How to Choose a Protection Relay Tester: 7 Things to Check
Published · 1 min read
Relay testers look alike on a data sheet. These seven checks show which one fits the relays you really test, today and in five years.
1. Channels
Most line protection needs three currents and three voltages. Transformer differential protection needs six currents, and some tests need extra voltage or binary channels. Choose for the hardest relay you will test, not the easiest.
2. Output range and power
Check the largest current each channel gives, for how long, and whether channels can be combined for more. Old electromechanical relays draw far more power than modern digital ones, so a tester that is fine for digital relays may fail on them.
3. Accuracy
A tester should be several times more accurate than the relay it checks. Read the accuracy as a percentage of reading plus a percentage of range, and ask when the unit was last calibrated and whether a calibration certificate comes with it.
4. Software
You will spend more time in the software than with the hardware. Look for ready test modules for the relay functions you use, automatic test sequences, editable report templates and an easy way to import relay settings.
5. More than relays
If the same tester can also check meters, current transformers, capacitor voltage transformers and circuit breakers, one device covers more of the work and one set of reports covers all of it.
6. Size and weight
A tester that is carried to many substations should be easy to carry. A heavy unit that stays in a lab can trade size for power.
7. Support and training
Ask where the nearest agent is, how fast software updates and calibration are done and whether training videos exist. A tester that nobody on your team can use well gives poor results however good it is.