Syncing The Signals

Minnkota, your cooperative’s wholesale power supplier, works to enhance demand response system

There was a lot of buzz in 2020 around Minnkota Power Cooperative’s ripple injection system – the set of equipment that drives the demand response/off-peak program that Nodak Electric is a part of. Two ripple injectors were replaced with new equipment, custom communication technologies were deployed and a full 17-injector system sync was performed for the first time.

Ripple injectors send tens of thousands of electronic signals throughout the entire transmission system and into the distribution system. Receivers in homes and businesses can read the signals, and when the appropriate message is sent, the receivers interrupt the power flowing to an electric heating system, water heater or other controllable load. When control is no longer needed, a signal is sent to turn the electric system back on.

All injectors need to work together and fire at the same time to ensure the signal reaches across the entire 35,000-square-mile system. The process of tuning and syncing the injectors is a combination of art and science.

“Tuning an injector is like tightening the strings of a musical instrument to make sure it vibrates at a certain frequency,” said Nick Gellerman, Minnkota’s lead engineer on the project. “Syncing all the injectors together is like coordinating an orchestra.”

Since Minnkota’s ripple injection system was built in the 1970s, the program has become one of the most successful in the country with more than 55,000 consumers participating, including 5,568 Nodak member accounts. By reducing the demand for electricity during peak usage times, Minnkota and Nodak are able to avoid purchasing costly excess power from the wholesale market, saving money for the membership.

Minnkota has installed two-way ripple monitoring devices at 50 substation sites and, over the next few years, plans to have the devices at nearly all 255 substations. Having this consistent data from the field will help ensure the system is performing reliably. Over the last five years, Minnkota has replaced 10 of the 17 injectors with new equipment. Plans are to have all injectors replaced by the end of 2024.