1. () is an important indicator of power system operation, reflecting the state of balance between supply and demand of active power in the power system. A: . Voltage B: . Current C: . Frequency Answer: C 2.4 The transformer differential protection based on the second harmonic braking principle consists of differential elements, second harmonic braking, () and TA disconnection detection, etc. A: . Time delay element B: . Voltage element C: . Power direction element D: . Differential quick-break element Answer: D 3. Class II equipment's protection against electric shock is achieved by adopting () measures. This type of equipment does not use protective earthing measures and does not rely on installation conditions. A: Safety voltage B: Double insulation C: Transformer oil insulation Answer: B 4. The safety qualification training time for safety production management personnel shall not be less than () class hours; the annual retraining time shall not be less than () class hours. A: 100, 40 B: 24, 8 C: 48, 16 Answer: C 5. The installation wiring diagram includes (), rear view wiring diagram of the panel, and terminal block diagram. A: . Schematic wiring diagram B: . Logic block diagram C: . Panel layout diagram Answer: C 6. The installation wiring diagram includes panel layout diagram, () and terminal block diagram. A: . Schematic wiring diagram B: . Rear view wiring diagram of the panel C: . Flow chart D: . Logic block diagram Answer: B 7. The installation wiring diagram includes panel layout diagram, rear view wiring diagram of the panel, and (). A: . Schematic wiring diagram B: . Flow chart C: . Terminal block diagram D: . Logic block diagram Answer: C 8. The setting value of the low voltage element of the automatic load shedding device based on voltage reduction should be () the critical voltage of voltage collapse, with a certain margin. A: . Higher than B: . Lower than C: . Equal to Answer: A 9. Designed by functional modules, adopting a master-slave CPU collaborative working mode, with no communication between functional modules, and the monitoring host communicating with each functional subsystem is called () substation automation system. A: . Distribution station B: . Transformer C: . Power plant Answer: C 11. The primary wiring scheme for automatic switching of standby power supply can be divided into () and dark standby modes according to the standby mode. A: . Line standby B: . Explicit standby C: . Transformer standby D: . Busbar. The primary wiring scheme for automatic switching of standby power supply can be divided into explicit standby and () modes. A: . Dark standby B: . Line standby C: . Transformer standby D: . Busbar. The automatic switching device for standby power supply ensures that after () fails and exits, continuous power supply can be obtained, so that the auxiliary power supply of the substation is normally supplied. A: . Standby line B: . Standby transformer C: . Working power supply Answer: C 14. When the automatic switching device for standby power supply operates, the standby power supply is put into operation by closing the standby line circuit breaker or () circuit breaker. A: . Working line B: . Working busbar C: . Standby transformer Answer: C 15. The operating time of the automatic switching device for standby power supply should be based on the principle of (), to reduce the self-starting time of motors. A: . The load outage time should be as short as possible B: . The load outage time should be as short as possible C: . The success rate of automatic switching should be as low as possible D: . The equipment failure rate should be as low as possible Answer: B 16. The operating time of the automatic switching device for standby power supply should be based on the principle of making the load outage time as short as possible, to (). A: . Improve the success rate of automatic switching B: . Reduce the equipment failure rate C: . Reduce the self-starting time of motors D: . Improve the insulation recovery time of the fault point Answer: C 17. When the automatic switching device for standby power supply operates, if the standby power supply is switched to a persistent fault, the standby power supply circuit breaker will (). A: . Accelerate disconnection B: . After disconnection, switch in again C: . Keep closed D: . Refuse to trip Answer: A 18. When the automatic switching device for standby power supply operates, the standby power supply can only be switched in ().