Confusing question on NETA 2 practice test

[IncredibleGreg]

Hey all,

I was taking the NETA 2 practice test when I encountered a question with what appeared to have two right answers. The question simply said "47" in reference to the IEEE device number, and the four answers were:

Distance relay
Directional relay
Phase balance relay
Phase sequence relay
Power factor relay

The correct answer, according to the IEEE device list I had printed off and sitting right next to me, is both phase balance and phase sequence. This was confirmed by the test itself a few questions later, with the question "Which of the following is the ANSI/IEEE device number for a phase-sequence or phase-balance relay?"

I got the first question wrong by answering phase sequence (I think) but I got the second question right by answering "47." So my question is, was the first question somehow only one of the two options and I just guessed incorrectly? I'm not sure how that's possible but I wanted to be sure. Here is the device number list I was using as a reference. Is it, and the second question, wrong? http://www.ece.uidaho.edu/ee/power/ECE525/Lectures/L3/L3.pdf

[Wanderer20001us]

Hey all,

I was taking the NETA 2 practice test when I encountered a question with what appeared to have two right answers. The question simply said "47" in reference to the IEEE device number, and the four answers were:

Distance relay
Directional relay
Phase balance relay
Phase sequence relay
Power factor relay

The correct answer, according to the IEEE device list I had printed off and sitting right next to me, is both phase balance and phase sequence. This was confirmed by the test itself a few questions later, with the question "Which of the following is the ANSI/IEEE device number for a phase-sequence or phase-balance relay?"

I got the first question wrong by answering phase sequence (I think) but I got the second question right by answering "47." So my question is, was the first question somehow only one of the two options and I just guessed incorrectly? I'm not sure how that's possible but I wanted to be sure. Here is the device number list I was using as a reference. Is it, and the second question, wrong? http://www.ece.uidaho.edu/ee/power/ECE525/Lectures/L3/L3.pdf


ANSI 47 - Negative sequence over-voltage protection against phase unbalance resulting from phase inversion, unbalanced supply or distant fault, detected by the measurement of negative sequence voltage. Or, Protection against phase unbalance resulting from phase inversion, unbalanced supply or distant fault, detected by the measurement of negative sequence voltage

This relay operates on the negative sequence voltage caused by voltage imbalance, reverse rotation, or combinations due to faults. In my experience, phase sequence is more common than phase balance as a descriptor as it measures/operates on negative sequence voltage caused by imbalance.

I would have answered Phase Sequence Relay.