The Type STV relay is a single-phase static overexcitation relay. It consists of an overexcitation sensing unit which has a linear volts per hertz pickup characteristic, and a timing unit to provide a definite time before initiating some protective action. A target seal-in unit is also provided to protect the timing unit contacts during tripping duty. The Type STV relay is designed specifically for equipment protection in case of overexcitation. Overexcitation of a generator or power transformer may occur during start-up, shutdown, or as result of remote load rejection. As as result, overheating due to core saturation within a very short time may cause severe damage. This relay, employing a constant volts per hertz pickup, recognizes overexcitation and initiates some appropriate action to protect the equipment.
