What Exactly Is Differential Protection?

Differential protection is a system that compares the current entering the transformer ( Incoming Current) with the current leaving it (Outgoing Current). This is achieved using current transformers (CTs) on both sides of the transformer, which send measurements to the differential relay.

How Does Differential Protection Work?

• Under normal conditions: The incoming current is almost equal to the outgoing current (considering natural losses).

• In the case of an internal fault (e.g., short circuit): A significant difference between the two currents is detected.

• The differential relay senses this difference and isolates the transformer to protect it.

Why is Differential Protection Important?

1. Detects internal faults: Focuses solely on internal faults without being affected by external ones.

2. Fast response: Provides immediate action to prevent fault escalation.

3. High reliability: Reduces the likelihood of secondary faults or equipment damage.

Applications:

• This protection is commonly used in:

• Power generation plants

• Major transmission substations

• Large industrial facilities