Main Electrical Equipment Of Electrical Substation

A electrical substation is an electrical device that converts voltage, receives and distributes electrical energy, controls power flow, regulates voltage power systems and connects transmission networks of various voltages through transformers.

The device that converts the voltage of the electrical substation is the transformer. In addition, substation equipment includes switchgear for switching circuits, busbars for collecting current, transformers for measurement and control, instruments, relay protection devices and lightning protection devices, transportation of communication equipment, etc. There is also an ineffective power compensation device in the departments electrical substation.

Part 1: Transformers

Transformer is the main equipment of substation, which is divided into two-winding transformer, three-winding transformer and autotransformer.

Transformers are divided into step-up transformers and step-down transformers according to their functions. The former is used in the transmitting end substation of the power system, and the latter is used in the receiving end substation. The transformer voltage must be compatible with the voltage at the power system. Under different load conditions, it may be necessary to switch the taps of the transformer to maintain the proper voltage. Depending on the tap switching method, there are two types of transformers: no-load regulator transformers and on-load regulator transformers.

The main function of the transformer is to convert the current flowing through the high-voltage line-to-ground voltage or high-voltage line of the substation into low-voltage or small current at a constant ratio, and convert the high-voltage line-to-ground voltage flowing through the substation to the high-voltage line-to-ground voltage. is to realize the voltage line. Effectively measure current.

Part II: Voltage Transformers

Transformers are divided into current transformers and voltage transformers, which are used for current and voltage conversion, respectively.

It is also called a measuring transformer because its conversion principle is similar to that of a transformer.

The main functions of the transformer:

(1) Transformers can separate measurement or protection equipment and meters from the main circuit of the system to prevent short-circuit currents from flowing through the equipment and meters, thereby ensuring the safety of equipment and individuals.

(2) Since the primary and secondary sides of the transformer are only magnetically connected and not directly electrically connected, the requirements for the insulation level of the secondary equipment are relaxed.

(3) The transformer can evenly change the high voltage of the primary circuit to the low voltage of 100V or 100/3V, and change the large current of the primary circuit to a small current of 5A. In this way, you can standardize the measurement or protection equipment and meter manufacturing on the secondary side of the transformer.

Current Transformer

Also, the secondary winding of the current transformer is usually connected to the load, which is close to a short circuit. NOTE: DO NOT OPEN IT. High voltage threatens the safety of equipment and individuals, and can cause burns to current transformers.

Part 3: Switchgear

switchgear. This includes circuit breakers, disconnect switches, load switches, high voltage fuses, etc.

Under normal operating conditions of the power system, circuit breakers are used to open and close circuits under the control of relay protection devices, automatically disconnect faulty equipment or lines under the control of relay protection devices, and have automatic reclosing functions. In China, air circuit breakers and sulfur hexafluoride circuit breakers are widely used in substations above 220 kV.

The main function of a disconnect switch (knife switch) is to isolate voltage for safety during equipment and circuit maintenance. Since the load current and short-circuit current cannot be separated, they must be combined with circuit breakers. In the event of a power failure, the circuit breaker must be pulled first, then the disconnect switch. When power is applied, the isolating switch must be closed before closing the circuit breaker. Incorrect operation can result in equipment damage and personal injury. The load switch can interrupt the load current during normal operation without interrupting the fault current. It is usually used in combination with high voltage fuses for transformers or sockets with voltages not exceeding 10 kV or more.

In recent years, in order to reduce the installation area of substations, sulfur hexafluoride fully sealed composite electrical appliances (GIS) have been introduced. The circuit breakers, insulating switches, busbars, earthing switches, transformers, outlet bushings, etc. are placed in their respective enclosed chambers to form the entire enclosure filled with sulfur hexafluoride gas as an insulating medium. The composite electrical equipment has the advantages of compact structure, small size, light weight, unaffected by atmospheric conditions, long maintenance interval, and no electric shock accident or electrical noise interference. Today, its disadvantages are high cost, high manufacturing and maintenance process requirements.

Part 4: Lightning Protection Devices

The substation is also mainly equipped with lightning protection equipment and lightning protection equipment such as lightning rods. The lightning rod is to prevent the substation from being directly hit by lightning. The lightning discharges itself, and the lightning current is introduced into the earth. When a line near a substation is struck by lightning, the lightning can enter the substation along the line and create an overvoltage. Also, due to the operation of the circuit breaker, overvoltage may occur. The lightning strike arrester function automatically discharges to the ground, reduces the voltage to protect the equipment, and automatically extinguishes the arc after discharge, so that the system can operate normally when the overvoltage exceeds a certain limit. At present, the most used is the zinc oxide arrester.