Product name:oil circuit breaker
A type of switchgear that uses sealed insulating oil as the arc-extinguishing medium for breaking faults. There are two forms of oil-breaker and oil-breaker. It was earlier used in power systems. The technology is very mature and the price is relatively cheap. A high-voltage switchgear that is widely used in power grids of all voltage levels. Oil circuit breakers are used to cut off and connect power and quickly and reliably cut off current in the event of a short circuit.
Oil-rich and oil-saving circuit breakers must be filled with oil, and their functions are arc extinguishing, heat dissipation and insulation. Its danger is not only that it may cause an explosion when a fault occurs, but also due to the high-temperature oil splashing in the oil circuit breaker after the explosion, which causes a large area of combustion, causing a phase-to-phase short circuit or a short to ground, and disrupting the normal operation of the power system. Enlarge the accident and even cause serious personal injury or death.
Arc extinguishing process: When the moving contact and the static contact of the circuit breaker are separated from each other, an arc is generated. The high temperature of the arc causes the insulating oil nearby to evaporate and gasify and thermally decompose, forming a gas with strong arc extinguishing ability (mainly hydrogen ) And high pressure bubbles, so that the arc quickly extinguished.
Therefore, the circuit breaker should be strictly checked before installation to ensure that it meets the technical requirements of the manufacturer. The interrupting capacity of the circuit breaker must be greater than the short-circuit capacity of the circuit where the circuit breaker is installed. During maintenance, an operation test should be carried out to ensure that the parts are flexible and reliable, and the synchronization of the three-phase action is adjusted. The connection between the circuit breaker and the electrical circuit should be tight, and the temperature can be observed with a temperature test wax, and the damaged contacts should be replaced. An insulation test should be performed after the maintenance, and a special person is responsible for inventorying the tools to prevent the tools from falling into the fuel tank and causing accidents. Before putting into operation, you should also check the sealing performance of the insulation sleeve and the fuel tank cap to prevent the water in the fuel tank from getting wet and causing the circuit breaker to explode and burn. After the circuit breaker cuts off the severe short-circuit fault, it is necessary to check the damage of the contacts and the oil quality.
The oil level should be checked frequently during operation, and the oil level must be strictly controlled within the range of the oil level indicator. When abnormality is found, such as oil leakage, oil leakage, abnormal sound, etc., measures should be taken, and if necessary, the load should be immediately reduced or the power failure should be repaired. When the fault trip and compound brake are not good, and the current changes greatly, when the circuit breaker has a gas odor, the operation must be stopped. Forced power transmission is strictly prohibited to avoid an explosion.
When the oil circuit breaker opens the circuit, as long as the current in the circuit exceeds 0.1A and the voltage exceeds tens of volts, an arc will occur between the moving and static contacts of the circuit breaker, and the current can continue to flow through the arc The circuit will only open when the arc is extinguished when there is a sufficient distance between the contacts. The arc power when a 10kV oil-free circuit breaker opens at 20KA can reach more than 10,000 kilowatts, and the temperature of the arc column between the contacts of the circuit breaker can reach six or seven thousand degrees, or even more than ten thousand degrees.
Oil circuit breakers can be divided into grounded-box multi-oil circuit breakers (referred to as multi-oil circuit breakers) and live box-shell low-oil circuit breakers (referred to as low-oil circuit breakers) according to the different insulation medium to ground.
Multi-oil circuit breaker
The arc extinguishing chamber is installed in a grounded metal box, which usually uses a large amount of oil, and the oil is used as both the arc extinguishing medium and the ground insulation. The multi-oil circuit breaker has a simple structure and reliable performance, can be made into an ultra-high voltage level, and can be conveniently equipped with a current transformer, which has strong matching properties and is less affected by atmospheric conditions when used outdoors. Multi-oil circuit breakers have a long history of use, mature use and manufacturing technology, and have played an important role in power systems. However, the multi-oil circuit breaker also has many shortcomings, especially in the ultra-high voltage level, which is bulky, consumes a large amount of steel and transformer oil, has great difficulties in transportation and installation, and poses a high risk of explosion and fire. So oil-rich circuit breakers have tended to be eliminated.
Less oil circuit breaker
The arc extinguishing chamber is installed in a tank insulated from the earth. The fuel tank can be made of metal or insulating material. The oil is only used for the arc extinguishing medium and the insulation between the fractures, not for the insulation to the ground, and the amount of oil is small.
The oil-less circuit breaker is mainly composed of a chassis, an insulator, a transmission system, a conductive system, contacts, an arc extinguishing chamber, an oil-gas separator, a buffer and an oil level indicator. When closing, the operating mechanism transmits the force to the main shaft through the transmission arm link (see the switching mechanism). The main shaft drives the three insulating pull rods to make the three-pole moving contact rod move straight up. Finally, it is inserted into the static contact. The moving mechanism fastens the contact rod to keep the circuit breaker in the closed position. In this process, the breaking spring stretches and stores energy to prepare for opening. The opening is when the operating mechanism is tripped, due to the action of the breaking spring force, the main shaft is rotated to drive the pull rod, so that the movable contact rod moves downward. Finally, due to the pre-tensioning force of the breaking spring, the main shaft crank arm abuts on the opening positioning member, so that the circuit breaker is maintained in the open position.
Outdoor type oil-free circuit breakers with a voltage level of 110kV and above mostly adopt the unit-breaking (or breaking unit) series-connected, building-block-type combined floor-type overall structure that interrupts the arc. The standard breaking unit voltage is 55 ～ 110kV. For example, SW6 type oil-free circuit breaker, the breaking unit is 55kV, 220kV and 330kV oil-saving circuit breakers belonging to this series will take the structure of double-column, four-break and three-column, six-break. The breaking unit is formed in series, and capacitors are connected in parallel on each of the fractures to uniformly break the voltage distribution of the fracture; each pole is operated by a separate hydraulic operating mechanism. SW7-220 type 220kV oil-free circuit breaker, because the breaking unit is 110kV, so each pole takes the structure of single column and double break.
The outstanding features of the oil-free circuit breaker are simple structure, easy manufacture and maintenance, low price, and convenient use. Compared with oil-rich circuit breakers, oil-saving circuit breakers are small in size, light in weight, and low in oil consumption. They can be assembled into ultra-high-voltage oil-saving circuit breakers using building blocks, and are widely used in power systems. The disadvantages are long arc burning time, slow action, short maintenance period, large maintenance workload, limited by the voltage of the unit fracture, and difficulty in developing UHV grade.
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