A substation is a power facility that converts voltage, receives and distributes electrical energy, controls the flow of electrical power, and adjusts voltage in a power system. It connects the power grids of the various stages through a transformer.
The equipment used to change the voltage in the substation is a transformer. In addition, the equipment of the substation also has switching devices for opening and closing circuits, busbars for collecting current, transformers for metering and control, instrumentation, relay protection devices and lightning protection devices. , scheduling communication devices, etc., some substations and reactive power compensation equipment.
Today, Xiaobian will take you to fully dissect the main electrical equipment of the substation, and let's go up together!
Part 1 transformer
The transformer is the main equipment of the substation and is divided into a double winding transformer, a three winding transformer and an autotransformer.
According to its function, the transformer can be divided into a step-up transformer and a step-down transformer. The former is used for the power system to send the substation, and the latter is used for the receiving substation. The voltage of the transformer needs to be adapted to the voltage of the power system. In order to maintain a qualified voltage under different load conditions, it is sometimes necessary to switch the tap of the transformer.
According to the tap switching mode, the transformer has a load-loaded voltage regulating transformer and a no-load unloaded voltage regulating transformer. The on-load tap changer is mainly used in the receiving substation.
Part 2 transformer
The main function of the transformer is to convert the voltage of the high-voltage conductor of the substation to the ground or the current flowing through the high-voltage conductor to a low voltage and a small current, thereby realizing the voltage of the high-voltage conductor to the ground and flowing through the high-voltage conductor. Effective measurement of current.
Voltage transformer
The transformer is divided into a current transformer and a voltage transformer for current and voltage conversion. Since their transformation principle is similar to that of a transformer, it is also called a measuring transformer.
The main role of the transformer:
1 The transformer can isolate the instrument for measurement or protection from the primary circuit of the system to prevent short-circuit current from flowing through the instrument and instrument, thus ensuring equipment and personal safety;
2 Since the primary side and the secondary side of the transformer have only magnetic contact, and there is no direct connection of electricity, the requirement of insulation level of the secondary instrument is reduced;
3 The transformer can change the high voltage of the primary circuit to a low voltage of 100V or 100/3V, and the large current in the primary circuit is unified into a small current of 5A. In this way, the measurement of the secondary side of the transformer or the manufacture of protective instrumentation can be standardized.
Current Transformer
In addition, the secondary winding of the current transformer is often connected to the load and is close to the 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 high voltage.
Part 3 switchgear
Switching device. It includes circuit breakers , disconnectors , load switches , high voltage fuses, and the like.
The circuit breaker automatically disconnects the faulty device and the line under the control of the relay protection device when the circuit breaker is used to close and disconnect the circuit under normal operating conditions of the power system, and may also have an automatic reclosing function. In China, more than 220kV substations use air circuit breakers and sulfur hexafluoride circuit breakers.
The main function of the isolating switch (knife) is to isolate the voltage during equipment or line maintenance to ensure safety. It cannot disconnect the load current and short-circuit current and should be used with the circuit breaker. In the event of power failure, the circuit breaker should be pulled first and then the disconnector should be pulled. If it is mistaken, it will cause equipment damage and personal injury.
The load switch can disconnect the load current during normal operation without breaking the fault current. It is generally used with high-voltage fuses for transformers or outlets that are operated at 10kV and above and are not frequently operated.
In order to reduce the footprint of substations, sulfur hexafluoride fully enclosed combined electrical appliances (GIS) have emerged in recent years. It installs the circuit breaker, the isolating switch, the busbar, the grounding switch, the transformer, the outlet bushing or the cable terminal head in their respective sealed rooms to form a whole casing filled with sulfur hexafluoride gas as the insulating medium. The combined electric appliance has the advantages of compact structure, small volume, light weight, no influence on atmospheric conditions, long maintenance intervals, no electric shock accidents and electrical noise interference. At present, its shortcomings are expensive, high manufacturing and maintenance processes.
Part4 lightning protection equipment
The substation is also equipped with lightning protection equipment, mainly lightning rods and lightning arresters . The lightning rod is to prevent the substation from being subjected to direct lightning strikes to discharge the lightning to itself and to introduce lightning current into the earth. When lightning strikes on a line near a substation, lightning waves enter the substation along the wire, creating an overvoltage. In addition, circuit breaker operation and the like can also cause overvoltage. The function of the arrester is that when the overvoltage exceeds a certain limit, the automatic ground discharge reduces the voltage protection device and then automatically extinguishes the arc automatically to ensure the normal operation of the system. At present, the most used is the zinc oxide arrester.
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Wuxi Trenty Machinery & Equipment Co., Ltd. , https://www.elec-inverter.com