The disconnector (disconnector) means that when it is in the sub-position, there is an insulation distance and an obvious disconnection mark between the contacts that meet the specified requirements; when it is in the closed position, it can carry the current under normal circuit conditions and abnormal conditions within a specified time (such as short-circuit) current switching device.
The isolating switch we are talking about generally refers to a high-voltage isolating switch, that is, an isolating switch with a rated voltage of 1kv and above, usually referred to as an isolating switch, which is the most used electrical appliance in high-voltage switching appliances. And the structure is relatively simple, but due to the large amount of use and high requirements for work reliability, it has a great impact on the design, establishment and safe operation of substations and power plants. The main feature of the knife switch is that it has no arc extinguishing ability, and can only divide and close the circuit without load current.
Isolation switch commonly used in coal mine switches:
1) After opening, establish a reliable insulation gap, and separate the equipment or lines that need to be repaired from the power supply with an obvious disconnection point to ensure the safety of maintenance personnel and equipment.
2) According to the operation needs, change the line.
3) It can be used to divide and combine small currents in the line, such as the charging current of bushings, busbars, connectors, short cables, the capacitive current of switch balancing capacitors, the circulating current when double busbars are switched and the excitation current of voltage transformers Wait.
4) According to the specific situation of different structure types, it can be used to divide and combine the no-load excitation current of a certain capacity transformer.
According to the different installation methods, high-voltage isolation switches can be divided into outdoor high-voltage isolation switches and indoor high-voltage isolation switches. Outdoor high-voltage isolating switches refer to high-voltage isolating switches that can withstand the effects of wind, rain, snow, dirt, condensation, ice and thick frost, and are suitable for installation on terraces. It can be divided into single-column disconnector, double-column disconnector and three-column disconnector according to the structure of its insulating struts. Among them, the single-column knife switch directly uses the vertical space as the electrical insulation of the fracture under the overhead busbar. Therefore, it has the obvious advantages of saving floor space, reducing lead wires, and at the same time, the opening and closing state is particularly clear. In the case of ultra-high voltage power transmission, the effect of saving floor space is more significant after the single-column knife switch is used in the substation.
In low-voltage equipment, it is mainly suitable for low-voltage terminal power distribution systems such as residential buildings and buildings. Main functions: with load breaking and connecting line
1. When the electrical equipment is overhauled, an electrical interval is provided, and it is an obvious disconnection point to ensure the personal safety of maintenance personnel.
2. The isolating switch cannot be operated with load: it cannot operate with rated load or large load, and cannot divide and combine load current and short-circuit current, but those with arc extinguishing chamber can operate with small load and no-load line.
3. In general power transmission operation: first close the isolating switch, then close the circuit breaker or load switch; when the isolating switch is powered off: first disconnect the circuit breaker or load switch, then disconnect the isolating switch.
4. The selection is no different from other electrical equipment, all of which must be rated voltage, rated current, dynamic stable current, thermal stable current, etc. must meet the needs of the application.
The function of the isolating switch is to disconnect the circuit of no-load current, so that the equipment to be repaired and the power supply have an obvious disconnection point to ensure the safety of the maintenance personnel. The isolating switch cannot cut off the load current and short-circuit current without a special arc extinguishing device. , so the isolating switch can only be operated when the circuit is disconnected by the circuit breaker.
Post time: Oct-29-2022