SN10-10/630A Indoor Oil-minus Circuit Breaker

The SN10 low-oil circuit breaker is an indoor high-voltage low-oil circuit breaker that has been widely used in China since the 1960s. It is mainly used in AC 50Hz power systems with rated voltages from 10kV to 35kV as control and protection equipment. Its structure and functions are as follows:

I. Main functions

Circuit breaking and closing: Safely connect or disconnect high-voltage circuits under normal or fault conditions such as short circuits.

Arc extinguishing function: Use a small amount of insulating oil as an arc extinguishing medium to quickly extinguish arcs and prevent equipment damage.

Used with supporting switchgear: It is often used with JYN1, GBC and other withdrawable high-voltage switchgear to realize the protection and control of high-voltage systems such as industrial and mining enterprises and substations.

Note: With technological progress, the SN10 series has gradually been replaced by vacuum circuit breakers, and its market application is declining day by day.

II. Typical structural composition taking SN10-10/35 as an example

The SN10 low-oil circuit breaker is mainly composed of the following three parts:

Frame (support and transmission part)

Welded from angle steel and steel plate, it provides mechanical support.

It is equipped with a opening spring, opening buffer, closing buffer, main shaft, bearing and insulator.

The transmission system connects the main shaft and the rotating shaft in the fuel tank through an insulating pull rod to realize opening and closing operations.

Fuel tank (core arc extinguishing unit)

Fixed on the supporting insulator, it is filled with a small amount of insulating oil, which is only used for arc extinguishing and insulation between contacts, not for ground insulation.

Base made of ductile iron: It includes rotating shaft, connecting rod, conductive rod, copper-tungsten alloy moving contact, oil buffer and oil drain bolt.

Insulating cylinder: It contains an arc extinguishing chamber, which adopts the combined action of cross-blowing + longitudinal blowing + mechanical oil blowing to improve arc extinguishing efficiency.

Upper outlet and upper cap: It includes static contact seat inlaid with copper-tungsten arc contact fingers, oil level gauge and oil-gas separator, which can recover oil droplets and reduce leakage.

Conductive circuit path

Upper outlet → static contact seat → moving contact rod (conductive rod) → rolling contact → lower outlet.

III. Key characteristics and precautions

Advanced arc extinguishing method: The cross and longitudinal blowing combined arc extinguishing structure can extinguish large, medium and small current arcs in a short time.

The oil buffer is very important: it absorbs kinetic energy at the final stage of opening. Without oil, the buffer will fail, which may cause the contact to hit the base and damage the mechanical parts.

Applicable voltage levels: Common models include SN10-10 (10kV), SN10-35 (35kV), SN10-40.5 (40.5kV) and others.

Operating mechanism: It can be equipped with CD10 electromagnetic mechanism, CT7 spring mechanism, and early CS2 manual mechanism which has been eliminated now.