This award-winning earth-fault detection and protection method is uniquely reliable and has undergone multiple field tests in real networks. It is now replacing the traditional earth-fault protection methods when older technology is modernized and brought up-to-date.
The novel protection function, based on multifrequency admittance (MFA) calculations, is the go-to solution when increasing amounts of underground cabling and variations of load currents cause challenges for conventional earth-fault protection methods. Traditional current-based earth-fault protection methods are not meeting existing requirements determined by the various types of earth faults occurring in distribution networks these days.
The MFA protection function reliably detects and locates both the high-ohmic faults in sections of networks with overhead lines and intermittent earth faults in the compensated underground cable networks. It identifies all types of earth-faults accurately, making MFA a one of a kind, all-in-one, protection function.
“Additionally, the MFA protection method is very easy to use,” states Ari Wahlroos, ABB’s leading protection specialist. “You can imagine multi-functional protection like this usually demands a lot of set-up work with several parameters, but here you need only a few basic parameters.”
Behind the novel protection function is an ingenious, patented algorithm, which has resulted from years of intensive research and practical experience gained from investigating the most demanding fault cases.
The reliability of the MFA protection method has been verified with thousands of recorded fault disturbances in several utility networks. The latest tests were performed at Seiverkot’s brand new primary substation. The substation was delivered by ABB and included a protection scheme built around the REF630 protection relays from ABB’s Relion® family. Seiverkot Oy serves about 25,000 households in Seinäjoki, Western Finland.
“The sensitivity and selectivity of the MFA protection method is excellent in all possible earth-fault situations,” says Reijo Kankaanpää, Commissioning Engineer at Seiverkot. “Traditional earth-fault protection methods meant that not all types of earth-faults could be detected, and it was possible that the whole substation was erroneously disconnected. This novel protection method with a simple, logical function can separate healthy from damaged feeders. It helps to limit the problem area and to keep power availability to consumers at a higher level. The MFA protection method allows continued reliability in the supply of electricity.”