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


2. Secondary equipment - secondary equipment is auxiliary equipment for monitoring, measuring, operating, controlling and protecting the work of primary equipment, such as: instruments, relays, control cables, control and signal equipment, etc.


3. Secondary circuit - a circuit formed by secondary equipment connected in a certain order is called a secondary circuit or a secondary circuit.


4. Low-voltage switch - is a switching appliance used to connect or disconnect AC and DC circuits below 1000 volts. Different from the low voltage in the "Safety Regulations" (the voltage to ground is below 250 volts).


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


6. Automatic air switch - Automatic air switch is referred to as automatic switch, which is the switch with the most perfect performance among low-voltage switches. It can not only cut off the load current of the circuit, but also cut off the short-circuit current, and 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 specially used in the excitation circuit of the generator.


8. Isolation switch - is a switch with a clearly visible fracture, without an arc extinguishing device. It can be used to switch on and off lines with voltage but no load, and also allows to connect or disconnect no-load lines, voltage transformers and no-load transformers with limited capacity. The main purpose of the isolation switch 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 quite complete arc extinguishing structure and sufficient current breaking capacity.


10. Arc suppression coil - is an adjustable inductance coil with iron core, which is installed at the neutral point of the transformer or generator. When a single-phase ground fault occurs, it can reduce the ground current and suppress the arc.


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


12. Eddy current phenomenon - if the coil is set on a monolithic iron core, the iron core can be regarded as composed of many closed iron wires, and the plane formed by the closed iron wires is perpendicular to the direction of the magnetic flux. Each closed wire can be regarded as a closed conductive loop. When an alternating current is passed through the coil, the magnetic flux passing through the closed wire is constantly changing, so an induced electromotive force is generated in each wire and an induced current is induced. In this way, in the whole iron core, a circle of induced current flows around the axis of the iron core, just like a vortex in water. This induced current in the iron core is called eddy current.


13. Eddy current loss - like current flowing through a resistor, the eddy current in the iron core consumes energy and causes the iron core to heat up. 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 in which the neutral point is directly grounded.


16. Armature reaction - when there is no armature current, the main magnetic field of the air gap is generated by the excitation current alone. When there is armature current, the main magnetic field of the air gap is superimposed by the magnetic field of the excitation current and the magnetic field of the armature current. become. This effect of the armature current on the main magnetic field is called the armature reaction.


17. Asynchronous motor - also known as induction motor, it works according to the two principles of the conductor cutting the magnetic field line to generate induced electromotive force, and the current-carrying conductor being affected by the magnetic permeability 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 less than the speed of the rotating magnetic field, so it is called an asynchronous motor.


18. Synchronous speed - when a three-phase symmetrical current is passed into the three-phase symmetrical winding of an asynchronous motor, a rotating magnetic field is generated in the air gap of the motor. Lots of slow speeds. We call the speed of this rotating magnetic field the synchronous speed.


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


20. Star-delta switching start-if the motor is in normal operation, the stator windings are connected in a delta shape, and the stator windings are connected in a star shape when starting, and then in a delta operation after the start. This starting method is called star-delta. Switching starts. 21. Absorption ratio - the ratio of the resistance at 60 seconds and 15 seconds after applying a DC voltage to an insulating sample.


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


22. Protective grounding - in order to prevent electrical shocks from damage to the insulation of electrical equipment, the metal shell or frame of electrical equipment that is not charged under normal conditions is connected to the ground, which is called protective grounding.


23. Protection zero connection - is to connect the metal shell or frame of electrical equipment with the neutral line drawn from the neutral point in the power neutral point grounding system. This is also an important measure to protect personal safety.


24. Isolation switch - is a switch with a clearly visible fracture, without an arc extinguishing device. It can be used to switch on and off lines with voltage but no load, and also allows to connect or disconnect no-load lines, voltage transformers and no-load transformers with limited capacity. The main purpose of the isolation switch is to isolate the power supply voltage when the electrical equipment is overhauled.


25. 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 quite complete arc extinguishing structure and sufficient current breaking capacity.


26. Arc suppression coil - is an adjustable inductance coil with iron core, which is installed at the neutral point of the transformer or generator. When a single-phase ground fault occurs, it can reduce the ground current and suppress the arc.


27. Reactor - A reactor is an inductive coil with a 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.


28. Eddy current phenomenon - if the coil is set on a monolithic iron core, the iron core can be regarded as composed of many closed iron wires, and the plane formed by the closed iron wires is perpendicular to the direction of the magnetic flux. Each closed wire can be regarded as a closed conductive loop. When an alternating current is passed through the coil, the magnetic flux passing through the closed wire is constantly changing, so an induced electromotive force is generated in each wire and an induced current is induced. In this way, in the whole iron core, a circle of induced current flows around the axis of the iron core, just like a vortex in water. This induced current in the iron core is called eddy current.


29. Eddy current loss - like current flowing through a resistor, the eddy current in the iron core consumes energy and causes the iron core to heat up. This energy loss is called eddy current loss.


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


31. High current grounding system - a system in which the neutral point is directly grounded.


32. Armature reaction - when there is no armature current, the main magnetic field of the air gap is generated by the excitation current alone. When there is armature current, the main magnetic field of the air gap is superimposed by the magnetic field of the excitation current and the magnetic field of the armature current. become. This effect of the armature current on the main magnetic field is called the armature reaction.


33. Arc - A large collection of sparks forms an arc.


34. Phase sequence - the sequence in which the sine quantities of each phase pass through the same value. Any group of asymmetric three-phase sinusoidal AC voltage or current phasors can be decomposed into three groups of symmetrical components: one group is the positive sequence component, which is represented by the subscript "1", and the phase sequence is the same as the phase sequence of the original asymmetric sinusoid. Consistent, that is, the order of ABC, the phases of each phase are 120° different from each other; one group is the negative sequence component, which is represented by the subscript "2", and the phase sequence is opposite to the phase sequence of the original asymmetric sinusoidal quantity, that is, the order of ACB, each phase The phases are 120° different from each other; the other group is the zero-sequence component, which is represented by the subscript "0", and the three-phase phases are the same. For example, the asymmetry of two-phase operation will have negative and zero sequence components.


35. Relay starting current - the minimum current value that can make the relay act.


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36. Current relay - a relay that determines whether it operates or not by responding to the current size of the coil connected to the relay is called a current relay.


37. Voltage relay - a relay that determines its action or not in response to the added voltage.


38. Fast relay - generally refers to the relay whose action time is less than 10 milliseconds.


39. Quick-break protection - no time limit, as long as the current reaches the set value, it can act instantaneously.


40. Differential protection - it is the protection that starts by using the current change when the electrical equipment fails.


41. Zero-sequence protection - the protection of the zero-sequence current and zero-sequence voltage electrical quantities unique to the ground fault of the power system.


42. Distance protection - a protection device that reflects the distance from the fault point to the protection installation.


43. Automatic reclosing - when the line fails and the circuit breaker trips, it can automatically reclose without manual operation. Reclosing is divided into single-phase and comprehensive reclosing.


44. Comprehensive reclosing - its functions are: single-phase fault trips single-phase, unsuccessful trips three-phase; interphase fault trips three-phase, three-phase coincidence, unsuccessful trips three-phase.


45. Acceleration after reclosing——Reclosing is on a permanent fault, and the protection device trips the circuit breaker without time limit again and is not reclosing, which is called acceleration after reclosing.


46. ​​Protection - It can meet the requirements of system stability and equipment safety, and can selectively and quickly remove the protected equipment and the protection of the entire line of faults.


47. Backup protection - protection used to remove faults when the main protection does not act or the circuit breaker refuses to act


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


49. Shutdown operation - when electrical equipment is converted from one state to another state, or the operating mode of the system is changed, a series of operations are required. We call this operation the shut-down operation of electrical equipment. The main switching operations are:


(1) Power outage of the transformer


(2) The power line is out of power


(3) Starting, paralleling and unloading of generators


(4) Loop closure and decoupling of the network


(5) Change of bus connection mode (ie, switching bus operation)


(6) Change of neutral grounding method and adjustment of arc suppression coil


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


(8) Installation and removal of ground wire


50. No-load loss - the power drawn by the transformer when the sinusoidal AC rated voltage of the rated frequency is applied to one coil of the transformer (at the rated tap position), and the rest of the coils are open circuit, to supply the transformer iron Core losses (eddy current and hysteresis losses)


51. No-load current - When the transformer is running at no-load, the main magnetic flux is established by the no-load current, so the no-load current is the excitation current. The rated no-load current is the positive and weak AC rated voltage of the rated frequency applied to one coil (at the rated tap position), and the three-phase arithmetic mean of the current drawn by the transformer when the other coils are open-circuited, calculated as the rated current. expressed as a percentage.


52. Short-circuit loss - the power absorbed by the transformer when the rated current of the rated frequency passes through one coil of the transformer and the other coil is short-circuited, it is the loss generated by the resistance of the transformer coil, that is, the copper loss (the coil is Contact position, temperature 70°C).


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


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