cbrazzil
May 21, 2019, 08:37 PM
This exam was harder than the previous one. It asked more practical field questions than straight and direct questions.
Multiply: magnitude 15 at 30 degrees and magnitude 20 at 60 degrees.
Why is a ground grid extended beyond the main system?
By bonding the wire and the moving equipment together, the individual on the equipment is not exposed and can’t get hurt. At the foot of the equipment install an equipotential mat so there is no step potential or touch potential for the individual standing next to, or climbing onto, the equipment.
A 4-20mA single has a max range of 150 amp what is the amps at 14mA?
1.) What is the theoretical maximum symmetrical fault current that would be available at the secondary terminals of a 3Ø, 12,470-480Y/277V, 1,000kVA, 6.25% impedance transformer?
2.) A current transformer with a current ratio of 60:1 is used with a current of 150 amperes. If an instrument with a total impedance of 4 ohms is connected to the secondary of the transformer, the secondary voltage is?
3.) In a 120V, 10A, AC circuit, the for 8 hours and 30 minutes at 30% lagging. What was the total power consumed?
4.) If a phasor B = 6 – j2 is subtracted from phasor A = -4 + j3, what is the resulting phasor C?
Given 750KVA with a PF of .75 but want a PF of .95 what is your needed KVAR?
You must solve for W first because your VA will change with your amperage when adding kvar
First Ø=41.4
Next
W= 562.5KW
Now with a PF of .95 what is your KVAR needed?
Power triangle – find Ø = 18.2
Next VAR = 185 KVAR
Chooses where 200 250 300 450
I used the following article to help solve the above.This was one of the harder problems to solve. https://www.eaton.com/ecm/groups/public/@pub/@electrical/documents/content/sa02607001e.pdf
5.) Convert Peak to RMS Voltage: 500V
6.) What is the primary full load current of a 13,800 – 480Y/277V, 1,500kVA padmount transformer with a nameplate impedance of 5.75%?
7.) What is the Resistance from A to B?
359
8.) Liquid-filled transformer bushing capacitance values that vary from nameplate by more than ____ percent should be investigated per NETA acceptance testing standards.
9.) A wye-delta transformer has a secondary phase voltage of 480 V. A delta-connected resistive load has a resistance of 12 ohms in each leg. What is the current in each load leg? (KNOW ALL SENARIOS )
10.) There were 2 different questions with pictures of a OLTC and 4.16KV reduced voltage starter
11.) A given 300:5 CT with 75A measured primary current is connected to a meter with a 4 ohm burden, which voltage would you expect to measure
12.) 1000kva 34.5kv to 480v secondary transformer 5% imp. Apply 480v to primary side and ground secondary. What is primary fault current?
13.) During the performance of an excitation current test on a power transformer, you notice that two of the currents are higher than the third reading. Why?
14.) Voltage dips are not caused by which of the following:
Don't remember the options
15.) What is the minimum size service grounded conductor for protective grounds
16.) Know how to test relays – 21, 47 had 2 questions over them
17.) Reverse power relays operate under what conditions?
18.) Three capacitors, a 12 µF, a 20 µF, and a 30 µF, are connected in series to a 400 Hz source. The total XC is
19.) 1 diagram pic of schematic and what operates first
20.) Stupid double bus double breaker diagrams
21.) For DLRO, which is acceptable results? Three capacitors, a 12 µF, a 20 µF, and a 30 µF, are connected in series to a 400 Hz source. The total XC is
22.) what is the temperature difference that would show a possible deficiency and warrant an investigation?
23.) Temperature corrected winding-resistance values should compare within _______ of
a. previously obtained results.
24.) For microprocessor to laptops, which are the most common problem
25.) At what voltage is it safe to wear cotton clothing?
a. It was worded different
26.) Know limit and restrictive approach boundary’s
27.) Know min save work distance from equipment
28.) Ups has something wrong with or loses power it opens ac incoming power supply breaker. Undervoltage protection for a UPS should:
29.) If the current flowing in an operating circuit must be approximately measured without interrupting the current, which of the following through type current transformers would you recommend?
30.) . If a = (5, -12), what is the magnitude and direction of a?
31.) What ppe equipment is needed around batteries
32.) Know breaker tripping timing and amp rating
An ATS does not transfer from utility to generator. The generator is running and producing voltage. Which of the following is the cause of it not transferring? What device uses controls for transients for capacitor switching?
33.) R rated fuses are used for:
34.) . 4/0 grounded cable is rated at 43kA for 15cycles. What is the minimum number of cables per phase required to safely ground a 2500kVA 5.75%Z transformer on the 480V side
Isc=52297.75 next if a single 4/0 cable can handle 43 but the Isc is 52ka you need one more cable to handle the KA rating
35.) . A utility defines their horizontal bus at the customer point as ABC left to right facing the customer with ABC rotation. The customer defines their buses as ABC left to right facing the utility but with CBA rotation. For a first-time connection the customer has to:
36.) Which statement is correct about I2T on/off settings? (Test asked me a in a different way)
37.) Which oil test do you perform on HV oil switch?
38.) Winding results on a motor indicate possible degradation when the output waveforms show:
39.) What would cause a phase reversal trip on a generator
a. feeder fault
b. generator failure
c. loss of power
40.) A CT supplies multiple devices. To confirm which devices are connected to it, the output of a single phase 5A source is connected to the X1 terminal of the CT without removing the existing wiring. The expected current at each correctly connected device would be:
41.) Which of the following statements is true pertaining to network protectors?
42.) If a synchronize motor is lagging to much how do you correct it?
a. Increase the field????
43.) which oil tests do you perform on HV oil switch?
44.) in a zone interlocked low voltage circuit breaker scheme and the trip unit in the breaker responsible for clearing is inoperative, then
45.) Coil A is rated for 24vdc, 500mA, and has a resistance of 48Ω. R1 is sized to limit the current in the coil to 500mA. If the supply voltage is 125vdc, what is the power dissipated in R1?
A) 12.0 W
B) 24.0 W
C) 50.5 W
D) 77.5 W
46.) If you have a 750 kva incoming power with a PF of .75, what additional KVAR is needed to achieve PF at .95?
47.) According to the NFPA 70, what is the max allowable time delay results for a ground fault relay to operate?
48.) What is an effect of neutral to ground connection on the load side of the neutral sensor in a 480Y/277V solidly grounded system?
A) Test feature on the ground-fault relay would not function
B) Ground fault may not be detected by the ground fault relay
C) Ground fault relay will trip at half of its pick-up setting
D) Current will only flow through the closed neutral to ground loop
49.) What does the flag indicate on a pistol grip type circuit breaker control device?
50.) If [cos] increases what other conditions must be present?
51.) : During a phasing test across a generator tie breaker cell where both sources have the same rotation, the voltage measure across any one phase (A-bus to A-gen) increases as the phase angle:
A) Increases between 0 and 90 degrees
B) Increases between 180 and 270 degrees
C) Decreases between 180 and 90 degrees
D) Decreases between 90 and 0 degrees
52.) How is lagging power factor improved using a synchronous motor?
53.) Know what should be printed on a name plate, bus duct, breaker, switchgear
54.) What test is performed on a surge arrestor
a. Watts-loss
b. Power-factor
c. Don’t remember them all
55.) What avg temp is the liquid level gauge set to?
56.) What of the following is damaging to insulating materials used in high voltage rotating machines?
a. Hysteresis
b. Corona
c. Eddy currents
57.) When measuring the ground resistance of an industrial grounding network, the ground resistance would normally be expected to be no greater than?
a. .01 ohms
b. .5
c. 5
d. 10
58.) When you are performing a PI test on a transformer and the test ends at 8 min what is the correct action?
a. I picked, discharge the xfmr for 4 time the applied time and retest
b. Restart the test
c. That the reading at 8min/1min
d. ?
59.) XFMR 2 highs and a low ?
60.) What class meter should be used in an industrial environment to measure voltage?
a. CAT I AND II
b. CAT II AND III
c. CAT 1 AND IV
61.) What does a Buchholz relay do?
a. Measurement of gas
b. Don’t remember the rest
62.) In a 750KVAR cap bank, 13.8kv 60hz, what is the calculated Xc?
a. Various options
b. 750kvar?
63.) What is a newer SCADA system that doesn’t require cables?
a. HMI
b. RS485
c. Goose
d. ?
64.) Something about a scada and older scada system(ocb, scb, cob,sob), don’t remember the wording
*I will upload all the diagram questions on a later date but know the following:
Gate logic mapping/sequening
Voltage drops at different points in a resistor circuit being in parallel series parallel.
In a AC 120V 60HZ circuit with a RLC in series calculate the power factor given Xc-3 XL=7 and R=4
Differential circuits-Given a XFMR- 138KV 2500KVA 5% primary unknown CT ratios, with secondary CTs at 2000:5 drawing 35 amps to ground. Which ratio is the most accurate and closes to the secondary current?
Multiply: magnitude 15 at 30 degrees and magnitude 20 at 60 degrees.
Why is a ground grid extended beyond the main system?
By bonding the wire and the moving equipment together, the individual on the equipment is not exposed and can’t get hurt. At the foot of the equipment install an equipotential mat so there is no step potential or touch potential for the individual standing next to, or climbing onto, the equipment.
A 4-20mA single has a max range of 150 amp what is the amps at 14mA?
1.) What is the theoretical maximum symmetrical fault current that would be available at the secondary terminals of a 3Ø, 12,470-480Y/277V, 1,000kVA, 6.25% impedance transformer?
2.) A current transformer with a current ratio of 60:1 is used with a current of 150 amperes. If an instrument with a total impedance of 4 ohms is connected to the secondary of the transformer, the secondary voltage is?
3.) In a 120V, 10A, AC circuit, the for 8 hours and 30 minutes at 30% lagging. What was the total power consumed?
4.) If a phasor B = 6 – j2 is subtracted from phasor A = -4 + j3, what is the resulting phasor C?
Given 750KVA with a PF of .75 but want a PF of .95 what is your needed KVAR?
You must solve for W first because your VA will change with your amperage when adding kvar
First Ø=41.4
Next
W= 562.5KW
Now with a PF of .95 what is your KVAR needed?
Power triangle – find Ø = 18.2
Next VAR = 185 KVAR
Chooses where 200 250 300 450
I used the following article to help solve the above.This was one of the harder problems to solve. https://www.eaton.com/ecm/groups/public/@pub/@electrical/documents/content/sa02607001e.pdf
5.) Convert Peak to RMS Voltage: 500V
6.) What is the primary full load current of a 13,800 – 480Y/277V, 1,500kVA padmount transformer with a nameplate impedance of 5.75%?
7.) What is the Resistance from A to B?
359
8.) Liquid-filled transformer bushing capacitance values that vary from nameplate by more than ____ percent should be investigated per NETA acceptance testing standards.
9.) A wye-delta transformer has a secondary phase voltage of 480 V. A delta-connected resistive load has a resistance of 12 ohms in each leg. What is the current in each load leg? (KNOW ALL SENARIOS )
10.) There were 2 different questions with pictures of a OLTC and 4.16KV reduced voltage starter
11.) A given 300:5 CT with 75A measured primary current is connected to a meter with a 4 ohm burden, which voltage would you expect to measure
12.) 1000kva 34.5kv to 480v secondary transformer 5% imp. Apply 480v to primary side and ground secondary. What is primary fault current?
13.) During the performance of an excitation current test on a power transformer, you notice that two of the currents are higher than the third reading. Why?
14.) Voltage dips are not caused by which of the following:
Don't remember the options
15.) What is the minimum size service grounded conductor for protective grounds
16.) Know how to test relays – 21, 47 had 2 questions over them
17.) Reverse power relays operate under what conditions?
18.) Three capacitors, a 12 µF, a 20 µF, and a 30 µF, are connected in series to a 400 Hz source. The total XC is
19.) 1 diagram pic of schematic and what operates first
20.) Stupid double bus double breaker diagrams
21.) For DLRO, which is acceptable results? Three capacitors, a 12 µF, a 20 µF, and a 30 µF, are connected in series to a 400 Hz source. The total XC is
22.) what is the temperature difference that would show a possible deficiency and warrant an investigation?
23.) Temperature corrected winding-resistance values should compare within _______ of
a. previously obtained results.
24.) For microprocessor to laptops, which are the most common problem
25.) At what voltage is it safe to wear cotton clothing?
a. It was worded different
26.) Know limit and restrictive approach boundary’s
27.) Know min save work distance from equipment
28.) Ups has something wrong with or loses power it opens ac incoming power supply breaker. Undervoltage protection for a UPS should:
29.) If the current flowing in an operating circuit must be approximately measured without interrupting the current, which of the following through type current transformers would you recommend?
30.) . If a = (5, -12), what is the magnitude and direction of a?
31.) What ppe equipment is needed around batteries
32.) Know breaker tripping timing and amp rating
An ATS does not transfer from utility to generator. The generator is running and producing voltage. Which of the following is the cause of it not transferring? What device uses controls for transients for capacitor switching?
33.) R rated fuses are used for:
34.) . 4/0 grounded cable is rated at 43kA for 15cycles. What is the minimum number of cables per phase required to safely ground a 2500kVA 5.75%Z transformer on the 480V side
Isc=52297.75 next if a single 4/0 cable can handle 43 but the Isc is 52ka you need one more cable to handle the KA rating
35.) . A utility defines their horizontal bus at the customer point as ABC left to right facing the customer with ABC rotation. The customer defines their buses as ABC left to right facing the utility but with CBA rotation. For a first-time connection the customer has to:
36.) Which statement is correct about I2T on/off settings? (Test asked me a in a different way)
37.) Which oil test do you perform on HV oil switch?
38.) Winding results on a motor indicate possible degradation when the output waveforms show:
39.) What would cause a phase reversal trip on a generator
a. feeder fault
b. generator failure
c. loss of power
40.) A CT supplies multiple devices. To confirm which devices are connected to it, the output of a single phase 5A source is connected to the X1 terminal of the CT without removing the existing wiring. The expected current at each correctly connected device would be:
41.) Which of the following statements is true pertaining to network protectors?
42.) If a synchronize motor is lagging to much how do you correct it?
a. Increase the field????
43.) which oil tests do you perform on HV oil switch?
44.) in a zone interlocked low voltage circuit breaker scheme and the trip unit in the breaker responsible for clearing is inoperative, then
45.) Coil A is rated for 24vdc, 500mA, and has a resistance of 48Ω. R1 is sized to limit the current in the coil to 500mA. If the supply voltage is 125vdc, what is the power dissipated in R1?
A) 12.0 W
B) 24.0 W
C) 50.5 W
D) 77.5 W
46.) If you have a 750 kva incoming power with a PF of .75, what additional KVAR is needed to achieve PF at .95?
47.) According to the NFPA 70, what is the max allowable time delay results for a ground fault relay to operate?
48.) What is an effect of neutral to ground connection on the load side of the neutral sensor in a 480Y/277V solidly grounded system?
A) Test feature on the ground-fault relay would not function
B) Ground fault may not be detected by the ground fault relay
C) Ground fault relay will trip at half of its pick-up setting
D) Current will only flow through the closed neutral to ground loop
49.) What does the flag indicate on a pistol grip type circuit breaker control device?
50.) If [cos] increases what other conditions must be present?
51.) : During a phasing test across a generator tie breaker cell where both sources have the same rotation, the voltage measure across any one phase (A-bus to A-gen) increases as the phase angle:
A) Increases between 0 and 90 degrees
B) Increases between 180 and 270 degrees
C) Decreases between 180 and 90 degrees
D) Decreases between 90 and 0 degrees
52.) How is lagging power factor improved using a synchronous motor?
53.) Know what should be printed on a name plate, bus duct, breaker, switchgear
54.) What test is performed on a surge arrestor
a. Watts-loss
b. Power-factor
c. Don’t remember them all
55.) What avg temp is the liquid level gauge set to?
56.) What of the following is damaging to insulating materials used in high voltage rotating machines?
a. Hysteresis
b. Corona
c. Eddy currents
57.) When measuring the ground resistance of an industrial grounding network, the ground resistance would normally be expected to be no greater than?
a. .01 ohms
b. .5
c. 5
d. 10
58.) When you are performing a PI test on a transformer and the test ends at 8 min what is the correct action?
a. I picked, discharge the xfmr for 4 time the applied time and retest
b. Restart the test
c. That the reading at 8min/1min
d. ?
59.) XFMR 2 highs and a low ?
60.) What class meter should be used in an industrial environment to measure voltage?
a. CAT I AND II
b. CAT II AND III
c. CAT 1 AND IV
61.) What does a Buchholz relay do?
a. Measurement of gas
b. Don’t remember the rest
62.) In a 750KVAR cap bank, 13.8kv 60hz, what is the calculated Xc?
a. Various options
b. 750kvar?
63.) What is a newer SCADA system that doesn’t require cables?
a. HMI
b. RS485
c. Goose
d. ?
64.) Something about a scada and older scada system(ocb, scb, cob,sob), don’t remember the wording
*I will upload all the diagram questions on a later date but know the following:
Gate logic mapping/sequening
Voltage drops at different points in a resistor circuit being in parallel series parallel.
In a AC 120V 60HZ circuit with a RLC in series calculate the power factor given Xc-3 XL=7 and R=4
Differential circuits-Given a XFMR- 138KV 2500KVA 5% primary unknown CT ratios, with secondary CTs at 2000:5 drawing 35 amps to ground. Which ratio is the most accurate and closes to the secondary current?