First, single-choice questions. Please fill in the code of the correct answer in parentheses (30 questions in total, 1 point for each question, 30 points in total)
1. In the sinusoidal AC resistance circuit, the relationship between the current and voltage is correctly reflected ( ).
A, i=U/RB, i=Um/RC, i=u/R
2. In the sinusoidal AC circuit of an ideal inductive component, the relationship between the current and voltage is correctly reflected as ( ).
A, i=u/XL B, i=u/ωL C, I=U/ωL
3. If the maximum values ​​of the sinusoidal AC voltage and current are Um(V) and Im(A), respectively, the apparent power expression is ( ).
A, UmIm/2 B, UmIm/ C, /UmIm
4. The resonant frequency f of the sinusoidal AC circuit in series with R, L, and C is ( ).
A, 2p B, 1/2p C, 1/2plc
5. In a purely capacitive circuit, the reactive power factor sinj of the circuit is ( ).
A, 0 B, 1 C, 0.8 D, 0.4
6. When measuring the grounding resistance with a ZC-8 type grounding resistance meter, set the conversion ratio switch to the ( ) position.
A, maximum B, minimum C, middle
7. When the three-phase power is measured by the two-meter method, the phenomenon that the two power meters are equal in reading occurs, and the three-phase power should be ( ).
A, the two tables are subtracted from B, the two tables are added C, and the two tables are multiplied.
8. In Figure II-1, in a single-phase bridge half-controlled rectifier circuit, for inductive loads, ( ).
A, can not connect the freewheeling diode B, must be connected to the freewheeling diode
9. The control angle of the thyristor is a = 60°, and its conduction angle is ( ).
A, 0° B, 60° C, 120°
10. The spatial distance between the independent lightning rod and the power distribution device should not be less than ( ).
A, 5m B, 8m C, 10m
11. In 10KV overhead distribution lines, the horizontally arranged conductors should have a sag that is not greater than ( ).
A, 100mm B, 80mm C, 50mm D, 30mm
12. When the first end of the 10KV line is short-circuited, the ( ) protection action circuit breaker trips.
A, over current B, fast cut C, low frequency load shedding
13. When laying the cable, the single-core cable used in the three-phase system should be arranged in a close ( ) arrangement, and the straps should be fastened every ( )m.
A, equilateral triangle B, phase sequence C, 1 D, 1.5
14. Generally, when the number of cables is small and the laying distance is large, ( ) is adopted.
A. Directly lay laying B, cable tunnel C, cable trench D, cable drain
15. When the overhead line is completed and accepted, it shall be closed ( ) times with the rated voltage.
A, 5 B, 3 C, 1
For the sliding line of bridge cranes above 16.10t, angle steels with a size not less than () mm shall be used, and the fixed spacing shall not be greater than ()m.
A, 50 Ì5 B, 40 Ì4 C, 2 D, 3
17. Three-phase asynchronous motor When the slip rate is 1, the motor is in the ( ) state.
A, braking state B, synchronous running state C, starting state
18. When the high voltage equipment is grounded, in order to prevent electric shock from striding voltage, the outdoor area must not be within the fault point ( ).
A, 3m B, 5m C, 8m
19. When the transformer capacity is 50kVA, the resistance of the grounding device is not allowed to exceed ()W.
A, 4 B, 10 C, 30
20. When operating the knife switch, the action should be ( ).
A, rapid B, slow C, stable
21. The short-circuit voltage of the power transformer is generally specified as the rated voltage ( ).
A, 4.5%-6% B, 2%-3% C, 8%-10%
22. The wiring group of a three-phase power transformer is Y1d11, indicating that the primary winding is Y-connected, and the secondary winding is connected by Δ, then the secondary winding leads the () corner.
A, 30° B, 60° C, 120°
23. The secondary coil of the voltage transformer has a little grounding. This grounding should be called ( ).
A. Repeat grounding B, working ground C, protective grounding
24. The main reason for insulation aging is ( ).
A, the voltage is too high B, the ambient humidity is high C, the temperature is too high
25. The condition for generating series resonance is ( ).
A, XL>XC B, XL<XC C, XL=XC
26. When the line or equipment is in power outage, the temporary grounding should be used ( ).
A. Multi-strand soft copper with a cross-section of not less than 25mm2, copper insulated wire C with a cross-section of not less than 1.5mm2, copper core with a cross-section of not less than 6mm2
27. When laying the cable, a spare length of ( ) m should be left near the terminal head and the intermediate joint.
A, 0.3-0.5 B, 1-1.5 C, 2-3
28. Transformer oil should be odorless. If it feels sour, explain ( ).
A. The moisture content in the oil is high B, the arc is generated in the oil, and the oil is seriously aging.
29. The connection of the grounding body should be ( ).
A, lap welding B, bolt connection C, butt welding
30. For insulating oil in operating 10kV electrical equipment, the electrical strength is specified as ( ).
A, not less than 10kV B, not less than 15kV C, not less than 25kV
Second, multiple choice questions. (20 questions in total, choose one for 0.5 points, choose two for 1 point, all for 2 points, choose the wrong one without points, a total of 40 points)
1. Measurement error is divided into.
A, system error B, basic error C, additional error D, accidental error E, negligence error
2. There are methods for measuring the grounding resistance.
A, grounding resistance measuring instrument measuring method B, ammeter - voltmeter measurement
C, current-power meter measurement method D, bridge measurement method E, three-point measurement method
3. The main technical indicators of electrical measuring instruments are.
A, accuracy B, sensitivity C, temperature resistance D, insulation strength E, constant method
4. The standard connection group of commonly used three-phase transformers prescribed in China is.
A, Y/Y0-12 B, Y/Δ-11 C, Δ/Y-11 D, Y0/Δ-11 E, Δ/Y0-11
5. Equipment that cannot be operated with load is.
A, less oil circuit breaker B, isolation switch C, load switch D, indoor high voltage fuse
E, outdoor high voltage fuse
6. Current transformer wiring is available.
A, single-phase wiring B, three-phase wiring C, star wiring D, angular wiring E, incomplete star wiring
7. The role of working grounding is.
A. Improve the insulation level of the equipment to the ground B and reduce the insulation level of the equipment to the ground.
C. Quickly cut off the faulty device D, reduce the human body's electric shock voltage E, and reduce the equipment fault current.
8. Common low-voltage wiring methods are available.
A, splint B, porcelain C, line pipe D, cable E, cable
9. There are faults in the operation of the power supply system.
A, short circuit B, disconnection C, overload D, overcurrent E, overvoltage
10. The principle of superposition applies to the calculation.
A, current B in DC circuit, voltage C in DC circuit, power in DC circuit
D, current E in the nonlinear circuit, voltage in the nonlinear circuit
11. Line shunt capacitors can increase the power factor of the circuit while reducing the loss of the line.
A, current B, resistance C, reactance D, voltage E, power
12. The condition of the thyristor conduction is.
A, a forward voltage is applied between the anode and the cathode, and a forward voltage is applied between the control electrode and the cathode.
C, a reverse voltage D is applied between the anode and the cathode, and a reverse voltage is applied between the control electrode and the cathode.
E, forward voltage is applied between the anode and the control electrode
13. If you want to turn off the thyristor of the forward conduction, you can.
A. Disconnect the pole B of the control, add a reverse voltage C to the control pole, and apply a reverse voltage to the anode.
D, disconnect the anode forward voltage E, so that the current through the thyristor is less than the holding current
14. Intermittent working mode The duty ratio of the motor is %.
A, 15 B, 25 C, 40 D, 50 E, 60
15. The number of turns per phase of the AC winding connected to each pole is divided into several slots.
A, single B, double C, whole D, minute E, half
16. Three-phase asynchronous motor air gap between mm and mm.
A, 0.1 B, 0.15 C, 0.2 D, 1.0 E, 1.5 F, 2.5
17. Busbar processing includes.
A, correct B, measure C, cut D, bend E, drill
18. The three-phase single-layer AC winding has the structural form.
A, concentric B, stacked C, wave-wound D, chain E, crossover #p#page title#e#
19. The open type of commonly used insulators for overhead power lines is
A, needle type B, suspension type C, stick type D, butterfly type E, porcelain cross arm
20. According to its function, the high-voltage power distribution device has an electrical switch.
A, circuit breaker B, isolation switch C, load switch D, fuse E, knife
Third, the judgment question. If the following judgments are correct, please call "√", the wrong one is "×" (30 questions in total, 1 point for each question, 30 points in total)
1. The phase of the AC voltage across an electrical component leads the current flowing through it, and the component is a capacitive load. ( )
2. The power in the linear circuit can also be calculated using the superposition principle. ( )
3. When several constant current sources are connected, their total current cannot be solved by Kirchhoff's current law. ( )
4. The resistance of the measuring shunt should be measured using a single-arm bridge, and the standard resistance measuring 200Ω should be measured using a double-arm bridge. ( )
5. Transformer transformation ratio error measurement is best to use the variable ratio bridge method. ( )
6. The DC potential difference meter is an instrument made by the principle of DC compensation. ( )
7. The commonly used AC energy meter is a sensor system. ( )
8. The general single arm bridge measurement range is 10 Ω - 106 Ω. ( )
9. The pulse front of the thyristor trigger circuit is steep, and the leading edge rise time does not exceed 10μs. ( )
10. In single-phase half-control bridges with three-phase half-control bridges with inductive loads, the freewheeling diodes should not be connected. ( )
The standard test voltage value of the DC voltage withstand test of 11.6.3kV-10kV oil-impregnated paper insulated power cable is 6 times of rated voltage value, and the continuous standard time value of DC withstand voltage test is 5min. ( )
12. The rated voltage of the arrester should be slightly higher than the voltage of the protected grid. ( )
The sag error of the 13.35kV overhead line shall not exceed +5%-2.5% of the design sag, and the maximum value of the positive error shall not exceed 1000mm. ( )
14. When making a 10kV epoxy cable intermediate joint, the distance between the poles is 18mm. ( )
15. In the case of running transformer oil, if it loses transparency and fluorescence, it means that it contains impurities such as high carbon. ( )
16. When two transformers with the same capacity are operated in parallel, the reason why the loop current is formed in the loop formed by the primary and secondary windings of the two transformers is that the transformation ratio is not equal or the connection group is different. The reason for the uneven load distribution is that the short-circuit voltages are not equal. ( )
17. Use the isolating switch to pull and connect the faultless voltage transformer and arrester. ( )
18. The action sequence of the main blade and the auxiliary blade of the load switch is that the main blade first contacts when the switch is closed, and the auxiliary blade contacts after the main blade is separated first, and the auxiliary blade leaves after the opening. ( )
19. The power plant and substation are equipped with a clearing coil to balance the lead current component of the ground fault current due to the line-to-ground capacitance. ( )
20. When the capacitor group is tested for closing at the rated voltage, the reclosing test can be performed immediately after each opening. ( )
21. When a single-phase ground fault occurs in a small current grounding system, short-term operation is generally allowed because the symmetry of the system voltage is not destroyed. ( )
22. The compensation method of shunt capacitors can be divided into three types: individual compensation, dispersion compensation and centralized compensation. ( )
23. Hemp rope is used for general crane operations with a safety factor of 3. The hemp rope for manned devices has a safety factor of 14. ( )
The 24.10kV line is generally grounded via a neutral point via an arc suppression coil. ( )
25. In order to prevent the combination of the electromagnetic mechanism of the circuit breaker, the iron core rust and the jam, the lubricating oil should be applied to the iron core during maintenance and repair. ( )
26. The new electrical equipment has a factory test report, and the construction unit can be put into operation without trial. ( )
27. In the process of handling the accident, you can not fill in the operation ticket. ( )
28. After the substation is equipped with parallel capacitors, the current of the upper line may not be smaller. ( )
29. The arc chamber of the vacuum switch is a highly vacuum glass cell. ( )
30. Tests performed on newly installed and overhauled equipment are preventive tests. ( )
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