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:
- Fault Occurs: A protection relay (e.g., 87B, 87L, 50/51) detects a fault.
- Trip Command: The protection relay sends a signal to the 86 Master Trip Relay.
- Master Trip Relay Activates: The 86 relay trips the associated circuit breakers and prevents automatic reclosing.
- 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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