Electrical Substation Equipment
Lightning Arrester
Power Transformer
Instrument Transformer
Current Transformer
Potential Transformer
Busbar
Wave Trap
Isolator
Circuit Breaker
Batteries
Capacitor Bank
Switchyard
Indicating and metering Instruments
Carrier-current Equipment
Relay
Insulator
Fuses
Shunt Capacitor and Reactor
Earthing Switch
Distribution Transformer
Earthing
Lightning Arrester
The device which is used for the protection of the equipment at the substations against traveling waves, such type of device is called a lightning arrester or surge diverter. In other words, the lightning arrester diverts the abnormally high voltage to the ground without affecting the continuity of supply. It is connected between the line and the earth, i.e., in parallel with the equipment to be protected at the substation.
Power Transformer
Power transformers are used for stepping up the voltage for transmission at generating station and for stepping down the voltage for further distribution at main step-down transformer substations. Usually naturally cooled, oil-immersed type two winding, three-phase transformers, are used for rating up to 10 MVA. The transformer for a rating of more than 10 MVA, is usually air blast cooled. For very high ratings, force oil, water cooling, and air blast cooling may be used.
Instrument Transformer
In high voltage A.C. circuits, the measurement cannot be done by using the method of extension of ranges of low range meters by providing suitable shunts. In such conditions, specially constructed accurate ratio transformers are used. These transformers are used to isolate the instruments from high current and high voltage A.C. circuits.
Current Transformer
A current transformer is a device for the transformation of current from a higher value to a lower value. It is used in parallel with AC instruments, meters or control apparatus so that the meter or instrument coil cannot conveniently be made of sufficient current carrying capacity.
Potential Transformer
The potential transformer may be defined as an instrument transformer used for the transformation of voltage from a higher value to a lower value. This transformer step down the voltage to a safe limit value which can be easily measured by an ordinary low-voltage instrument like a voltmeter, wattmeter and watt-hour meter, etc.
Busbar
A busbar is an electrical junction used for collecting electric power from the incoming feeders and distributing them to the outgoing feeders. The main purpose of a busbar is to carry electricity and distribute it. Busbars are used to make the systems more efficient.
Wave Trap
Wave trap is used to create a high impedance to the carrier wave high-frequency communication entering into unwanted destinations typically substations. Carrier wave communication uses up to 150kHz to 800kHz frequency to send all the communication. These high-frequency damage the power system components which are designed to operate 50 or 60 Hz. Wave traps are also called line traps.
Isolator
The isolator is a manually operated mechanical switch that isolates the faulty section of the substation. It is used to separate a faulty section for repair from a healthy section in order to avoid the occurrence of severe faults. It is also called a disconnector or disconnecting switch.
Circuit Breaker
The circuit breaker is a type of electrical switch which is used for opening or closing of electrical circuit whenever faults occur in the system. It consists of two moving contacts which are normally closed. Whenever the fault occurs in the system, the relay sends the tripping command to the circuit breaker and hence their contacts are moved apart. Thus, the fault that occurs in the system becomes clear.
Batteries
In electric power stations and large capacity substations, the operation and automatic control circuits the protective relay system, as well as emergency lighting circuits, are supplied by station batteries. The station battery is assembled of a certain number of accumulator cells depending on the operating voltage of the respective DC circuit.
Capacitor Bank
It is a series-parallel combination of capacitors required to improve power factor of the system. They act as reactive power generators and provide the needed reactive power to accomplish active power of the circuit. This reduces the amount of reactive power, and thus total power (kVA) or the demand.
Switchyard
The switch yards, houses transformers, circuit breakers, and switches for connecting and disconnecting the transformers and circuit breakers. It also has lightning arrestors for the protection of the power station against lightning strikes.
Indicating and metering Instruments
Ammeters, Voltmeters, Wattmeter's, kWh meters, KVARH meters, power factor meters reactive volt-amperes meters are installed in substations to control and maintain a watch over the current flowing through the circuits and over the power loads.
Carrier-current Equipment
Such equipment is installed in the substations for communication, relaying, telemetered, or for supervisory control. The equipment is suitably mounted in a room known as the carrier room and connected to the high-voltage power circuit.
Relay
A relay is an automatic device that senses an abnormal condition of an electrical circuit and closes its contacts. These contacts in turn close and complete the circuit breaker trip coil circuit hence making the circuit breaker tripped for disconnecting the faulty portion of the electrical circuit from the rest of the healthy circuit.
Insulator
The main function of an insulator is to insulate live conductors or equipment at different voltages with reference to the ground structures as well as provide mechanical support.
Fuses
A fuse is a non-adjustable, direct-acting, single-phase device that responds to both the magnitude and duration of current flowing through it. Fuses may be used both in low-voltage and high-voltage lines. Fuses are protective devices.
Shunt Capacitor and Reactor
These capacitors supply reactive power to the loads and thus help in improving the power factor. Sometimes, reactors may also be used to absorb reactive power supplied by the line.
Earthing Switch
It is connected between the conductor and the earth. Normally, it is in an open position. However, when the line is disconnected, this switch closed to discharge the trapped charge to the ground.
Distribution Transformer
The distribution transformer is the main and largest equipment of the distribution substation. It is basically a static electrical device that steps down the primary voltage of 33kV or 11 kV to secondary distribution voltage of 415-440 volts between phases and 215 volts between phases and neutral through delta-star windings by electromagnetic induction without change in frequency.
Earthing
The provision of effective, durable, and dependable earthing in a substation and switching stations is very important for the safety of operating personnel as well as electrical devices. The voltage levels do not rise above tolerable thresholds and the earth connection is rugged to dissipate the fault to the earth. Earthing has a very low resistance and connects the electrical equipment to the general mass of the earth.