Stormy at Loch Ness

In December 2013, inclement weather caused widespread power outages around Loch Ness in Scotland. The electricity supply was affected for 22 hours, and the threat of more disruption lasted for three days. Scottish and Southern Energy restored power, but it wanted to be ready for any additional failures in the 33-kilovolt overhead supply. Generator Power, SSE’s preferred generator supplier, put two trailer-mounted Atlas Copco QAC 1250 generators in place at a primary substation on the bank of Loch Ness. Both generators were connected to a step-up transformer unit on the front of their trailer. Supplying 2 megawatts together at 11 kilovolts directly onto the network, a single high-voltage connection could provide power to more than 200 homes. Due to the wide range of loads in the network, the generators were used in Power Management System (PMS) mode. This meant the second generator would start up only when demand on the first went above 60% capacity. When demand dropped below 40%, the first generator would shut down. PMS mode reduces wear on the lead unit and avoids having the second generator only run on light loads. The generators change priority when the lead set achieves 80% of its service hours. This balances out the running hours and allows both generators to be checked and serviced equally during a job. “With the PMS mode, these Atlas Copco generators are some of the most flexible units available on the market today,” says Michael Yeadon, Service Manager at Generator Power. Written by Linas Alsenas