch box body is sealed with stainless steel to ensure that the internal components are not affected by the external environment. SF6 has excellent load breaking capacity, high insulation capacity and excellent arc extinguishing characteristics. This means that the safety of operators and the public is improved and the power supply reliability is greatly improved. Sectos NXA has different installation forms. All manual operating mechanisms can be easily upgraded to electric operation by adding motors, and then upgraded from electric operation to remote control without incurring high costs. All electrical components are installed in a stainless steel corrosion-resistant casing.

(2) Outdoor SF6 circuit breaker
The OHB series is an outdoor SF6 circuit breaker with a rated working voltage of 24~40.5kV, a rated working current of 1250~3150A (40℃), and a rated short-time withstand current of 25~31.5kA (3s), as shown in the figure below. The OHB series is mainly used for the control and protection of distribution lines, substations, transformers, rectifiers, and capacitor banks. The OHB series does not generate operating overvoltages and is also very suitable for the renewal of old stations, especially in places that are sensitive to insulation.

2. GE Company
The PowerVac VB2 vacuum circuit breaker of General Electric (GE) is shown in the figure below.
The PowerVac VB2 12kV series indoor high-voltage vacuum circuit breaker (VB2 for short) is a composite-insulated indoor switch element. It is the best choice for control and protection in the high-voltage power supply and distribution series, especially for places that require frequent operation. The installation of the VB2 circuit breaker in the switch cabinet can be removable or fixed. It adopts high-end three-dimensional computer-aided settings (pro-engineer) and dynamic simulation optimization design (pro-mechanical); adopts the design principle of electromagnetic field optimization distribution to minimize local discharge and local overheating; adopts the world's most advanced miniaturized and high-function vacuum interrupter, and uses the longitudinal rotating magnetic field arc extinguishing principle to effectively ensure that the cut-off value is less than 3A, making the breaking performance extremely stable; has extremely superior and extremely reliable insulation performance, successfully passed the condensation test, suitable for operation under the worst environmental conditions, and has higher creepage distance and electrical clearance than the standard requirements; has a reliable grounding method (grounding knife) to ensure the continuity of the circuit breaker from the working position to the test position; passed the 1.1 times rated current temperature rise test.

3. Siemens
Siemens' 8BK40 vacuum circuit breaker cabinet is shown in the figure below.
8BK40 switch cabinet is a metal armored air-insulated switchgear equipped with a removable vacuum circuit breaker. The circuit breaker trolley is reliably interlocked with the interrupter and switch room. The circuit breaker trolley can be moved horizontally from the connection position behind the closed front door by hand without any auxiliary equipment. The completely isolated low-voltage room is an integrated system in which all common branch lines and auxiliary components can be installed.