Medium-voltage indicators (2-43 kV) keep workers away from voltage and lets them know if there’s voltage or not. The indicator is a single-phase device mounted onto each phase of a power bus. Energy from the bus flows through the indicator circuit through a capacitive ground connection. This means when higher voltages exist, the air becomes slightly conductive, allowing current to flow “through the air,” which completes the flashing LED circuit. As the voltage increases, more current flows, thereby increasing the flash rate. The indicator is not hard wired to a ground connection, which eliminates a potential point of failure. The enclosure size and the distance between the adjoining phases will also affect the flash rate. Medium- or high-voltage equipment applicable for this indicator include motor starters, metal clad switchgear, open bus work, medium-voltage drives, isolation switches, substation switches, transfer switches, and high-resistance ground switches.
Grace Engineered Products, 5001 Tremont Ave., Davenport, IA 52807; 800-280-9517; 563-386-9639 (fax); email@example.com; www.graceport.com
Grace Engineered Products: Medium-Voltage Indicators
November 22, 2010