Mechanical Writings

】 【Electrical & Automation and its calculation of short circuit current chapter
】 【Electrical & Automation and its calculation of short circuit current chapter
Three-phase short circuit current calculation
Curriculum design - Power system short circuit fault current calculation
Power system short-circuit current calculations
Power system short-circuit current calculations
】 【Electrical & Automation Utility computing short-circuit current chapter
】 【Electrical & Automation Utility computing short-circuit current chapter
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GJBZ 95-97 ship power system short-circuit current calculation method
GJBZ 95-97 ship power system short-circuit current calculation method
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GBT 15544-1995 three-phase short circuit current calculation
Electrical and Automation】 【Synchronous generator terminal short-circuit the process of computer analysis of electromagnetic transient feature
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GBT 15544-1995 three-phase short circuit current calculation
Chapter V short-circuit current calculation - Hebei Engineering and Technical College
DLT 5163-2002 hydropower projects short-circuit current calculation of three-phase AC system guide
Electrical and Automation】 【sudden short-circuit synchronous generator

【3】 reactor reactance calculation
Reactor Anti-rated resort Jiuzhe than the rated capacity.
Example: There is a reactor U = 6KV I = 0.3KA rated reactance X = 4%.
Rated capacity S = 1.73 * 6 * 0.3 = 3.12 MVA. Reactor reactance X *= {4/3.12} * 0.9 = 1.15
Reactor capacity unit: MVA
【4】 overhead lines and cables the calculation of reactance
Overhead lines: 6KV, equal to the number of kilometers; 10KV, take 1 / 3; 35KV, from 3% 0
Cable: 0.2 multiplied by overhead lines.
Example: 10KV 6KM overhead lines. Overhead line reactance X *= 6 / 3 = 2
10KV 0.2KM cable. Cable reactance X *= {0.2 / 3} * 0.2 = 0.013.
Been simplified here, in fact, the electric overhead lines and cables and their cross resistance is related to the smaller section of the larger reactor.
【5】 calculation of short-circuit capacity
Reactance plus set, remove the 100.
Example: the components are known before the short circuit reactance What values and standards for the X * Σ = 2, then the short circuit short-circuit capacity
Sd = 100 / 2 = 50 MVA.
Short-circuit capacity unit: MVA
【6】 short-circuit current calculation
6KV, 9.2 In addition to reactance; 10KV, 5.5 In addition to reactance; 35KV, 1.6 In addition to reactance; 110KV, 0.5 In addition to reactance.
0.4KV, 150 in addition reactance
Example: Given the components of a short circuit reactance of the former What values and standards for the X * Σ = 2, short circuit voltage rating of 6KV,
The short circuit short circuit current Id = 9.2 / 2 = 4.6KA.
Short-circuit current unit: KA
【7】 Short Circuit Current Calculation
1000KVA for transformer secondary short circuit: the impact of current RMS Ic = Id, the impact of peak current ic = 1.8Id
1000KVA above transformer secondary short circuit: the impact of current RMS Ic = 1.5Id, the impact of peak current ic = 2.5Id
Example: Known short circuit} {1600KVA transformer secondary short-circuit current of Id = 4.6KA,
RMS is the point of impact of current Ic = 1.5Id, = 1.5 * 4.6 = 7.36KA, the impact of peak current ic = 2.5Id = 2.5 * 406 = 11.5KA.
Visible short-circuit current calculation is the key to calculate the total before the short circuit reactance What value {standard}. But be sure to include the system reactance
5. For example,
System is shown below. From the electrical department sent all the way to regional substations 10KV overhead lines, after 10KM arrived at the company substations, substation into a 200M cable before. 1600KVA one transformer substation located. Seeking K1, K2 point short-circuit parameters.
System diagram maps of the reactance reactance diagram
System capacity: S = 1.73 * U * I = 1.73 * 10.5 * 31.5 = 573 MVA
Using the above formulas, it is easy to obtain the value of the electrical resistance standard Mody, a total of four.
System reactance X0 = 100/573 = 0.175
10KM, 10KV overhead line reactance X1 = 10 / 3 = 3.333
200M, 10KV cable line reactance X2 = (0.2 / 3) * 0.2 = 0.133
1600KVA transformer reactance X3 = 4.5/1.6 = 2.81
Please note: The above are standard What reactance value (X *)
Reactance of each section were added together, are K1 point total reactance = X0 X1 = 3.51
K2 point total reactance = X0 X1 X2 X3 = 6.45 (not 2.94!)
Then formulas, you can calculate the short circuit current
U (KV) X * Id (KA) IC (KA) ic (KA) Sd (MVA)
Formulas 5.5 / X * 1.52 * Id2.55 Id100 / X *
K110.53.511.562.374.028.5
Formulas 150 / X * 1.52 * Id2.55 Id100 / X *
K20.46.4523355915.5
Calculated using formulas and calculated using the formula in Section 3 What is the difference?
Calculated with the formulas is the real name system unit, KA, MVA, and calculated using the formula What is the standard value.
Observant people will see that in the calculation of the coefficient of short circuit current formulas 150,9.2,5.5,1.6. In fact, at all levels of voltage reference value. Just been simplified. 144,9.16,5.5,1.56 be accurately calculated.
With short-circuit parameters of what's the use? Is checking switches the main parameters. Example: This sets 1600KVA transformer low voltage main switch using M25, N1. Rated current 2500A, rated breaking current 55KA.
Checking: Transformer rated current 2253A
Switch rated current> transformer rated current; switch rated breaking current of> short-circuit current Id . checking pass.
Three-phase short-circuit current classification system, the short circuit occurred in 4 basic types: three-phase short circuit, two-phase short circuit, single relatively short and relatively short-circuit the two. Which, in addition to three-phase short circuit, still symmetrical three-phase circuit, which is also called symmetrical short-circuit, the other three are asymmetrical short. In the neutral ground of the power network, to a maximum of relatively short-circuit failure, accounting for 90% of all failures. In the neutral ground of non-direct the power network, mainly various phases short circuit short circuit. A short circuit, the power system transition from the normal steady state to steady state short circuit, which normally takes 3 to 5 seconds. In this transient process, the short-circuit current of change is complex. It has many components, the calculation requires the use of electronic computer. In about half of the cycle in the short (0.01 seconds) will occur when the instantaneous value of the maximum short circuit current, called the impact of current. It will have a huge electric power, its size can be used to check electrical equipment in the event of short circuit
Schematic diagram of short circuit current when the mechanical stress related to the dynamic stability. Short-circuit current analysis, power system analysis computing is an important part. It is the power system planning and design and operation of electrical equipment selection, setting protection, provided an effective means of accident. Short-circuit power supply network, the large short-circuit current, or overheating electrical equipment will be damaged the role of electric power, while the voltage of the network greatly reduced, thereby undermining the electrical equipment within the network to work properly. To eliminate or mitigate the consequences of short-circuit, you need to short-circuit current calculation, the correct choice of electrical equipment, design and selection limits short-circuit current protection components. calculation conditions 1. assume that the system has infinite capacity. users at the short circuit, the system bus voltage to remain unchanged. that is calculated impedance is much greater than the system impedance. specifically provides that: For the 3 ~ 35KV Power Network in the short-circuit current calculation, 110KV and above that the system capacity is infinite. as long as the calculation of 35KV and the impedance of the following network components 2. in the calculation of short-circuit current in high voltage apparatus, just consider the generators, transformers, reactance of the reactor, while ignoring the resistance; for overhead lines and cables, and only when the resistance is greater than 1 reactor / 3, only to be included in the resistance, reactance general terms only and ignore resistance. 3. short-circuit current calculation formula or chart to calculate all three-phase short-circuit conditions. because the single-phase or two-phase short circuit short circuit short-circuit current is less than the three-phase short-circuit current. to three-phase short-circuit breaking current of electrical appliances, will be able to short-circuit breaking current of single-phase or two-phase short-circuit current. simplified calculation method even set some assumptions, to correctly calculate the short circuit current is very difficult, for General users is not necessary. some of the design manual provides a simplified calculation of the charts. eliminating the calculation of trouble. with more convenient. But if there is no design manual hand a moment how to do? Here are a kind of "formulas" type of calculation method just remember the simplicity of seven formulas, you can master the short circuit current calculation. Before introducing the simplified calculation method must first understand some basic concepts of .1. Sd main parameters of three-phase short-circuit capacity (MVA) referred to short-circuit breaking capacity switching capacity of checking the three Id periodic component of the phase short-circuit current rms (KA) referred to short-circuit breaking current of the current check switch IC-phase short-circuit and thermal stability of the first cycle of the full current rms (KA) referred to as dynamic stability check of the impact of current RMS three-phase short-circuit the first ic the whole cycle peak current (KA) referred to the impact of current peaks checking dynamic stability x reactance (Ω) where Sd and calculated short circuit capacity reactance x is the key point .2. What value standard when selecting a baseline capacity (Sjz) and reference Voltage (Ujz). the short circuit calculation of each parameter and the parameter converted to the ratio of baseline
Short-circuit current related books (as opposed to the ratio of baseline), known as the standard What value (which is short-circuit current calculation of the most special place, designed to simplify the calculation). (1) baseline baseline capacity Sjz = 100 MVA provides the reference voltage UJZ to 8. 230, 115, 37, 10.5, 6.3, 3.15, 0.4, 0.23 KV with the above two, the voltage levels of reference current can be calculated, for example: UJZ (KV) 3710.56.30.4 as S = 1.73 * U * I so IJZ (KA) 1.565.59.16144 (2) What value standard value of the capacity standard Mody S * = S / SJZ. For example: When the 10KV bus bar short circuit capacity of 200 MVA, its capacity value of S * What standards = 200/100 = 2. What value of the voltage scale U *= U / UJZ; current standard What value I * = I / IJZ 3 infinite three-phase short-circuit current capacity of the system short-circuit current standard formula What values: I * d = 1 / x * (What the total value of the reactance standard countdown.) RMS short circuit current: Id = IJZ * I * d = IJZ / x * (KA) the impact of current RMS: IC = Id * √ 1 2 (KC-1) 2 (KA) where KC impact factor, taking the impact of 1.8 so the peak current IC = 1.52Id: ic = 1.41 * Id * KC = 2.55 Id (KA) when 1000KVA for transformer secondary circuit, the impact factor KC, take 1.3 At this time: the impact of current RMS IC = 1.09 * Id (KA) the impact of current peaks: ic = 1.84 Id (KA) mastered the above knowledge, we can calculate the short circuit current. formula small, and easy. but the problem is short-circuit point total reactance how to get? For example: Regional reactance transformer substation, transmission line reactance, the reactance of the transformer substation enterprises, and so on. One way is to check the design manual, which you can find a common transformer, transmission line and reactor reactance scale Mody value. obtained after the total reactance, then the above formula short-circuit current; design manual and some charts that can directly detect short-circuit current. Here are a kind of "formulas" type of calculation method just remember the simplicity of seven formulas, you can master the short-circuit current calculation method. formulas are simplified algorithm for a system of computing the reactance reactance, Fast one. Volume change, electrical resistance is inversely proportional. In addition to system capacity of 100 patients: baseline capacity of 100MVA. When the system capacity of 100MVA, the system reactance XS *= 100/100 = 1 when the system capacity of 200MVA, the system reactance XS *= 100/200 = 0.5 when the system capacity is infinite, the system reactance XS *= 100 / ∞ = 0 system capacity unit: MVA system capacity by the local power sector. When can not be, you can switch the power supply outlet switching capacity as the system capacity. Known as the electricity sector outlet switch W-VAC 12KV 2000A rated breaking current 40KA. That the system can be
Schematic diagram of short circuit current capacity of the relevant S = 1.73 * 40 * 10000V = 692MVA, the system reactance XS *= 100/692 = 0.144. 2 Transformer reactance calculations 110KV, 10.5 In addition to transformer capacity; 35KV, 7 In addition to transformer capacity; 10KV {6KV } 4.5 In addition to the transformer capacity. Example: a 35KV 3200KVA transformer reactance X *= 7/3.2 = 2.1875 a 10KV 1600KVA transformer reactance X *= 4.5/1.6 = 2.813 transformer capacity unit: MVA factor here is actually a transformer short-circuit 10.5,7,4.5 reactance of the% number. Different voltage levels have different values. 3 Reactor Reactor Reactor Calculation of resistance than the rated capacity of rated call Jiuzhe. Example: There is a reactor U = 6KV I = 0.3KA rated reactance X = 4%. Rated capacity S = 1.73 * 6 * 0.3 = 3.12 MVA. Reactor reactance X *= {4/3.12} * 0.9 = 1.15 reactor volume unit: MVA4 overhead lines and cable reactance calculation overhead lines: 6KV, equal to the number of kilometers; 10KV, take 1 / 3; 35KV, from 3% 0 cable: then multiply by 0.2 for overhead lines. Cases: 10KV 6KM overhead lines. Overhead line reactance X *= 6 / 3 = 2 10KV 0.2KM cable. Cable reactance X *= {0.2 / 3} * 0.2 = 0.013. Been simplified here, in fact, the electric overhead lines and cables and their cross resistance is related to the smaller section of the larger reactor. 5 Calculation of short circuit reactance increases the capacity set to remove 100. Example: the components are known before the short circuit reactance What values and standards for the X * Σ = 2, then the short circuit short-circuit capacity Sd = 100 / 2 = 50 MVA. Short-circuit capacity of unit: MVA6 short circuit current calculation 6KV, 9.2 In addition to reactance; 10KV, 5.5 In addition to reactance; 35KV, 1.6 In addition to reactance; 110KV, 0.5 In addition to reactance. 0.4KV, 150 in addition reactor example: before known the components of a short circuit reactance What values and standards for the X * Σ = 2, short circuit voltage rating of 6KV, the short circuit short circuit current Id = 9.2 / 2 = 4.6KA . Short-circuit current unit: KA7 Short Circuit Current Calculation 1000KVA for transformer secondary short circuit: the impact of current RMS Ic = Id, the impact of current above the peak ic = 1.8Id 1000KVA transformer secondary short circuit: the impact of current RMS Ic = 1.5Id, the impact of peak current ic = 2.5Id cases: known short circuit} {1600KVA transformer secondary short-circuit current of Id = 4.6KA, then the point of impact of current RMS Ic = 1.5Id, = 1.5 * 4.6 = 7.36KA , the impact of peak current ic = 2.5Id = 2.5 * 406 = 11.5KA. Visible short-circuit current calculation, the key is calculated short circuit before the total reactance {standard What value}. But be sure to include the system reactance ANSI / IEEE standard short-circuit current calculation standards: the ANSI / IEEE and UL standards as a basis for short-circuit current calculation generally the following criteria:
Schematic diagram of short circuit current standards related to the name of IEEE C37.04IEEE C37.04fIEEE C37.04gIEEE C37.04hIEEE C37.04iIEEE C37.04 symmetrical high voltage circuit breaker current structure of the standard and constant Appendix IEEE C37.010IEEE C37.010bIEEE C37.010eIEEE C37. 010 AC high voltage circuit breaker symmetrical current basis in the application guidelines and Appendix IEEE C37.013 voltage generator circuit breaker based on the symmetrical current rating of Standard IEEE C37.20.1 for low voltage power circuit breaker switch is closed metal box standard IEEE Std 399 Power System Analysis - Brown Book IEEE Std 141 workers grid power distribution system recommended by the Red Book IEEE Std 242IEEE commercial power system configuration and protection of industrial yellow book UL 489_9 instance circuit breaker type casting, casting-type switches and circuit breakers housing safety standards
Schematic diagram of short circuit current short-circuit current related hazards and preventive measures 1, the power system short-circuit failure, sudden changes in the distribution system power and voltage of the serious decline, could undermine the stability of parallel operation of the plant so that the whole system splitting, Then some of the generator may overload and therefore must be removed part of the user. Short-circuit the greater the voltage drop, the longer the duration, destroy the power system the greater the possibility of stable operation. Short-circuit current restrictions to ensure safe and reliable operation of the system, reducing the impact of short-circuit, except in the operation and maintenance should be efforts to eliminate all possible reasons cause a short circuit, short circuit should be removed as soon as possible part of the system voltage in a relatively short period of time to return to normal. 2, precautionary measures first, do the calculation of short circuit current, correct selection and calibration of electrical equipment, electrical equipment, the rated voltage and line voltage to match. The second is the right choice of relay protection setting value and the rated current of the melt, the use of fast break protection device to a short circuit, they can quickly cut off the short circuit current, reducing the duration of short circuit current, reducing the losses caused by short circuit. Third, install a lightning rod in the substation, the transformer is installed on the sides and line arresters to reduce lightning damage. Fourth, construction of overhead lines to ensure quality and strengthen line maintenance, and always maintain the same Sag and compliance. Fifth, live electrical equipment installation and maintenance, ability to focus attention, to prevent false wiring, misuse, short distance in the charged parts of the site work, to take measures to prevent short circuits. Sixth, strengthen governance, to prevent small animals into the power distribution room, climb the electrical equipment. Seven is the timely removal of conductive dust, to prevent conductive dust into the electrical equipment. Eighth, set the mark at the cable laying, it was digging in around the construction, care to send someone to the position of construction workers laying the cable to prevent cable damage caused by short circuit. Nine are power system operation and maintenance personnel should conscientiously study the procedures, strict compliance with rules and regulations, the correct operation of electrical equipment, prohibition of negative Hela switch, grounding switch live together. Line construction, maintenance work is completed, immediately remove the grounding wire. Always on the line, inspection equipment inspection to detect defects quickly overhaul.