In this article, you will find the power system protection quiz questions and answers for electrical, and electronics engineers.
Power System Protection Quiz
The below list provides all the objective questions and answers related to electrical power systems.
Answers are available at the bottom of the article.
1. What is the pick-up value of the relay?
| A) | Setting up the relay to start |
| B) | Adjusting multipliers to accelerate relays to help reduce damage. |
| C) | Adjustment settings to compensate for the performance of the relay. |
| D) | The setting for the relay to stop working |
2. Pressure Relay is used to protect which of the following devices.
| A) | Devices that use SF6 gas as insulation medium. |
| B) | Capacitor |
| C) | Generator |
| D) | Power insulator transformer |
3. Purpose of current transformers (CT) to detect Zero-Sequence is
| A) | To prevent circuit from under voltage fault |
| B) | To prevent circuit from Phase Fault |
| C) | To ensure circuit’s Differential Protection |
| D) | To protect circuit from Earth Fault |
4. Phase Directional Overcurrent Relay (67) For Phase Faults protection, Which quantity is required as a Polarizing Quantity
| A) | Can use both voltage and current, as the case of protection. |
| B) | Use only voltage. |
| C) | Use only electrical frequencies. Use only electrical frequencies |
| D) | Use current only |
5. Faults detection principle of relays in general, In an electrical systems with good grounding Relay detects fault at
| A) | Increasing current and increasing pressure |
| B) | Increased current and increased power |
| C) | Increased current and reduced pressure |
| D) | Increased current and increased resistance |
6. According to IEC 60617 (IEC Relay Symbols) symbol of the relay as shown Means
| A) | Revers-Phase Relay |
| B) | Directional Overpower Relay |
| C) | Phase Angle Relay |
| D) | Power Factor Relay |
7. When will the Over-Voltage Relay connect to the “a” type?
| A) | The pressure drops to zero. |
| B) | The voltage is higher than the set value. |
| C) | Voltage is lower than the set value |
| D) | Pressure to the set value |
8. Number 87 relay according to ANSI Standard represents
| A) | Instantaneous Overcurrent Relay |
| B) | Differential Protective Relay |
| C) | Distance Relay |
| D) | Reverse-Phase or Phase-Balance Current Relay |
9. Earth Fault Protection of 3-phase generators that are grounded by the Ground Return method.
How many current transformers (CT) are required?
| A) | Using 2 CT |
| B) | Use 3 CT |
| C) | Use only one CT. |
| D) | Use all 4 CTs. |
10. According to IEC 60617 (IEC Relay Symbols) symbol of the relay as shown Means
| A) | Underpower Relay |
| B) | Under speed Relay |
| C) | Phase Angle Relay |
| D) | Distance Relay |
11. Voltage Relay cannot be used
| A) | to check the heat abnormalities with Bimetal |
| B) | to Check Synchronism |
| C) | as detector to protect the motor while starting the machine. |
| D) | to detect phase reversal |
12. Directional Overcurrent Relay, which amount is the Operating Quantity
| A) | voltage |
| B) | both voltage and current, as the case of protection. |
| C) | electrical frequency |
| D) | Current |
13. Very Inverse Overcurrent Relay has the following settings:
Time Multiplier Setting (TMS) = 0.3, CT Ratio = 1000/1 A by adjusting the current to 100%, if the Fault current occurs 10,000 A then Calculate tripping time.
| A) | 0.24 seconds |
| B) | 0.45 seconds |
| C) | 4.00 seconds |
| D) | 0.90 seconds |
14. Directional Power Relay (32) used in any of the following cases
| A) | Used in case you want to do Electric System Synchronization |
| B) | Used to measure the amount of power |
| C) | Used to detect overload conditions in electric motors |
| D) | Used to detect the direction of power flow. |
15. Which of the following codes and device names are all right?
| A) | 49-Frequency Relay, 50-Instantaneous Overcurrent Relay, 67-Undervoltage Relay |
| B) | 21-Distance Relay, 50-Instantaneous Overcurrent Relay, 51-Time Overcurrent Relay |
| C) | 40-Loss of Excitation Relay, 59-Overvoltage Relay, 78-Differential Relay |
| D) | 50-Time Overcurrent Relay, 51-Instantaneous Overcurrent Relay, 87-Differential Relay |
16. Over-current relays with very Inverse operation (VI) [IEC 60255] by setting TMS to 0.6 if using CT Ratio 600/5 A and adjusting the current to 100% when occurring the fault current is equal to 4,000 A.
Relay’s tripping time is
| A) | 2.382 seconds |
| B) | 2.025 seconds |
| C) | 3.375 seconds |
| D) | 1.429 seconds |
17. Number 67 relay according to ANSI Standard represents
| A) | Ground Protective Relay |
| B) | AC Directional Overcurrent Relay |
| C) | Reverse-Phase or Phase-Balance Current Relay |
| D) | AC Time Overcurrent Relay |
18. Within the structure of the relay model Microprocessor or Digital Relays that are used in modern times.
Need to have a Multiplexer (MUX) to
| A) | Use as a clock signal builder within the relay. |
| B) | Use to select and sort the signal before entering the ADC device. |
| C) | Use the noise filter before entering the ADC device. |
| D) | Use to expand the signal size before entering the ADC device. |
19. Equipment used to analyze and process signals in Digital Relays is
| A) | Analog to Digital Converter |
| B) | Memory Unit |
| C) | Microprocessor Unit |
| D) | Sample and Hold Device |
20. Which is not the difference between Instantaneous Relay and Inverse Time Relay
| A) | Instantaneous Relay has a Hinged Armature structure, but Inverse Time Relay is Induction Type. |
| B) | Instantaneous Relay has an Armature Attractive structure, but Inverse Time Relay is an Induction Disc. |
| C) | Instantaneous Relay is easier to create than Inverse Time Relay. |
| D) | Instantaneous Relay will run immediately when the Fault current flows through Coil in excess of the set value, but Inverse Time Relay will operate with varying amounts Current |
21. According to IEC 60617 (IEC Relay Symbols) symbol of relay as shown Means
| A) | Revers-Phase Relay |
| B) | Phase Angle Relay |
| C) | Directional Overcurrent Relay |
| D) | Voltage Restrained / Controlled Overcurrent Relay |
22. According to IEC 60617 (IEC Relay Symbols) symbol of relay as shown Means
| A) | Under speed Relay |
| B) | Overspeed Relay |
| C) | Phase Angle Relay |
| D) | Over frequency Relay |
23. Number 81 relay according to ANSI Standard means what kind of relay
| A) | Over Frequency Relay |
| B) | Differential Relay |
| C) | Regulating Relay |
| D) | Under Frequency Relay |
24. What are the main equipments used to protect the electrical system?
| A) | Fuse, Circuit Breaker and Relay |
| B) | Fuse, Circuit Breaker and Delay |
| C) | Fuse, Circuit Breaker and Cutout |
| D) | Circuit Breaker, Cutout and Relay |
25. Which of the following mentioned statement about Electromagnetic Relays is wrong?
| A) | Electromagnetic Induction Relay relies on electromagnetic attraction to force relay contact to change status. |
| B) | Electromechanical Relay is an old relay. That cannot save any electrical data |
| C) | Electromechanical Relay relies on gravitational force or mechanical electrical torque to operational at time of fault and testing |
| D) | Electromagnetic Attraction Relay will work immediately. (Instantaneous) without delay |
26. Overcurrent Relay, connected to circuit through the current transformer (CT) with Ratio of 1000/5 A, set to run at 125%.
If the Fault Current is 15,000 A, find the PSM value. how much
| A) | PSM = 20 |
| B) | PSM = 15 |
| C) | PSM = 12 |
| D) | PSM = 10 |
27. Which is not the Directional Overcurrent Relay working condition?
| A) | All of these answers |
| B) | When the current value is greater than the value of Pick up |
| C) | When the Power Factor angle value is higher than the set value |
| D) | When the direction of the current exceeds the limit given to the relay |
28. What is Time Multiplier Setting (TMS)?
| A) | The reserve factor for adjusting the working time of the overload relay For work safety |
| B) | Reduction factor for adjusting the working time of the overload relay. To allow the relay to run faster |
| C) | Time allowance for adjusting the working time of the overcurrent relay to work together |
| D) | Working time multiplier of overcurrent relay for determining the actual working time of a relay at a certain value of PSM |
29. Under-Voltage Relay will operate when the voltage is lower than the value set by
| A) | The relay will connect the type “a” to each other. |
| B) | The relay will connect the type “b” to each other. |
| C) | Relay will separate contact type “b” from each other. |
| D) | Relay will separate contact type “a” from each other. |
30. Which quantities Voltage Restraint Overcurrent Relay Uses?
| A) | Using both current and impedance Changed Values |
| B) | Using both current and voltage Changed Values |
| C) | Use both current and frequency Changed values |
| D) | Use both voltage and frequency Changed Values |
31. What type of relay is High Impedance Relay?
| A) | Reactance Relay |
| B) | Distance Relay (Distance Relay) |
| C) | Impedance Relay (Impedance Relay) |
| D) | Differential Relay |
32. Number 50 relay according to ANSI Standard represents
| A) | AC Time Overcurrent Relay |
| B) | Instantaneous Overcurrent Relay |
| C) | Differential Protective Relay |
| D) | Distance Relay |
33. Which of the following relay groups operational with CT only?
| A) | Relay number 50 and relay number 87 |
| B) | Relay Number 25 and Relay Number 27 |
| C) | Relay Number 51 and Relay Number 59 |
| D) | Relay Number 21 relay and Number 67 |
34. Which is not the method of detecting faults in the relay power system?
| A) | Level Detection |
| B) | Phase Angle Comparison |
| C) | Differential Current Comparison |
| D) | Comparison of current flow velocity when shortening |
35. ANSI Standard Number 21N relays refer to which type of relay.
| A) | Ground Fault Over Voltage Relay |
| B) | Ground Fault Distance Relay |
| C) | Ground Fault Under Voltage Relay |
| D) | Ground Fault High Impedance Relay |
36. Which of the following devices do Not need Directional Overcurrent protection?
| A) | Parallel Source with Transformer |
| B) | Induction Motor |
| C) | Parallel Source without Transformer |
| D) | Ring Main |
37. What is the characteristic of the Inverse Time Overcurrent Relay?
| A) | The relay will work. When detecting that the Fault current exceeds the current value Then relay will work immediately at the beginning. And the faster the operation is, if the current is less |
| B) | The relay will work. When detecting that the Fault current exceeds the current value and there is a time to work as an inversely proportional to the amount of current |
| C) | The relay will work. When detecting the measured impedance is less than the set value then relay will work immediately at the beginning. and the faster the operation is, if the impedance is less. |
| D) | The relay will work. When detecting that the Fault current exceeds the current value, and has a variable working time according to the amount of faulty currents |
38. Which of the following relays have Adjustable Logic Elements?
| A) | Electromagnetic induction relays |
| B) | Electromagnetic suction relays |
| C) | Static Relays |
| D) | Plunger Relays |
39. What are the meanings of “overcurrent” in electrical protection?
| A) | There are 3 styles: Short Circuits, Over Load and Transient. |
| B) | There are 2 characteristics, Short Circuits and Interrupting Current. |
| C) | There are 2 styles, Short Circuits and Over Load. |
| D) | There are 2 characteristics, Short Circuits and Inrush Current. |
40. What are the characteristics of the definite current overcurrent relay overcurrent relay?
| A) | The relay will work. When detecting that the Fault current is equal to or exceeds the set current value the relay will work immediately, not depending on the current value. |
| B) | The relay will work. When detecting that the Fault current is equal to or exceeds the set current value and there is a time to work as an inversely proportional to the amount of current |
| C) | The relay will work. When detecting that the Fault current is equal to or exceeds the set current value and has a variable working time according to the amount of faulty currents |
| D) | The relay will work. When detecting that the Fault current is equal to or exceeds the set current value the relay will work with a fixed delay time according to the set value. |
41. Directional overload relay detects Faults by
| A) | Harmonic detection |
| B) | Comparison of current differences |
| C) | Comparison of phase angle |
| D) | Level measurement |
42. What is Grading Margin?
| A) | Working time multiplier of overcurrent relay for determining the actual working time of a relay at a certain value of PSM |
| B) | The reserve factor for adjusting the working time of the overload relay for work safety |
| C) | The difference in the minimum working time for the timing of the main current overload relay with overload current relay |
| D) | Reduction factor for adjusting the working time of the overload relay. To allow the relay to run faster |
43. Under Voltage Relay uses the method of detecting faults
| A) | Comparison of power size |
| B) | Level measurement |
| C) | Comparison of phase angle |
| D) | Comparison of current differences |
44. Number 49 relay according to ANSI Standard represents
| A) | Instantaneous Overcurrent Relay |
| B) | Thermal Relay |
| C) | Under Voltage Relay |
| D) | Ground Protective Relay |
45. Overcurrent Relay, connected to circuit through the current transformer (CT) with current ratio of 1000/1 A, set to run at 125%.
What is the starting current of the relay?
| A) | 1.0 A |
| B) | 2.0 A |
| C) | 1.25 A |
| D) | 1.5 A |
46. What are the working conditions of Directional Overcurrent Relay?
| A) | When the current of the relay is visible Greater than or equal to the adjusted current value and have the opposite direction Relay will work |
| B) | When the current at the relay is visible Greater than or equal to the adjusted current value and have the right direction Relay will work |
| C) | When the current at the relay is visible Less than or equal to the adjusted current value and have the right direction Relay will work |
| D) | When the current at the relay is visible Greater than or equal to the adjusted current value Relay will work |
47. Incomplete Sequence Relay (48) is
| A) | Use to protect the power transmission line |
| B) | Use to protect the generator. |
| C) | Use to protect the transformer |
| D) | Use to protect the electric motor |
48. The main function of the Relay is
| A) | to detect the position of faults in the electrical system. |
| B) | to direct circuit breaker when Faults occurs. |
| C) | to break circuit when the Fault occurs. |
| D) | to record abnormalities that occur in the electrical system |
49. Which of the following types of relays uses Impedance Pick up to allow relay to operate?
| A) | Distance Relay |
| B) | Under Voltage Relay |
| C) | Overcurrent Relay |
| D) | Differential Relay |
50. High Setting Instantaneous Overcurrent protection device’s number relay is
| A) | 32 |
| B) | 51 |
| C) | 43 |
| D) | 50 |
51. Polarizing Quantity of Directional Overcurrent Relays define as
| A) | is the amount of current compared to the current value set in percentage in order for the relay to work |
| B) | It is a reference quantity for comparing the direction of the current. In order for the relay to work |
| C) | It is a reference quantity for comparing the size and direction of the current. In order for the relay to work |
| D) | It is a reference quantity for comparing the size of the over current. In order for the relay to work |
52. Device ID number 52-a according to ANSI Standard it means what kind of device
| A) | Normal Auxiliary Relay Open (Normally Open) |
| B) | Normally Closed Normally Auxiliary Contact |
| C) | Normally Closed Normally Auxiliary Relay |
| D) | Auxiliary Contact normally open (Normally Open) |
53. Phase Directional Overcurrent Relay with 90-degree connection – 45 degrees MTA, considering phase relays the relay will correct Correctional Tripping Zone, when the phase A phase has an angle
| A) | From 45 degrees Leading to 135 degrees Lagging |
| B) | From 45 degrees leading to 90 degrees Lagging |
| C) | From 45 degrees Lagging to 135 degrees Leading |
| D) | From 0 degrees to 180 degrees Lagging |
54. Relay number 47 in accordance with ANSI Standard means what kind of relay
| A) | Zero Sequence Current Relay |
| B) | Zero Sequence Voltage Relay |
| C) | Negative Sequence Current Relay |
| D) | Negative Sequence Voltage Relay |
55. Which of the following types of relays detect faults by using the Phase Angle Comparison method?
| A) | Differential Relay |
| B) | Frequency Relay |
| C) | Current Balance Relay |
| D) | Directional Overcurrent Relay |
56. Which of the mentioned use of Overcurrent Relay is wrong?
| A) | Overcurrent Relay is used to prevent short circuit only. |
| B) | Overcurrent Relay can prevent both short circuit and overload conditions in electrical equipment. |
| C) | None of these answers |
| D) | Overcurrent Relay has better protection properties than fuses. |
57. Which of the following relays uses the Faults detection method in the electrical system with the Magnitude Comparison?
| A) | Current Balance Relay |
| B) | Differential Relay |
| C) | Directional Overcurrent Relay |
| D) | Distance Relay |
58. Which of the following codes and device names are incorrect?
| A) | 49-Frequency Relay, 50-Instantaneous Overcurrent Relay, 51-Time Overcurrent Relay |
| B) | 21-Distance Relay, 40-Loss of Excitation Relay, 59-Overvoltage Relay |
| C) | 32-Power Direction Relay, 60V-Voltage Balance Relay, 87-Differential Relay |
| D) | 27-Undervoltage Relay, 37-Undercurrent Relay, 78-Out of Step relay |
59. One power system has a maximum short circuit current of 8,000 A.
Use an overcurrent relay to protect by passing the current transformer (CT) with a test rate of 500/5 A to calculate Plug Setting Multiplier (PSM) value?
When adjusting the current to 150%
| A) | 8.76 |
| B) | 6.0 |
| C) | 9.56 |
| D) | 10.67 |
60. According to IEC 60617 (IEC Relay Symbols) symbol of relay as shown, is
| A) | Directional Overcurrent Relay |
| B) | Negative Sequence Relay |
| C) | Definite Time Earth Fault Overcurrent Relay |
| D) | Differential Relay |
61. The principle of harmonic detection in relays with the Harmonics Restraint function is
| A) | used to prevent the relay of the relay in Abnormal Conditions but not in the protection zone. |
| B) | Use to order a circuit breaker when the relay detects the number of harmonics beyond the set value. |
| C) | used to prevent the relay trip when there are faults occurring outside the protection zone. |
| D) | use to prevent the order of the relay in the overlap of other defensive zones so that the relays in that protective zone first |
62. What is the Fault Detection principle of the relay?
| A) | The relay is working when the amount of electricity has multiple differences that exceeds the set level |
| B) | The relay works when the amount of electricity in the system is higher than the set level. |
| C) | All of these answers |
| D) | The relay works when the amount of electricity in the system is lower than the set level. |
63. Phase Directional Overcurrent Relay What kind of connection can be used?
| A) | All of the answers |
| B) | 90-degree connection |
| C) | 30-degree connection |
| D) | 60-degree connection |
64. In any of the following cases, the Overcurrent Relay used for
| A) | Over flux protection in the transformer |
| B) | Overheating protection in the stator coil of the electric motor |
| C) | Protection of overload conditions in an induction motor |
| D) | Protection of Locked Rotor conditions in an induction motor |
65. We have Non-Directional Overcurrent Relay, how we will detect faults any direction
| A) | Comparison of power size |
| B) | Comparison of current differences |
| C) | Level measurement |
| D) | Comparison of phase angle |
66. Number 21 relay according to ANSI Standard represents
| A) | Instantaneous Overcurrent Relay |
| B) | Distance Relay |
| C) | Reverse-Phase or Phase-Balance Current Relay |
| D) | Differential Protective Relay |
67. Which of the following describes the principle of preventing overcurrent?
| A) | The amount used to detect the Fault in the system may be used as current, voltage or time. |
| B) | Short circuit protection must always be set to the closest relay to the Fault. |
| C) | Over current relay is the most used relay in Phase Faults and Earth Faults protection. |
| D) | The amount used to detect the Fault in the system may be used as current, time, or both current and time |
68. According to IEC 60617 (IEC Relay Symbols) symbol of relay as shown Means
| A) | Definite Time Earth Fault Over-current Relay |
| B) | Directional Over-current Relay |
| C) | Differential Relay |
| D) | Instantaneous Over-current Relay |
69. What is the current overload protection Discrimination system?
| A) | It is a sequence of protection. By allowing the main relay (Primary Relay) near the point of short circuit to work first and the backup relay that is far away has Grading margin is long enough to ensure that the backup relays are secure (Secure) |
| B) | It is set to allow relays in many systems. Coordinate By allowing relays that are far from the most paid source to work first and relays that are in the position near the source, work in the next order without the need for grading margins. |
| C) | It is a sequence of protection. By allowing relays that are near the source to work first and a remote relay to act as a backup |
| D) | It is set to allow relays in many systems. Work group by allowing the same type of relay to work simultaneously |
70. According to IEC 60617 (IEC Relay Symbols) symbol of relay as shown Means
| A) | Underpower relay |
| B) | Undervoltage relay |
| C) | Underfrequency relay |
| D) | Under speed relay |
71. The mechanism of digital relays
| A) | Depending on the input and display section |
| B) | Depending on the memory |
| C) | Depending on the order from the software used |
| D) | Depending on the signal data received from the ADC |
72. To adjust the current setting of the Overcurrent Relay, it must be adjusted at the Plug Setting which is available in 7 Tap, i.e 50%, 75%, 100%, 125%, 150%, 175%, 200%.
Which will be current rate of 1000/5 A CT.
If Plug Setting is 150%, CT will deliver
| A) | 6.25 A |
| B) | 7.5 A |
| C) | 8.75 A |
| D) | 5.0 A |
73. Number 51 relay according to ANSI Standard represents
| A) | Instantaneous Overcurrent Relay |
| B) | Reverse-Phase or Phase-Balance Current Relay |
| C) | Ground Protective Relay |
| D) | AC Time Overcurrent Relay |
74. Equipment code number 25 in accordance with ANSI Standard, means which device
| A) | Over Voltage Relay |
| B) | Thermally Operated Circuit Breaker |
| C) | Synchronizing or Synchronism-Check Device |
| D) | Relay Operated Circuit Breaker |
75. From the following message Which is correct?
A. 59-Overvoltage Relay and 27-Undervoltage Relay used to protect the voltage in the electrical system.
B. 25-Synchronism Relay Use to check the frequency And the phase angle of the voltage in two circuits that will be connected in parallel
C. Overvoltage Relay and 81-Undervoltage Relay used to protect the frequency in the wrong electrical system.
D. 21-Distance Relay and 87-Differential Relay to protect transformer equipment in electrical systems
| A) | Both B and C |
| B) | Both A and C |
| C) | Both A and B |
| D) | Both C and D |
76. Over Load Relay with Bimetal, how does it work?
| A) | Use the principles of different metals. When receiving heat simultaneously, the growth rate is not equal. |
| B) | Using the principles of different metals When not being heated simultaneously, the rate of contraction is not equal |
| C) | Use the principle of electromagnetic fields to induce the metal sheet to open – close the contactor face. |
| D) | Use the magnetic field principle of the contactor Through metal plates |
77. Which of the following codes and device names are all right?
| A) | 27-Undervoltage Relay, 51-Time Overcurrent Relay, 59-Overvoltage Relay |
| B) | 27-Undervoltage Relay, 51-Overvoltage Relay, 59-Time Overcurrent Relay |
| C) | 27-Overvoltage Relay, 51-Undervoltage Relay, 59-Time Overcurrent Relay |
| D) | 27-Overvoltage Relay, 51-Time Overcurrent Relay, 59-Undervoltage Relay |
78. In the 3-phase 3-wire electrical system, Earth Fault Protection with the “Residual Connected” method requires how many current transformers (CT)
| A) | Use all 4 CTs. |
| B) | Use only one CT. |
| C) | Use 3 CT. |
| D) | Using 2 CT |
79. From the following message Which is correct
| A) | Solid State Relay is a relay that does not require electricity from the outside. |
| B) | Microprocessor Relay is a relay with a complex internal circuit structure. |
| C) | Solid State Relay is a relay that has no moving parts. |
| D) | Microprocessor Relay is a relay that can perform many functions in one. |
80. You have Electro-mechanical relay, and you want to use High Speed Relay, what type of relay structure is required for this operation?
| A) | Split Ring |
| B) | Attractive Armature |
| C) | Induction Disc |
| D) | Induction Cup |
81. Which of the following not related to Distance Relay?
| A) | Quadrilateral |
| B) | Lenticular |
| C) | Mho |
| D) | High Impedance Relay |
82. According to IEC 60617 (IEC Relay Symbols) symbol of relay as shown What device does it mean?
| A) | Directional Relay |
| B) | Circuit Breaker |
| C) | Thermal Relay |
| D) | Switch |
83. Which of the following relays uses Impedance as a Pick-up quantity?
| A) | Relay Number 21 |
| B) | Relay number 27 |
| C) | Relay Number 67 |
| D) | Relay Number 87 |
84. Dual Polarizing Earth-Fault Relay fault protection relay is not intended to solve any problems, because
| A) | Residual Voltage and Residual Current values are too low. |
| B) | The residual current value is too low. |
| C) | Too many Phase Shift angles |
| D) | Residual Voltage is too low. |
85. Which of the following relays Relying on the current stimulation that comes from CT as pick up quantity?
| A) | Relay number 50 |
| B) | Relay number 27 |
| C) | Relay Number 67 |
| D) | Relay Number 21 |
86. Directional Overcurrent Relay can use which quantity as a Polarizing Quantity.
| A) | electricity |
| B) | pressure or electricity, depending on the case of protection. |
| C) | electrical frequency |
| D) | voltage |
87. Phase Directional Overcurrent Relay and Ground Directional Overcurrent Relay according to IEEE C37.2 (ANSI Device Numbers) means relay with number
| A) | 67 and 67N |
| B) | 32 and 32N |
| C) | 50 and 50N |
| D) | 51 and 51N |
88. Which of the following device is not the basic equipment for the protection of power system?
| A) | Magnetic contactors |
| B) | Circuit breaker |
| C) | Fuse |
| D) | Relay |
89. Which of the following types of relays Based on the principle of using both the amount of current and pressure to encourage the relay to work?
| A) | Direct current overload relay (Non-Directional Overcurrent Relay) |
| B) | Current Differential Relay |
| C) | Low frequency detection relay (Underfrequency Relay) |
| D) | Distance Relay (Distance Relay) |
90. According to IEC 60617 (IEC Relay Symbols) symbol of relay as shown Means
| A) | Definite Time Overcurrent Relay |
| B) | Inverse Time Overcurrent Relay |
| C) | Negative Sequence Relay |
| D) | Directional Overcurrent Relay |
91. Device code 52-b according to ANSI Standard means what kind of device
| A) | Normally Closed Normally Auxiliary Relay |
| B) | Auxiliary Contact normally open (Normally Open) |
| C) | Normal Auxiliary Relay Open (Normally Open) |
| D) | Normally Closed Normally Auxiliary Contact |
92. Relay number 46 according to ANSI Standard means which relay?
| A) | Zero Sequence Current Relay |
| B) | Zero Sequence Voltage Relay |
| C) | Negative Sequence Current Relay |
| D) | Negative Sequence Voltage Relay |
93. Which is not a feature of Digital Relay
| A) | Can measure and display the electrical quantity value of the system, such as voltage, watt, volt amperage, etc. |
| B) | Single Phase / Single Function Relay |
| C) | Can record events or statistical data of fault occurrences in the system. |
| D) | Multiphase Multifunction Relay |
94. Which of the following relay groups Must be used with both CT and VT measuring devices?
| A) | Relay Number 50 and Relay Number 51 |
| B) | Relay Number 51 and Relay Number 27 |
| C) | Relay number 25 and Number 67N relay |
| D) | Relay Number 32 and Relay Number 21 |
95. Grading Margin depends on which of the following factors
| A) | Device error |
| B) | Circuit Breaker Time of Circuit Breaker |
| C) | All of these answers |
| D) | Overshoot time of relay |
96. If you analyze evolution of Relays from the past to the present, what are the different groups?
| A) | Solid-state relay, Static Relay and Digital Relay |
| B) | Electro-mechanical Relay, Static Relay, Digital Relay and Numerical Relay |
| C) | Static Relay, Digital Relay and Numerical Relay |
| D) | Electro-mechanical Relay, Static Relay and Digital Relay |
97. Which is not an important factor in determining the time value of grading margins for the working time sequence of overcurrent relay
| A) | Allowance for errors |
| B) | Overshoot Time of Relay |
| C) | The duration of the short-circuit current |
| D) | Circuit Breaker Time of Circuit Breaker |
98. The principle of Relaying Pilot is
| A) | To protect the power transmission line |
| B) | To protect the electric motor |
| C) | Use to protect the transformer |
| D) | Use to protect the generator. |
99. Discrimination Of the relay in the overcurrent protection system Which method is use?
| A) | 3 Quantities methods: using current, time and using both current and time |
| B) | 2 Quantities method is using current and phase angle |
| C) | 2 Quantities method is by using current and time. |
| D) | 3 Quantities method is by using current, time and phase angle. |
100. Which of the following Can be used as a Polarizing Quantity of Directional Overcurrent Relay?
| A) | Real Power |
| B) | Voltage |
| C) | Frequency |
| D) | Power Factor |
101. Overcurrent Relay, connected to circuit through the current transformer (CT) with Current Ratio of 1000/5 A, set to run at 100%.
If the Fault Current is 10,000 A, find the PSM value
| A) | PSM = 5 |
| B) | PSM = 20 |
| C) | PSM = 15 |
| D) | PSM = 10 |
102. Which quantity from mention below quantities to be compared for phase angle comparison?
| A) | Current and Current. |
| B) | Current and voltage. |
| C) | Power and Voltage. |
| D) | Negative Sequence and Positive Sequence when the Fault occurs. |
103. Overcurrent Relay, connected to circuit through current transformer (CT) with Current Ratio of 800/5 A, set to run at 80%.
What is the starting current of the relay?
| A) | 5 A |
| B) | 4 A |
| C) | 2.5 A |
| D) | 3 A |
104. According to IEC 60617 (IEC Relay Symbols) symbol of relay as shown Means
| A) | Overspeed Relay |
| B) | Power Factor Relay |
| C) | Phase Angle Relay |
| D) | Overtemperature Relay |
105. Which of the following technique is not used to detect Earth Fault with Overcurrent Relay?
| A) | Detection of Zero Sequence Current |
| B) | Residual Current measurement |
| C) | Ground Return Current Measurement |
| D) | Positive Sequence Current Detection |
106. Which of the following relay groups operational with VT only?
| A) | Relay Number 81 and Relay Number 21 |
| B) | Relay Number 25 and Relay Number 27 |
| C) | Relay Number 51 and Relay Number 67 |
| D) | Relay number 50 and relay number 87 |
107. Relay number 50 (Relay Device Number 50) What is a relay?
| A) | Frequency Relay |
| B) | AC Time Overcurrent Relay |
| C) | Undervoltage Relay |
| D) | Instantaneous Overcurrent Relay |
108. What is Plug Setting Multiplier (PSM)?
| A) | Reducing factor for setting the value of overcurrent relay to allow the relay to run faster |
| B) | Multiplier for adjusting the current relay for work safety |
| C) | The current value in the circuit that needs protection is the number of times the normal continuous current |
| D) | The voltage setting value is the number of voltage coordinates of VT to allow the overcurrent relay to work |
109. Over current relays have a Standard Inverse operation (SI) [IEC 60255] with a TMS setting of 0.5.
If using the CT Ratio 800/5 A and adjusting the current to 100% The fault current is equal to 5,000 A.
The relay’s tripping time is
| A) | 0.500 seconds |
| B) | 3.750 seconds |
| C) | 0.945 seconds |
| D) | 1.875 seconds |
110. What are the characteristics of the definite time overcurrent relay over current relay?
| A) | The relay will operate. When detecting that the Fault current exceeds the continuous current value and have a fixed working time according to the designed value |
| B) | The relay will operate. Whenever detecting the Fault current exceeds the normal continuous current value and having the fastest working time, almost immediately |
| C) | The relay will operate. When detecting that the Fault current exceeds the continuous current value and there is a time to work as an inversely proportional to the amount of fault current |
| D) | The relay will operate. When detecting that the Fault current exceeds the current value and has a variable working time according to the amount of faulty currents |
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