电力系统基础知识Basic knowledge of power systemWord文档格式.docx

1、Power system: power generation equipment on the basis of the power grid. Based on the power system, the power plant parts （such as thermal power plant boiler, steam turbine and hydro power plant reservoir, hydraulic turbine and nuclear power plant reactor etc.） are included in the system.Three. Char

2、acteristics of power system operationFirst, the total amount of economy is big. At present, Chinas power industry asset size has more than 2 trillion, accounted for a total of 1/4 of the state-owned assets, electricity production directly affects the healthy development of the national economy.The t

3、wo is at the same time, a large number of electricity can not be stored, unity composed of all sectors can not be separated, the transition process is very rapid, instant production power must be equal to the moment for every aspect of power, so the power production of the power generation, transmis

4、sion and distribution are very important to the user.The three is concentrated, electricity production is highly centralized and unified, no matter how many power plants, power companies, power grid must be unified, unified management, unified management; safety production, organization and discipli

5、ne, occupation morality has strict requirements.The four is applicability, the service object of power industry is all-round, involving all the people in the whole society, power quality, electricity price level and the interests of the vast number of power users are closely related.Five is advance,

6、 the development of the national economy, electricity must first.Four. Rated voltage of power systemThere is a level of power grid voltage, rated voltage is reasonable according to the needs of national economic development, technology economy and electrical equipment manufacturing level, through th

7、e comprehensive analysis and demonstration, enacted by the national unity.Five 、 neutral operation mode of power systemIn the power system, neutral grounding or neutral small impedance （low resistance） grounding system is called grounding system, neutral or neutral Petersen coil grounded system is c

8、alled small current grounding system. The operation mode of neutral point mainly depends on the insulation requirement of electrical equipment and the reliability of power supply in single phase grounding.Comparison of advantages and disadvantages of different operation modesNeutral point direct gro

9、unding mode: when a relative insulation failure occurs, the single-phase short-circuit is formed, the power supply is interrupted, and the reliability is reduced. However, under this mode, the non fault relative voltage is constant, and the insulation level of the electrical equipment can be conside

10、red in terms of phase voltage. The 220V/380V and 110KV in our country use neutral point direct grounding to higher system, and operate in large current grounding mode.Ungrounded or grounded by arc suppression coil: when single-phase grounding fault occurs, the line voltage is constant, and the non f

11、ault phase voltage to phase voltage of the original tick 3 times, uninterrupted power supply, high reliability. The 10KV and 35KV systems in our country use neutral ungrounded or arc suppression coils to operate in small current neutral grounding mode.Six 、 power supply qualityVoltage, frequency, an

12、d reliability are the indicators that determine the quality of the users power supply.1. voltageThe ideal supply voltage should be a three-phase symmetrical sinusoidal voltage whose amplitude is constant. Due to the presence of impedance, power supply system with the change of power load and electri

13、city load properties and other factors, the actual supply voltage regardless of the amplitude, waveform and phase symmetry and ideal voltage exists between the deviation.（1） voltage deviation: voltage deviation is the difference between the actual voltage and the rated voltage of the power grid. The

14、 actual voltage is too high or low, which has an impact on the good operation of the power equipment.The national standard provides that the allowable value of voltage deviation is:A and 35 thousand volts and above voltage supply, the sum of the absolute value of voltage positive and negative deviat

15、ion shall not exceed 10% of the rated voltage;B, 10 thousand volts and below three-phase power supply, voltage deviation is rated voltage of + 7%. In theC, 220 volts single-phase power supply, voltage deviation is rated voltage of +7%, -10%.The allowable value of voltage fluctuation is stipulated by

16、 the national standard:10KV and below are 2.5%35 to 110KV is 2%220KV and above is 1.6%（3） harmonic generation: the generation of higher harmonics is nonlinear electrical equipment, which is put into operation in the power grid, which makes the voltage and current waveforms of the network distorted i

17、n different degrees and deviated from the sine wave.In addition to the background harmonics of the power system,It is mainly caused by nonlinear power equipment, such as large power converter and electric arc furnace. The existence of higher harmonics leads to the increase of energy consumption, the

18、 aging of electrical equipment insulation, and interference with the normal operation of automation devices and communication facilities.（4） three-phase asymmetry: three-phase voltage asymmetry refers to the amplitude and phase relation of the three phase voltages. The three-phase asymmetry is mainl

19、y caused by the asymmetry of the system operating parameters and the unbalanced three-phase load. The asymmetric operation of power supply system is harmful to the power supply equipment and power supply and distribution system. The asymmetrical operation of the low-voltage system will lead to devia

20、tion of the neutral point, thus endangering the safety of the people and equipment.Under the normal mode of operation of the common connection point of the power system, the allowable value of the imbalance by the State shall be 2%, not exceeding 4% for a short period of time, and no more than 1.3%

21、of the individual users2. permissible deviation of supply frequencyThe sinusoidal alternating current generated by a generator in a grid is called frequency per second, and the standard frequency 50HZ. is specified in ChinaChinas national standard stipulates that the allowable value of the normal fr

22、equency deviation of the power system is + 0.1Hz, and in actual implementation, when the system capacity is less than 300Mv, the deviation value can be relaxed to + 0.5Hz.3. reliability of power supplyThe reliability of power supply refers to the time and frequency of the power failure of a power su

23、pply enterprise during a certain statistical period, which directly reflects the continuous power supply capability of the power supply enterprise.Power supply reliability rate reflects the national economy can meet the power needs of the electric power industry, has become one of the standard measu

24、re of a countrys level of economic development; the power supply reliability can be measured with the following year a series of indicators: power supply reliability rate, the average user outage time, user average power frequency, the average user fault outage times.The reliability rate of urban po

25、wer supply prescribed by the state is 99.96/100. That is, the average annual outage time is not more than 3.5 hours;Electrical load: the sum of the actual power used by a users electrical equipment at a given point.There are many methods to classify power load, and the most significant is to classif

26、y the load classification according to the time that the load occurred in the power system and the degree of loss caused by the sudden interruption of power supply.Load classification by time1, peak load: refers to the power grid or the user in a days time the maximum load value. The average daily l

27、oad is 24 hours a day. The average load is the maximum load, usually with 1 month peak load and one month peak load.2, minimum load: refers to the power grid or the user in 24 hours a day, the minimum electricity consumption load. Usually, there are 1 months daily minimum load, one month minimum loa

28、d and so on.3. Average load: the average hourly power consumption of a grid or a user at a certain period of time.Classification of degree of damage caused by interruption of power supply1, a load: a sudden power outage will cause casualties or cause serious pollution to the surrounding environment,

29、 causing huge economic losses, such as large important equipment damage, important products or raw materials for the production of a large number of scrap products, continuous production process is disrupted, it takes a long time to resume production; and a sudden power outage will cause serious pub

30、lic disorder or in politics have significant adverse effects, such as the electricity load important transportation and communication hub, international social places etc.2, two load: a sudden power outage in the economy will cause more losses, such as the production of major equipment damage, large number of scrapped products or production, continuous production process takes a long time to recover; and a sudden power failure can cause social disorder or in politics caused great influence, such as transportation and communications hub, the citys main water source el