Power Transformer Protection Relay

Power transformer protection relay

There are various types of power transformer protection relays, each designed to protect transformers from specific types of faults. Here are some of the most common types of power transformer protection relays:

• Differential relays: These are the most common type of protection relays used for power transformers. Work by comparing the current entering the transformer with the current leaving it. If there is a difference between the two currents, it indicates that there is a fault somewhere in the transformer, and the differential relay sends a signal to trip the circuit breaker.
• Earth fault relay : A power transformer earth fault relay is a protective relay that is used to detect earth faults in a power transformer,The purpose of the earth fault relay is to provide fast and accurate detection of earth faults in the transformer, thereby protecting it from damage and reducing the risk of injury to personnel.
• Standby earth fault relay: power transformer standby earth fault relay is another type of protective relay used to protect power transformers. It works by detecting any earth fault that may occur in the transformer's standby or auxiliary power supply system,
 The purpose of the standby earth fault relay is to provide an additional layer of protection to the transformer
• OTI & WTI Relay: They are commonly referred to in the industry as Oil Temperature Indicators (OTI) and Winding Temperature Indicators (WTI). Electrical utilities often utilize oil and winding temperature indicators to provide alarm and control signals that are used to activate cooling control systems on a transformer.
•Oil surge relay : A power transformer oil surge relay is a protective relay used to detect sudden pressure surges within a power transformer's oil-filled tank.
the oil surge relay is to provide early detection of pressure surges within the transformer tank and prevent potential damage to the transformer. By detecting and isolating the transformer from the system, the oil surge relay helps to maintain the stability and reliability of the power system.
•PRD : A power transformer PRD (Pressure Relief Device) relay is a protective relay used to detect and respond to excessive pressure within a power transformer's oil-filled tank.
the PRD relay is to prevent the transformer tank from rupturing due to excessive pressure, the PRD relay helps to maintain the stability and reliability of the power system.
•Magnetic Oil Gauge (MOG): A power transformer magnetic oil gauge relay is a protective relay used to monitor the oil level and temperature in a power transformer's oil-filled tank. The relay uses a magnetic float, which is located inside the transformer tank, to detect the level of oil in the tank. The magnetic float is connected to a pointer, which indicates the oil level on a gauge.
• REF (Restricted Earth Fault): power transformer  relay is a type of protective relay used to protect power transformers from internal faults. The REF relay operates on the principle of detecting the fault current that flows through the transformer's earthed winding due to a fault in the transformer. This current is known as the zero-sequence current.

• Overcurrent relays: These protection relays are designed to detect when there is an excessive current flow in the transformer's windings. They operate by measuring the current flow and comparing it to a preset value. If the current exceeds the set value, the relay sends a signal to trip the circuit breaker.

• Overvoltage relays: These protection relays detect when there is an excessive voltage on the transformer's secondary side. They operate by measuring the voltage and comparing it to a preset value. If the voltage exceeds the set value, the relay sends a signal to trip the circuit breaker.

• Underfrequency relays: These protection relays are designed to detect when there is a drop in the frequency of the power system. They operate by measuring the frequency and comparing it to a preset value. If the frequency drops below the set value, the relay sends a signal to trip the circuit breaker.

• Buchholz relays: These protection relays detect the presence of gas inside the transformer's oil tank, which indicates a fault. They operate by measuring the gas and oil levels in the tank and sending a signal to trip the circuit breaker if necessary.

• Thermal overload relays: These protection relays are designed to detect when the transformer's temperature exceeds a safe limit. They operate by measuring the temperature and comparing it to a preset value. If the temperature exceeds the set value, the relay sends a signal to trip the circuit breaker.