The decision was taken following a successful collaboration at its Sonkajärvi substation, where ABB’s UniGear ZS1 medium-voltage switchgear equipped with REX640 protection relays have been installed.
Safety and reliability are never compromised in Savon Voima Verkko’s operations. The distribution system operator supplies electricity to 117,000 customers in Eastern Finland and is known for its pioneering attitude to the development of the power distribution grid.
Its mixed network consists of underground cabling in built-up areas and long-distance overhead lines and is one of Finland’s most extensively automated. State-of-the-art primary substations, smart secondary substations and the application of the Zone concept ensure that power distribution functions well, even in harsh conditions.
Maintaining the power distribution grid and responding to rapidly changing requirements requires continuous investment, which also improves the reliability and quality of power distribution for consumers.
Savon Voima renews at least one of its forty substations each year. The brand-new substation in Sonkajärvi was completed in the spring of 2020, replacing a 45/20 kilovolt substation, which had reached the end of life. Currently installations are underway in the new replacement substation in Leppävirta and will be completed before the end of 2020
The latest protective technology
The state-of-the-art new substation in Sonkajärvi is based on ABB’s latest REX640 protection and control relays and offers reactive power compensation and earthing protection, presented by the increasing amount of underground cabling. The station also takes account of changes to the network such as the increasing amount of decentralized electricity generation.
The substation is the first in Finland to be protected by relays from this series. The REX640 relays comply with the IEC 61850 standard and protect the substation’s six cable outputs, two 45 kilovolt fields and three other cells. The solution is based on IEC 61850 in a number of respects such as the trippings and interlockings using GOOSE messages, allowing better monitoring of the functionality of the entire substation.
The quantity of equipment has been optimized through the combination of functionality such as compensation control and wire output backup protections with the same protection relays. Arc protection is also implemented as an integrated system for REX640 relays.
“I was interested in REX640 relays because we’ve previously used ABB’s 630 series protection relays of the Relion® family and we were pleased with them. The latest technology was attractive to us because it includes the best solutions and meets the latest requirements. The REX640 is really interesting due to the ability to extend the use of the protection relay by adding application modules. Updating the relay with new security functions is also easy,” says Savon Voima Verkko’s Matti Pirskanen, the substation electrician in charge of the protective system.
“Backing up between the display and the relay is a great feature that provides additional security. The relay functionality also enables numerous simulations, which speeds up and facilitates commissioning and seasonal testing,” he continues.
“This is an interesting and evolving industry. You’re always learning new things. I’m happy to work with ABB’s experts,” says Matti Pirskanen, who is responsible for safety solutions at Savon Voima Verkko’s substations. 
Development in earth-fault protection
Pirskanen was impressed with the ability of the REX640 relays to precisely locate short-circuit failures and selective earth-fault protection based on multi-frequency admittance calculations. This selective earth-fault protection prevents “sympathy” trippings. “The protection is based on solid research. Earth-fault tests have been carried out on our networks and in many other Finnish electricity companies,” Pirskanen says of the award-winning protection functionality.
The Savon Voima expert, who follows the advances in protection technology, expects to see continuous development in earth-fault protection, and especially in locating earth-faults. He believes that soon ABB’s relays, which are being developed by its leading experts, will have new and interesting features.
Protection configurations tailored to Savon Voima Verkko’s requirements were standardized in the implementation and testing of the Sonkajärvi substation by ABB’s Digital Solutions Center team. Specializing in safety and automation solutions, the team ensures that customers always have access to the latest expertise and the best features of the solution they choose. The solution that is now standardized will be easy to adapt both in Leppävirta and in future substations undergoing renewal.
