What are the types of SF6 circuit breaker interrupter chambers- SF6在线监测系统_SF6检漏仪_SF6传感器_SF6密度继电器

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What are the types of SF6 circuit breaker interrupter chambers

发布时间：2017-12-17 来源：ydlcb 浏览次数：44次

SF6 circuit breaker interrupter chamber structure according to the pressure of the interrupter medium is different, divided into double pressure type and single pressure type, but the double pressure type is generally not used because of the complex structure and auxiliary equipment. According to the direction of the blowing arc, it can be divided into double blowing, single blowing, external blowing and internal blowing. According to the direction of movement of the contact, it is divided into fixed quenching distance (also known as fixed opening distance) and variable quenching distance (also known as variable opening distance). In addition, on behalf of the development and research of self-energetic arc extinguishing chamber.

SF6 circuit breaker development history

one Simple breaking: that is to say, only through the continuous extension of the distance between the dynamic and static contacts to break, that is, there is no air blowing, and there is no magnetic field force to let the arc move in SF6 gas to cool the arc, this method is relatively simple, the effect is of course not ideal, and now it is no longer needed;

2. Double pressure arc blowing: That is, there are two kinds of pressure SF6 gas in the SF6 circuit breaker, the low-pressure SF6 gas is only used for internal insulation, generally 3-5 atmospheres, the high-pressure SF6 gas generally has more than a dozen atmospheres, only in the breaking process, the blow valve is opened, the high-pressure SF6 gas flows from the high-pressure area to the low-pressure area, the contact nozzle blows to the arc, so that the arc is quenchable; After the breaking process is over, the blow valve is closed and the air blow process is over. The SF6 circuit breaker has the advantages of strong arc extinguishing ability, large breaking capacity, metal short connection time, natural opening time and full opening time are shorter than the single pressure type; However, its structure is more complex, auxiliary equipment, between the low pressure area and the high pressure area of SF6 gas to have compressors and pipelines, in addition, the pressure of high pressure SF6 gas is relatively large, it is easy to liquify (such as under 16 atmospheres, the liquefaction temperature of SF6 gas is 5 ° C), so there is a need for heating devices.

SF6 circuit breaker structure

Porcelain pillar

The breaking element is placed on the insulating pillar to insulate the contacts at high potential, the conductive part and the interrupter chamber from the ground potential, and the insulating pillar is installed on the grounded base. It is called the housing live circuit breaker, also known as the insulated pillar type circuit breaker.

can-type

The breaking element is placed in the grounded box shell, during which the insulation depends on gas to bear, the conductive part is introduced through the sleeve, the structure is relatively stable, often used in high voltage and ultra-high voltage circuit breakers with high rated voltage, good seismic performance, known as the shell ground circuit breaker (also known as the floor tank). \

The arc extinguishing principle of SF6

(1) The decomposition temperature of SF6 gas (2000K) is lower than that of air (mainly nitrogen, decomposition temperature of about 7000K), and the decomposition energy required (22.4eV) is higher than that of air (9.7eV), so it absorbs more energy during decomposition and has a strong cooling effect on the arc column. Due to the decomposition of gas molecules, the thermal conductivity of gas peaks at the corresponding decomposition temperature.

(2) SF6 decomposed S atoms, F atoms and positive and negative ions at high temperatures, and had a larger freeness than other arc-extinguishing media. When the same freeness is maintained, the arc column temperature is lower. Therefore, the arc voltage in SF6 gas is also low, and the arc energy is small during arc burning, which is favorable for arc extinguishing.

(3) Due to the strong electronegativity of SF6, it can adsorb electrons and positive ions, so the composite effect is fast and the ionization effect is strong. Especially before and after the current crossing, the charged particles in the arc gap can be reduced, and the conductivity can be reduced. The time constant of SF6 gas arc is also very small, which is microsecond or smaller. After the arc current crosses zero, the temperature of arc column will drop sharply, and the decomposition will recompound sharply. Therefore, the dielectric strength and recovery speed of SF6 arc gap are very high, which can withstand the action of high recovery voltage, and the arc is not easy to reignite after the current crosses zero.

The extinguishing principle of the arc in SF6 gas is different from that in air arc and oil arc. It not only relies on the isentropic cooling effect formed by the pressure gradient of air flow, but mainly uses the specific thermochemical properties and strong electronegativity of SF6 gas to make SF6 gas have a strong arc extinguishing ability. It is an effective method to supply a large number of fresh SF6 neutral molecules and make them in contact with the arc.

SF6 circuit breaker operation and overhaul

Walking inspection in operation

1) Check the outer insulation part of the circuit breaker (porcelain sleeve) should be intact, no damage, dirt and flashover discharge phenomenon;

2) Compare the temperature-pressure curve, observe that the pressure gauge (or with an indicated density controller) indicates that it should be within the specified range, and record the pressure and temperature value regularly;

3) The opening and closing position indicator should indicate correctly, and the opening and closing should be in place;

4) The overall fasteners should not be loose or fall off;

5) There should be no abnormal sound inside the energy storage motor and circuit breaker;

6) The dividing and closing coils of the circuit breaker should be free of burnt smell, smoke and burn;

7) Circuit breaker grounding housing or support grounding should be good;

8) Circuit breaker housing or operating mechanism box should be complete, no corrosion;

9) The circuit breaker should have no damage, deformation, serious corrosion and other phenomena.

SF6 circuit breaker operation and maintenance

1) The rusty part of the shell shall be treated with anti-corrosion and repainted every year;

2) The circuit breaker rotation and transmission parts should be regularly lubricated (once a year), and the operation should be normal for 3 times;

3) Qualitative leak detection of all sealing surfaces of circuit breakers every two years, there should be no leakage points above 10-6atm.cm3/s;

4) The SF6 gas trace moisture test should be carried out once a year, and the test results should be compared with the water-temperature curve, which should not exceed 300ppm (20℃);

5) Other items, such as insulation, operating tests, etc. can be carried out regularly according to relevant regulations, and the test results should meet relevant standards;

6) Maintenance precautions:

(1) The circuit breaker is not allowed to operate in the vacuum state, so as not to damage the arc extinguishing chamber parts;

(2) When the mechanism is in normal maintenance, the energy of the parting and closing spring should be released.

SF6 circuit breaker application

1. Overhead lines and cables: When used to cut off and protect the distribution network based on overhead lines, vacuum circuit breakers and SF6 circuit breakers can meet the requirements.

2. Transformer: suitable for cutting off the excitation current of no-load transformer, and the overvoltage multiple is less than 3.0.

3. Capacitor bank: suitable for capacitor bank no reignition switch. When switching between groups, it may be necessary to install a reactor to shock current. The synchronous control technology of circuit breaker is an effective solution to this problem, SF6 circuit breaker is suitable for rated voltage above 27 kV occasions.

4. Electric arc furnace: Switching electric arc furnace is characterized by frequent operation, large current and short interval. Vacuum circuit breakers are especially suitable for such occasions.

5. Shunt reactor: SF6 circuit breaker is suitable for switching shunt reactors, usually its overvoltage multiple is less than 2.5.

6. Electrified railway traction.