1. Judgment Questions 1. For power-off oil-filled equipment, dry sand or foam fire extinguishers should be used to extinguish fires. (√) 2. To ensure the safety of electrical operations, new factory workers must receive two-level safety education from the factory, workshop, and other departments before engaging in electrical work. Electricians should comply with relevant safety regulations, rules, and systems based on actual conditions. (×) 4. Reasonable rules and regulations are effective measures to ensure safe production. Industrial and mining enterprises and other units with conditions should establish safety production rules and regulations suitable for their own situations. (×) 5. When cutting off live wires for fire extinguishing during power-off, the cutting position should be selected near the support of the power source direction. (√) 6. When cutting off low-voltage wires for fire extinguishing during power-off, all three phases should be cut simultaneously. (×) 7. When extinguishing a fire, firefighters should stand on the downwind side. (×) 8. To ensure safety, the height of the fence around outdoor substation devices should generally not be less than 3 meters. (×) 9. Non-conductive fire extinguishing agents should be used for live equipment. (√) 10. When a rotating motor catches fire, it is prohibited to use dry powder fire extinguishers and dry sand to directly extinguish the fire. (√) 11. When using a fire extinguisher outdoors, the user should stand on the upwind side. (√) 12. Electrical equipment and devices that may produce electric sparks, arcs, and high temperatures during operation should not be placed in flammable dangerous places. (√) 13. A work ticket is a written order allowing work on electrical equipment and a written basis for implementing safety technical measures. Generally, there are three formats. (×) 14. Due to unreasonable selection of wire cross-sections and equipment, heat generation exceeding the long-term allowable temperature of the equipment can cause overheating and lead to electrical fires. (√) 15. The two conditions for causing an electrical fire are: the presence of combustible materials and ignition conditions. (√) 16. When rescuing a person from electric shock, without taking any insulation measures, rescuers must not directly touch the victim's skin or wet clothes. (√) 17. When electrical equipment catches fire, it is strictly prohibited to use conductive fire extinguishing agents for live firefighting. (√) 18. To prevent personal electric shock, water cannot be used for live firefighting. (√) 19. When cutting off power for electrical fire, insulating gloves and insulating boots should be worn, and insulating tools of corresponding voltage levels should be used. (√) 20. National regulations require that electricians engaged in electrical work must receive training from institutions stipulated by the state and can only work with certificates after passing assessments. (√) 21. When indoor electrical devices or equipment catch fire, the switch should be pulled off as soon as possible to cut off the power, and appropriate fire extinguishers should be selected for firefighting. (√) 22. As an electrical worker, any violation of the "Safety Regulations for Electric Power Industry" by any personnel should be immediately stopped. (√) 23. In electrical construction, national safety rules and regulations must be followed. When installing electrical lines, the principle of convenience for users should be considered based on actual conditions. (×) 24. When electrical devices or equipment catch fire or ignite nearby combustibles, the first step is to cut off the power. (√) 25. Electric sparks and arcs have very high temperatures, which can not only cause combustibles to burn but also melt and splash metal, constituting dangerous fire sources. (√) 26. Water can only be used to extinguish fires after completely cutting off the power. (√) 27. The voltage element action voltage setting of the overcurrent protection with low voltage starting for transformers is set according to avoiding the lowest possible operating voltage on the normal busbar. (√) 28. The transformer excitation inrush current contains obvious high-order harmonics, among which the second harmonic component has the largest proportion. (√) 29. The intermediate relay in the transformer gas protection wiring should be a relay with delay. (×) 30. The transformer excitation inrush current decays over time, and the decay speed is related to the transformer capacity. (√) 31. Utilizing the characteristic that the transformer excitation inrush current contains obvious non-periodic components, the second harmonic braking principle is usually adopted to constitute transformer differential protection. (×) 32. When the switching piece XB in the transformer gas protection wiring is switched to the test position, in the event of a serious internal fault in the transformer, only the low-voltage side circuit breaker will be disconnected when the gas protection acts. (×) 33. When the transformer is energized with no load or after an external short circuit fault is cleared and voltage recovers, the excitation current can reach 6-8 times the transformer rated current. (√) 34. The amplitude adjustment and phase compensation of microcomputer-based transformer differential protection are generally achieved through software calculation algorithms. (√) 35. When the transformer has excitation inrush current, if no measures are taken, the differential protection will malfunction. (√) 36. The transformer zero-sequence overvoltage protection consists of a zero-sequence voltage element and a time element. (√) 38. The transformer excitation current exists on the power supply side. (√) 39. The main component of transformer gas protection is the gas relay, installed in the connecting pipe between the transformer oil tank and the oil conservator. (√) 40. According to the characteristics of transformer excitation inrush current, when it is identified not to be excitation inrush current, the protection is blocked. (×) 41. The transformer excitation inrush current contains obvious non-periodic components, and the waveform deviates to one side of the time axis. (√) 42. When a serious internal fault occurs in the transformer, a large amount of gas is generated in the oil tank, causing the heavy gas relay to act, connecting the protection trip circuit and disconnecting the circuit breakers on all sides of the transformer. (√) 43. The intermediate relay in the transformer gas protection wiring has a delay function to prevent unstable contact due to unstable gas and oil flow during operation. (×) 44. During normal operation of transformer differential protection, the current flowing into the differential circuit is the vector difference of the currents on both sides of the transformer. (√) 45. The intermediate relay in the transformer gas protection wiring should be a fast-acting relay. (√) 46. Transformers in power systems usually adopt the Y,d11 connection mode. The current element action current of the transformer overcurrent protection on both sides is set according to avoiding the possible excitation inrush current of the transformer. (×) 48. For double-winding transformers, overload protection is installed on the power supply side. (√) 49. The overcurrent protection with low voltage starting for transformers consists of a current element, a voltage element, and a time element. (√) 50. The low voltage element of the compound voltage starting overcurrent protection consists of a negative sequence voltage element and a single low voltage element. (√) 51. The main component of transformer gas protection is the gas relay, installed inside the transformer oil tank. (×) 52. Transformer differential protection responds to the magnitude and phase of the currents on both sides of the transformer to determine whether the protection operates. (√) 53. When the switching piece XB in the transformer gas protection wiring is switched to the trip position, in the event of a serious internal fault in the transformer, the gas protection will disconnect the circuit breakers on all sides of the transformer. (√) 54. Transformers in power systems usually adopt the Y,d11 connection mode. To make the current in the differential circuit zero during normal operation, the secondary windings of the three current transformers on the Y side of the transformer are connected in a delta configuration, and the transformation ratio is adjusted to the original (√) 55. The current element of the overcurrent protection with low voltage starting for transformers is connected to the secondary side of the current transformer on the power supply side of the transformer. (√) 56. When the transformer has an external short circuit, the differential protection will not operate. The transformer zero-sequence overvoltage protection consists of a current element and a time element. (×) 58. In microcomputer protection, the zero-sequence current for the grounding protection of a transformer with a directly grounded neutral point can be self-produced, that is, obtained by summing the three-phase currents input to the device. (√) 59. When the transformer leaks oil, causing the oil level to drop, a heavy gas signal will be issued. (×) 60. The scope of transformer gas protection is inside the transformer oil tank. (√) 61. The fundamental reason for the generation of transformer excitation inrush current is that the magnetic flux in the transformer core cannot change abruptly. (√) 62. After the transformer is closed with no load, the generated excitation inrush current gradually increases over time. (×) 63. When the transformer heavy gas protection acts, it will trip the circuit breakers on all sides of the transformer. (√) 64. When the switching piece XB in the transformer gas protection wiring is switched to the trip position, in the event of a serious internal fault in the transformer, the gas protection will only send a signal and not trip. (×) 65. The transformer excitation current exists on both the power supply side and the load side. (×) 66. During external faults, the current flowing into the differential relay in transformer differential protection is the unbalanced current. (√) 67. According to the characteristics of transformer excitation inrush current, when it is identified as excitation inrush current, the protection must be blocked. (√) 68. The overcurrent protection with low voltage starting for transformers consists of a current element, a voltage element, and a power element. (×) 69. The scope of transformer gas protection is outside the transformer oil tank. (×) 70. During normal operation of transformer differential protection, the current flowing into the differential circuit is the vector sum of the currents on both sides of the transformer. (×) 71. For transformer differential protection using the second harmonic braking principle, when excitation inrush current occurs, the protection is enabled. (×)