Summary of 47 practical electrical knowledge

Come and see how much knowledge you still lack

1. Primary loop -- from the generator through the transformer and transmission and distribution lines to the electrical equipment of the main wiring, usually called primary loop.

2. Secondary equipment -- Secondary equipment is auxiliary equipment for monitoring and measuring, operation control and protection of primary equipment, such as instruments, relays, control cables, control and signal equipment, etc

3. Secondary circuit - secondary equipment in a certain order of the circuit, called the secondary circuit or secondary circuit.

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

5. Contactor -- it is a low-voltage switch used to turn on or off the load current in the circuit at a distance. It is widely used to frequently start and control the motor circuit.

6. Automatic air switch - automatic air switch referred to as automatic switch, is the best performance of low-voltage switches. It can not only cut off the load current of the circuit, but also cut off the short circuit current, commonly used in low-voltage high-power circuit as the main control appliance.

7. Demagnetization switch is a special DC monopole air automatic switch for generator excitation loop.

8. Disconnecting switch - is a switch with visible break, no arc extinguishing device. It can be used to turn on and off lines with voltage and no load. It also allows to turn on or off no-load lines, voltage transformers and limited capacity no-load transformers. The main purpose of the disconnecting switch is to isolate the supply voltage when the electrical equipment is being repaired.

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 relay protection device when the system fails. It has a fairly complete arc extinguishing structure and sufficient flow interruption capacity.

10. Arc suppressor coil -- an adjustable inductor coil with a core, installed at the neutral point of a transformer or generator, in the event of a single-phase grounding fault, to reduce ground current and arc suppression.

96ef5ef4e381d3df27e1c97c4ddfef1e11 asynchronous motor, also known as induction motor, it is in accordance with the conductor cutting magnetic field line to generate induced electromotive force, and the current carrying conductor in the magnetic field by the permeability of the two principles of work. In order to maintain a relative motion between the magnetic field and the rotor conductor, the rotor speed is always smaller than the speed of the rotating magnetic field, so it is called asynchronous motor.

12. Synchronous speed -- When three-phase symmetric current is passed into the three-phase symmetric winding of asynchronous motor, a rotating magnetic field will be generated in the air gap of the motor. According to the different number of poles of the motor, the rotating magnetic field will have different speed, and the speed will be slow if the number of poles is large. We call the rotational speed of this rotating magnetic field the synchronous speed.

13. Slip -- The difference between the synchronous speed N1 and the motor speed N (N1-N) is called the speed difference, and the ratio of the speed difference to the synchronous speed is called the slip. S is usually expressed as a percentage, that is, S=(N1-N)/ N1 ╳100%

14. Star-triangle swap start -- if the motor is in normal operation, the stator windings are connected into triangles, and the stator windings are connected into stars when the motor is started, and then connected into triangles after the motor is started, this starting method is called star-triangle swap start. 21. Absorption ratio -- the ratio of resistance 60 seconds to 15 seconds after DC voltage is applied to insulation samples.

15. Working grounding - In order to ensure the safe and reliable operation of electrical equipment in normal or fault conditions, to prevent high voltage caused by equipment failure, must be grounded at a certain point in the power system, called working grounding.

16. Protective grounding - In order to prevent the insulation damage of electrical equipment and electric shock accident, the electrical equipment in normal circumstances not charged metal shell or frame is connected with the earth, called protective grounding.

17. Protection zero - is in the power neutral ground system to connect the metal shell or frame of electrical equipment and the neutral point out of the neutral line. It is also an important measure to protect personal safety.

18. Disconnecting switch - a switch with a visible break and no arc extinguishing device. It can be used to turn on and off lines with voltage and no load. It also allows to turn on or off no-load lines, voltage transformers and limited capacity no-load transformers. The main purpose of the disconnecting switch is to isolate the supply voltage when the electrical equipment is being repaired.

19. 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 relay protection device when the system fails. It has a fairly complete arc extinguishing structure and sufficient flow interruption capacity.

20. Arc suppressor coil -- an adjustable inductor coil with a core, installed at the neutral point of a transformer or generator, to reduce ground current and arc suppressor in the event of a single-phase ground fault.

21. Reactor -- A reactor is an inductive coil with little resistance. Each turn of the coil is insulated from each other, and the whole coil is insulated from the ground part. The reactor is connected in series in the circuit to limit the short circuit current.

22. Eddy current phenomenon - such as a wire snare on a monolithic iron core, the iron core can be seen as composed of many closed wire, the closed wire formed a plane perpendicular to the direction of the magnetic flux. Each closed wire can be regarded as a closed conductive loop. As an alternating current passes through the coil, the flux across the closed wire is constantly changing, thus generating an induced electromotive force in each wire and causing an induced current. Thus, throughout the core, loops of induced current flow around the axis of the core, like vortices in water. This induced current in the core is called eddy current.

23. Eddy current loss - just like the current flowing through a resistance, the eddy current in the core consumes energy and heats the core. This energy loss is called eddy current loss.

24. Small current grounded system -- neutral point is not grounded or grounded by arc suppression coil.

25. High current grounded systems - systems where the neutral point is directly grounded.

26. Armature reaction -- When there is no armature current, the main airgap magnetic field is generated by the excitation current alone. When there is armature current, the main airgap magnetic field is generated by the superposition of the magnetic field of the excitation current and the armature current. This effect of the armature current on the main magnetic field is called the armature reaction.

27. Electric arc - a large number of point sparks to form an electric arc.

28. Phase sequence - the order in which the sinusoids of each phase pass through the same value. Any group of asymmetric three-phase sinusoidal AC voltage or current phasor can be decomposed into three groups of symmetric components: one group is the positive sequence component, represented by the subscript "1", the phase sequence is consistent with the original asymmetric sinusoidal phase sequence, namely A-B-C order, each phase difference 120°; The first group is the negative sequence component, denoted by the subscript "2". The phase sequence is opposite to that of the original asymmetric sinusoidal quantity, that is, the order of A-C-B, and the phase difference of each phase is 120°; The other group is the zero sequence component, denoted by the subscript "0", with the same phase of the three phases. For example, two - phase operation asymmetry will have negative and zero - order components.

29. Relay starting current -- the minimum current that will enable the relay to operate.

30. Current relay -- the relay whose action is determined by the current size of the coil of the reaction access relay is called current relay.

31. Voltage relay -- the relay whose action is determined by the voltage added to the reaction.

32. Fast relay -- generally refers to the relay operation time less than 10 milliseconds.

33. Quick break protection -- without time limit, as long as the current reaches the setting value can be instantaneous action protection.

34. Differential protection - the protection of electrical equipment to start up by the change of current in the event of failure.

35. Zero sequence protection -- the protection of zero sequence current and zero sequence voltage, which is characteristic of ground fault in power system.

36. Range protection - a protection device that reflects the distance from the point of failure to the protection installation.

37. Automatic reclosing - a device that can be automatically reclosing without manual operation when the circuit breaker trips after a fault occurs on the line. Reclosing is divided into single phase and comprehensive reclosing.

38. Comprehensive reclosing -- its function is: single-phase fault jump single-phase, unsuccessful jump three-phase; Phase fault jump three phase, three phase coincidence, unsuccessful jump three phase.

39. Post-reclosing acceleration - In the event of a permanent failure, the protective device will act again without time limit to jump the circuit breaker without reclosing, called post-reclosing acceleration.

40. Protection -- can meet the requirements of system stability and equipment safety, selectively and quickly remove the protected equipment and the protection of the whole line failure.

41. Backup protection - the protection to remove the fault when the main protection is not working or the circuit breaker is not working

42. Power factor - the ratio of active power P to apparent power S.

43. Switching operation - When an electrical device changes from one state to another, or changes the way the system operates, a series of operations are required. We call this operation the switching operation of an electrical device. The main reversing operations are:

(1) the shutdown of the transformer

(2) The power line stops sending power

(3) Start the generator, parallel and parallel operation

(4) Network ring closing and ring breaking

(5) Change of bus connection mode (i.e., bus switching operation)

(6) Change the neutral grounding mode and adjust the arc suppression coil

(7) Changes in the use state of relay protection and automatic devices

(8) Installation and removal of ground cables

44. No-load loss -- is the power absorbed by the transformer when the rated sinusoidal AC voltage at rated frequency is applied to a coil of the transformer (at the rated sub position), and the other coils are open circuit, which is used to supply the transformer core loss (eddy current and hysteresis loss).

45. No load current - when the transformer is running no load, the main flux is established by the no-load current, so the no-load current is the excitation current. Rated no-load current is the three-phase arithmetic mean value of the current drawn by the transformer when the rated voltage of positive and weak AC at the rated frequency is applied to a coil (at the rated sub position) and the other coils are open circuit, expressed as a percentage of the rated current.

46. Short-circuit loss - is the rated current at rated frequency through a transformer coil, while the other coil is short-circuited, the power absorbed by the transformer, it is the loss of the transformer coil resistance, that is, the copper loss (coil in the rated contact position, temperature 70℃).

47. Short circuit voltage -- when a coil is short-circuited, the voltage at rated frequency applied in the other coil to generate rated current (at rated tap position), expressed as a percentage of rated voltage, which reflects the transformer impedance (resistance and leakage reactance) parameters, also known as impedance voltage (temperature 70℃).

About the Author

Leave a Reply

You may also like these