Earth fault tests at Oy Herrfors nät-Verkko Ab

Earth faults are one of the most common fault types in electricity distribution networks. For this reason, verifying the correct operation of protection relays by performing earth fault tests is often desired. In these tests, various earth faults are intentionally created on the primary side of the distribution network.

Our customer Herrfors Nät-Verkko Oy Ab organized earth fault tests at their new substation in Oravainen, where the tests were carried out by Mr. Mikael Forsblom from Multirel Oy. The tests consisted of several permanent and transient intermittent earth faults with different earth fault current compensation degrees and fault resistances. Arcteq’s AQ-F255 protection relays used in the Oravainen substation proved to be very reliable, and they worked exactly as they should with all fault types. The relays even protected against the challenging transient intermittent earth faults, thanks to Arcteq’s patented transient intermittent earth fault function.

Mr. Carl-Johan Nylund, 110kV Grid Engineer for Herrfors Nät, commented on the tests: “I am very pleased with the results, everything worked exactly as planned.”

During the earth fault tests, five overhead lines were used, and the earth fault current level was approximately 67.6 A.