Question: In accordance with NETA and IEEE standards the correct maintenance test voltage (dc) for 5kV rated EPR 100% insulation level cable is?
14kV
11kV
9kV
5kV
18kV
According to Table 100.6.1, the answer is 28. perhaps i am missing something.
[Transformers]
1. A wye-delta transformer has a primary line voltage of 7200 V and a secondary voltage of 360 V. What is the turns ratio?
Your Answer: 20:1
Correct Answer: 11.55:1
Help: [What is the turns ratio?]
A 4160V circuit is equipped with 200/5 CTs, at full scale what should the panel ammeter read if the circuit was operating with a power factor of 0.8%?
Should the question provide primary side amps so I can convert to Panel readings using CT ratio?
7200/360 = 20
20/1.732 = 11.55 Turns ratio
Convert the vector (â1.0, 1.0) into magnitude/angle form.
Answers have -45, 0, 2, 45, and 135 degrees as potentials. -1,1 is in the third quadrant, meaning the angles should be between 180 and 270 degrees (in this case 215), vice the I believe 135 degree which is marked as the correct answer.
- Which of the following acceptance tests is optional for a 13200-480Y/277V 2500kVA dry-type transformer?
Your Answer: Power-factor or dissipation-factor tests on all windings
Help: NETA ATS-2021 7.2.1.2.B
Per NETA ATS-2025 7.2.1.2.B.3 Power-factor or dissipation factor tests on all windings is optional.
3 Likes
11. Pressurizing a liquid-filled transformer tank with N2 will prevent the entrance of water.
Your Answer: True
Correct Answer: False
IEEE Std C57.140 (2006) guide for evaluation and reconditioning of liquidâimmersed power transformers:
âPositive nitrogen pressure (along with a good gasket) keeps oxygen and moisture out.â
1 Like
- Which IEEE trip curve would produce the shortest trip time given the relay information below?
Relay Pickup Current (A): 1000
Relay TD Setting: 1
Fault Current (A): 10000
Your Answer: IEEE Moderately Inverse
Correct Answer: IEEE Extremely Inverse
Help: Inverse Time Overcurrent Relays and Curves Explained
As shown in the link in the Help section, IEEE Extremely Inverse has the slowest trip time. Moderately Inverse should be the correct answer.
Testing motor circuits would best be achieved by use of Ohmmeter
Phase-angle meter
Ammeter
Megohmetter
Voltmeter
Testing in what way? These meters all have merit for different tests.
Which chapter of NFPA 70B specifically addresses personnel safety?
Your Answer: Chapter 4
Correct Answer: Chapter 5
new nfpa 70b 2023 is chapter 4 for safety
Which insulation material is known for its resistance to water treeing?
Your Answer: EPR (Ethylene Propylene Rubber)
Correct Answer: XLPE (Cross-Linked Polyethylene)
EPRâs are generally across the board are known for being water tree resistant. XLPE especially first generation was known for water treeing very quickly. Newer WTR-XLPE (Water Tree Resistant) formulations are significantly better that gen 1 XLPE.
Question: Which instrument is used to locate a 15kV underground cable fault?
Your Answer:
Thumper
Correct Answer:
Time domain reflectometer
The question is to vague for a correct answer. If the cable has a bolted fault then yes a TDR would work in this application. If the fault is arcing with say 100k ohms of resistance than a TDR would not work, then a thumper would be the correct tool. If the fault is non arcing and also high resistance than neither a thumper or TDR would work. You would need something like a digital wheatstone bridge to locate that fault.
Question: When present, how often does partial discharge occur within insulation?
Your Answer:
Constantly
Correct Answer:
Twice a cycle
In off line PD testing for example considering even at 0.1Hz PD events can happen 10âs to hundreds of times per cycle depending on the size of the defect and the applied voltage. The linked question / answer is incorrect. Inception and extinction voltage have nothing to do with the number of PD events that happen between those 2 points.
15. Harmonics will _____ the resistance of a conductor.
Your Answer: not change
Correct Answer: increase
The question should specify âeffective resistanceâ of a conductor, because resistance is a property of the conductor and doesnât change for a given temperature, but the effective resistance can increase due to the skin effect.
An electric motor is running on 120 V. The current is measured to be 2 A. How many ohms of resistance is the motor?
The resistance cannot be known from the current when running, only the locked-rotor current. The voltage divided by the current when running will give the impedance.
