CN102324722B - Current differential protection method based on fault component current amplitudes and phase differences - Google Patents
Current differential protection method based on fault component current amplitudes and phase differences Download PDFInfo
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- CN102324722B CN102324722B CN201110266262.9A CN201110266262A CN102324722B CN 102324722 B CN102324722 B CN 102324722B CN 201110266262 A CN201110266262 A CN 201110266262A CN 102324722 B CN102324722 B CN 102324722B
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Abstract
The invention relates to a current differential protection method based on fault component current amplitudes and phase differences. The current differential protection method is characterized in that: a differential protection criterion is formed by the adoption of the current fault component amplitudes at two sides of a protected line and the phase differences at the two sides of the protected line, wherein the differential current value (Icd) is equal to the sum of the current fault component amplitude (the absolute value of [delta]IM) at one side and the product of the current fault component amplitude (the absolute value of [delta]IN) at the opposite side and a cosine function of the phase difference ([phi]) between the absolute value of [delta]IM and the absolute value of [delta]IN, i.e. Icd= (the absolute value of [delta]IM)+(the absolute value of [delta]IN)cos[phi]; and the braking current (Ir) is equal to the difference between the absolute value of [delta]IM and the product of the absolute value of [delta]IN and the cos[phi], i.e. Ir= (the absolute value of [delta]IM)-(the absolute value of [delta]IN)cos[phi], and the differential protection criterion is the following inequation: Icd-KIr>= Idz, wherein K is a braking coefficient and Idz is an action current threshold. If the differential protection criterion is satisfied, an internal fault is determined and the differential protection acts; if the differential protection criterion is not satisfied, an external fault is determined and the differential protection does not act. The current differential protection method related to the invention has the advantages of higher sensitivity for internal faults, higher safety for external faults, fewer effects subjected from the factors, such as the transition resistance, the distributed capacitance, the TA saturation and the like, and good performances.
Description
Technical field
The present invention relates to a kind of current differential protection method of field of relay protection in power, especially a kind of current differential protection method based on fault component current amplitude and phase difference.
Background technology
Current differential protection principle realizes according to Kirchhoff's first law, and whether the electric current that is flowed into, flowed out protected object by calculating equates, thereby judge whether protected object internal fault has occurred.Current differential protection principle has the ability of stronger extraction internal fault information, and without voltage, in electric power system, is applied widely, and most equipment and circuit all preferentially adopt current differential protection as main protection.According to the difference of adopted electric current; current differential protection can be divided into full current differential protection philosophy, current failure component Differential Protection Theory, Zero sequence current differential protection principle, current phase differential protecting principle etc.; wherein, full current differential and the application of current failure component Differential Protection Theory are comparatively extensive.
Current differential protection performance is subject to the impact of unsymmetrical current.In electric power system, the source of unsymmetrical current is more, as capacitance current, each measurement point non-synchronous sampling, TA characteristic is inconsistent, TA is saturated etc.For overcoming the impact of unsymmetrical current on differential protection, introduced stalling current and proportional brake coefficient, but the existence of braking amount can affect again the sensitivity of differential protection conversely, cause generation inside sensitivity deficiency in the time of high resistance earthing fault in some situation.Therefore adopt which amount to form differential and stalling current, and then form the comparatively desirable current differential protection criterion of operating characteristics, become the key issue of research current differential protection.
Fault current component have be not subject to that load current affects, sensitivity is compared with high; be subject to people's generally attention; the phasor differential protection forming based on fault current component has higher sensitivity and reliability compared with total current phasor differential protection; but occurring under some operational mode in the time of the troubles inside the sample space of great transition grounding through resistance still can tripping, the large and TA of line distribution capacitance is serious there is external area error when saturated still may malfunction.
Chinese patent application 200910022923 discloses a kind of current differential protection of direct current electric transmission line algorithm; the method is according to Transmission Line Distributed Parameter model; in time domain, utilize modular transformation that the sampled value of direct current, direct voltage is converted to modulus; then utilize respectively two ends mode voltage, Current calculation to go out circuit from circuit two ends and put the mould electric current in each moment; directly construct current differential protection criterion with mould electric current; or through the synthetic electrode current of utmost point mould inverse transformation, then according to electrode current structure current differential protection criterion.This invention, only for the DC power transmission line in electric power system, is distributed parameter transmission line model due to what adopt, therefore requires system to have very high sample frequency.In addition introduce phase-model transformation and inverse transformation and also increased amount of calculation.
Chinese patent application 201010034085 discloses a kind of for the steady-state quantity of transformer inside and the compound current differential protection method of fault component and compound current differential relay.Relay in the method adopts steady-state quantity to calculate differential current and stalling current forms the two K differential relays of a steady-state quantity, adopt fault component calculating differential current and stalling current to form the two K differential relays of another fault component, then by the compound current differential relay of both synthetic steady-state quantities and fault component.What this invention related to is transformer differential protection but not line differential protection, adopt multiple restraint coefficients can make to adjust to calculate to become complicated.
Chinese patent application 201010165606 discloses a kind of phase relevant current differential protection method.This invention adopts circuital phase relevant current differential protection criterion; basic principle is exactly that the current and phase difference of differential circuit both sides is introduced to current differential criterion; braking Xiang Qu internal and external fault time-division in criterion is not presented as and drives and braking two states, and propose four kinds and realize criterion and computational methods.This invention is compared conventional method and is judged aspect reliability and sensitivity and improve a lot in fault, but has much room for improvement in the performance aspect reply unsymmetrical current.
Summary of the invention
The object of the invention is for overcoming above-mentioned the deficiencies in the prior art, a kind of current differential protection method based on fault component current amplitude and phase difference is provided, the method is not subject to that load current affects, criterion is highly sensitive, has the ability of good differentiation district internal and external fault; Stalling current in the time of troubles inside the sample space is very little; can improve differential protection and judge the sensitivity of troubles inside the sample space, the differential current in the time of external area error is very little, can improve differential protection and judge the fail safe of external area error; be subject to distributed capacitance, impact that TA is saturated less, anti-transition resistance ability is stronger.
For achieving the above object, the present invention adopts following technical proposals:
Based on a current differential protection method for fault component current amplitude and phase difference, comprise the following steps:
The first step: after fault occurs, the current value after circuit both sides occur by fault respectively deducts the current value before fault occurs, and then adopts Fourier algorithm can obtain amplitude and the phase place of current failure component;
Second step: make differential current (I
cd) equal this side current failure component amplitude | Δ I
m| add offside current failure component amplitude | Δ I
n| with the two phase difference
the product of cosine function,
stalling current (I
r) equal | Δ I
m| deduct | Δ I
n| with
product,
The 3rd step: differential protection criterion is I
cd-KI
r>=I
dz, wherein K is restraint coefficient, I
dzfor operating current threshold value.If meet differential protection criterion, be judged to troubles inside the sample space, differential protection action, otherwise be external area error, differential protection is failure to actuate.
The computational methods of the current failure component in the described first step are: the current value after occurring by fault deducts fault and occur the current value in previous cycle, with the current failure component value in multiple cycles after obtaining fault and occurring.
Differential current in described second step forms expression formula
stalling current forms expression formula
wherein | Δ I
m| be the amplitude of this side current failure component, | Δ I
n| be the amplitude of offside current failure component,
for the cosine value of phase difference between the current failure component of both sides.
Differential protection criterion in the 3rd described step is I
cd-KI
r>=I
dz, wherein K is restraint coefficient, span is between 0.5～0.8, I
dzfor operating current threshold value, adjust by the maximum imbalance current that escapes system.If meet differential protection criterion, be judged to troubles inside the sample space, differential protection action, otherwise be judged to external area error, differential protection is failure to actuate.
The present invention adopts the amplitude of current failure component and phase difference to form differential protection criterion, compares tool have the following advantages with existing similar technology:
1. adopt failure of the current component to form criterion, there is advantages such as not being subject to load current affects, criterion sensitivity height;
2. the poor impact that is not subject to load current and transition resistance of current failure component phase, is subject to distributed capacitance, impact that TA is saturated less, only determines to have the ability of good differentiation district internal and external fault by the impedance angle of the comprehensive impedance of fault point two side systems;
3. the stalling current of criterion that the present invention carries in the time of troubles inside the sample space is very little; can improve differential protection and judge the sensitivity of troubles inside the sample space; differential current in the time of external area error is very little; can improve differential protection and judge the fail safe of external area error; be subject to distributed capacitance, impact that TA is saturated less, anti-transition resistance ability is stronger.
Accompanying drawing explanation
Fig. 1 is two ends source power system model structure schematic diagrames;
Differential current and braking current curve schematic diagram in Tu2Shi district when F1 point failure;
New criterion of the present invention and relatively schematic diagram of traditional criterion operating current when F1 point failure in Tu3Shi district;
Differential current and braking current curve schematic diagram outside Tu4Shi district when F2 point failure;
New criterion of the present invention and relatively schematic diagram of traditional criterion operating current when F2 point failure outside Tu5Shi district;
Relatively schematic diagram of new criterion of the present invention and traditional criterion operating current when F2 point failure and TA are saturated outside Tu6Shi district.
Embodiment
Below in conjunction with drawings and Examples, the present invention is further described.
1. current differential protection criterion performance evaluation when troubles inside the sample space
In the Double-End Source electric power system model shown in Fig. 1; F1 point in protection zone arranges A phase metallic earthing fault; differential current designed according to this invention and stalling current computational methods; differential, the braking current curve obtaining as shown in Figure 2; wherein solid line represents stalling current, and dotted line represents differential current.While there is internal fault, differential current is much larger than stalling current.For the superiority of criterion of the present invention is described, compare with at present conventional current change quantity differential criterion (traditional criterion) performance.When F1 place fault, the comparable situation of the two operating current curve as shown in Figure 3.Visible, in the time of the internal fault of generating region, the operating current of criterion that the present invention carries is greater than the operating current of traditional criterion, show criterion that the present invention carries in the time of troubles inside the sample space compared with traditional criterion, there is higher sensitivity.
2. current differential protection criterion performance evaluation when external area error
Outside protection zone, F2 place arranges A phase metallic earthing fault, and as shown in Figure 4, now differential current is very little and stalling current is very large for the differential current of criterion that the present invention carries and braking current curve.Corresponding operating current curve and traditional criterion operating current curve comparable situation are as shown in Figure 5.Visible, occurring when external area error, the operating current of criterion that the present invention carries is less than the operating current of traditional criterion, show criterion that the present invention carries in the time of external area error compared with traditional criterion, there is higher fail safe.
3. current differential protection criterion performance evaluation when external area error and TA are saturated
Be located at that F2 place breaks down and left side TA is saturated, the comparable situation of the operating current curve of criterion that the present invention carries and traditional criterion operating current curve as shown in Figure 6.Now compared with situation 2, the operating current of the two all has reducing in various degree, but the operating current of criterion that the present invention carries is still less than the operating current of traditional criterion, shows that criterion that the present invention in this case carries still has higher fail safe.
Claims (1)
1. the current differential protection method based on fault component current amplitude and phase difference, is characterized in that, comprises the following steps:
The first step: after fault occurs, the current value after circuit both sides occur by fault respectively deducts fault and occur the current value in previous cycle, then adopts Fourier algorithm to obtain amplitude and the phase place of circuit both sides current failure component;
Second step: make differential current (I
cd) equal the amplitude of this side current failure component | Δ I
m| add the amplitude of offside current failure component | Δ I
n| and phase difference between the current failure component of circuit both sides
the product of cosine function,
stalling current (I
r) equal | Δ I
m| deduct | Δ I
n| with
product,
wherein | Δ I
m| be the amplitude of this side current failure component, | Δ I
n| be the amplitude of offside current failure component,
for the cosine value of phase difference between the current failure component of both sides;
The 3rd step: differential protection criterion is I
cd-KI
r>=I
dz, wherein K is restraint coefficient, span is between 0.5～0.8, I
dzfor operating current threshold value, adjust by the maximum imbalance current that escapes system, if meet differential protection criterion, be judged to troubles inside the sample space, differential protection action, otherwise be judged to external area error, differential protection is failure to actuate.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201110266262.9A CN102324722B (en) | 2011-09-08 | 2011-09-08 | Current differential protection method based on fault component current amplitudes and phase differences |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201110266262.9A CN102324722B (en) | 2011-09-08 | 2011-09-08 | Current differential protection method based on fault component current amplitudes and phase differences |
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| Publication Number | Publication Date |
|---|---|
| CN102324722A CN102324722A (en) | 2012-01-18 |
| CN102324722B true CN102324722B (en) | 2014-06-04 |
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| CN201110266262.9A Expired - Fee Related CN102324722B (en) | 2011-09-08 | 2011-09-08 | Current differential protection method based on fault component current amplitudes and phase differences |
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Families Citing this family (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102904227A (en) * | 2012-09-29 | 2013-01-30 | 天津大学 | Six-sequence component-based double circuit lines on same pole phase difference protection method |
| CN103346540B (en) * | 2013-03-25 | 2016-04-27 | 浙江大学 | A kind of hybrid line traveling wave differential protecting method adopting phase current to brake |
| CN103746335B (en) * | 2013-12-23 | 2017-03-29 | 北京四方继保自动化股份有限公司 | Relay protecting method based on amplitude com parison principle |
| CN104242268B (en) * | 2014-09-11 | 2017-06-16 | 国电南瑞科技股份有限公司 | A kind of three zone current differential protecting methods |
| CN104377668B (en) * | 2014-11-21 | 2017-08-01 | 三峡大学 | A kind of Line Current Differential Protection method converted based on secondary data |
| CN105244860B (en) * | 2015-10-10 | 2018-02-16 | 国家电网公司 | A kind of differential protecting method based on positive sequence admittance |
| CN105576623B (en) | 2016-01-29 | 2020-01-17 | 中国电力科学研究院 | Self-adaptive half-wavelength line differential protection method based on time difference method |
| CN106356822B (en) * | 2016-10-10 | 2019-02-05 | 许继集团有限公司 | A kind of deficient range combinations formula guard method of half-wave power transmission route and device |
| CN107359602B (en) * | 2017-08-29 | 2019-02-01 | 山东大学 | A kind of motor synchronizing current comparison pilot protection method suitable for transmission line of electricity |
| WO2019120517A1 (en) * | 2017-12-20 | 2019-06-27 | Abb Schweiz Ag | Phase selection using multi-terminal measurements of a transmission line |
| CN108879622A (en) * | 2018-06-13 | 2018-11-23 | 国网浙江省电力有限公司电力科学研究院 | Distribution protection method and system based on compound ratio amplitude differential criterion |
| CN113945858B (en) * | 2021-02-02 | 2024-03-01 | 保定钰鑫电气科技有限公司 | Three-phase non-effective grounding power supply system convenient for processing single-phase grounding fault |
| CN113671315B (en) * | 2021-08-18 | 2023-10-27 | 北京四方继保工程技术有限公司 | ITn power supply insulation fault positioning method based on proportional differential principle |
| CN114221307B (en) * | 2021-12-09 | 2024-06-18 | 南京南瑞继保电气有限公司 | Circuit differential protection braking coefficient adjusting method and device and electronic equipment |
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| CN101752835B (en) * | 2010-01-13 | 2012-02-08 | 华中电网有限公司 | Transformer compound current differential protection method and compound current differential relay |
| CN101814715B (en) * | 2010-05-07 | 2012-05-09 | 天津大学 | Phase relevant current differential protection method |
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