Overvoltage and Under Voltage Relay (59/27) Test

This article is to guide the responsible persons in conducting Overvoltage and Under Voltage Relay (59/27) Test procedure. Testing overvoltage (59) and undervoltage (27) relays ensures the protection of electrical equipment from voltage deviations beyond acceptable limits.

Test Equipment: Secondary Injection test kits; Multimeter; Digital Timer

Safety Precautions: The following Safety precautions shall be taken in consideration prior, during and after conducting the test measurements.

• Safety tagging shall be implemented.
• Isolate the Area by Safety Warning Tape.
• Keep a Safe Distance from the device being tested.
• Wear Appropriate Personal Protective Equipment(PPE) Prior to starting any testing activity.
• Implementation of Proper Grounding.

Overvoltage and Under Voltage Relay (59/27) Test.

1. Perform General Visual Inspection as per Work Instructions and check for any physical defects in the relay.
2. Check the relay’s configuration, disturbance recorder, contact resistance of all relay outputs and the operation of binary inputs and outputs on the relay’s LCD display.
3. Configure LED’s as per required functions.
4. Perform Voltage measurement test by applying the correct VT ratio to the relay and checking both the primary and secondary measurements.

5. Overvoltage.
   • 5.1 Measure and Record the relay’s Pick-up voltage for L1 to L2(Phase R), L2 to L3(Phase Y), L3 to L1(Phase B), by applying secondary voltage values as per PED’s Overvoltage Setting until such time the pick-up voltage is reached.
     
   • 5.2 Measure and Record the relay’s drop-off voltage for L1 to L2(Phase R), L2 to L3(Phase Y), L3 to L1(Phase B), by applying secondary voltage values as per PED’s Overvoltage Setting until such time the drop-off voltage is reached.
     
   • 5.3 Calculate the Reset Ratio with the formula: Reset Ratio = (V_drop-off / V_pick-up ) x100%
     
6. Undervoltage
   
   • 6.1 Measure and Record the relay’s Pick-up voltage for L1 to L2(Phase R), L2 to L3(Phase Y), L3 to L1(Phase B), by applying secondary voltage values as per PED’s Undervoltage Setting until such time the pick-up voltage is reached.
     
   • 6.2 Measure and Record the relay’s drop-off voltage for L1 to L2(Phase R), L2 to L3(Phase Y), L3 to L1(Phase B),by applying secondary voltage values as per PED’s Undervoltage Setting until such time the drop-off voltage is reached.
     
   • 6.3 Calculate the Reset Ratio with the formula:
     Reset Ratio = (V_drop-off / V_pick-up ) x100%.

It’s essential to follow manufacturer specific testing procedures outlined in the relay’s manual and adhere to any industry standards and guidelines applicable to protective relay testing. Qualified personnel with expertise in protective relaying should conduct these tests.