The PGR-3100 indicates the presence of voltage on each
phase of a three-phase system. The LEDs on the panel
illuminate when voltage is present. When a ground-fault
occurs, the voltage on the faulted phase reduces to ground
potential, causing the LEDs for the faulted phase to dim.
On a resistance grounded or ungrounded system the LEDs for the unfaulted phases become brighter.
Ungrounded ac systems are required by the National
Electrical Code (NEC®) Article 250.21(B) and the Canadian
Electrical Code Part 1, Section 10-106 (2) to have ground
detectors, such as the PGR-3100, installed on the system.
External potential transformers (PTs) can be used to step
down system voltage, allowing the PGR-3100 to be applied to
any system voltage. PTs are not required for system voltages
up to 600 Vac.