Schneider Electric PowerLogic™ MiCOM P821 Breaker Failure Protection Relay

Schneider Electric PowerLogic™ MiCOM P821 Breaker Failure Protection Relay is designed to provide dependable backup protection when a circuit breaker fails to clear a fault. In high-voltage and medium-voltage protection schemes, breaker failure protection plays a critical role because the fault has already been detected and the trip command has already been issued. If the breaker still does not open, the fault has to be cleared by an upstream breaker before it spreads further into the network. That is where the MiCOM P821 fits in.

The relay is built for advanced breaker failure protection and gives more flexibility than a basic breaker failure scheme. It can be used in either **single-stage breaker failure protection** or **two-stage breaker failure protection**. In a two-stage arrangement, the relay can first issue a re-trip to the same circuit breaker and, if the fault remains, send a second-stage trip to an upstream breaker. This makes it suitable for schemes where fast and selective backup tripping is important.

MiCOM P821 also adds monitoring and supervision functions that improve the overall reliability of the protection scheme. It supports residual current detection, negative sequence current detection, dead zone protection and pole discrepancy supervision, helping operators identify abnormal breaker behaviour and respond more effectively during fault conditions.

Specifications

• Manufacturer: Schneider Electric
• Product Family: PowerLogic™ MiCOM
• Model: MiCOM P821
• Relay Type: Numerical Breaker Failure Protection Relay
• Protection Application: Breaker Failure Protection
• Main Protection Function: Two-stage breaker failure protection
• Suitable Voltage Levels: HV, MV and other protection applications requiring breaker failure backup protection

Protection Functions:

• Two-stage breaker failure function (50BF)
• Residual current detection (50BFN)
• Negative sequence current detection
• Dead zone protection (DBI)
• Pole discrepancy function
• Output relay latching / lockout function
• Breaker Failure Logic:

Single-stage breaker failure protection

• Two-stage breaker failure protection with re-trip and upstream trip logic

User Interface:

• 2 x 16 back-lit alphanumeric display
• 8 LEDs including 4 programmable LEDs
• 7-button tactile keypad

Communication Ports:

• Front RS232 port
• Rear RS485 port

Communication Protocols:

• Modbus RTU
• Courier
• IEC 60870-5-103
• DNP3
• Data Rate: 300 to 38400 baud
• Reset Logic: Configurable via digital inputs

Features

• Advanced breaker failure protection for HV and MV systems.
• Supports both single-stage and two-stage breaker failure schemes.
• Can re-trip the local breaker first and then issue backup tripping to the upstream breaker if required.
• Includes residual current and negative sequence current detection for breaker failure logic.
• Dead zone protection improves coverage around the breaker and protection zone boundary.
• Pole discrepancy supervision helps detect abnormal pole operation.
• Fast reset time helps improve scheme responsiveness.
• Event handling and communication options support system monitoring and integration with protection schemes.

Applications

• Breaker failure protection in transmission substations
• Breaker failure protection in distribution substations
• High-voltage switchgear protection schemes
• Medium-voltage switchgear protection schemes
• Utility protection panels
• Industrial power system protection
• Backup tripping schemes for circuit breakers
• Protection systems requiring dead zone and pole discrepancy supervision

Schneider Electric PowerLogic™ MiCOM P821 Breaker Failure Protection Relay is a practical solution for substations and power systems where dependable breaker failure backup protection is essential for maintaining system security during fault conditions.