What is a switch-yard and sub-station? What is the purpose of a switch-yard and how are they different from a switch-gear

What is a switchyard and sub-station

Switchyard is a switching station which is the main link between the generating plant and the transmission system. It can be considered as the heart of the power plant, the generated power will only be worthy if it can be transmitted and received by the consumers. Switchyard is a junction which carries the generated power to the destination, it plays a major part in the security of the system, it can control the reactive power devices which plays a major role in power quality. It is mostly an assemblage of switches, power circuits, breakers, and the auxiliary equipment which is used to collect power from the generators at the power plant and then it will be distributed to the transmission lines at a load point.

Switchyard means a collection of electrical equipment, where high voltage electricity is switched using the various components. Electrical switchyards are one of the important parts in a substation where electricity is transferred from one voltage to another from transmission and distribution. Switchyard can be considered as the interconnection of generating station and the grid. The generated power from the generating station is transmitted to the grid through the switchyard. Switchyard gives a secured power to the grid. A switchyard or substation is an assembly of apparatus which transforms the characteristics of electrical energy from one place to another and controls the flow of power. Switchyard controls the exchange of electrical energy. It monitors the electrical parameters in each transmission line like the voltage, current, power, frequency. The important part of the power system is the switchyard, it can be considered as the backbone of the power system. Switchyard is inevitable in a power system.

What are the main functions of switchyard

Switchyard makes available the generated power at the plant to the people. The power generated at a power station is transmitted via a switchyard. When there is sudden damage outside the plant switchyard can protect the plant.

What are the types of switchyard

  • Conventional air insulated type
  • Gas-insulated type
  • Outdoor gas-insulated type

Air-insulated switchyard

This is the most common type of switchyard used in power plants. They use air to insulate different components of the substation from each other as well as for grounding the charge. Most of the substation does the copper grounding on equipment and in the ground so that the system can be protected and it would be properly grounded.

Gas-insulated switchyard

A gas-insulated substation uses a superior dielectric gas like SF6, at moderate pressure for the phase to phase and phase to ground insulation. GIS is used whenever space is less. The active parts in a GIS are protected from atmospheric contamination. In this type of switchyard the equipment like a current transformer, switches, or circuit breaker… are in SF6 gas inside a grounded metal enclosure.

What is the purpose of a switchyard

Switchyard is an open area where many different kinds of equipment are located such as an isolator, circuit breakers… and it is used for the connecting and disconnecting of the transmission lines as per the requirement. Basically switchyard main role is to transmit the generated power to the destination the power will be switched through isolators, bus bars…

Switchyard does the protection of the transmission system, they isolate the faulty network from the healthy ones. Switchyard controls the exchange of power, by controlling the power transmission to the load points according to the requirements. It does the maintenance of the system frequency within targeted limits and this can be done by raising or lowering of generation or load schedule. Power transfer is determined through transmission lines. It also does the fault analysis and subsequent improvement. Switchyard can maintain a certain voltage level, they can step up or step down the voltage so that it is used in power plants for transmission and distribution.

What are the types of equipment in a switchyard

Bus bar – Bus bar receives power from incoming circuits and delivers power to the outgoing circuit

Insulators – insulators are used to support conductors and insulate high current to the conductor. Suspension type insulators are the most commonly used insulators but post and strain type insulators are used in the switchyard.

Surge arrestor – This device is connected between the phase conductor and ground that prevents a transient voltage or surges from lightning.

Current transformer – This is used for stepping down the current for measurement and they are connected in series with the transmission line.

Voltage transformer – This is used to step down the voltage for measurement and they are connected in parallel with a transmission line.

Isolators – Isolation of the live parts can be done with the help of isolators, and this will be helpful during maintenance and they are located at either side of the circuit breaker. Isolators operate under no-load condition, they are used for breaking and charging the transmission line.

Relays – It detects the faults and isolates the faulty part from the rest of the system

Earth switch – They are mounted on the isolator base, it would be either the line side or breaker side it would be according to the position of the isolator. Earth switch is required to discharge the trapped charges on the line or equipment to earth for safety.

Wave trap – Wave trap provides high impedance path for high-frequency signals and low impedance path for power frequency current. This would keep the carrier signal confined to the protected line section and won’t allow the carrier signal to flow into the neighboring sections.

What is the difference between switchyard and switchgear

Switchgear consists of electrical disconnect switches such as fuses or circuit breakers, which is used to control protect and isolate the electrical equipment in case of fault conditions. Switchgears are devices that are used for the switching, protection and controlling of an electrical circuit. But switchyard is entirely different from it, maybe switchgear can be a piece of equipment in a switchyard, the transmission of the power which is generated in a power plant is done by the help of a switchyard it acts as a junction where the power transmission takes place. Switchyard can secure the power plant and can help in the transmission of power.