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Electrical Engineering Review for REE Pre-Board Exam April 2023 - Prof. Columbres, Lecture notes of Accounting

Polytechnic University of the Philippines (PUP)Accounting

Prof. Dexter Columbres

A review material for the electrical engineering ree pre-board exam scheduled for april 2023. It covers a wide range of topics in electrical engineering, including transmission line analysis, fault analysis, power distribution systems, motor characteristics, circuit analysis, and more. Multiple-choice questions and solutions, providing a comprehensive review of the key concepts and principles in the field of electrical engineering. The level of detail and the range of topics covered suggest that this document could be useful for university-level electrical engineering students preparing for their exams, as well as for professionals in the industry who need to stay up-to-date with the latest developments and best practices in the field.

Typology: Lecture notes

2023/2024

Uploaded on 07/26/2024

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EXCEL REVIEW CENTER ELECTRICAL ENGINEERING REE PRE BOARD EXAM APRIL 2023

1

1. Which of the following

transformer has only one

winding?

Current

Distribution

Power

Autotransformer

2. In long transmission line, at

no-load, the receiving end

voltage as compared to the

sending end voltage is

I. Higher

II. Lower

III. Remains the same

I only

III only

Either I or II

II only

3. Ds is the GMR of each sub

conductor of a four-sub

conductor bundled and d is the

bundle spacing. What is the

GMR of the equivalent single

conductor?

1.09 (Ds*d^2)^1/3

1.09 (Ds*d^2)^1/4

1.09 (Ds*d^3)^1/4

1.09 (Ds*d)^1/2

4. Which of the following type of

fault that used only the

equivalent positive impedance

of the circuit in the short-circuit

calculation?

3-phase fault

Double line to ground

Line to line

Line to ground

5. The definition of ambient

temperature is _____.

the temperature of the area

surrounding the conductor

the maximum heat the

insulation can be used within

the insulation rating of the

conductor

the temperature of the

conductor

6. Given a transfer function of T(s)

= 5/(s + 3)(s + 6), state the

nature of the response.

Critically damped

Underdamped

Undamped

Overdamped

Solution:

7. _____ is an instrument

connected across the load.

Ammeter

Ohmmeter

Wattmeter

Voltmeter

8. The Zbus of a system is Z11 =

0.1; Z12 = 0.1, Z13 = 0.1; Z22

= 0.2; Z33 = 0.30. If a three-

phase fault occurs at Bus 2,

the p.u. fault current in each

phase is ______.

5 pu

10(sqrt 3) pu

10 pu

5(sqrt 2) pu

Solution:

9. Two 110-V light bulbs, one

25W and the other 100W are

connected in series to a 110-V

source. Then which of the

following statement is correct

with regard to above sentence?

Each bulb will have a potential

difference of 55V.

None of the choices.

The current in the 100-W bulb

is less than that in the 25-W bulb.

The current in the 100-W bulb

is greater than that in the 25-W

bulb.

10. What is the allowable rating for

branch overload protection if

fuse is used for hermetic motor

compressor with a rated load

current of 25 A?

20 A

15 A

35 A

30 A

Solution:

11. This is the region where the

transistor is working as a

switch.

Saturation region

Cutoff region

Active region

Analog region

Partial preview of the text

Download Electrical Engineering Review for REE Pre-Board Exam April 2023 - Prof. Columbres and more Lecture notes Accounting in PDF only on Docsity!

1. Which of the following transformer has only one winding? Current Distribution Power Autotransformer 2. In long transmission line, at no-load, the receiving end voltage as compared to the sending end voltage is I. Higher II. Lower III. Remains the same I only III only Either I or II II only 3. Ds is the GMR of each sub conductor of a four-sub conductor bundled and d is the bundle spacing. What is the GMR of the equivalent single conductor? 1.09 (Dsd^2)^1/ 1.09 (Dsd^2)^1/ 1.09 (Dsd^3)^1/ 1.09 (Dsd)^1/ 4. Which of the following type of fault that used only the equivalent positive impedance of the circuit in the short-circuit calculation? 3 - phase fault Double line to ground Line to line Line to ground 5. The definition of ambient temperature is _____. the temperature of the area surrounding the conductor the maximum heat the insulation can be used within the insulation rating of the conductor the temperature of the conductor 6. Given a transfer function of T(s) = 5/(s + 3)(s + 6), state the nature of the response. Critically damped Underdamped Undamped Overdamped Solution: 7. _____ is an instrument connected across the load. Ammeter Ohmmeter Wattmeter Voltmeter 8. The Zbus of a system is Z11 = 0.1; Z12 = 0.1, Z13 = 0.1; Z = 0.2; Z33 = 0.30. If a three- phase fault occurs at Bus 2, the p.u. fault current in each phase is ______. 5 pu 10(sqrt 3) pu 10 pu 5(sqrt 2) pu Solution: 9. Two 110 - V light bulbs, one 25W and the other 100W are connected in series to a 110-V source. Then which of the following statement is correct with regard to above sentence? Each bulb will have a potential difference of 55V. None of the choices. The current in the 100-W bulb is less than that in the 25-W bulb. The current in the 100-W bulb is greater than that in the 25-W bulb. 10. What is the allowable rating for branch overload protection if fuse is used for hermetic motor compressor with a rated load current of 25 A? 20 A 15 A 35 A 30 A Solution: 11. This is the region where the transistor is working as a switch. Saturation region Cutoff region Active region Analog region

12. 1 Weber is the same as : 1 T/s 1 V/s 1 T m² 1 T/m 13. A 230-kV transmission line is sending 100 MW power at 230 kV and 90% power factor. The impedance is 5 + j20 ohms and its capacitive reactance is - j2500 ohms. Determine the receiving end voltage. 224.28 kV 221.72 kV 222.83 kV 226.15 kV Solution: 14. Which of the following shall be included in the calculation of the reliability standard indices of the distributor asset by the Philippine Distribution Code? Outages that occur on the secondary lines of the distribution system Planned outages where the customers have been notified at least three (3) days prior to the loss of power. Outages that occur in the transmission line Outages that occur on the primary lines of the distribution system 15. The type of AC distribution system commonly used to supply both light and power is the _____. 3 - phase wye with neutral 3 - phase delta Open Delta 3 - phase wye 16. A 4 pole, 60Hz, induction motor, has a full load slip of 5%. What is the full load rotor speed? 1750 rpm 1780 rpm 1730 rpm 1710 rpm Solution: 17. In PEC, continuous load shall not be greater than _____ of the branch circuit rating. 80% 100% 75% 125% 18. Find the output response c(t) for the given transfer function C(s) = 5/s(s+5). c(t) = - 1 + e^- 5 c(t) = 1 – e^-5t c(t) = 1 + e^-5t c(t) = 5 – 10e^-5t Solution: 19. At a 34.5 kV substation, the available fault current is 10 p.u. What is the available fault MVA if the base is 50 MVA? 100 50 250 500 Solution: 20. During load shedding: System voltage is reduced. Some loads are switched off. System frequency is reduced. System power factor is changed. 21. A 3 Ω and 1.5 Ω resistors are wired in parallel and the combination is wired in series to a 4 Ω resistor and a 10-V emf device. What is the current in the 3 Ω resistor? 6.7 A

30. An RL circuit will have a time constant of: R/L L/R - R/L RL 31. Which of the following instruments is suited for high frequency measurements? Moving iron vane Oscilloscope Thermocouple Dynamometer 32. Slip rings are made of: Copper Mica Steel Bakelite 33. If the reference bus is changed in two load-flow runs with the same system data and power obtained for reference bus taken as specified P and Q in the latter run, the system losses as well as complex bus voltage will be unchanged the system losses as well as complex bus voltage will change the system losses will be unchanged but complex bus voltages will change the system losses will change but complex bus voltages remain unchanged 34. The effect of the dielectric is to: Increase the capacitance Decrease the capacitance Increase the working voltage Reduce the working voltage 35. What is the main reason that alternating current replaced direct current for general used? AC generators do not need slip rings AC minimizes magnetic fields. AC voltages conveniently transformed. A given AC current does not heat a power line as much as the same as DC current. 36. Silica gel prevents air moisture from entering the outdoor transformer tank. It is placed in: Windings Breather Core Conservator 37. A certain amount of fuel contains 15 x 10^10 BTU of energy. What is the corresponding energy in kilocalories? 3.87 x 10¹⁰ 3.78 x 10¹⁰ 3.25 x 10¹⁰ 3.52 x 10¹⁰ Solution: 38. The emf induced in a coil by the charging of current in the neighboring coils is known as _______ emf. speed series mutually Induced self-Induced 39. If the input of the prime mover of an alternator is kept constant but excitation is increased then: kW will be changed kVA will be lagging the pf of the load remains constant kVA will be leading 40. It is defined as the total number of sustained Customer power interruptions within a given period divided by the total number of Customers served within the same period. Customer Average Interruption Duration Index Customer Average Interruption Frequency System Average Interruption Frequency Index System Average Interruption Duration Index 41. These are type of materials that has 5 – 8 valence electrons. Insulators Conductors Resistors Semiconductors 42. It is the barrier potential for a silicon diode. 0.5 V

0.7 V

1 V

0.3 V

43. A lamp gives an average output of 628 lumens. What is its MSCP? 50 45 49 40 Solution: 44. A generator delivers a load through a pair of wires, each of which has a resistance of 0. ohm. If the load voltage and power are 120 V and 4.8 kW, respectively. What is the generated voltage? 124.8 V 123.5 V 126.8 V 125.5 V Solution: 45. A conductor 15 cm in length is carrying 25 Amp current is placed 30 deg. to the magnetic field, if the strength is 1 Tesla, calculate the force exerted on it. 1.187 N 2.125 N

1.875 N

2.225 N

Solution:

46. The force between two electrons in a vacuum is 1 x 10^-15 N. Approximately how far apart are the electrons? 1.4 x 10^-12 m 5.1 x 10^-12 m 4.8 x 10^-7 m 1.7 x 10^-6 m Solution: 47. Guy wire is used in the construction of distribution lines for what purpose? I. Transposition II. Interchange Both I and II Either I or II II I 48. Three impedances, Z₁ = 6 cis 20 °, Z₂ = 8 cis 40°, Z₃ = 10 are connected in wye and supplied by a 480 V three phase source. What is the equivalent delta connected impedance at phase 2? 28.66 + j9. 14.17 + j11. 22.68 – j0. 74.6 + j99. Solution: 49. Given three unbalanced line currents Ia = 0+j12 A, Ib = 5- j10A and Ic = - 10 - j5A. Find the negative sequence component of Ic in amperes. 3.12cis14.3deg 3.12cis-14.3deg 2.25cis-14.3deg 2.25cis14. Solution: 50. The turbine used for high head in hydro power plant is: Kaplan turbine Francis turbine None of the choices Pelton turbine 51. A certain galvanometer has resistance of 100 Ω and requires 1mA for full scale deflection. To make this into a voltmeter reading of 1 full scale, connect a resistance of _____. 1000 Ω in series 900 Ω in series 900 Ω in parallel 1000 Ω in parallel

Skin effect Thompson effect

62. A load of 50 A must be protected by _____ AT inverse time circuit breaker. 80 A 125 A 250 A 62.5 A Solution: 63. If the field of a dc shunt motor is opened: The motor will stop. The speed of the motor will become very high. The speed of the motor will decrease. It will continue to run at its rated speed. 64. A short transmission line with an impedance of 5+j6 ohms is supplying a balanced load at receiving end voltage of 13. kV. Under this condition, the voltage regulation is at 8%. Calculate the sending end voltage. 13.5 kV 13.8 kV 15.2 kV 14.3 kV Solution: 65. A distributor is designed from the point of view of _____. Voltage drop Voltage drop and current carrying capacity Current carrying capacity Load capacity 66. The government agency created under presidential decree 269, whose additional mandates includes preparing electric cooperatives in operating and competing under a deregulated electricity market. National Electrification Administration National Power Corporation National Electrification Commission National Grid Corporation 67. The units of the electric field are NC² C/N N/C N 68. A 15-ohm resistor is connected in parallel with a series combination of resistors of 8 and 12 ohms. If the voltage drop across the 8-ohm resistor is 48 V, what is the total current in A? 18 A 22 A 16 A 14 A Solution: 69. Modulation is used to: Allow the use of practical antennas Increase the carrier power Shorten the transmission channel Reduce the bandwidth used 70. What is the value of the resistor with color coded Green-Blue- Red-Gold? 5,600 ohm ± 5 56,000 ohm ± 10 56,000 ohm ± 5 5,600 ohm ± 10 71. Measured in Hertz, it is the number of cycles of alternating current per second. Period Wavelength Peak to peak Frequency 72. An air core toroidal coil has 120 turns. The length is 12 cm and 12 sq.cm in area. What is the current required to set up a flux of 1.2x10¯⁶ Wb? 0.786 A 0.842 A 0.796 A

0.812 A

Solution:

73. Calculate the resistance of 1 km long cable composed of 19 strands of similar copper conductors, each strand being 1.32 mm in diameter. Allow 5% increase in length for twisting of each strand in completed cable. 0.956 Ω 0.694 Ω 0.665 Ω 0.726 Ω Solution: 74. Consider a system with sequence impedance of Z₁ = j0.2577 p.u, Z₂ = j0.2085 p.u, and Z₀ = j0.14 p.u, determine the fault current at phase A for single line to ground fault at A. - j11 pu - j3 pu - j 6.4 pu - j5 pu Solution: 75. Three equal impedances Z_A = Z_B = Z_C = 4 – j7 ohm are connected in wye; fin the equivalent impedance in ohm if these impedances are connected in delta. Underscore (_) means subscript 6 – j 12 – j 4 – j 2.31 – j4. Solution: 76. Current has units of _____. Coulomb Volt Ohm Coulomb/second 77. Two wattmeter method of measuring three phase power is applied to a three-phase balanced load. Two wattmeter reads 6717 watts and 2658 watts, respectively. What is the pf of the load? 0. 0. 0. 0. Solution: 78. Centrifugal switch disconnects the auxiliary winding of the motor at about _____ percent of synchronous speed. 70 to 80 30 to 40 80 to 90 100 79. A single-phase transmission line is 30 km long, consist of two solid round conductor each of 1 cm in diameter. If the conductor spacing is 2.5 m, calculate the inductance per conductor? 35 mH 36 mH 39 mH 46 mH Solution: 80. The causes of nearly all high voltage flashovers in transmission lines are due to one of the following. Which one is the following? Lightning discharges Corona

91. Across a 230-V, 60 Hz power supply is a 15 - ohm noninductive resistor. What is the equation of the resulting current? i = 15.33 sin(377t) i = 26.56 sin(377t) i = 28.16 sin(377t) i = 21.68 sin(377t) Solution: 92. The percent impedance of a line is 6 % at 34.5 kV and 100 MVA base. What is the ohmic impedance? 0.72 Ω 2.23 Ω 1.2 Ω 3 Ω Solution: 93. A three-phase circuit, 60 Hz, 230 kV transposed transmission line is composed of two 1272 MCM, 54/ conductors per phase with horizontal configuration. The bundle spacing is 50 cm while phase spacing between the centers of the bundle is 10 m. If the GMR of the ACSR conductors is 0.0466 ft, what is the inductive reactance in ohm/km/phase of the transmission line? 0. 0. 0. 0. Solution: 94. Five resistors are connected in parallel: 5 Ω, 10 Ω, 15 Ω, 20 Ω and 25 Ω. The total resistance is: 75 Ω 2.2 Ω 25 Ω 0.46 Ω Solution: 95. Find the mutual inductance of a 6.0 H and 4.0 H inductor having a k = 0.9.

Solution:

96. Find the average current during the half cycle given the instantaneous maximum value of 20 amperes. 12.73 A 20 A 14.14 A 10 A Solution: 97. The resistance of resistor 1 is twice of resistor 2. The two are connected in series and a potential difference is maintained across the combination. What is the rate of thermal energy generation in resistor 1? Twice that in Resistor 2 Four times that in Resistor 2 Half that in Resistor 2 The same as that in Resistor 2 98. A generating plant has a minimum and maximum outputs of 50 MW and 100 MW, respectively. It generates an energy of 1,800,000 kWHR for 24 hours at average power factor of 90%. What is the load factor of the plant?

Solution:

99. Calculate the capacitance per kilometer per phase of the single-circuit, two-bundle conductor line that has horizontal spacing of 5m. The diameter of each conductor is 5 cm and spacing of 30 cm. 0.126 μF/km 0.0126 μF/km 0.00126 μF/km 0.0216 μF/km Solution: 100. A transformer has negligible resistance and a p.u. reactance of 0.1. What is its voltage regulation on full load with a leading p.f. angle of 30°? - 5% - 10% 5% 10% Solution:

Electrical Engineering Review for REE Pre-Board Exam April 2023 - Prof. Columbres, Lecture notes of Accounting

Related documents

Partial preview of the text

Download Electrical Engineering Review for REE Pre-Board Exam April 2023 - Prof. Columbres and more Lecture notes Accounting in PDF only on Docsity!

0.7 V

1 V

0.3 V

1.875 N

2.225 N

0.812 A

Understand the

SOLUTION, and/or

Memorize the ANSWER.