Protective Relay Setting Calculator

Calculate overcurrent relay pickup, time dial, and coordination settings for 50/51 protection schemes.

Current transformer ratio. e.g., 200/5 = 40.
Maximum continuous load current.
A
Maximum available short-circuit current.
A
Time dial setting. Higher = slower. Typical: 1-5.
Relay pickup as multiple of CT secondary. Typical: 1.25-1.5x FLC.

Results

Pickup Current (Secondary)-A
Pickup Current (Primary)-A
Fault Current Multiple of Pickup-x
Trip Time at Max Fault-seconds
Instantaneous Setting (50)-A pri
References: IEEE C37.112 — Inverse-Time Relays; NEC Article 240