Ground Fault Relays
Differential Protection Relays
Differential Protection for Power Transformers
Digital or Numerical Relays
Reliability Issues in Numerical Relays
Solid-State Relays (SSR)
SSRs for Renewable Energy Systems
Distance Protection Relays
Artificial Intelligence and Distance Protection
Overcurrent Relays
Enhancing Reliability with Overcurrent Protection
Protective Relays
The Vital Role of Differential Protection Relays
The backbone of a reliable electrical power system hinges on its ability to safeguard equipment and maintain service continuity. Protective relays play a critical role in achieving this objective by detecting abnormal operating conditions like faults, overloads, and voltage deviations. Among these intelligent devices, differential protection relays stand out for their high sensitivity and selectivity, making them ideal for protecting critical equipment such as transformers, generators, and busbars.
Understanding Differential Protection
Differential protection operates on the fundamental principle of Kirchhoff's Current Law (KCL). This law states that the algebraic sum of currents entering a junction must equal the sum of currents leaving the junction under steady-state conditions. In simpler terms, the current entering a protected zone (e.g., a transformer) should be equal to the current exiting the zone.
Differential relays measure the currents entering and exiting the protected zone using current transformers (CTs). These CTs provide proportional, scaled-down replicas of the actual currents. The relay then compares the phasor magnitudes and angles of these secondary currents. Under normal operating conditions, the entering and exiting currents should be nearly identical, resulting in a minimal differential current within the relay. However, during a fault within the protected zone, the current balance is...