Voltage Study Turns Up Surprises at Black River

Growing demand for electricity coupled with rising energy prices have driven new interest in automated peak load shedding programs at many utilities. At Black River Electric Cooperative in Sumter, S.C., engineers are experimenting with voltage regulation as a way to lower coincident peak load.

“We have largely a residential, resistive load, which makes voltage regulation an attractive alternative to controlling individual appliances during peak,” said Charlie Allen, Vice President of Engineering at Black River.

Located in the center of South Carolina, Black River serves 32,000 members in parts of four counties. Despite its location, the utility is a winter peaking utility. Before the utility moved forward with voltage adjustments, it needed to verify voltages across the distribution system and make any needed infrastructure improvements to ensure minimum voltage specifications would be maintained.

During a summer coincident peak usage period, the utility used the TS2 advanced metering system to conduct a voltage study. Using Command Center software to request a coincident peak “snapshot” of its distribution system, Black River retrieved instantaneous voltage, current kW demand, and the daily peak kW demand from 90 percent of its meters. Advanced metering endpoints in the TS2 system are time synched with each other and “always on” providing simultaneous communication back to the utility. This allows the utility to request coincident data from all meters at a selected time. Black River’s residential meters are Landis+Gyr FOCUS with a direct register read that allows a wide selection of voltage data to be collected and transmitted by the AMI system.

With voltage and demand data in hand, Allen ran the numbers through a database query looking for meters showing voltage outside of the normal range. He was able to visually display the results using Partner Software’s Map Viewer software. What he found surprised him.

“We expected to find areas of critical low voltage where we’d have to make infrastructure improvements. We were surprised to find situations of high voltage,” he said. “Turns out we were having problems with the high voltage coils beginning to short circuit in some of our transformers. We were able to change those [transformers] out and before we experienced a possible damage claim or outage.”

Voltage ranges, using a 120 volt base, ran from a low of 105.25 VAC to the highest at 139.31 VAC. A few meters reported 60 VAC but turned out to be two wire services. In all, 2.4 percent of meters reported low voltage, 92.4 percent normal and 5.1 percent high voltage during this summer’s coincident peak.

“The report highlighted areas where infrastructure improvements were needed,” Allen said. “And it gave us the confidence to move ahead with our voltage regulation project.”