Data name: GWZC-9811 Line Protection Relay Drawings and User Manual

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A comprehensive protection relay is an intelligent device that safeguards electrical systems by detecting faults (e.g., overcurrent, short circuits) and isolating affected equipment. It integrates multiple protection functions, ensures system reliability, and prevents damage. This guide covers its definition, working principle, protection targets, activation conditions, and outcomes.

IEC 63522-6:2025 Electrical Relays – Tests and Measurements – Part 6: Contact Circuit Resistance (or Voltage Drop)； IEC 63522-35:2025 Electrical Relays – Tests and Measurements – Part 35: Resistance to Cleaning Agents，IEC 63522-36:2025 Electrical Relays – Tests and Measurements – Part 36: Fire Hazard，Issuing Body: International Electrotechnical Commission (IEC)

Transformer Protection Relay Panel is primarily used in automation systems for substations and distribution stations in power systems of 11kV, 33kV, 132kV and above. Its main function is to ensure that the transformer can promptly trip the faulty circuit in case of overload, short circuit, gas relay activation, and other abnormal operating conditions, thereby protecting the main transformer from damage and preventing the expansion of faults.

Feeder protection relays are a type of line protection relay and serve as critical devices in distribution systems for protecting power cables (feeders). They integrate multiple protection functions to achieve comprehensive, reliable, and selective protection. Below are the commonly used protection functions of feeder protection relays, along with their corresponding ANSI codes.

The working principle of the Transformer Differential Protection Relay is based on Kirchhoff's Current Law. This law states that the sum of currents entering a node is zero. Ideally, for a healthy (non-faulted) transformer, the current entering the primary winding should equal the current leaving the secondary winding (after accounting for the transformer's turns ratio and phase shift).

Capacitor Unbalance Voltage Protection is used to monitor the voltage distribution among individual units within a capacitor bank, particularly in series-connected banks. Its operating principle is based on Kirchhoff's Voltage Law and capacitor voltage division. Under normal operating conditions, the voltage across each unit in the bank is relatively balanced, resulting in a minimal unbalance voltage. When a capacitor unit fails (e.g., internal short circuit, open circuit, or performance degradation), the voltage distribution becomes unequal, generating a significant unbalance voltage.