Current Transformer Protection Units
Metrosil Current Transformer Protection Units (CTPU) are used to prevent dangerous voltages being developed on the secondary side of a current transformer if it is accidentally open circuited. CTPUs also provide excellent protection against over voltage in the secondary circuit by high frequency switching surges in the primary, even when the correct secondary burden is connected.
At normal operating voltages (with the CT burden connected) the CTPU will pass insufficient current to affect the accuracy of the measuring equipment. If the burden is disconnected then the whole of the CT secondary current passes through the CTPU, which limits the voltage to a safe level.