Electrical Equipment
1. What is a power distribution unit? What devices does it include?
A: The distribution device is the switch electrical appliances. Current carrying conductor and protection and measurement of electrical equipment, according to certain requirements formed from the electrical construction, known as the distribution device. A device for receiving and distributing electrical energy. Power distribution devices, including switchgear (circuit breakers. Isolating switch. Load switch, etc.). Protection of electrical appliances (fuses. Relays. Surge arresters, etc.) Measurement of electrical (current transformer, voltage transformer, ammeter, voltmeter, etc.) and bus and Current carrying conductor. Power distribution devices according to their settings can be divided into indoor distribution equipment and outdoor power distribution devices, according to their voltage level is divided into high-voltage power distribution devices and low-voltage power distribution devices, according to its structure is divided into complete sets of power distribution equipment (switchgear) and assembly.
2. High-voltage circuit breaker. Load switch. Fuse role?What are their main structures and main types?
A: 1) high-voltage circuit breakers: high-voltage circuit breakers, also known as high-voltage switchgear in power plants and substations it is an important power distribution equipment. Its role has two aspects:
① under normal circumstances, the separation of high-voltage circuit in the no-load current and load current. (In accordance with the requirements of power grid operation, starting for some of the power lines to stop. Transmission control role);
② When the power system failure, it works with relay protection devices. Cooperated to quickly cut off the fault (short circuit) To reduce the power outage, to prevent the accident to expand, to ensure the safe operation of power systems. (I.e., protection)
The main structure of high-voltage switch can be divided into:
① diversion part;
② part of the arc device;
③ part of the insulation;
④ operating mechanism.
The main types of high-voltage circuit breakers, according to arc quenching medium: oil switch (oil and less oil.) Compressed air breaker. Sulfur hexafluoride breaker. Vacuum breaker. At present the original high-pressure (110kV.220kV) and ultra-high voltage (330kV.500kV) power system plays a major role in the low oil breaker.Compressed air breaker are almost all replaced by SF6 switch; 10kV ~ 35kV power switch in the basic vacuum switch .
SF6 circuit breaker due to the development of SF6 gas it has excellent insulation properties and arc performance, making the switch off capacity greatly improved (a single fracture of the rated breaking current of 50kA ~ 63kA, 80kA), switch size and weight To reduce the maintenance and maintenance of the switch has become a great convenience and simple.
The development of vacuum switch and contact materials are closely related to the use of CuCr alloy contacts, making 12kV vacuum circuit breaker breaking current for a reach of 73kA or even 100kA. Vacuum switch interrupter is not overhauled, once the leak can only be replaced.
2) high-voltage load switch: high-voltage load switch is a small-capacity high-voltage circuit breakers. It has an arc extinguishing mechanism, but the interrupter capacity is small, it is mainly used to cut off or connected to the normal load current, can not be used to cut short-circuit current. In most cases, the load switch with the use of high-voltage fuses, load switch from the no-load or load current, by the fuse for short-circuit protection.Load switch for a large number of load switchgear. Ring power supply units and prefabricated substation. Load switch is mainly produced by gas-type load switch. Pressure gas load switch. Vacuum load switch. SF6 load switch. Vacuum and SF6 load switch in urban and rural areas in a large number of use.
3) High-voltage fuses:
High-voltage fuse is divided into current limiting and drop-type.
In the factory power supply system, the capacity is relatively small and relatively less important load, widely used fuses for power distribution lines and power transformers (including 35KV and below level voltage transformer) overload and short circuit protection. It is economical and can meet a certain degree of reliability, its structure is simple, easy maintenance and repair.
Fuse is dynamic. Static contact. Insulation support and indicators and other components. The action of the fuse has an inverse time characteristic, that is, the greater the short-circuit current through the melt, the shorter the time of the melt-blown current.
fuse usually made of Lead, tin, lead antimony (ti), aluminum alloy or zinc, etc. made of different specifications of round wire or flake,its specification is rated current.
