Technology Literature

Explanation of 60 Commonly Used Terms in Power System

1.Active power - the part of the energy that is converted into electromagnetic form during the transmission and transmission of AC electrical energy is called active power

2. Reactive power - in the process of AC power transmission and transmission, the part of the energy used for the exchange of electromagnetic fields in the circuit is called reactive power.

3. Power system - The whole composed of generators, power distribution devices, step-up and step-down substations, power lines and power users is called the power system. Neutral point displacement: In a three-phase circuit, when the three-phase load of the power supply voltage is symmetrical, if the three-phase load is also symmetrical, the voltage of the neutral point is zero regardless of whether there is a neutral point. However, if the three-phase load is asymmetrical, and there is no neutral line or the neutral line impedance is large, a voltage will appear at the neutral point, which is called the neutral point displacement phenomenon.

4. Operational overvoltage - the transient voltage rise caused by the opening and closing operation of the circuit breaker and the short circuit or ground fault is called the operation overvoltage;

5. Resonance overvoltage - The grid circuit is divided or the components with iron core tend to be saturated due to the operation of the circuit breaker, resulting in the inductive and capacitive reactance of a certain circuit meeting the resonance conditions, which may cause the resonance and the voltage rise, which is called resonance overvoltage. Voltage.

6. Electrical main wiring—mainly refers to the electric power transmission circuit designed to meet the predetermined power transmission mode and operation requirements in power plants, substations, and power systems, indicating the interconnection between high-voltage electrical equipment .

7. Double busbar wiring - It has two sets of busbars: working busbar I and standby busbar l. Each circuit is connected to two sets of busbars through a circuit breaker and two sets of isolating switches, respectively, and the busbars are connected through a busbar connecting circuit breaker (referred to as a busbar connection), which is called double busbar connection.

8. One and a half circuit breaker wiring—every two components (outgoing line or power supply) use three circuit breakers to form a series connection to two sets of busbars, which is called one and a half circuit breaker wiring, also known as 3/2 wiring.

9. Power consumption of the plant - During the start-up, operation, decommissioning and maintenance of the power plant, there are a large number of mechanical equipment driven by electric motors to ensure the main equipment of the unit and the coal transportation, coal crushing, ash removal, dust removal and water removal. The normal operation of processing and other auxiliary equipment. These motors and electrical equipment for operation, operation, testing, maintenance, and lighting of the whole plant are all plant loads, and the total power consumption is collectively referred to as plant electricity.

10. Plant electricity consumption rate - the percentage of plant electricity consumption in the total power generation of the power plant, which is called the plant electricity consumption rate. Plant electricity consumption rate is one of the main economic indicators of power plant operation.

11. Regular load - a motor that is used continuously and continuously every day;

12. Infrequent load - load used only during maintenance, accident or start and stop of the furnace;

13.Continuous load - the load that runs continuously for more than 2 hours each time;

14.Short-time load - load that only runs for 10-120min each time;

15.Intermittent load - repeated periodic work, each cycle does not exceed the load of 10min.

16.Self-starting of electric motors—motors in normal operation in the factory system, "when the voltage of the power supply bus suddenly disappears or decreases significantly, if after a short period of time (usually 0.5-1.5s), its speed drops a lot at the end. Or before it stops, the factory bus voltage returns to normal (such as power failure removal or automatic backup power supply), the motor will accelerate by itself and return to normal operation. This process is called self-starting of the motor.

17.Loss of excitation - the sudden partial or complete loss of excitation of a synchronous generator is called loss of excitation

18.Excitation Control System - The entire system consisting of the excitation regulator, the excitation power unit and the generator itself is called the excitation control system

19.Self-shunt static excitation system - using a transformer connected to the generator outlet. (called the excitation transformer') as the excitation power supply, which is supplied to the generator excitation after being rectified by silicon. Because the excitation transformer is connected in parallel with the generator outlet, this excitation method is called the self-shunt excitation method. The excitation transformer and rectifier are all static components, so it is also called the self-shunt excitation static excitation system.

20.Transformer—is a sensor that obtains electrical primary circuit information from secondary equipment such as measuring instruments, relay protection and automatic devices in the power system. The role of the transformer is to convert high voltage and large current into low voltage and small current in proportion

21.Sulfur hexafluoride circuit breaker - a circuit breaker that uses SFe gas with excellent arc extinguishing performance and insulating properties as the arc extinguishing medium, called SF 6 circuit breaker. It has the characteristics of strong breaking capacity and small size, but the structure is more complicated, the metal consumption is large, and the price is more expensive.

22.Vacuum circuit breakers - circuit breakers that use the high dielectric strength of vacuum to extinguish arcs, called vacuum circuit breakers. This kind of circuit breaker has the characteristics of fast arc extinguishing speed, non-oxidizing contact material, long life and small size.

23. Working grounding - is the grounding required to ensure the normal operation of the power system. For example, the neutral point of the transformer in the neutral point direct grounding system is grounded, and its function is to stabilize the potential of the power grid to the ground, thereby reducing the insulation to the ground.

24 Lightning protection grounding - is the grounding set for the needs of lightning protection. For example, the grounding of lightning rods (wires) and arresters is to make the lightning current smoothly lead to the ground, so as to reduce the lightning overvoltage, so it is also called overvoltage protection grounding.

25.Protective grounding - also known as safety grounding, is a grounding set for personal safety, that is, the casing (including cable sheath) of electrical equipment must be grounded to prevent the casing from being charged and endangering personal safety.

26.Instrumentation and control grounding—the thermal control system, data acquisition system, computer monitoring system, transistor or microcomputer type relay protection system and telecontrol communication system of the power plant, etc., are set up to stabilize the potential and prevent interference. Instrument control grounding is also known as electronic system grounding.

27.Grounding resistance - refers to the resistance encountered when the current enters the earth through the grounding body and spreads around.

28. Voltage - When a unit positive charge is shifted from a high potential to a low potential, the work done by the electric field force on it is called voltage.

29. Current——_ is a physical phenomenon in which a large number of electric charges move in a regular direction under the action of electric field force.

30. Resistance - When the current passes through the conductor, there will be resistance, because the free electrons are constantly colliding with the atoms and molecules in the conductor during the movement, so that the free electrons are subject to a certain resistance. The resistance of a conductor to current flow is called resistance.

31. The rated current of the motor - is the maximum working current of the motor in normal continuous operation.

32. The power factor of the motor - is the ratio of the rated active power to the rated apparent power

33. The rated voltage of the motor - the line voltage in the rated working mode.

34. The rated power of the motor - refers to the mechanical power that the rotating shaft can output when working under rated conditions.

35. The rated speed of the motor - refers to its speed at rated voltage, rated frequency and rated load

36. Power System Oscillation——Due to the failure or tripping of the lead wire or line switch of the power plant, the dynamic stability of the power system is destroyed, causing the frequency meter to indicate abnormally, and the load meter and voltmeter swing greatly. The unstable phenomenon is called power System oscillates.

37. Protective grounding—reliably connect the metal casing and frame of electrical equipment to the ground through grounding devices; it is an important measure to protect personal safety in a system where the neutral point of the power supply is not grounded.

38. Protection zero connection - in the neutral point grounding system, connecting the metal shell, frame, etc. of the electrical equipment with the neutral point lead-out neutral line is also an important measure to protect personal safety.

39. Bus bar - The bus bar plays the role of collecting and distributing electric energy, also known as the bus bar. In principle, it is an electrical node in the circuit, which determines the number of power distribution equipment, and indicates how to connect generators, transformers and lines, and how to connect with the system to complete the transmission and distribution tasks.

40. Short circuit - in a three-phase circuit, the phase-to-phase and phase-to-ground are connected by a small impedance or directly, resulting in a sharp increase in the current in the circuit. This phenomenon is called a short circuit.

41. Line voltage - In a three-phase circuit, no matter which connection method is used, there are three phase lines leading out, and the voltage between the phase lines is called the line voltage.

42. Automatic reclosing - when the line fails and the circuit breaker trips, it can automatically reclose without manual operation.

43. Breakdown voltage - When the insulating medium breaks down, the voltage applied across the medium is called the breakdown voltage.

44. Direct current - The magnitude and direction of voltage or current that do not change with time is called direct current.

45. DC equipment - DC equipment refers to a DC power supply device that supplies DC operating power to relay protection and control circuits, as well as emergency lighting.

46. Short-circuit ratio - the ratio of the excitation current when the synchronous generator is at the rated speed and the no-load voltage is the rated value to the excitation current when the three-phase symmetrical steady-state short-circuit current is the rated value.

47. Induced electromotive force – the electromotive force generated in a conducting loop when the magnetic flux in the area enclosed by that loop changes or at both ends of a wire when the wire cuts magnetic lines of force.

48. Generator efficiency - the ratio of generator output power to drilling power expressed as a percentage. Unless otherwise specified, it refers to the value at rated operating conditions.

49. Shaft current - current flowing from one end of the shaft of the turbo-generator set to the other end of the shaft through the bearing, bearing seat and base plate with damaged oil film insulation caused by the shaft voltage.

50. Auxiliary protection of generators - protections that supplement the main protection, backup protection and abnormal operation protection performance in the generator relay protection. For example, the circuit of the voltage sensor may be disconnected, the circuit breaker may fail or flashover, and the power generation Accidents may occur in the process of starting, synchronizing, and stopping the engine. These main protections and backup protections cannot be detected. Therefore, some auxiliary protections are added to large units as a supplement.

51. Generator backup protection - In the generator relay protection, when the main protection is out of operation or fails and refuses to act, it can still respond to the fault and act on the relevant circuit breaker and automatic device relay protection. There are mainly composite current quick-break protection, impedance protection, and directional overcurrent protection for composite voltage starting.

52. Forced excitation - when the automatic voltage regulator of the synchronous generator measures the grid voltage below a certain set value, usually 80% to 85% of the rated value, it outputs a step signal. Control the excitation system to make the excitation voltage The ability to quickly rise to the top value. The use of relays to achieve forced excitation is usually called relay forced excitation.

53. De-excitation - a measure to quickly disconnect the excitation power of the synchronous generator and quickly consume the magnetic field energy stored in the excitation winding. In order to reduce the harm caused by the internal fault current of the generator or the overvoltage during disconnection, when the relay protection device for short-circuit protection of the generator or the protection of abnormal operation of the generator trips the circuit breaker, it is required to demagnetize as soon as possible at the same time.

54. Exciter item value voltage multiple – the ratio of the maximum DC voltage that the exciter of the synchronous generator can provide to its rated excitation voltage at rated speed and specified conditions.

55. Excitation system voltage response ratio—the value obtained by dividing the output voltage growth rate determined from the excitation system voltage response curve by the rated excitation voltage, is an important indicator to measure the dynamic performance of the excitation system. Also known as the excitation system nominal response.

56. Split Transformer - A multi-winding power transformer in which each phase consists of one high-voltage winding and two or more low-voltage windings of the same voltage and capacity. The normal power transmission of the split transformer is only carried out between the high and low voltage windings. In the event of a fault, it has the function of limiting the short-circuit current. The low-voltage winding of the split transformer is also called split winding

57. Isolation switch - a switchgear that has a specified insulation distance and visible fracture between its contacts when it is in the opening position. It can withstand normal working current and short-circuit current when it is in the closing position. When the working current is small or the voltage between the two terminals of each pole of the isolating switch does not change significantly before and after making and breaking, the isolating switch has the ability to make and break the circuit, and has both operation and isolation functions.

58. Non-excitation voltage regulating device - a device that switches the coil taps in the winding to realize voltage regulation under the condition that the transformer is not charged, also known as non-excitation tap-up. This pressure regulating device is simple in structure, low in cost, reliable in parts, but has a small pressure range. It is only suitable for occasions where frequent pressure regulation is not required.

59. On-load voltage regulating device - a device for regulating voltage in a live state where the transformer does not interrupt operation. It is also called an on-load tap-changer. The voltage is adjusted by the on-load voltage regulating device, which can not only stabilize the voltage of the power grid but also improve the reliability and economy of the power supply.

60. Primary Equipment - Primary equipment is equipment that directly produces, transmits and distributes energy. Such as: generators, transformers, switchgear, power cables, etc.

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