03.What are the main equipments in the substation?
Below are some of the major pieces of equipment used in a substation.
Busbar
Circuit breaker
Disconnector/ Isolator / Earth Switch
Current transformer
Capacitive Voltage transformer / Potential transformer
Power Transformer
Tap Changers
Lightning Arrestor
Wave trap / Line trap
Post insulator
Protection & Control System
Substation Automation System
Busbar
A busbar is a conductor typically made of highly conductive material such as aluminium or copper used in electrical power distribution systems. It often takes the form of a hollow round pipe or a solid, thick bar, depending on the current-carrying requirements. The primary property of a busbar is high electrical conductivity, which ensures efficient and smooth operation. Functionally, the busbar serves as a central junction point, connecting multiple incoming and outgoing feeders, thereby distributing electrical power within a substation or switchgear system.
Disconnector/ Isolator / Earth Switch
We also call it an isolator or off-load switch. It operates manually or motorized when there is no-load. Sometimes, it may also be operated under load conditions during load transfer situations. But be sure it cannot discriminate faults.
The main purpose of disconnectors is to isolate the circuit under no-load conditions or during maintenance. During maintenance, the earth switch will be closed and the main disconnector will be open. Under normal operating conditions, the earth switch will be open and the main disconnector will be closed.
You can observe that during operation, the earth switch, disconnector, and auxiliary contacts will change their positions—NO to NC and NC to NO
Only one typical unit is shown below. There will be a total of three such units to control a three-phase circuit
Current transformer
The main purpose of the Current Transformer (CT) is to measure current.
The measured current is used for protection and metering purposes.
The primary winding is connected in series with the load, while the secondary winding is used for applications such as protection, metering, and spare connections.
Voltage transformer
The main purpose of the Voltage Transformer (VT) is to measure voltage.
The measured voltage is used for protection and metering.
The primary winding is connected in parallel with the load, while the secondary winding is used for applications such as protection, metering, and spare connections.
Circuit breaker
It is one of the major pieces of equipment in any substation. It can operate manually or automatically during load or no-load conditions. The main purpose of the circuit breaker is to discriminate the fault with the help of protection control relays. The circuit breaker consists of a spring-charged motor, trip coil, closing coil, and the arc quenching medium, which can be air, oil, or gas. You can see that during operation, the CB and auxiliary contacts will change their positions—NC to NO and NO to NC. We can say that the CB is a one-load switch.
Power transformers
Power transformers are a critical asset in any substation. Their main function is to convert electrical voltage from one level to another without altering the frequency. In future videos, we will explore the specific purposes of step-up and step-down transformers.
Tap changers
Tap changers operate in conjunction with power transformers. Under load conditions, voltage levels may drop, leading to increased current and, consequently, higher losses. To maintain a consistent output voltage, the number of winding turns must be adjusted—since voltage is directly proportional to the number of turns. This adjustment is done using tap changers, which connect to the secondary winding through various taps. The appropriate tap is selected based on the load conditions. The design and application of tap changers vary depending on the size and capacity of the transformer.
Lightning arresters
Lightning arresters are used to protect substation equipment from external voltage surges caused by lightning strikes or switching operations. These high-voltage surges are safely diverted to the ground through the lightning arresters, thereby safeguarding the equipment. The arrangement of surge arresters is typically placed close to the equipment they protect, ensuring rapid and effective response to transient overvoltages.
Wave traps /Line Traps
Wave traps also known as line traps, are connected in parallel with Capacitive Voltage Transformers (CVTs). Substations often operate with high-frequency communication systems, such as telephone voice or video channels, alongside the transmission conductors. These high-frequency signals can enter the substation and potentially damage the equipment. Wave traps are designed to bypass these high-frequency signals, allowing them to pass through the CVT for communication purposes while protecting the substation's equipment from any harmful effects.
Post insulators
Post insulators have a simple yet effective design. They are used to securely hold conductors in place, providing a stable connection between two points. During windy or adverse weather conditions, post insulators ensure that the conductors remain in a stable position, preventing displacement or damage.
Protection and control System
it is one of fundamental equipment in any substation. It will protect the substation when there is a like Over current / Earth faults or any other abnormal condition in the substation. The protection control panel is equipped with protection and control relays, controlling switches, Meters & Auxiliary trip relays. You can see the all the items are equipped in the Protection & Control cabinet.
Substation Automation System (SAS/SCADA)
A Substation Automation System, often referred to as SCADA (Supervisory Control and Data Acquisition), is an advanced software solution designed to monitor and control substation events. It allows real-time monitoring of the status of bays showing which bays are active and which are inactive. Additionally, the system can track important parameters such as frequency, current, voltage, and energy flow (import/export) from each feeder bay.
Substation automation also enables remote operation of switchgear through the substation's Human-Machine Interface (HMI). Relays and meters are connected to an Ethernet switch via fiber optics or Ethernet cables, facilitating communication with SCADA. For seamless integration and communication, it is essential that all relays and meters are IEC 61850 compliant.
