GREENFIELD, Mass. (WWLP) - An issue affecting a power substation in Greenfield led to approximately 10,000 Eversource customers in Franklin County losing power for a short time Thursday night. Greenfield organization awarded MassDEP cleanup grant Eversource spokesperson Priscilla Ress told 22News the Cumberland substation in Greenfield lost power at around 11:00 P.M., leading to about 10,000 customers losing electricity. The majority of those customers- about 6,000- saw their power restored less than a minute later due to Eversource's remote switching capabilities. The remaining 4,000 customers had their power back in about an hour. "The outage was caused when the transmission line relays tripped," Ress wrote in an email to 22News. "Relays are devices that protect transmission lines and also control power flow. When the relays to the substation tripped, it shut down the flow of power. We are still investigating what caused the relays to open." The outage only affected customers in Franklin County that are served by the Cumberland substation. Local News Headlines Death investigation at Panera Bread in East Longmeadow Penguin Plunge in Westfield that supports Amelia Park Children’s Museum canceled 10,000 lost power in Franklin County due to issue at substation Suspect arrested for armed robbery at Sam’s Food Store in Sturbridge WWLP-22News, an NBC affiliate, began broadcasting in March 1953 to provide local news, network, syndicated, and local programming to western Massachusetts. Watch the 22News Digital Edition weekdays at 4 p.m. on WWLP.com.