1. engineering construction standard design is divided into:
A. national, industry and local level three;
B. national, industry and local level two;
C. not graded;
D. national and industry level, local level two.
Answer:D
2. One of the following descriptions of the economic evaluation of a construction project is correct:
A. Only the financial indicators of the project itself are evaluated;
B. In addition to A, the contribution to the local finances is also evaluated;
C. In addition to A, the impact on the environment is also evaluated;
D. In addition to A, B and C, the contribution to the macroeconomy and the social environment is also evaluated. , also evaluate the impact on macroeconomic and social development.
Answer:D
3. Where the electrical project discharges exhaust gases and wastewater to an area with local emission standards, the measures for environmental protection control should be implemented:
A. National emission standards;
B. Local emission standards;
C. Industry emission standards;
D. National standards as a mainstay, with reference to local standards.
Answer: B
4. When non-conductive site protection is used as an indirect contact protection measure, the resistance of each f-point of insulated floors and walls shall not be less than the following values under the specified conditions for electrical installations with a nominal voltage not exceeding 500V:
A. 20 kΩ; B. 30 kΩ; C. 40 kΩ; D. 50 kΩ.
Answer: B
D. Local emission standards;
C. Industry emission standards;
D. National standards. p>Answer: D
5. Hospitals are divided into 0,1,2 groups of places according to the condition of contact between medical electrical equipment and the human body. The use of TT system, group 1 and 2 in the use of automatic cut-off power supply protection measures should meet the following requirements:
A.; B.;
C.; D..
Where: Ia-action current of the protective appliance, A;
RA-the sum of the resistance of the protective wire and the grounding electrode, Ω;
ZS-the impedance of the fault circuit including the phase wire and PE wire, Ω.
Answer: B
6. Which of the following measures is incorrect when SELV (Safety Extra Low Voltage) protection is used as an electric shock protection measure?A. The power supply of SELV circuits uses a safety isolation transformer;
B. SELV circuits are electrically isolated from other circuits;
C. Exposed conductive parts should be connected to the protective conductors of the low-voltage system;
D. Sockets should not be plugged into sockets of other voltages.
Answer: C
7. Which group of the following conditions is correct for the power supply requirements of different load levels?
Ⅰ. First-class loads should be powered by two sources, when a power supply failure, the other power supply should not be damaged at the same time;
Ⅱ. Primary load in the particularly important load, in addition to a normal power supply, there should be additional emergency power supply;
Ⅲ. Secondary load should be powered by two lines;
Ⅳ. Simultaneous power supply of two or more supply and distribution lines, a circuit interruption of power supply, the rest of the line should be able to meet all the primary load and secondary load.
A. Ⅰ, Ⅱ; B. Ⅰ, Ⅱ, Ⅲ;
C. Ⅰ, Ⅲ, Ⅳ; D. Ⅱ, Ⅳ.
Answer: C
8. A processing plant has a small batch production of cold processing machine group, connected to the 380V line on the three-phase AC motors: 6 sets of 5kW, 8 sets of 4.5KW, 15 sets of 2.8kW (the equipment are of the same type, and its need for coefficient of 0.16, cos = 0.5. With the need for systematic method of calculating the load on the line for:
A. 108kVA; B. 29.89kVA;
C. 17.28kVA; D. 34.56kVA.
Answer:D.34.32kVA; Calculate as follows.
Pe=5×6+4.5×8+2.8×15=108kW
Pis=108×0.16=17.28kW
Qis=17.28×1.73=19.89kvar
Sis=(17.282+29.892)1/2=34.56kV?A < /p>
9. Which of the following considerations is correct in determining the group of supply voltages, etc., of an electricity consumer?
A. the number of power equipment;
B. the technical and economic indicators of the power unit;
C. the path of the power supply line and the way of erection;
D. the rated voltage of the power equipment, the reliability of the power supply requirements of the power supply is determined by technical and economic comparison.
Answer: D
10. Cage-type motor using full-voltage starting mode, in addition to its mechanical ability to withstand the motor starting shock torque, the motor manufacturer of the starting mode of no special provisions should be considered in addition to which of the following conditions?
A. The cross-section of the distribution conductor; B. The voltage drop of the distribution bus;
C. The action of the protective device; D. The temperature rise of the motor.
Answer: B
11. In a shunt capacitor bank, the discharger is connected to the capacitor bank in the following manner:
A. The discharger is connected in series with a current-limiting resistor and then connected in parallel with the capacitor.
B. The discharger, current limiting resistor, and capacitor are connected in series.
C. The discharger is connected in direct parallel with the capacitor.
D. The discharger is connected in series with the capacitor bank.
Answer: C
12. When lighting or other loads sensitive to voltage fluctuations are not connected to the distribution bus and AC motors are not started frequently, the voltage on the distribution bus should not be less than what percent of the rated voltage?
A. 90%; B. 85%; C. 80%; D. 95%.
Answer: C
13. The minimum relative ground and phase-to-phase air gaps for charged conductors of 6kV indoor high-voltage power distribution units in areas not exceeding 1,000m above sea level should be:
A. 7.5cm relative to the ground, 7.5cm between phases;
B. 10cm relative to the ground, 10cm between phases;
C. 12.5cm relative to the ground, 12.5cm between phases. 12.5cm, 12.5cm between phases;
D. 15cm relative to ground, 15cmo between phases
Answer:B
14.When a ground fault occurs in a TT system, the resistance contained within the fault circuit is:
A. The ground resistance of the exposed conductive part of the grounding electrode and the power supply ground electrode;
B. The resistance of the exposed conductive part of the grounding electrode and the PE wire. The impedance of the grounding electrode and PE wire;
C. The grounding resistance of the power supply grounding electrode;
D. The resistance of the exposed conductive part of the grounding electrode.
Answer: A
15. Which of the following statements is true of the short-circuit inrush current used to verify dynamic stability when selecting an appliance?
A. The initial value of the short-circuit current;
B. The initial value of the non-periodic component of the short-circuit current;
C. The maximum possible instantaneous value of the short-circuit current;
D. The instantaneous value of the full current at each peak value of the periodic component of the short-circuit current.
Answer: C
16. In the design of a substation, if you calculate the short-circuit current of the 0.4 kV outgoing line on the low-voltage side of the transformer, the system is generally considered to be an infinite system, and its characteristics are compared with the calculation of short-circuit currents in high-voltage systems. which of the following statements is not correct?
A. The non-periodic component of the short-circuit current decays more slowly;
B. It is permissible to consider the high voltage side terminal voltage of the step-down transformer to be unchanged;
C. Generally, the three-phase short-circuit current is the maximum and is independent of whether or not the neutral point is grounded;
D. Resistance is not generally neglected in low-voltage systems.
Answer: A
17. Which of the following principles is correct when configuring a 110kV disconnecting switch with a grounding gate knife in a project?
A. The grounding gate knife must be calibrated for dynamic and thermal stability;
B. If the main disconnecting switch meets the requirements, the grounding gate knife does not need to be calibrated;
C. If the main disconnecting switch meets the requirements, the grounding gate knife is calibrated only for thermal stability;
D. Whether or not to calibrate the dynamic and thermal stability of the grounding gate knife should be determined according to the location of its installation.
Answer: A
18. It is not advisable to lay cables on the same cable tray, which of the following answers is correct?
Ⅰ．Cables above 1kV and below 1kV.
II. Double circuit power cables supplying power to primary loads from the same path.
Ⅲ. Normal power and emergency power cable lines.
Ⅳ. Strong power cable and weak power cable.
A. Ⅰ, Ⅲ; B. Ⅲ, Ⅳ;
C. Ⅰ, Ⅲ, Ⅳ; D. Ⅰ, Ⅱ, Ⅲ, Ⅳ.
Answer:D
19. The cross-section of the main bus of the total equal-voltage link shall be greater than half of the maximum protective line cross-section of the installation, but not less than:
A. 16mm2; B. 10mm2; C. 6mm2; D. 4mm2.
Answer:C
20. In selecting the conductor for outdoor use, the conductor susceptible to vibration from breeze is:
21. The conductor is:
A. rectangular busbar; B. multi-piece rectangular busbar;
C. channel busbar; D. tubular busbar.
Answer: D
21. The temperature of the cable core under the action of the maximum working current shall not exceed the permissible value determined by the service life of the cable. The operating temperature of the cable core of the continuous working circuit shall not exceed the maximum permissible temperature of the cable, for l0kV and below cross-linked polyethylene insulated cables in normal operation, what is the maximum permissible temperature?
A. 70°C; B. 75°C; C. 80°C; D. 90°C.
Answer: D
22. When what of the following conditions are met, the transformer should be equipped with longitudinal differential protection?
A. The transformer capacity is 1000~1600kV?A, and the current interruption protection cannot meet the sensitivity requirement;
B. The transformer capacity is 2000~5000kV?A, and the time limit of overcurrent protection is more than 0.5s;
C. The transformer capacity is 2000~5000kV?A, and the current interruption protection cannot meet the Sensitivity factor requirements;
D. Transformer capacity of 1000~1600Kv?A, overcurrent protection time limit is greater than 0.5so
Answer: C
23. Selection of three-phase voltage transformer used in neutral non-directly grounded system, the third winding voltage should be:
A. 100V; B. 100/3V; C. 100V; D. 100V; C. 100V; D. 100V; C. 100V; D. 100V; C. 100V; C. 100V; D. 100V; C. 100V; C. 100V; D. 100V; C. 100V; D. 100V; D. 100V. 100/V; D. 100V or 100/V.
Answer: B
24. The purpose of setting up automatic low-frequency load-shedding devices is:
A. to shed part of the load during peak loads in order to ensure the power supply to important users;
B. to shed part of the load when the voltage is lowered by accidents in order to ensure the power supply quality of important users;
C. to shed part of the load when the power shortage occurs in accidents.
C. Shedding part of the load when power shortage occurs in an accident to ensure the power supply to important users;
D. Shedding part of the load when the motor feedback causes frequency reduction during reclosing.
Answer: C
25. When the residual current protective appliances installed at the upper and lower levels need to be selective, the rated residual action current of the appliance located on the power side should be at least several times that of the appliance located on the load side?
A. 1 times; B. 2 times; C. 3 times; D. 4 times.
Answer:C
26. Which of the following loads should not be counted as recurring loads when calculating the substation battery capacity t?
A. Electrically charged relays and signal lamps;
B. Frequent DC lighting;
C. Inrush current when the circuit breaker is closed;
D. AC uninterruptible power supply connected to the DC system of the substation.
Answer:C
27.Which of the following four dimensions is correct for the grid of lightning protection grids installed on a Type II lightning protected building?
A. ≤5×5 or ≤6×4; B. ≤10×10 or ≤12×8;
C. ≤15×15 or ≤18×12; D. ≤20×20 or ≤24×16.
Answer: B
28. An overhead lightning line is provided on an overhead transmission line. The height of the overhead lightning line is known to be 20 m. When using Fig. 1 to calculate its protection range, try to determine the angle of protection θ and the height influence factor P. That choice is correct:
A. θ=45?, P=1; B. θ=25?, P=1;
C. θ=45?, P=5.5/D. Use the rolling ball method.
Answer:B
29. High-voltage distribution units outside the house of 35kV and below are suitable to be protected by independent lightning rods and lightning wires. Lightning rod, lightning line should be equipped with an independent grounding device. Its grounding resistance requirement does not exceed which of the following values?
A.1Ω; B.4Ω; C.10Ω; D.30Ω.
Answer:C
30.Which of the following statements is correct?
A. Grounding devices should be set up separately for different purposes and voltages of electrical installations in a substation;
B. In order to check whether the grounding resistance of a grounding device meets the required value, the measured grounding resistance must also take into account the influence of seasonal coefficients;
C. A substation is a 10 kV ungrounded system, and the Guiyeolang resistivity of the place where its grounding device is located is 400 Ω?m. The resistance of the span of its grounding device is 400 Ω?
C. A substation is a 10kV ungrounded system with a soil resistivity of 400 Ω?m. The step voltage of the grounding device should not exceed 150V.
D. Among the horizontal artificial grounding electrodes of various shapes of a certain total length, the grounding resistance of the horizontal artificial grounding electrode of a rectangular shape is the smallest.
Answer: B
31. A 110kV substation, using the square hole grounding network shown in Figure 2, which covers an area of 60m2 × 60m2, the material is 40mm2 × 4mm2 flat outline, buried in the depth of 0.8m, and its grounding resistance R = 0.1Ω, the calculation of the short-circuit current into the ground with the 20kA, so that the substation outside the grounding network of the ground surface of the maximum step voltage is:
A.140V;B.160V;C.200V;D.300V.
Answer:B; Calculate as follows.
A. Equivalent diameter of equalizing belt d/40/2=20mm=0.02m, mistakenly taken as d=4/2=2mm=0.002m, which results in Dsmax=0.07
B. [Calculation method is shown in Appendix B of "Grounding of AC Electrical Installations" DL/T621-1997B], the potential of the grounding device, the maximum of the earth's surface outside the grounding network Step voltage so
C. Step distance T = 0.8m, was mistakenly taken as T = 1m,
which leads to
D. The unit of d should be taken as m, but it was mistakenly taken as mm, which leads to, so
32. Which group of the following narratives is correct with regard to the characteristics of the lighting method?
Ⅰ, the general lighting mode, indoor can get better brightness distribution and illumination uniformity.
II, zoning general lighting methods, not only can improve the quality of lighting, but also favorable energy savings.
III, local lighting, in the local can get high illumination, but also can reduce the reflection of the work surface glare.
IV, mixed lighting mode, can be in the vertical and inclined surface to obtain the same illumination, reduce the work surface of the shadow and light class.
A.Ⅰ, Ⅱ, Ⅲ, ⅣB.Ⅱ, Ⅲ, ⅣC.Ⅰ, Ⅱ, ⅢD.Ⅰ, Ⅱ, Ⅳ.
Answer: A
33. Which of the following methods should be used to calculate the illuminance of a point on an arbitrary plane by direct light from a line source?
A. Inverse square method; B. Shape factor method; C. Orientation factor method; D. Utilization factor method.
Answer: C
34. Evacuation lighting on the main corridor of the standard value of the degree of evacuation illumination should not be less than:
A.0.2lx; B.0.5lx; C.1.0lx; D.1.5lx
Answer: B
35. Mechanical parameters of the water pump process: flow rate of 0.5m3 / s, head 25m The calculated value of motor power is closest to which of the following values?
Note: Transmission efficiency ηc is taken as 1; pump efficiency η is taken as 0.8; margin coefficient k is taken as 1.05.
A.214.7kW; B.180.2kW; C.171.7kW; D.225.3kW.
Answer: D; Calculated as follows.
36.Of the motor operating systems S1 to S8, S1 belongs to which of the following operating systems?
A. Intermittent cycle system; B. Continuous cycle system;
C. Short time system; D. Continuous system.
Answer: D
37. Which of the following statements is true about the effect on the mechanical characteristics of a he-excited DC motor when the magnetic flux is reduced?
A. Ideal no-load speed decreases, and the mechanical characteristics become stiff;
B. Ideal no-load speed decreases, and the mechanical characteristics become soft;
C. Ideal no-load speed increases, and the mechanical characteristics become stiff;
D. Ideal no-load speed increases, and the mechanical characteristics become soft.
Answer: D
38. An electric motor with a protection rating of IP44 indicates which of the following?
A. Protection against solids greater than 12 mm and against drenching;
B. Protection against solids greater than 2.5 mm and against splashing;
C. Protection against solids greater than I mm and against splashing;
D. Protection against dust and immersion.
Answer: C
39. When a DC motor is used for constant torque or constant power speed control, its rotor heat is related to the following physical A:
A. directly proportional to the product of the motor speed and the output torque of the motor;
B. directly proportional to the output power of the motor;
C. directly proportional to the product of the motor armature voltage and current;
C. directly proportional to the product of the armature voltage and current;
C. proportional to the product of the armature voltage and current;
C. directly proportional to the product of the motor voltage and current.
D. is proportional to the square of the rotor current.
Answer: D
40. Q: (1) electromagnetic differential clutch speed control, (2) hydraulic coupling speed control, belong to which type of speed control?
A. 1) change the pole pair number p; 2) change the rate of rotation s;
B. 1) change the rate of rotation:; 2) change the pole pair number p;
C. 1) change the frequency f; 2) change the frequency f;
D. 1) change the rate of rotation s; 2) change the rate of rotation s.
Answer:D
41. Among the many alternating current (AC) regulating systems. Inverter speed control has the best performance, large adjustment range, good static stability and high operating efficiency. The working principle of frequency conversion speed control is described as follows:
A．Changing the supply frequency of an AC motor can change its synchronous speed and realize speed control operation;
B．For asynchronous motors used in large numbers in the industry, it is hoped that the main flux of the motor will be kept unchanged at its rated value when the motor is subjected to speed control and can be controlled according to the requirements;
C．The main flux of the air-gap of the motor will be kept unchanged at its rated value when it is kept in the air-gap of the motor. The purpose of keeping the main flux of the air gap of the motor unchanged is to maintain the load capacity of the motor; and the control of the main flux as required is for the purpose of constant power control;
D. In order to carry out the constant power control, when the motor is increased upward from the rated frequency, its main flux should be increased upward accordingly. Which of the above descriptions of the principle of variable frequency speed control is incorrect?
Answer: D
42. The response time of a PLC's conventional AC switching input module is usually in the range of:
A.1~20ms;B.20~50ms;C.1~20ms;D.100~500ms.
Answer: B
43. In a DC electrical drive system, which of the following metrics are is used to describe the dynamic process of the system under the action of a unit step control signal:
A. span-following error; B. recovery time; C. overshoot; D. dynamic fluctuation amount.
Answer:C
44.A PID control algorithm represents the relationship between the regulator output U(t) and the error e(t):
Which of the following descriptions is correct?
A. a proportional component to quickly suppress the error;
B. an integral quantity to suppress the upward tendency of the error;
C. a differential component to ultimately eliminate the error;
D. Kp is a proportional component to amplify the error.
Answer:A
45.A broadband hybrid amplifier at the front end of a cable system has a nominal maximum output level of 110 dBμV, the number of channels transmitted by the system is 12, and the cross-talk modulation ratio assigned to the front end is 0.2.To find the design value of the front end's output level, which one of the following answers is correct?
A.96.2dBμV;B.95.2dBμV;C.94.2dBμV;D.93.2dBμV.
Answer:B
Two, Multiple Choice Questions
46. The following descriptions of the projects that should be put out to bid are correct:
A.Large infrastructure projects;
B. State-invested projects;
C. Projects using funds from foreign government assistance;
D. No organization or individual other than the owner shall be allowed to make additions.
Answer：A,B,C
47. The following belong to the engineering design qualifications in China at present:
A. special qualification; B. comprehensive qualification;
C. industry qualification; D. special qualification.
Answer: B,C,D
48. The following belong to the mandatory implementation of the standard provisions:
A. Measures must be taken between the emergency power supply and the normal power supply to prevent parallel operation;
B. In the operating dust environment, it is strictly prohibited to use insulated wires or plastic tubes in the open installation;
C. The battery packs dedicated to power loads should be 220V;
C. The voltage of power loads should be 220V;
C. The voltage of power loads should be 220V;
C. The voltage of power loads should be 220V. The voltage should be 220V;
D. The working zero wire of the electrical line shall not be used as the protective grounding wire.
Answer: A,B,D
49. The following are safe voltage in China:
A. AC60V; B. AC24V; C. AC12V; D. AC6V.
Answer: B,C,D
50. The code of ethics for survey and design workers requires survey and design staff to:
A. not engage in technological blockade; B. not engage in technological blockade; B. not engage in technological blockade; C. not engage in technological blockade; D. not engage in technological blockade; E. not engage in technological blockade. B. not to engage in technology blockade; B. not to engage in unlicensed survey and design;
C. not to engage in social welfare; D. not to engage in private survey and design.
Answer: A,B,D
51. narrow electrically conductive places, which of the following measures should be used can be protected by direct contact?
A. Protecting by shielding or external guards, and the protection level of its shell should not be lower than IP2X;
B. Insulating, and its withstand test voltage is 500V for Imin;
C. Adopting barrier;
D. Placing it outside the range of the extended arm.
Answer:A,B
52. Which of the following statements are not completely correct?
A.35kV substations include 35/10kV substations and 10/6kV substations;
B.35kV substations include 35/10(6)kV substations and 6/0.4kV substations;
C. 35kV substations include 35/10(6)kV substations and 35/0.4kV substations;
D.35kV substations include 35/10kV substations and 10/0.4kV substations.
Answer: A,B,D
53.110kV power distribution unit when the number of outgoing circuits exceeds 5, generally using double busbar wiring, the advantages of double busbar wiring are:
A. When the busbar is faulty or overhaul, the disconnecting switch as a reversal of the operation of the electrical apparatus, it is not easy to misoperation;
B. Increase the number of a group of busbars, the loads of each circuit can be distributed to a group of busbars, the loads of the circuits are distributed to a group of busbars, and the loads of the circuits can be distributed to a group of busbars.
B. By adding a group of buses, the loads of each circuit can be distributed to a group of buses at will, which makes the operation flexible;
C. By reversing the operation of the disconnecting switches of the two groups of buses, it is possible to take turns in overhauling the buses without interrupting the power supply;
D. The wiring is simple and clear, which makes it easy to use complete sets of devices.
Answer: B,C
54. low-voltage power distribution design, the selection of electrical appliances, in addition to comply with the current national standards, which of the following requirements are correct?
A. The rated voltage of the appliance should be compatible with the nominal voltage of the circuit, and its rated current should not be less than the calculated current of the circuit;
B. The appliance should meet the short-circuit conditions of the dynamic and thermal stability requirements;
C. may not take into account the requirements of the power supply frequency of the circuit;
D. are selected according to the normal environmental conditions.
Answer: A,B
55. indoor mechanical maintenance of power outages for electrical appliances should meet the requirements, which of these is correct?
A. It should be connected within the mains circuit and the N phase can be disconnected;
B. The electrical gap between the disconnecting contacts should be visible or obvious;
C. The appliance should be designed and installed to prevent accidental closure;
D. The appliance, or the control switch used for the appliance, should be automatically operated.
Answer:B,C
56. Which of the following laying is not suitable for cables passing through sites subjected to high forces in backfilled soil lots with uneven settlement?
A. direct burial; B. through the steel pipe;
C. through the concrete pipe; D. through the flexible plastic pipe.
Answer: A,C,D
57.6 A HOW line overcurrent protective device action current setting value should be dodged which current is incorrect?
A. to avoid the calculated current of the line;
B. to avoid the three-phase short-circuit current of the line;
C. to avoid the two-phase short-circuit current of the line;
D. to avoid the overload current of the line.
Answer: A, B, C
58. Which of the following requirements is correct for a switching device installed in a substation for use with shunt capacitor units?
A. For high-voltage shunt capacitor devices, when there are no more than three times a day, it is desirable to use manual casting and cutting;
B. For automatic casting and cutting of low-voltage shunt capacitor devices, the time parameter can be used as the control quantity;
C. For low-voltage shunt capacitor devices, when there is an automatic cutting device, there should not be a selector switch to change the casting and cutting mode in case of misthrowing,
D. Automatic reclosing is not normally provided for automatic cutting devices, and is only considered when reactive power requirements are stringent.
Answer: A, B
54. low-voltage power distribution design, the selection of electrical appliances, in addition to comply with the relevant national standards in force, which of the following requirements are correct?
A. The rated voltage of the appliance should be compatible with the nominal voltage of the circuit, and its rated current should not be less than the calculated current of the circuit;
B. The appliance should meet the short-circuit conditions of the dynamic and thermal stability requirements;
C. may not take into account the requirements of the power supply frequency of the circuit;
D. are selected according to the normal environmental conditions.
Answer: A,B
55. indoor mechanical maintenance of power outages for electrical appliances should meet the requirements, which of these is correct?
A. It should be connected within the mains circuit and the N phase can be disconnected;
B. The electrical gap between the disconnecting contacts should be visible or obvious;
C. The appliance should be designed and installed to prevent accidental closure;
D. The appliance, or the control switch used for the appliance, should be automatically operated.
Answer:B,C
56. Which of the following laying is not suitable for cables passing through sites subjected to high forces in backfilled soil lots with uneven settlement?
A. direct burial; B. through the steel pipe;
C. through the concrete pipe; D. through the flexible plastic pipe.
Answer: A,C,D
57.6 A HOW line overcurrent protective device action current setting value should be dodged which current is incorrect?
A. to avoid the calculated current of the line;
B. to avoid the three-phase short-circuit current of the line;
C. to avoid the two-phase short-circuit current of the line;
D. to avoid the overload current of the line.
Answer: A, B, C
58. Which of the following requirements is correct for a switching device installed in a substation for use with shunt capacitor units?
A. For high-voltage shunt capacitor devices, when there are no more than three times a day, it is desirable to use manual casting and cutting;
B. For automatic casting and cutting of low-voltage shunt capacitor devices, the time parameter can be used as the control quantity;
C. For low-voltage shunt capacitor devices, when there is an automatic cutting device, there should not be a selector switch to change the casting and cutting mode in case of misthrowing,
D. Automatic reclosing is not normally provided for automatic cutting devices, and is only considered when reactive power requirements are stringent.
Answer: A, B
Three, case questions
65. In the current transformer selection and inspection test questions, which answer is correct in each question?
(1) Determine which of the following is not a step in the 10% error and curve calibration of a current transformer?
A. Determine the rated voltage of the current mutual inductance shun;
B. Calculate the primary calculated current multiplier of the current transformer;
C. Check the 10% error curve;
D. Determine the calculated value of actual secondary load of the current transformer.
(2) Which of the following is not a factor affecting current transformer error?
A. The magnitude of the primary current I1;
B. Current frequency variations;
C. Secondary side power factor variations;
D. Current transformer variations.
(3) The magnitude of the primary current of the current transformer;
A. affects only the current error;
B. affects only the angular error;
C. affects both the current error and the angular error;
D. does not affect the current transformer error.
Answer: (1) A; (2) D; (3) C.
66.Make the correct choice for the following questions on protection against lightning EMP.
(1) Which of the following values can be taken for the insulation withstand impulse overvoltage rating of Class II electrical equipment for a 220/380V three-phase distribution system when the impulse withstand voltage of the equipment is not available?
A.1.5kV; B.2.5kV; C.4.0kV; D.6.0kV.
(2) High impedance occurs when there is no surge, and the impedance is continuously reduced as the surge current and voltage grow, and a varistor is usually used to make the components of this type of SPD. Which of the following types of SPDs should this SPD belong to?
A. Voltage-switching SPD; B. Voltage-limiting SPD; C. Combination SPD; D. Short-circuit-switching SPD.
(3) Lightning protection code for lightning electromagnetic pulse, the space to be protected is divided into different lightning protection zones (LPZ). For example, the exterior windows of a high-rise public **** building with lightning protection devices should be classified in which of the following zones is correct?
A. LPZ0A zone; B. LPZ0B zone; C. LPZ1 zone; D. LPZ2 zone.
Answer: (1) B; (2) B; (3) B.
67.Which set of answers is correct in each of the multiple choice questions in the following test on ground fault protection for low voltage systems?
(1) Protection against indirect electric shock to a person using which of the following groups of measures may not be provided with ground-fault protection?
Ⅰ, Class I electrical equipment;
Ⅱ, electrical equipment;
Ⅲ, the use of safety extra low voltage;
Ⅳ, set up ungrounded equipotential connection.
A. Ⅰ, Ⅱ, Ⅲ; B. Ⅱ, Ⅲ, Ⅳ; C. Ⅰ, Ⅲ, Ⅳ; D. Ⅰ, Ⅱ, Ⅳ.
(2) Which of the following sets of answers is a basic measure to reduce the contact voltage of electrical installations in buildings?
Ⅰ, electrical isolation;
Ⅱ, grounding;
Ⅲ, general equipotential connection;
Ⅳ, shielding.
A. Ⅰ, Ⅱ; B. Ⅱ, Ⅲ; C. Ⅲ, Ⅳ; D. Ⅰ, Ⅳ.
(3) In the TN system distribution line with a nominal phase-to-ground voltage of 220V, when the distribution box supplies fixed electrical equipment and hand-held electrical equipment and end lines of mobile electrical equipment at the same time, the time to cut off the faulty circuit shall be:
A. no more than 0.4s; B. no more than 5s; C. no more than 1s; D. no more than 0.5s.
A. no more than 0.4s; B. no more than 5s; C. no more than 1s; D. no more than 1s; D. no more than 1s; D. no more than 1s; D. no more than 0.5s; D. no more than 0.5s; D. no more than 0s. >
(4) Which set of requirements for PEN conductors in a TN system is correct.
Ⅰ, to the fixed installations of the power supply circuit, the PEN conductor copper core cross-sectional area of not less than 10mm2, aluminum core cross-sectional area of not less than 16mm2;
Ⅱ, can be used to protect the circuit of the PEN conductor RCD;
Ⅲ, shall not be utilized to the residual current action protector, to protect the circuit of the PEN conductor;
Ⅳ, the complete set of switchgear and control equipment within the PEN conductor. Switchgear and control equipment inside the PEN conductor does not need to be insulated up.
A. Ⅰ, Ⅱ, Ⅲ; B. Ⅱ, Ⅲ, Ⅳ; C. Ⅰ, Ⅲ, Ⅳ; D. Ⅰ, Ⅱ, Ⅳ.
(5) The nominal voltage of the installation is 220/380V, and the IT system is distributed with a neutral wire, the maximum cut-off time at the second fault should be:
A.5s;B.0.8s;C.0.4s;D.0.2s.
Answer: (1) B; (2) B; (3) A; (4) C; (5) B.
68.A factory has a power supply capacity of 5000kW and the loads in the factory are supplied at two levels of voltage, 10kV and 380V.
(1) If the active calculated load of the 10kV system of the plant is 4000kW, the reactive calculated load is 3000kvar, its average annual active load factor is 0.75, the average annual reactive load factor is 0.85, such as the use of shunt capacitors to compensate for the power factor to 0.95, should be added to the shunt capacitor capacity is greater than which of the following values?
A.2080kvar;B.1680kvar;C.1260kvar;D.2120kvar.
(2) If the rated current of the shunt capacitor bank selected for a 10kV system is 88A, the long-term permissible current-carrying capacity of the cables and conductors that supply the system should be not less than which of the following values?
A.88A; B.118.8A; C.132A; D.100A.
(3) The plant's 380V B-bus has a calculated load of 400kW and a calculated reactive load of 300kvar, and its average annual active load factor is 0.75 and its average annual reactive load factor is 0.85. If the power factor is increased to 0.95, then How many BW0.4-12-1 capacitor banks need to be installed?
A.15; B.18; C.9; D.21.
Answer: (1) A; Calculate as follows.
10kV average power factor
The tangent of the calculated load power factor angle before compensation
The tangent of the power factor angle after compensation
There are therefore
(2) A; calculated as follows
GB50059-1992 "35~110kV substation design specification", page 8, article 3.7.3 < /p>
(3) B; calculated as follows.
380V natural power factor
Calculated
Therefore, there is
BW0.4-12-1 type capacitor bank capacity of 12kvar