Question 211Electricity & Electronics - 1st Asst/Chief

The correct answer is B) current transformer. The current transformer (CT) provides the input signal to the over current inverse time relay (OCIT), the over current instantaneous trip (OC (inst.)), and the negative phase sequence relay (NPS) in the illustrated alternator protection scheme diagram EL-0067. The CT is responsible for stepping down the high current from the alternator to a lower, safer level that can be used by the protective relays. The other options are incorrect because: A) a potential transformer is used to step down voltage, not current; C) thermal monitors and D) infrared sensors are not the primary source of input to the protective relays shown in the diagram.