CN100348990C - Adaptive approach for route selection of grounded system connected to arc suppression coil - Google Patents

Abstract

The present invention relates to a self-adaptive method for selecting a fault line of an arc suppression coil grounding system, which belongs to the technical field of relay protection of an electric power system. The method comprises the steps that when instantaneous value u0(t) of zero sequence voltage of a bus of the arc suppression coil grounding system is greater than K<u>U<n>, a fault line selecting device is started immediately and records zero sequence currents of each outgoing line and zero sequence voltage of a bus of 2 cycles before a fault occurs and 3 cycles after the fault occurs, wherein K<u> is generally taken for 0.35, and U<n> represents rated voltage of the bus; the time is traced back from the time for starting the line selecting device, sampling points with value less than 0.01 U<n> are searched on the zero sequence voltage of the bus, and the time corresponding to the sampling points is considered as the occurring time t<f> of a single-phase grounding fault; a period of sampling points of the zero sequence voltage of the bus are selected from t<f>, phase angles theta <u0> of the sampling points and I<DC> of each line are computed, criteria 1, 2, 3 and 4 are obtained, and line selection is carried out on a system fault according to the criteria. The method and a transient component line selecting method are matched to form a perfect fault line selecting scheme. A great amount of digital simulation results show that the method is effective and reliable.

Description

A kind of adaptive approach for route selection of grounded system connected to arc suppression coil

Technical field:

The present invention relates to a kind of adaptive approach for route selection of grounded system connected to arc suppression coil, belong to the relay protection of power system technical field.

Background technology:

The system with non-effectively earthed neutral that single-phase earthing electric arc can extinguish voluntarily is called small grounding current system, mainly with isolated neutral, occur through high resistance grounding or through ground connection forms such as grounding through arc.The power distribution network of China 6～66kV all belongs to small grounding current system (list of references 1) usually.

Power network neutral point is generally through arc suppression coil or isolated neutral, when singlephase earth fault took place, owing to do not form short circuit, rules allowed to continue operation 1-2h, but the ground connection operation very easily forms the two phase ground short circuit for a long time, and arc grounding also can cause the total system superpotential.For preventing that fault from enlarging, and must send signal and get rid of fault.For preventing that fault from further enlarging, must select faulty line in time, exactly and be excised (list of references 2).

Through studying for a long period of time, occurred the various faults selection method at present, and developed corresponding device thereof, but effect in actual applications is not very good.Existing single-phase ground fault line selecting method of small-electric current grounding system can be divided three classes steady method (list of references 3-5), transient state method (list of references 6-7) and signal injection method (list of references 8) substantially from the signal that uses.Typical method in the steady method has: amplitude relative method, phase-comparison method, zero sequence node-pair method, homopolar power method etc.Amplitude relative method and phase-comparison method are only applicable to the system of isolated neutral, but in the reality because the more single-phase-to-ground current of transformer station's outlet is excessive, so arc suppression coil is widely used, so these two kinds of method scope of applications are very little; Zero sequence node-pair method and homopolar power method are interfered easily owing to zero-sequence current after the stable state is less, have influenced effect in practice.The high frequency transient component that the transient state method utilizes fault to cause carries out failure line selection, but the size of high frequency transient component and fault switching angle are closely related.The signal injection method needs external signal, need change the wiring of the PT of system during practical application, is unfavorable for the practical application of device.Because the transient state selection method can not be subjected to the influence of small grounding current system neutral grounding mode, and does not need to inject signal, therefore obvious superiority is arranged in actual applications.Though most of faults are Fault of Insulating Breakdown in the reality, voltage near zero, can not produce tangible transient signal, but the possibility of voltage zero cross near fault neither not take place during fault, as: in the actual motion of Kunming power supply administration, voltage zero cross near fault also occurs now and then.The high frequency transient component is very little when voltage zero cross near breaks down, and considers various interference, and the transient state selection method may lose efficacy.But this moment, fault caused bigger attenuating dc component.Proposed in the document 9 a kind ofly to utilize the selection method of attenuating dc component based on wavelet transformation, this method is used the db10 small echo, and the sampled signal of 4kHz is decomposed 6 layers, selects for use the signal of 0～31.25Hz and 31.25～62.5Hz to form the route selection core algorithm.The bearing length of db10 small echo is 19, and therefore the time window of the wavelet filter of 0～31.25Hz is 19 * 2 ⁵=608 sampled points, time corresponding are 608/4000 second, about 7.5 cycles.Therefore to accomplish that accurate route selection just need be more than the data of 7.5 cycles.As seen the algorithm in the document 9 needs a large amount of sampled datas, and this is unfavorable for practical application, and this method is not considered the situation of bus-bar fault.Therefore, this method has proposed a kind of failure line selection self-adaptation new method of utilizing attenuating dc component, data of a cycle after the operational failure only, and it and transient state selection method are complementary, both are in conjunction with forming perfect fault-line selecting method.

List of references:

[1] Xiao Bai, Shu Hongchun, peak (Xiao Bai, Shu Hongchun, Gao Feng) single-phase ground fault line selecting method of small-electric current grounding system summary (Survey of The Methods of Fault Line Selection for Single-to-earth Fault in NetworkWith Ungrounded Neutral). relay (Relay), 2001,29 (4): 16-20

[2] Xiao Bai; Shu Hongchun; Mu Gang; Deng (Xiao Bai; Shu Hongchun, Mu Gang, et al). based on the power distribution network ground protection research (Study of Grounding Fault Protection In Distribution System Based On TheTheory of Modular maxima) of modulus maximum theory. relay (Relay); 2004,32 (10): 36-39

[3] Hao Yushan, Yang Yihan, Ren Yuanheng, etc. (Hao Yushan, Yang Yihan, Ren Yuanheng). the colony of small current neutral grounding microcomputer route selection is than amplitude ratio facies principle (Principle of magnitude; Phase comparison for micro computerbased small current grounding system line selection). electric power information (Information on ElectricPower), 1994 (2): 15-19

[4] easily eastern; the Lie group Zhan; Huang Yanquan (Yi Dong; Li Qunzhan; Huang Yanquan). zero sequence node-pair method earthing wire-selecting protection philosophy (Principle of selective grounding fault protection based on zero sequenceadmittance). power system automation apparatus (Power System Automation Equipment); 2002,22 (10): 40-42

[5] Du Dingxiang, Xu Yuqin (Du Dingxiang, Xu Yuqin). the meritorious route selection of arc suppression coil earthing electric network (Faulted linedetecting with active power in a auto-compensated distribution network). relay (Relay), 2002,30 (5): 33-36

[6] Shu Hongchun, Xiao Bai (Shu Hongcun, Xiao Bai). the single-phase electric arc earth fault line selection of power distribution network transient analysis method (Atransient-based study of fault line selection for single-phase to ground faults on distributionsystem). Automation of Electric Systems (Automation of Electric Power Systems) 2002,26 (21): 58-61

[7] Jia Qingquan; Liu Lianguang; (Jia Qingquan such as Yang Yihan; Liu Lianguang; Yang Yihan). use Wavelet Detection fault catastrophe characteristics and realize power distribution network low current fault fault line detection (Abrupt change detection with wavelet forsmall current fault relaying). Proceedings of the CSEE (Proceedings of the CSEE); 2001,21 (10): 78-82

[8] Wang Xinchao, Sang Zaizhong (Wang Xincao, Sang Zaizhong). based on a kind of localization of fault new method of " S injection method " (A new approach of fault location based on " S injecting signal ". relay (Relay), 2001,29 (7): 9-12

[9] Dai Jianfeng, Zhang Yanxia, wait Zhe (Dai Jianfeng, Zhang Yangxia, Hou Zhe). the application (Application of Wavelet Reconstruction Algorithm inPhase-to-ground Fault Detection of Distribution Networks) of wavelet reconstruction algorithm in the power distribution network earthing wire-selecting. electric power network technique (Power SystemTechnology), 2004,28 (3): 43-47

[10] to shine year Cao Meiyue. the electric system resonance grounding. the .2000:54-58 of China Electric Power Publishing House

[11] Hou Youtao, open and lift, Li Wei (Hou Youtao, Zhang Ju, Li Wei). extract the improvement algorithm (AnImproved Algorithm for Extraction Decaying DC Component) of attenuating dc component parameter. North China Electric Power University's journal (Journal ofNorth China Electric Power University), 2004,31 (3): 23-25

Summary of the invention:

The objective of the invention is to overcome the deficiency of existing Grounded Fault in Small Grounded Current System route selection technology, on basis to the electro-magnetic transient signature analysis of neutral point in arc suppression coil earthing system, after a large amount of emulation, a kind of attenuating dc component that utilizes has been proposed to accurately carry out the adaptive approach of failure line selection through the small grounding current system of grounding through arc.

1 attenuating dc component distribution character

For the neutral by arc extinction coil grounding system that this method is carried out Digital Simulation, when singlephase earth fault took place, distribution of current as shown in Figure 1.

Among Fig. 1, C ₁, C ₄, C ₅And C _fDeng each line mutual-ground capacitor of expression, L _nExpression arc suppression coil inductance, L _rThe expression equivalent inductance, R _fThe transition resistance of expression earth point, F ₁, F ₂Be earth point.

When electrical network generation singlephase earth fault, flow through the zero-sequence current i of faulty line _dBy transient state capacitance current i _cWith transient state inductive current i _LTwo parts are formed by stacking (list of references 10).Promptly

$i_d=i_c+i_L$

In the formula (1), first is the ground current steady-state component, equals amplitude poor of stable state capacitance current and stable state inductive current; All the other are the transient state component of ground current, equal the transient DC component sum of the transient state free oscillation component and the inductive current of capacitance current.For non-fault line, only contain transient state capacitance current component in its zero-sequence current of flowing through, and do not contain the inductive current component.When fault occurred in the phase voltage near zero-crossing point, the characteristic of its transient zero-sequence current of faulty line depended primarily on the transient state inductive current, and with respect to non-fault line, the DC component that contains in the faulty line transient zero-sequence current is bigger.

5 outlets are arranged, as circuit L in this method Digital Simulation System ₅At F ₁When A phase earth fault takes place during the point voltage zero passage (transition resistance is 20 Ω), faulty line L ₅With non-fault line L ₄Zero-sequence current as shown in Figure 2.As can be seen from Figure 2, very significantly attenuating dc component is arranged in the faulty line zero-sequence current, the decaying dc composition is then very little in the non-fault line zero-sequence current.When bus A takes place at F ₂During point earth fault, circuit L ₄With circuit L ₅In zero-sequence current as shown in Figure 3, in Fig. 3, attenuating dc component is almost nil in the zero-sequence current of two circuits, this is because attenuating dc component has flowed directly into arc suppression coil, and does not flow through the reason of circuit.

2 fault-line selecting methods

By the distribution character of attenuating dc component when the small grounding current system singlephase earth fault of grounding through arc as seen, when circuit during not at the voltage max near fault, system will have attenuating dc component to produce, it only flows through faulty line and arc suppression coil and does not flow through non-fault line, though when bus-bar fault, also there is attenuating dc component to produce, but it does not flow through any circuit, but flows directly into arc suppression coil.According to these characteristics, can constitute the small grounding current system fault-line selecting method that utilizes attenuating dc component.Implementation step is as follows:

1. as bus residual voltage instantaneous value u _n(t) greater than K _uU _n, fault line selection device starts immediately, notes each outlet and bus zero-sequence current and bus residual voltage, the wherein K of 3 cycles after preceding 2 cycles of fault and the fault _uGeneral value is 0.35, U _nExpression bus rated voltage;

2. start from line selection apparatus and constantly review forward, on the bus residual voltage, seek less than 0.01U _nSampled point, its moment corresponding is thought the moment t that singlephase earth fault takes place _f

3. from t _fBegin to choose the sampled point of a cycle, make the attenuating dc component initial value I that calculates in the following method in each circuit and the bus zero-sequence current _DC, wherein, τ is a damping time constant.

Only ask DC component, can ignore the influence of mark subharmonic, might as well suppose that being sampled signal has following form:

I in the formula _DCBe the attenuating dc component initial value, τ is a damping time constant, I _{M, n}And  _nBe respectively the amplitude and the initial phase angle of nth harmonic.X (t) discretize is got (list of references 11):

In the formula (3), Δ t is a sampling time interval, and N is weekly the sampling number of ripple.In signal Processing, x (k, Δ t) generally is abbreviated as x (k).Make r=e ^{-Δ t/ τ}, in one-period, x (k) sued for peace

Because

$\underset{k=1}{\overset{\mathrm{<figure-callout\; id="2"\; label="N\; cos"\; filenames="C20051001079300111.png"\; state="\{\{state\}\}">N</figure-callout>}}{\mathrm{\&Sigma;}}}\cos \frac{2\mathrm{\&pi;}}{N}\mathrm{nk}=0,$ $\underset{k=1}{\overset{N}{\mathrm{\&Sigma;}}}\sin \frac{2\mathrm{\&pi;}}{N}\mathrm{nk}=0$

So

$\underset{k=1}{\overset{N}{\mathrm{\&Sigma;}}}x\left(k\right)=\underset{k=1}{\overset{N}{\mathrm{\&Sigma;}}}{I}_{\mathrm{DC}}{r}^k=I_{\mathrm{DC}}\underset{k=1}{\overset{N}{\mathrm{\&Sigma;}}}{r}^k---\left(5\right)$

Introduce the sampled value that N+1 is ordered, x (k) suing for peace in 2 to N+1 these one-periods of ordering, is in like manner had

$\underset{k=2}{\overset{N+1}{\mathrm{\&Sigma;}}}x\left(k\right)=\underset{k=2}{\overset{N+1}{\mathrm{\&Sigma;}}}{I}_{\mathrm{DC}}{r}^k=I_{\mathrm{DC}}r\underset{k=1}{\overset{N}{\mathrm{\&Sigma;}}}{r}^k---\left(6\right)$

Get by (5) formula, (6) formula

$r=I_{\mathrm{DC}}r\underset{k=2}{\overset{N+1}{\mathrm{\&Sigma;}}}{r}^k/I_{\mathrm{DC}}r\underset{k=1}{\overset{N}{\mathrm{\&Sigma;}}}{r}^k---\left(7\right)$

Get by (5)

$I_{\mathrm{DC}}=\underset{k=1}{\overset{N}{\mathrm{\&Sigma;}}}x\left(k\right)/\underset{k=1}{\overset{N}{\mathrm{\&Sigma;}}}{r}^k---\left(8\right)$

4. being without loss of generality, being provided with feeder line more than 3, by attenuating dc component initial value absolute value more in the line, seek preceding 3 maximal values, is I by descending order _{DC, j}, I _{DC, k}And I _{DC, m}, corresponding circuit is respectively L _j, L _kAnd L _m:

5. judge whether near voltage max, to break down.Concrete grammar is: from t _fBegin to choose the sampled point of bus residual voltage one-period, calculate its phase angle theta _U0(establishing residual voltage is sine function, and θ _U0∈ [180 °, 180 °]), and the definition criterion 1:

| θ _U0-90 ° |≤30 ° or | θ _U0+ 90 ° |≤30 ° (9)

When satisfying criterion 1, think near the phase voltage maximal value, to break down, because this method sensitivity is lower in this case, may cause erroneous judgement, for guaranteeing the accuracy of route selection, so this method is with locking, use the transient state selection method and change over to, do not give unnecessary details here.When not satisfying criterion 1, then distinguish line fault or bus-bar fault;

6. judge whether to be line fault, and definition criterion 2:

| _IDC，j|＞|I _DC，k|+|I _DC，m| (10)

When satisfying criterion 2, circuit L is described _jAttenuating dc component I _{DC, j}Attenuating dc component on other circuit, this method are thought circuit L _jFault.When not satisfying criterion 2, then think bus-bar fault.

7. when having only 1 or 2 circuits in the system, will not have 3 I _{DC, n}Both of these case is carried out following processing:

Article 1, feeder system: only need to distinguish belong to bus-bar fault or line fault, under the situation that satisfies criterion 1, locking this method; Under the situation of criterion 1, establishing the bus attenuating dc component is I _{DC, B}, the Line Attenuation DC component is I _{DC, L}, definition criterion 3 is: work as I _{DC, B}＞2I _{DC, L}The time, be judged as bus-bar fault, otherwise be judged as line fault;

Article 2, feeder system: under the situation that satisfies criterion 1, locking this method; Under the situation that does not satisfy criterion 1, establishing the bus attenuating dc component is I _{DC, B}, the fast by size series arrangement of Line Attenuation DC component initial value is respectively I _{DC, j}And I _{DC, k}, definition criterion 4 is: work as I _{DC, B}And I _{DC, j}Direction is opposite, then is judged as circuit j fault, works as I _{DC, B}And I _{DC, j}Direction is identical, is judged as bus-bar fault.

The present invention compared with prior art has following advantage:

1, theoretical foundation of the present invention is comparatively directly perceived, method is simple and practical, reliable, effective.

2, a large amount of emulation show: this method when fault switching angle θ≤60 ° and transition resistance are big, route selection correctly; At transition resistance hour, also correctly route selection when the fault switching angle is big;

3, this method can combine with the transient state selection method, forms perfect small grounding current system failure line selection technology.

Description of drawings:

Distribution of current in Fig. 1 arc suppression coil earthing electric network during single-phase earthing.

Faulty line during Fig. 2 line fault and non-fault line zero-sequence current.

Circuit zero-sequence current during Fig. 3 bus-bar fault.

Fig. 4 route selection process flow diagram.

Embodiment:

This method specific implementation process flow diagram as shown in Figure 4.The concrete steps of this method are as follows:

(1) as the bus residual voltage instantaneous value u of small current neutral grounding system ₀(t) greater than K _uU _n, failure line selection road device starts immediately, notes each the outlet zero-sequence current and the bus residual voltage of 3 cycles after preceding 2 cycles of fault and the fault.Wherein, K _uGeneral value is 0.35, U _nExpression bus rated voltage;

(2) constantly chase after the first day of the lunar month forward from the line selection apparatus startup, on the bus residual voltage, seek less than 0.01U _nSampled point, its moment corresponding is thought the moment t that singlephase earth fault takes place _f

(3) from t _fBegin to choose the sampled point of bus residual voltage one-period, calculate its phase angle theta _U0, establishing residual voltage is sine function, and θ _U0∈ [180 °, 180 °], and definition criterion 1 is: | θ _U0-90 ° |≤30 ° or | θ _U0+ 90 ° |≤30 °; Calculate the attenuating dc component I of each bar circuit _DC, $I_{\mathrm{DC}}=\underset{k=1}{\overset{N}{\mathrm{\&Sigma;}}}x\left(k\right)/\underset{k=1}{\overset{N}{\mathrm{\&Sigma;}}}{r}^k,$ N is weekly the sampling number of ripple, and x (k Δ t) is abbreviated as x (k), r=e ^{-Δ t/ τ}, Δ t is a sampling time interval, τ is a damping time constant; And definition criterion 2 is: | I _{DC, j}|＞| I _{DC, k}|+| I _{DC, m}|, wherein, I _{DC, j}, I _{DC, k}, I _{DC, m}Represent all Line Attenuation DC component I respectively _DCIn maximum three, be I by descending order _{DC, j}, I _{DC, k}And I _{DC, m}, corresponding circuit is respectively L _j, L _kAnd L _m, judge it is line fault or bus-bar fault according to criterion 1 and criterion 2, perhaps should lockout algorithm;

A. when satisfying criterion 1, think near the phase voltage maximal value, to break down, so, use the transient state selection method and change over to locking this method;

B. when not satisfying criterion 1, then distinguishing according to criterion 2 is line fault or bus-bar fault; When satisfying criterion 2, circuit L is described _jAttenuating dc component I _{DC, j}Attenuating dc component on other circuit is thought circuit L _jFault; When not satisfying criterion 2, then think bus-bar fault;

C. when having only 1 or 2 circuits in the system, will not have 3 I _{DC, n}, both of these case is carried out following processing:

Article 1, feeder system: only need to distinguish belong to bus-bar fault or line fault, under the situation that satisfies criterion 1, locking this method; Under the situation of criterion 1, establishing the bus attenuating dc component is I _{DC, B}, the Line Attenuation DC component is I _{DC, L}, definition criterion 3 is: work as I _{DC, B}＞2I _{DC, L}The time, be judged as bus-bar fault, otherwise be judged as line fault;

Article 2, feeder system: under the situation that satisfies criterion 1, locking this method; Under the situation that does not satisfy criterion 1, establishing the bus attenuating dc component is I _{DC, B}, the fast by size series arrangement of Line Attenuation DC component initial value is respectively I _{DC, j}And I _{DC, k}, definition criterion 4 is: work as I _{DC, B}And I _{DC, j}Direction is opposite, then is judged as circuit j fault, works as I _{DC, B}And I _{DC, j}Direction is identical, is judged as bus-bar fault.

The inventor adopts this method to carry out a large amount of Digital Simulations, and its result shows: this method is effectively, reliably.

Claims (2)

1. adaptive approach for route selection of grounded system connected to arc suppression coil, utilize the measurement of attenuating dc component to carry out, the DC component that it is characterized in that first cycle after the operational failure replaces the calculating of attenuating dc component, and realizes the failure line selection of small current neutral grounding system according to the DC component size; Concrete steps are as follows:

(1) as the bus residual voltage instantaneous value u of small current neutral grounding system ₀(t) greater than K _uU _n, failure line selection road device starts immediately, notes each the outlet zero-sequence current and the bus residual voltage of 3 cycles after preceding 2 cycles of fault and the fault.Wherein, K _uGeneral value is 0.35, U _nExpression bus rated voltage;

(2) constantly chase after the first day of the lunar month forward from the line selection apparatus startup, on the bus residual voltage, seek less than 0.01U _nSampled point, its moment corresponding is thought the moment t that singlephase earth fault takes place _f

(3) from t _fBegin to choose the sampled point of bus residual voltage one-period, calculate its phase angle theta _U0, establishing residual voltage is sine function, and θ _U0∈ [180 °, 180 °], and definition criterion 1 is: | θ _U0-90 ° |≤30 ° or | θ _U0+ 90 ° |≤30 °; Calculate the attenuating dc component I of each bar circuit _DC, $I_{\mathrm{DC}}=\underset{k=1}{\overset{N}{\mathrm{\&Sigma;}}}x\left(k\right)/\underset{k=1}{\overset{N}{\mathrm{\&Sigma;}}}{r}^k,$ N is weekly the sampling number of ripple, and x (k Δ t) is abbreviated as x (k), r=e ^{-Δ t/ τ}, Δ t is a sampling time interval, τ is a damping time constant; And definition criterion 2 is: | I _DC, j|＞| I _{DC, k}|+| I _{DC, m}|, wherein, I _{DC, j}, I _{DC, k}, I _{DC, m}, represent all Line Attenuation DC component I respectively _DCIn maximum three, be I by descending order _{DC, j}, I _{DC, k}And I _{DC, m}, corresponding circuit is respectively L _j, L _KAnd L _m, judge it is line fault or bus-bar fault according to criterion 1 and criterion 2, perhaps should lockout algorithm;

A. when satisfying criterion 1, think near the phase voltage maximal value, to break down, so, use the transient state selection method and change over to locking this method;

B. when not satisfying criterion 1, then distinguishing according to criterion 2 is line fault or bus-bar fault; When satisfying criterion 2, circuit L is described _jAttenuating dc component I _{DC, j}Attenuating dc component on other circuit is thought circuit L _jFault; When not satisfying criterion 2, then think bus-bar fault;

C. when having only 1 or 2 circuits in the system, will not have 3 I _{DC, n}, both of these case is carried out following processing:

Article 1, feeder system: only need to distinguish belong to bus-bar fault or line fault, under the situation that satisfies criterion 1, locking this method; Under the situation of criterion 1, establishing the bus attenuating dc component is I _{DC, B}, the Line Attenuation DC component is I _{DC, L}, definition criterion 3 is: work as I _{DC, B}＞2I _{DC, L}The time, be judged as bus-bar fault, otherwise be judged as line fault;

Article 2, feeder system: under the situation that satisfies criterion 1, locking this method; Under the situation that does not satisfy criterion 1, establishing the bus attenuating dc component is I _{DC, B}, the fast by size series arrangement of Line Attenuation DC component initial value is respectively I _{DC, j}And I _{DC, k}, definition criterion 4 is: work as I _{DC, B}And I _{DC, j}Direction is opposite, then is judged as circuit j fault, works as I _{DC, B}And I _{DC, j}Direction is identical, is judged as bus-bar fault.

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