Elementary electrician examination

Elementary examination questions and reference answers for electricians

, name explanation:

1, three-phase alternating current: the power system is called three-phase alternating current, which consists of three alternating current circuit groups with the same frequency, the same potential amplitude and the phase difference of120.

2. Equipment: Equipment directly related to power generation and transmission and distribution includes various high-voltage circuit breakers, disconnectors, buses, power cables, voltage transformers, current transformers, reactors, lightning arresters, arc suppression coils, shunt capacitors and high-voltage fuses.

3. Second equipment: auxiliary equipment for monitoring, measuring, manipulating, controlling and protecting, various relays, signal devices, measuring instruments, wave recording devices, telemetry and telecommunication devices, various control cables and buses, etc.

4. High-voltage circuit breaker: It is said that the high-voltage switch only cuts off or closes the no-load current of the high-voltage circuit, and the system fails to cut off the load current through the relay protection device. Short-circuit current has perfect arc extinguishing structure and sufficient breaking capacity.

5. Unloading: The structure of unloading is similar to that of secret isolation. A simple arc extinguishing device is installed, which has obvious breaking point and constant breaking ability, and can directly break short-circuit current when running with load. It needs to be realized by connecting high voltage fuses in series.

6. Air switch (self-closing): Keep the closed position by hand (or electricity). The tripping mechanism acts on the tripping device, and the low-voltage turn-off device with arc extinguishing device is widely used in the circuits of 500V AC and DC devices, which automatically cuts off the circuit when the load occurs, the short circuit occurs, the voltage drops or disappears.

7. Cable: A conductor consisting of a core wire (conductive part) and an outer insulating layer is called a cable.

8. Bus: The electrical bus integrates the distribution energy channel equipment, determines the number of distribution equipment and clearly connects the generator and transformer lines to complete the power transmission and distribution task with the system.

9. Current transformer: a current conversion instrument for weighing instruments.

10, transformer: one kind of static electrical equipment uses a certain value of AC voltage to change the frequency, and another or several kinds of equipment with the same value of AC voltage.

1 1. High-voltage test pen: used to check whether high-voltage network distribution equipment, overhead lines and cables are electrified.

12. Wiring: The wiring of important tools for emergency voltage protection personnel of power outage equipment lines must adopt 25mm 2 bare copper core according to the regulations issued by the Ministry.

13. notice board: use the warning near the live part of the equipment to instruct the staff to prepare for the working point, remind them to take safety measures and prohibit a small number of equipment or a section of lines from closing and energizing. Signboards used for warning, permission and tips are prohibited.

14. Shielding fence: There are two kinds of shielding fences to prevent the staff from intentionally touching the equipment screen installed in the live equipment department.

15. Insulating rod: Insulating rod, such as ruler rod, insulating pull rod and operating rod, consists of working part and insulating rod handle, and is used to close or isolate portable wiring for measurement and test.

16, stride voltage: the potential difference between two points with a horizontal distance of 0.8m When two feet touch two points, the body bears voltage. Step voltage is called step voltage. Now, the step voltage is between the connector and the horizontal distance of 0.8m from the connector surface.

17. Phase sequence: the negative value of instantaneous value of alternating current changes in turn through zero value.

18. power network: the power system department of power network is a unified network formed by connecting various transmission and distribution lines with the same voltage level in all substations (institutes).

19. power system: the power system force system department consists of step-up and step-down substations of generators and distribution devices in power plants, transmission and distribution lines and user electrical equipment.

20. Power system: Power plants, substations and electrical equipment are collectively referred to as power systems when their interphase power networks are connected with thermal networks (or hydraulic systems).