What are the protection system used in transformers?

Transformers are critical components in power systems. To ensure their safe and reliable operation, they are typically equipped with various protection systems. These systems can detect and respond to different types of faults and abnormal conditions, promptly cutting off the power supply to prevent the fault from escalating. Below are some common transformer protection systems:

1. Overcurrent Protection

1.1 Instantaneous Overcurrent Protection

• Function: Detects and rapidly responds to short-circuit faults, immediately cutting off the power supply.

• Application: Suitable for quickly isolating short-circuit faults to prevent transformer overheating and damage.

1.2 Time-Delay Overcurrent Protection

• Function: Detects sustained overcurrent and cuts off the power supply after a certain delay.

• Application: Suitable for handling overload conditions, preventing the transformer from overheating over extended periods.

2. Differential Protection

2.1 Transformer Differential Protection

• Function: Compares the currents on both sides of the transformer to detect internal faults.

• Principle: Under normal conditions, the currents on both sides of the transformer should be equal and in opposite directions. Any discrepancy indicates a potential internal fault.

• Application: Suitable for large transformers, capable of quickly detecting and isolating internal faults.

3. Gas Protection (Buchholz Relay)

3.1 Light Gas Protection

• Function: Detects small amounts of gas generated inside the transformer and triggers an alarm.

• Application: Used for early warning, prompting maintenance personnel to perform inspections.

3.2 Heavy Gas Protection

• Function: Detects large amounts of gas generated inside the transformer and immediately cuts off the power supply.

• Application: Used to quickly isolate severe internal faults, preventing fires and explosions.

4. Temperature Protection

4.1 Winding Temperature Protection

• Function: Monitors the temperature of the transformer windings and triggers an alarm or cuts off the power supply if the temperature exceeds a set value.

• Application: Prevents the transformer from overheating, extending its lifespan.

4.2 Oil Temperature Protection

• Function: Monitors the temperature of the transformer oil and triggers an alarm or cuts off the power supply if the temperature exceeds a set value.

• Application: Prevents the oil from overheating, which can cause insulation materials to degrade and fail.

5. Pressure Protection

5.1 Pressure Relief Protection

• Function: Monitors the internal pressure of the transformer and releases the pressure if it exceeds a set value to prevent explosion.

• Application: Suitable for oil-immersed transformers, ensuring safe pressure release when internal pressure is too high.

6. Insulation Monitoring

6.1 Insulation Resistance Monitoring

• Function: Monitors the insulation resistance of the transformer windings and triggers an alarm if it falls below a set value.

• Application: Early detection of insulation aging or damage, preventing faults.

7. Zero-Sequence Current Protection

7.1 Zero-Sequence Current Protection

• Function: Detects zero-sequence currents in a three-phase system to identify single-phase ground faults.

• Application: Suitable for systems with grounded neutrals, preventing equipment damage due to single-phase ground faults.

8. Voltage Protection

8.1 Overvoltage Protection

• Function: Monitors system voltage and triggers an alarm or cuts off the power supply if the voltage exceeds a set value.

• Application: Prevents insulation breakdown and equipment damage due to overvoltage.

8.2 Undervoltage Protection

• Function: Monitors system voltage and triggers an alarm or cuts off the power supply if the voltage falls below a set value.

• Application: Prevents equipment from malfunctioning due to undervoltage.

9. Non-Electrical Protection

9.1 Oil Level Protection

• Function: Monitors the oil level in the transformer and triggers an alarm if it falls below a set value.

• Application: Prevents reduced cooling efficiency and equipment damage due to low oil levels.

9.2 Oil Chromatography Analysis

• Function: Periodically analyzes the gas content in the transformer oil to detect internal faults.

• Application: Used for early detection of internal faults, guiding maintenance and repairs.

10. Digital Protection

10.1 Microprocessor-Based Protection

• Function: Utilizes microprocessors and intelligent algorithms to integrate multiple protection functions, enhancing the accuracy and reliability of protection.

• Application: Suitable for modern smart grids, enabling remote monitoring and automated protection.

Summary

Transformer protection systems use various methods to detect and respond to different types of faults and abnormal conditions, ensuring the safe and reliable operation of transformers. These protection systems include overcurrent protection, differential protection, gas protection, temperature protection, pressure protection, insulation monitoring, zero-sequence current protection, voltage protection, and non-electrical protection. The choice of protection system depends on the type, capacity, and application environment of the transformer. Through these protection measures, transformer faults can be effectively prevented and minimized, extending the equipment's lifespan and ensuring the stable operation of the power system.