There required various types of instruments and equipments in an electrical substation for transferring the electrical energy from generating station to load center which are listed below.
- Power transformer
- Instrument transformers
- Bus-bar
- Wave Trapper
- Isolator
- Circuit Breaker
- Lightning Arrestor and Surge Arrestor
- Batteries
- Capacitor Bank
- Carrier-Current Equipment
- Indicating and Measuring instrument
- Relays
- Insulators
- Earthing and Grounding
- Switch-yard
- Proper fencing
- Stones
Power Transformer
Power transformer are those transformers that are used for transferring high power either by step-up or step-down the voltage or only for electrically isolating two high power electrical transmission circuit in power system. All the transformer used in power system for transferring high power from one circuit to another are the power transformer.
They are used to step-up the voltage at the generating end and step-down the voltage at the load center. Sometimes used to electrically isolate two transmission line circuit for protection or switching purpose.
Instrument Transformer
Instrument transformers are used to convert high value of voltage and current to low safe value for the measurement purpose and safety purpose. In order word, they are used to extend the range of voltmeter and ammeter so that high value of voltage and current can be measure using low range voltmeter and ammeter.
It reduces high value of voltage and current to low which is safe for both the measuring instrument and the operator and also electrically isolate the measuring instrument.There are two types of instruments transformers used in electrical power system. They are current transformer and voltage transformer.
Current transformer is an instrument transformer that step-up the voltage and step-down the high value of current to low safe value so that the high current can be measured with a low range ammeter safely in a ratio i.e it extends the range of ammeter. Voltage transformer is an instrument transformer that step-down the high voltage to low safe value so that high voltage can be measured with a low range voltmeter safely in a ratio i.e it extends the range of voltmeter.
Bus-bar
Wave Trapper
A wave trap or line trap or high frequency stopper is a cylindrical shaped device placed in ac transmission line in-order to stop high frequency signal of power line communication from entering a low frequency device. It is maintenance free parallel resonant circuit connected in series with ac transmission lines. It blocks high frequency communication signal to enter into low frequency device in-order-to prevents low frequency devices from harmful effect of high frequency signals
Isolator
Circuit Breaker
A circuit breaker is a semi-automatic switch designed to break a circuit when the current flowing through the circuit is more than the predetermined value. In-other word, it disconnect the circuit when excess or over-current flow through a circuit due to the short circuit or any other fault. It can be operated both automatically or manually.
It is used to protect the equipment connected in a circuit or person working in or near the circuit from the short circuit or any other fault that increases circuit current. It is also used to prevent the overloading of any equipment or overloading of the whole circuit.
Lighting Arrestor and Surge Arrestor
A lightening arrestor is a device used in an electric power system to protect the equipments from the high voltage lightning. Lightning can lead to high transient voltage and sparks which can damage insulators or equipments connected to the substation or power system so a lightning arrestor is used to divert this high voltage lightning to the earth.
A surge arrestor is a device used in an electric power system to protect the equipment from the high voltage surge due to lightning, over-voltage surge or switching surge. High voltage surge due to lighting, over-voltage surge or switching surge can damage the insulators or connected equipments inside a substation or any building within the power system so a surge arrestor is used to divert these surges to the earth.
Batteries
A battery is a device that can store dc power and can be used as the source of dc power when needed. In large substation or power station, substation batteries are used to supply alarm circuit or control circuit in-order to control power or sound alarm even when power from the transmission line is unavailable so that fault removable or repairing become easier.
These batteries are also used for emergency lighting and to supply communication equipment.
Capacitor Bank
Capacitor bank consists of a number of capacitors connected in series or parallel used to improve power factor and efficiency of the substation or whole power system. The capacitor banks improves power factor and efficiency either by providing or absorbing reactive power to or from a substation or a electric power system depending on its connection mode and operation.
Shunt capacitor bank and series capacitor bank are two main classification of capacitor banks depending on the mode of connection and operation that are used on substations or whole power system.
Carrier-Current Equipment
Indicating and Measuring Equipment
There are various types of indicating and measuring equipments are used in substations to measure different parameters such as voltage, current, power, power factor, frequency e.t.c. The indicating and measuring instrument equipment used in substation are instrument transformer, voltmeter, ammeter, watt-meter, pf meter, frequency meter and so on.
Relays
Relays are sensing equipment that are used to sense the rise in electrical parameters i.e voltage and current which rise due to any types of internal and external fault. Relays senses rise in these parameter and provide signals to the alarm circuit and trip circuit in-order-to prevent damage to the rest healthy portion of the system.
Insulators
Insulators are those materials that do not conduct electricity and used in electrical power system to insulate the live part of the system. They protect operators as well as measuring and controlling devices and instruments in an electrical substations.
Earthing and Grounding
Earthing and grounding both means connecting the electrical conductor to the earth for safety purpose. The different is that earthing represents connecting the metallic parts to the earth whereas grounding means connecting the overhead ground-wire to the earth.
Switch-yard
Switch-yard is that part of an electrical substation used for switching electrical power between two or more electrical circuits. It consists of switches, circuit breakers and auxiliary equipments which is used to collect and distribute electrical power between different electrical circuits.
Proper Fencing
Proper fencing prevents different animals to enter into the substation and also prevent different equipments and machine of substation from being theft.
Stones
Stones are used in substation to avoid weeds in substations and to isolate worker from ground to prevent step-potential and touch potential.