Testing a New Direct Load Control Power Line Communication System

South Carolina Electric and Gas is currently performing direct load control communications over power lines without using a power line carrier. This is the result of testing a load management system that combines the existing substation solid-state recording with voltage regulation capability. Using the solid-state recorder´s extended control functions, the existing substation tap changer, a new patent-pending power line communications technique, and a patented voltage-step load control receiver, the system extends normal two-way communication between the utility operations and the substation with a one-way power line link to virtually any load. By varying the voltage level slightly, the system digitizes up to 32 different load control messages. The new voltage-step communication technique uses the substation´s load tap changer to communicate one-way with the receivers over existing power lines. South Carolina Electric and Gas and the manufacturer have been performing a two-phase test of the load control system. Phase one testing showed that the percentage of successful load control message reception was 98%. Phase two testing is still in progress. Results to date show no deterioration of reception or equipment. Conclusions thus far are that the load management system is compatible with all installed utility equipment, and offers reliable direct load control.