POF inductive voltage transformers are of single-phase design and intended for connection between phase and ground in networks with insulated or direct-grounded neutral points..
The extremely low core flux density enables the POF to withstand continuous 100 percent rated voltage continuously, and provide either 173 percent over voltage for 1 minute (POF-550) or 190 percent for 8 hourse (POF-350 and lower). Hermetic sealing of the design is accomplished using a gas cushion above the oil to prevent free-breathing outside moisture-laden air.