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    Practical knowledge of electrical automation

    1. Primary circuit-The electrical main wiring from the generator through the transformer and the transmission and distribution lines to the electrical equipment, usually called the primary circuit.
    2. Secondary equipment-Secondary equipment is auxiliary equipment that monitors, measures, controls and protects the work of the primary equipment, such as: meters, relays, control cables, control and signal equipment.

    3. Secondary circuit-A circuit in which secondary equipment is connected in a certain order is called a secondary circuit or a secondary circuit.

    4. Low voltage switch-is used to switch on or off AC and DC circuits below 1000 volts. Different from the low voltage in “Safety Regulation” (the voltage to ground is below 250V).

    5. Contactor-is a low-voltage switch used to remotely switch on or off the load current in the circuit. It is widely used in circuits that frequently start and control motors.

    6. Automatic air switch-Automatic air switch is referred to as automatic switch for short. It is the most complete switch in low-voltage switch. It can not only cut off the load current of the circuit, but also cut off the short-circuit current. It is often used as the main control appliance in low-voltage high-power circuits.

    7. De-excitation switch-is a DC unipolar air automatic switch dedicated to the generator's excitation circuit.

    8. Isolating switch-It is a switch with obvious visible break, without arc extinguishing device. It can be used to switch on and off lines with voltage and no load. It also allows to connect or disconnect no-load lines, voltage transformers and no-load transformers with limited capacity. The main purpose of the disconnector is to isolate the power supply voltage when the electrical equipment is overhauled.

    9. High voltage circuit breaker-also known as high voltage switch. It can not only cut off or close the no-load current and load current in the high-voltage circuit, but also cut off the short-circuit current through the action of the relay protection device when the system fails. It has a fairly complete arc extinguishing structure and sufficient current interrupting capacity.

    10. Arc Suppression Coil-is an adjustable inductor coil with a core, which is installed at the neutral point of the transformer or generator. When a single-phase ground fault occurs, it plays a role in reducing ground current and arc suppression.

    11. Reactor-Reactor is an inductive coil with very small resistance. The turns of the coil are insulated from each other, and the entire coil is insulated from the ground. Reactors are connected in series in the circuit to limit short-circuit current.

    12. Eddy current phenomenon-If the coil is sheathed on a solid iron core, the iron core can be regarded as consisting of many closed iron wires, and the plane formed by the closed iron wires is perpendicular to the magnetic flux direction. Each closed wire can be regarded as a closed conductive loop. When an alternating current is passed in the coil, the magnetic flux passing through the closed iron wire is constantly changing, so an induced electromotive force is generated in each wire and an induced current is caused. In this way, in the entire iron core, an inductive current flowing around the core axis is formed like a vortex in water. This induced current generated in the iron core is called eddy current.

    13. Eddy current loss—Like current flowing through a resistor, eddy current in the iron core consumes energy and heats the iron core. This energy loss is called eddy current loss.

    14. Small current grounding system-the neutral point is not grounded or grounded through the arc suppression coil.

    15. High current grounding system-a system where the neutral point is directly grounded.

    16. Armature reaction—When there is no armature current, the main air gap magnetic field is generated by the excitation current alone. When there is an armature current, the main air gap magnetic field is superimposed by the magnetic field of the excitation current and the magnetic field of the armature current to make. This effect of the armature current on the main magnetic field is called the armature response.

    17. Asynchronous motor-also called induction motor, it works according to the two principles of the induction electromotive force generated by the cutting of the magnetic field lines of the conductor and the magnetic permeability of the current-carrying conductor in the magnetic field. In order to maintain relative motion between the magnetic field and the rotor conductor, the speed of the rotor is always smaller than the speed of the rotating magnetic field, so it is called an asynchronous motor.

    18. Synchronous speed-When three-phase symmetrical current is passed in the three-phase symmetrical winding of the asynchronous motor, a rotating magnetic field is generated in the air gap of the motor. According to the number of poles of the motor, the speed of the rotating magnetic field is also different. Many speeds are slow. We call the speed of this rotating magnetic field a synchronous speed.

    19. Slip rate—The difference (n1-n) between the synchronous speed n1 and the motor speed n is called the speed difference, and the ratio of the speed difference to the synchronous speed is called the slip ratio. The slip ratio S is usually expressed as a percentage, that is, S = (n1-n) / n1╳100%

    20. Star-delta switch start-up—If the motor is in normal operation, the stator winding is connected to a triangle, the stator winding is connected to a star during startup, and it is connected to run in a triangle after starting. Switchover starts. 21. Absorption ratio——The ratio of resistance between 60 seconds and 15 seconds after applying DC voltage to the insulation sample.