As shown in the alternator protection scheme...

Question 1 of 2707066636eed28f7522a1c51daf4

As shown in the alternator protection scheme diagram, what device provides the input to the overcurrent inverse time relay "OCIT", the overcurrent instantaneous trip "OC (inst.)", and the negative phase sequence relay "NPS"? Illustration EL-0067

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Question 1 of 27070

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🔍 Key Concepts

• Relationship between current transformers (CTs) and overcurrent/negative phase sequence relays • Difference between current transformers (CTs) and potential (voltage) transformers (PTs) in protection schemes • Which signals (current vs temperature vs voltage) are needed for OCIT, OC (inst.), and NPS relays to operate

💭 Think About

• Look at the diagram and trace the line feeding into the OCIT / OC (inst.) / NPS box. What symbol is shown on the line just upstream of those relays? • Ask yourself: do overcurrent and negative phase sequence relays need to sense current, voltage, or temperature in order to detect faults? • Which device in the options is normally drawn in series with the line to measure current, and which is drawn across the line to measure voltage?

✅ Before You Answer

• Verify which device in the diagram is labeled CT and where its secondary leads go • Confirm that overcurrent and negative phase sequence protection depend on measuring line current, not temperature or infrared radiation • Check that PT (potential transformer) in the figure is shown supplying the voltage-based relays (like over/under voltage), not the overcurrent relays