86 Master Trip Relay

Purpose:

The 86 Master Trip Relay is a lockout relay used to trip and hold circuit breakers in the open position after a fault or abnormal condition occurs. It requires manual resetting to restore the system.


How It Works:

  1. Fault Occurs: A protection relay (e.g., 87B, 87L, 50/51) detects a fault.
  2. Trip Command: The protection relay sends a signal to the 86 Master Trip Relay.
  3. Master Trip Relay Activates: The 86 relay trips the associated circuit breakers and prevents automatic reclosing.
  4. Lockout Condition: The system remains locked out until the 86 relay is manually reset.

Where It’s Used:

The 86 Master Trip Relay is commonly used in:
Busbar Protection – To isolate all breakers connected to a faulty bus.
Transformer Protection – To trip breakers on both HV and LV sides in case of transformer faults.
Line Protection – To ensure a faulted line remains isolated until inspected.


Example Scenario – Transformer Fault:

➡️ Suppose a transformer’s Differential Relay (87T) detects an internal fault.
➡️ The 87T relay signals the 86 Master Trip Relay.
➡️ The 86 relay trips:
✅ The HV Breaker
✅ The LV Breaker
✅ The Bus Coupler (if needed)
➡️ The 86 relay locks out the system, preventing auto-reclosure until it’s manually reset.


Key Features:

✅ Ensures system safety by requiring manual inspection before re-energizing.
✅ Prevents accidental reclosing on faulted equipment.
✅ Commonly wired with Trip Circuit Supervision Relays (95/195/295) for additional safety.


Key Takeaway:

The 86 Master Trip Relay acts as a final lockout mechanism to ensure safety, isolating faulty equipment until confirmed safe to re-energize.

Exercise: Scenario: Sudden Trip Coil Failure + Fault Occurs Simultaneously. Let’s Go!!

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