Maintenance Electrician [http://www.bangyuanedu.com] Primary Tutorial:
1. Three-phase AC: A power system composed of three AC circuits with the same frequency, equal potential amplitude, and phase differences of 120° is called three-phase AC.
2. Primary Equipment: Devices directly related to the production and transmission of electric energy are called primary equipment. These include various high-voltage circuit breakers, disconnect switches, busbars, power cables, voltage transformers, current transformers, reactors, surge arresters, arc-suppression coils, shunt capacitors, and high-voltage fuses.
3. Secondary Equipment: Auxiliary devices that monitor, measure, control, and protect primary equipment through correspondence education [http://www.bangyuanedu.com]. Such as various relays, signaling devices, measuring instruments, recording devices, as well as telemetry, telecontrol devices, and various control cables and small busbars.
4. High-Voltage Circuit Breaker: Also known as a high-voltage switch, it can not only open or close the no-load current and load current in a high-voltage circuit but also, through the action of relay protection devices, cut off overloads and short-circuit currents. It has a relatively complete arc-extinguishing structure and sufficient current-breaking capability.
5. Load Switch: The construction of a load switch is similar to that of a disconnect switch, except it is equipped with a simple arc-extinguishing device. It has a clear disconnection point, some current-breaking ability, and can operate under load, but cannot directly interrupt short-circuit currents. If necessary, it relies on high-voltage fuses connected in series with it.
6. Air Circuit Breaker (Automatic Switch): A low-voltage switch operated manually (or electrically), locked in the closed position, tripped by a tripping mechanism, and equipped with an arc-extinguishing device. It is widely used in AC and DC installations below 500V. When there is an overload, short circuit, voltage drop, or disappearance in the circuit, it can automatically cut off the circuit.
7. Cable: Wires consisting of a core (conductive part), an outer insulation layer, and a protective layer are called cables.
8. Busbar: Electrical busbars are passage devices for collecting and distributing electric energy. They determine the number of distribution devices and indicate how generators, transformers, and lines are connected, as well as how they connect to the system to complete the task of transmitting and distributing electric energy.
9. Current Transformer: Also known as an instrument transformer, it is a device that converts large currents into smaller ones.
10. Transformer: A stationary electrical device used to convert one value of alternating voltage into another or several different values of alternating voltage at the same frequency.
11. High-Voltage Tester: A tool used to check if high-voltage network distribution equipment, overhead lines, and cables are energized.
12. Grounding Wire: An important tool used to ensure the safety of workers when unexpected voltages appear on already de-energized equipment and lines. According to regulations, grounding wires must be made of bare copper flexible wire with a cross-sectional area of more than 25mm².
13. Signage: Used to warn people not to approach equipment and live parts, indicate work locations for staff, remind them to take safety measures, and prohibit closing certain equipment or sections of lines. They can be divided into warning, permission, indication, and prohibition types.
14. Barrier: Protective screens installed to prevent workers from accidentally touching live parts, divided into temporary barriers and permanent barriers.
15. Insulating Rod: Also known as a command rod, insulating pull rod, operation rod, etc. An insulating rod consists of a working head, an insulating rod, and a grip. It is used to close or open high-voltage disconnect switches, install and remove portable grounding wires, and perform measurements and tests.
16. Step Voltage: If there is a potential difference between two points on the ground with a horizontal distance of 0.8m, when a person's feet touch these two points, a voltage will be borne on the body, which is called step voltage. The largest step voltage appears between a point 0.8m horizontally away from the grounding body and the grounding body.
17. Phase Sequence: The order of phases, which is the sequence in which the instantaneous value of alternating current changes from negative to positive through zero.
18. Power Grid: The power grid is a part of the power system, consisting of various substations and transmission and distribution lines of different voltage levels, forming a unified network.
19. Power System: The power system is a part of the power system, consisting of generators and distribution equipment in power plants, step-up and step-down substations, transmission and distribution lines, and user's electrical equipment.
20. Power System: The overall system consisting of power plants, substations, and users' electrical equipment, interconnected by the power grid and thermal (or hydraulic) systems, is called the power system.
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