WAZIPOINT Engineering Science & Technology: Relays Use in Electrical Substations and Their Functions

## Tuesday, July 18, 2023

### Relays Use in Electrical Substations and Their Functions

Relays play a crucial role in electrical substations by monitoring various parameters and controlling the operation of equipment. Here are some common relays used in electrical substations and their functions:

## What Types of Relays Use in Electrical Substations?

Overcurrent Relay: Overcurrent relays are used to protect electrical equipment from excessive currents. They sense the current flowing through a circuit and, if it exceeds a predetermined threshold, the relay trips and sends a signal to a circuit breaker to interrupt the current flow, thereby protecting the equipment from damage.

What is Over Current Relay and How Does It Work?

Differential Relay: Differential relays are used to protect transformers and other equipment from internal faults. They compare the currents entering and leaving the equipment, and if a fault causes an imbalance between these currents, the relay trips, indicating the presence of a fault. In another episode, we discussed the Differential Relay in detail.

Distance Relay: Distance relays are used to protect transmission lines from faults. They measure the impedance or distance to the fault location and compare it to a pre-set threshold. If the measured impedance exceeds the set value, the relay operates to isolate the faulted section of the line. Regarding Distance Relay is discussed in another episode.

Voltage Relay: Voltage relays monitor the voltage levels in a substation and can initiate actions if the voltage exceeds or falls below predetermined thresholds. They are used to maintain proper voltage levels and protect equipment from voltage fluctuations. Different Types of Voltage Relays are discussed in another episode.

Frequency Relay: Frequency relays monitor the frequency of the power system. They protect equipment from damage due to abnormal frequency conditions, such as over-frequency or under-frequency events. They can trip the circuit breaker or initiate load shedding if the frequency deviates from the acceptable range. Frequency Relay's details are discussed in a separate episode.

Transformer Protection Relay: Transformer protection relays are specifically designed to protect transformers from various faults, including overcurrent, overvoltage, under voltage, differential, and temperature abnormalities. These relays monitor the transformer's electrical and thermal conditions and take appropriate actions to protect the transformer. Transformer Protection Relay was discussed in a separate episode.

Generator Protection Relay: Generator protection relays monitor the electrical and mechanical parameters of generators. They provide protection against faults such as overcurrent, overvoltage, under voltage, loss of excitation, reverse power, and more. They help ensure the safe and reliable operation of generators. Generator Protection Relay and its different types are discussed in another episode.

These are just a few examples of the relays used in electrical substations. There are several other relays available that perform specific functions depending on the requirements of the substation and the equipment being protected. The selection and configuration of relays in a substation depend on the system design, equipment characteristics, and desired level of protection.