Chengde power grid 1 10 kV bus protection was successfully put into operation.
It will be safer to use electricity in cities.
(correspondent Liu Zhenyu reporter Hong Fan) At the end of February 2002, the differential protection of 1 10 kV bus passed the operation smoothly. The completion of the project has greatly ensured the reliability of power supply in Chengde area, played an important role in the stable operation of power grid in Chengde area, and ensured the safety of electricity consumption for ordinary people and industrial and agricultural production in our city.
Bus protection in power system is very important for the safe and stable operation of power grid, and it is also one of the most important protections in power system. To this end, the city power supply company made great efforts to transform the bus protection last year.
Zhuang Yuan 220 kV substation is the largest substation with the highest voltage level in Chengde City and the only hub substation in Chengde area. It is related to the power demand in most areas of Chengde, and bus protection is very important. The 1 10KV bus differential protection adopted in this bus protection transformation is PNH- 150 brake bus full current differential protection with high impedance, which is the most advanced bus protection device in the world at present.
It is understood that this bus protection transformation is the protection device with the largest investment and the highest technical content in the history of the power supply protection department of our city, with an investment of nearly 1 10,000 yuan, which was fully completed by the protection class of Chengde Power Supply Company. At present, it has achieved good operational results and presented a generous gift for the 2003 New Year.
electric power substation
Substation is equipped with some equipment to cut off or connect, change or adjust voltage. In power system, substation is the assembly point of transmission and distribution, which is mainly divided into: booster substation, main network substation, secondary substation and distribution station.
Substation is a power facility that converts voltage, receives and distributes electric energy, controls the flow direction of electric power and adjusts voltage in power system. It is connected to the power grid of all levels of voltage through transformers.
Transformer is a device for converting voltage in substation. In addition, substation equipment also includes switching devices for opening and closing circuits, buses for collecting current, transformers, meters, relay protection devices, lightning protection devices, dispatching communication devices and so on. Some substations also have reactive power compensation equipment. The main equipment and connection mode of substation are different according to their functions.
Transformer is the main equipment of substation, which is divided into two-winding transformer, three-winding transformer and self-destructive transformer, that is, one winding is used for each phase of high and low voltage, and a head is led out from the middle of high voltage winding as the outlet of low voltage winding. Voltage is proportional to the number of turns of the winding, and current is inversely proportional to the number of turns of the winding.
Transformers can be divided into boost transformers and buck transformers according to their functions. The former is used in the sending substation of power system, and the latter is used in the receiving substation. Substation should adapt to the voltage of power system. In order to maintain the qualified voltage under different load conditions, it is sometimes necessary to switch the tap of the transformer.
According to tap-changer mode, there are voltage regulating transformers with and without load. On-load voltage regulating transformer is mainly used in receiving substation.
Voltage transformer and current transformer. Their working principle is similar to that of transformers. They change the operating voltage and large current of high-voltage equipment and buses into low voltage and small current of measuring instruments, relay protection and control equipment according to the specified proportion. In rated operation, the secondary voltage of voltage transformer is l00V/, and the secondary current of current transformer is 5A or1a.. The secondary winding of current transformer is often connected to the load, which is close to short circuit. Please note that it must not be opened, otherwise it will endanger the equipment and personal safety or burn the current transformer due to excessive voltage.
Switchgear. It includes circuit breakers, disconnectors, load switches, high-voltage fuses, etc., all of which are devices for opening and closing circuits. Circuit breakers are used to connect and disconnect circuits when the power system is in normal operation. When the line fails, they can automatically disconnect the faulty equipment and lines under the control of relay protection devices, and also have the function of automatic reclosing. In China, air switches and SF6 circuit breakers are widely used in substations above 220kV.
The main function of disconnector (circuit breaker) is to isolate voltage when equipment or line is overhauled to ensure safety. It can't disconnect load current and short-circuit current, and should be used in conjunction with circuit breakers. In case of power failure, the circuit breaker should be pulled first, and the isolating switch should be closed first and then the circuit breaker should be closed when sending power. Misoperation will cause equipment damage and personal injury.
The load switch can cut off the load current during normal operation, but it has no ability to cut off the fault current. Generally used for transformers or outgoing lines with voltages of 10kV and above, with high-voltage fuses.
In recent years, in order to reduce the area of substation, sulfur hexafluoride totally enclosed combined electrical apparatus (GIS) has been actively developed. Circuit breakers, disconnectors, busbars, earthing switches, transformers, outgoing bushings or cable terminal heads are respectively installed in their respective sealed chambers to form an integral shell, and sulfur hexafluoride gas is filled as an insulating medium. This kind of combined electrical apparatus has the advantages of compact structure, small volume, light weight, long maintenance interval, no electric shock accident and electrical noise interference, etc. Before development, it has been put into operation in 765kV substation. At present, its disadvantages are high price and high technical requirements for manufacturing and maintenance.
The substation is also equipped with lightning protection equipment, mainly lightning rods and lightning arresters. The lightning rod is used to prevent the substation from being directly struck by lightning, discharge the lightning to itself, and introduce the lightning current into the earth. When lightning strikes the line near the substation, the lightning wave will enter the substation along the conductor, resulting in overvoltage. In addition, the operation of the circuit breaker will also cause overvoltage. The function of lightning arrester is to automatically discharge to the ground when the overvoltage exceeds a certain limit, so as to reduce the discharge of voltage protection equipment, and then quickly and automatically extinguish the arc to ensure the normal operation of the system. At present, zinc oxide arrester is the most widely used.