Important G59/3.1 updates to MainsPro and InteliPro

July 31st, 2017

G59/3.1 updates require that RoCoF protection is now set to 1.0Hz/s with a measurement period of 3 cycles and a time delay of 500ms.

This update prohibits the previous practice of setting the time delay in cycles. The ComAp MainsPro and InteliPro used these cycles to determine time delay.

The time delay should now begin when the measured rate exceeds the threshold expressed in Hz/s. The relay should not trip unless the measured rate remains above the threshold expressed in Hz/s continuously for 500ms. However, should the Hz/s drop below the trip threshold during the 500ms, the relay will automatically reset.

We can confirm that all ComAp MainsPro and InteliPro new relays supplied from ComAp and older relays (once upgraded with new software) are fully compliant to G59/3-1. The relays have undergone substantial field-testing with DNOs.

For further information on G59/3.1 compliance or your relay, please contact our G59 product manager via email: or phone: 07767112262.