1. True or False Questions
1. When the movable blade of the high-voltage isolation switch is disconnected from the static contact, the arc generated is blown out by compressed air. ( )
2. The high-voltage load switch can open and close the circuit load current and short-circuit current. ( )
3. The high-voltage sulfur hexafluoride circuit breaker has fast action, large interruption distance, and allows a large number of continuous interruptions. ( )
4. The high-voltage circuit breaker can not only make and break normal load current, but also can make and break certain short-circuit current. ( )
5. When oil injection occurs in the oil conservator or explosion-proof pipe of the power transformer, a dedicated person should be immediately organized to monitor changes in the situation. ( )
6. The insulation resistance of the power transformer winding is generally not less than 25% of the factory test value, and the absorption ratio is greater than 1.3. ( )
7. Lightning rods are actually lightning rods, which introduce lightning from high-voltage clouds into the earth to prevent buildings and power distribution equipment from lightning strikes. ( )
8. When one phase of the 10kV power supply system is grounded, due to the high voltage, the grounding current will be very large, up to several hundred amperes. ( )
9. The neutral point of the 35kV power supply system is grounded through the arc suppression coil. Therefore, when a single-phase grounding occurs, the two ungrounded phase-to-ground voltages remain phase voltages. ( )
The power supply of 10 and 10kV power supply systems adopts a neutral point ungrounded operation mode in order to continue operation when a single-phase grounding occurs. ( )
11. In order to avoid breakage of the protective neutral line (PE line), no switches or fuses are allowed on the protective neutral line. ( )
12. The total grounding resistance of two vertical buried grounding electrodes connected together, the distance between the poles is smaller than the distance between the poles. ( )
13. As long as the iron pipe is buried underground, it can be used as a natural grounding body. ( )
14. The ground resistance measurement should be carried out during the dry season of the soil and under conditions of power outage. When the soil moisture content is large, the measured ground resistance value should be multiplied by a seasonal coefficient less than 1. ( )
15. The power frequency AC withstand voltage test is a reference condition for determining whether electrical equipment can be put into operation. ( )
16. To measure the absorption ratio of insulation resistance, the ratio of insulation resistance at 15s (numerator) and 60s (denominator) can be used to judge the insulation condition. ( )
17. The double-arm bridge is used to measure the DC resistance of 1~10 6 Ω. ( )
18. Measuring the insulation resistance of electrical equipment is the only effective way to check the insulation status of electrical equipment and determine whether it can be put into operation or continue to operate. ( )
19. Basic safety equipment can be used to work or operate on high-voltage live equipment. ( )
20 and 35kV voltage indicators (electroscopes) can be used to test electricity on lines or equipment with a voltage level of 10kV. ( )
21. Single cross arm is used for straight poles and angle poles below 15 degrees. The single cross arms of the linear pole are installed on the power supply side. ( )
22. When overhead line conductors cross roads, railways, rivers, power and communication lines, each conductor and lightning protection wire can only have one joint. ( )
23. When installing a chuck on a linear pole, its installation direction should be perpendicular to the overhead line and should be installed on the same side of each pole. ( )
24. Cables buried directly underground can be unarmored cables, such as rubber cables. ( )
25. One of the reasons why underground cables and other pipelines must be kept at a certain distance is that electrical corrosion occurs at the contact point between the two pipelines due to different ground potentials.
( )
26. When laying cables using mechanical traction, if a traction head is used, the cable protection will be subject to traction force; if a steel wire sheath is used for traction, the cable core will be stressed. ( )
27. In the production of wrapped terminals for cross-linked cables, a stress cone is wrapped at the fracture of the outer semiconductive layer of the cable. The purpose is to improve the electric field distribution and increase the withstand voltage level. ( )
28. When using paper insulated cables as intermediate joints, use the connecting tube crimping method to connect the wires. The order of point crimping is to crimp the middle part of the connecting tube, and then press the end of the connecting tube. ( )
29. When measuring leakage current, the microammeter is connected to the high-voltage side. The measurement accuracy is high, but it is inconvenient and there is a risk of high voltage; the microammeter is connected to the low-voltage side, although the measurement is convenient. , but the accuracy is poor. ( )
30. When measuring the leakage current of power cables, if the leakage current increases with the extension of the test time, the cable insulation may be defective. ( )
31. When filling the terminal head of paper insulated cable tripod type (WD76 type) with asphalt insulating glue, pour it in from the opening on the top of the lid and exhaust from the opening on the side of the lid. ( )
32. After the directly buried cable is placed at the bottom of the trench, it should be covered with protective plates to prevent external force from damaging the cable; the ends of the newly cut cables should be sealed and welded (lead-wrapped paper insulated cables ) or seal it with heat shrink (rubber and plastic cable) to prevent water from entering. ( )
33. When adjusting the neutral line position of a DC motor, the brushes should be offset in the opposite direction of rotation for the generator. The brushes should be offset in the opposite direction of rotation for the generator. piece; the motor should be offset in the direction of rotation. ( )
34. The principle of realizing pole-changing speed regulation is: as long as you try to change the current direction of the half-phase winding in each phase winding of the three-phase winding at the same time, the number of magnetic pole pairs of the motor can be reduced to the original half, the speed will be reduced by 1 times. ( )
35. Among the pole-changing speed-regulating motors, the motor with YY-Δ shape transformation has constant power rate speed regulation characteristics; the motor with YY-Y shape transformation has torque speed regulation characteristics. ( )
The driving motors of the 36 and 30/5t bridge cranes are five wound rotor asynchronous motors. （ ）
37. It is not allowed to use electrical equipment that exceeds the design requirements in this explosion hazard place, which is tantamount to laying hidden dangers. ( )
38. In explosive hazardous locations, the incoming cables of explosion-proof electrical equipment are connected to the junction boxes of explosion-proof electrical equipment through introduction devices. Among them, the cast solidified filler seal introduction device is mainly suitable for rubber or plastic sheathed low-voltage cables. ( )
39. In explosion-risk areas, at least one end of the grounding trunk should be connected to the grounding body. ( )
40. In fire-risk environments, the metal shell of electrical equipment should be reliably grounded (zero), and the neutral trunk line should be grounded repeatedly before entering the area and at the end. When the wires are laid through steel pipes, all the wire pipes can be connected as a whole through welding wires and reliably grounded; when passing through plastic pipes, the protective neutral line and the phase wire should be passed through the same ground pipe, and the size of the neutral wire's carrying area should be the same as the phase wire cross-section. ( )
41. The typical daily load curve refers to the load curve actually used by each enterprise on a certain day. ( )
42. Induction motors, transformers and welding machines all consume reactive power to establish a magnetic field when working. ( )
43. The wiring method of factory power lines has nothing to do with the level of power load. ( )
44. The organizational measures for maintenance of electrical equipment in substations include: work ticket system, work permit system, work supervision system and work interruption, transfer and termination system. ( )
45. When filling in the work ticket for maintenance of the substation, use a pen or ballpoint pen to fill in the form in duplicate. One will be collected by the person in charge of the work, and the other will be collected by the dispatcher and handed over on time. （ ）
46. The working steps during power outage in transformation and distribution are: disconnect the power supply, check electricity, install temporary grounding wire, hang signs and install barriers.
( )
47. The conditions for the unidirectional thyristor to trigger conduction are to add "+" to the anode and "-" to the cathode, and add a negative voltage to the gate, that is, the gate is "-" and the cathode is When it is "+", the thyristor can be turned on. ( )
48. One-way thyristor cannot be triggered to conduct in an AC circuit. ( )
49. Use the analog multimeter R × 1k Ω range to measure the forward and reverse resistance between the anode and cathode of the unidirectional thyristor. The values ??are below tens of k Ω, indicating that the tube is intact. ( )
50. Generally, the bolt of a bolt-type unidirectional thyristor is the cathode, and the thick copper braid leads to the anode. ( )