CN1180273C - Sectional detection method of small current earthing fault of power system - Google Patents

Sectional detection method of small current earthing fault of power system Download PDF

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Publication number
CN1180273C
CN1180273C CNB011455403A CN01145540A CN1180273C CN 1180273 C CN1180273 C CN 1180273C CN B011455403 A CNB011455403 A CN B011455403A CN 01145540 A CN01145540 A CN 01145540A CN 1180273 C CN1180273 C CN 1180273C
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sequence current
zero
transient
fault
transient zero
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CN1421704A (en
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徐丙垠
薛永端
冯祖仁
王敬华
王俊江
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KEHUI ELECTRICS CO Ltd ZIBO
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Abstract

The present invention relates to a segmenting method of the small current earthing faults of a power system, particularly to a segmenting method of the single-phase earthing faults of a long-distance system with a single outgoing line. The segmenting method is suitable for a system that a plurality of detecting devices are arranged on a line of the system according to segments. Each detecting device uses the change of a zero-sequence voltage or a zero-sequence current as a fault restarting condition and the amplitude and the initial polarity of a transient zero-sequence current generated by faults are calculated. A main station determinates fault segments according to fault information reported by each detecting device. The basic criteria of the main station is that the initial polarities of the transient zero-sequence currents on both sides of a fault point are opposite after the faults occur and the distance from the amplitude of the transient zero-sequence current on each side of the fault point to the fault point is in a contravariant relation. The segmenting method is suitable for a neutral point earth free system, an arc-suppression coil earthing system and a high-resistance earthing system, and also suitable for a system that a reactance load is connected to a line of the system.

Description

Sectional detection method of small current earthing fault of power system
Technical field
Sectional detection method of small current earthing fault of power system, the medium voltage distribution network singlephase earth fault segmentation method that relates to a kind of isolated neutral, grounding through arc or high resistance ground, relate in particular to a kind of small current neutral grounding system that singly goes out the line length distance, as the singlephase earth fault segmentation method of railway signal power supply electric power system (self-closing or perforation circuit).
Background technology
China's distribution system adopts isolated neutral or resonance grounding (grounding through arc) processing mode mostly.The reasons such as ground connection process instability little owing to fault current, that arc light causes, it is a problem that is difficult to thorough solution that singlephase earth fault is detected always.
The fault overwhelming majority that power distribution network takes place is a single-phase earthing.Therefore, constantly perfect along with the development of distribution feeder automation and fault management capability, requirement also can realize that fault section is isolated fast and recovery perfects the power supply of circuit, and not only be confined to traditional failure line selection as short trouble singlephase earth fault.
For picture railway signal power supply electric power system (self-closing, connect circuit), line length is generally 40-60km especially, do not have suitable power source or stride powered in particular cases may reach kilometers up to a hundred.Railway is meteorological along the line, geologic media is complicated, searches very difficulty of trouble spot.Especially wish when singlephase earth fault, to reduce fault coverage, and further with fault isolation.Pressure regulator and the isolation of conventional bus have been passed through in the output that railway is self-closing, connect circuit, and the feature of its single-phase earthing is equal to and singly goes out the line length system of distance.
Existing singlephase earth fault fragmentation technique mainly is that the stable status zero-sequence current and the negative-sequence current that utilize fault to produce are referred to as steady method.The stable status zero-sequence current method only is suitable for isolated neutral system, and is not suitable for arc suppression coil earthing system or has three reactance load systems relatively.The negative-sequence current method also exists little, the difficult measurement of signal amplitude, is subjected to load variations to influence big and can not be applicable to the shortcomings such as system that have the three-phase reactance load.Simultaneously, actual earth fault great majority are the flashing fault, and power frequency component will very faintly even not exist.Therefore, utilize the steady method of power current will have great limitation.Also have and utilize fault phase transient voltage current relationship to determine abort situation, as: " Chinese patent communique " on November 25th, 1998 is disclosed, application number: 96197635.7, and denomination of invention: the method for measuring singlephase earth fault position in the power distribution network.This method is to determine the zero hour of fault transient process earlier according to the variation of neutral point voltage, electric current and voltage transient signal filtering to the fault phase, determine the time span of this transient state process, calculate the fault transient wave frequency, the voltage and current transient signal of measuring is carried out low-pass filtering, the frequency spectrum U (ω) of calculating voltage and current temporary state procedure and I (ω), computing impedance spectrum (1), and by equation (2) according to the walk-off angle frequencies omega kCalculate fault distance, according to this invention, adopt the voltage and current signal filtering of comb filter to the fault phase, along the voltage and current signal filtering of both direction to measuring, estimate the frequency of charge/discharge transient state process according to the auto correlation function of transient state process, and adopt that the parametric spectrum estimation algorithm calculates the voltage and current transient state process but the complex values of frequency spectrum U (ω) and I (ω).But the precision of this method is high not enough, uses also to be restricted.
Summary of the invention
The technical problem to be solved in the present invention provides and a kind ofly can be suitable for all small current neutral grounding systems, and is not subjected to flashing fault, load variations, three reactance influence relatively, the segmentation method of the single-phase fault that is easy to detect.Behind circuit generation singlephase earth fault, utilize various checkout equipments to determine the guilty culprit section as early as possible, reduce the troubleshooting scope.Can perfect line powering by the operation isolated fault section and the recovery of respective switch on this basis.
The technical scheme that technical solution problem of the present invention is adopted is: by pressing pick-up unit, main website and the definite fault section of communication system cooperation that section is installed on the circuit, detailed process is:
Line detection apparatus:
A according to the variation of line zero sequence voltage or zero-sequence current as the fault initiating condition;
B is according to the variation search initial moment of fault of transient zero-sequence current;
C calculates fault segmentation information needed: the segmentation information needed comprises the amplitude of the transient zero-sequence current that fault produces and the initial polarity of transient zero-sequence current, and the formula that wherein is used for calculating the transient zero-sequence current amplitude is: I f = 1 T 0 ∫ 0 T 0 i 0 2 ( t ) dt , I fBe the transient zero-sequence current amplitude, i 0Be transient zero-sequence current, T 0Be the delay time of transient zero-sequence current, T 0Choose reservation transient signal that must be as much as possible and try one's best the reservation power frequency component few, and wherein calculate the initial polarity of transient zero-sequence current as follows, if the scene can obtain residual voltage, zero sequence current signal simultaneously, then the electric current initial polarity defines according to the variation tendency of instant of failure transient zero-sequence current with respect to the transient state residual voltage, if the scene can only obtain zero sequence current signal, then initial polarity defines according to the variation tendency of instant of failure transient zero-sequence current itself.
Main website:
D according to each pick-up unit of faulty line report the amplitude and the initial polarity of transient zero-sequence current determine fault section.
The method that transient zero-sequence current amplitude that main website reports according to each pick-up unit of faulty line in the steps d and initial polarity are determined fault section is as follows: its initial polarity of plurality of detection point comparison of selecting transient zero-sequence current amplitude maximum, if certain section both sides transient zero-sequence current initial polarity on the contrary then this section is the guilty culprit section, if all participations check point initial polarity relatively is all identical and the transient zero-sequence current amplitude is monotone variation trend with circuit, the check point of amplitude maximum must be positioned at all and participate in the relatively end of check point, and then fault section does not participate in the relatively section of a side for there is check point near it.
Adopt following method to determine the initial polarity of transient zero-sequence current: if the scene can obtain residual voltage, zero sequence current signal simultaneously, the polarity of then initial transient zero-sequence current defines according to the variation tendency of instant of failure transient zero-sequence current with respect to the transient state residual voltage, the initial polarity of the identical then transient zero-sequence current of this trend is for just, the initial polarity of the opposite then transient zero-sequence current of this trend is judged transient state residual voltage u for negative 0, transient zero-sequence current i 0Variation tendency whether identically can adopt first formula:
P = ∫ 0 T 1 u 0 ( t ) i 0 ( t ) dt
If the scene can only obtain zero sequence current signal and can not obtain the residual voltage signal, then the electric current initial polarity defines according to the variation tendency of instant of failure transient zero-sequence current itself, can adopt second formula:
P = ∫ 0 T 1 i 0 ( t ) dt
If wherein in first and second formula T1 be carved into time P>0 that makes P first extreme value occur when initial from fault the initial polarity of transient zero-sequence current for just, otherwise the initial polarity of P<0 transient zero-sequence current is for negative, and second formula is equally applicable under the condition of residual voltage signal.
Compared with prior art the invention has the beneficial effects as follows:
When singlephase earth fault took place, the ratio of maximum transient zero-sequence current and stable status zero-sequence current was approximately equal to the ratio of resonance frequency and work frequency, and promptly its amplitude may be bigger several times to tens times than steady-state value.Therefore, compare with steady-state signal, transient signal by force, easier detection.
In resonant earthed system, because the electric current in the arc suppression coil can not suddenly change, the transient current pace of change of the arc suppression coil of flowing through is far smaller than the variation of transient state capacitance current.Simultaneously, the induction reactance of arc suppression coil increases along with increasing of frequency, and the capacitive reactance of electric capacity descends simultaneously.Therefore, when adopting transient zero-sequence current, can not consider the influence of arc suppression coil.Characteristic and the arc suppression coil of three-phase reactance load when fault is similar, can ignore its influence to transient signal equally.
The variation of power distribution network load can not cause the variation of circuit zero-sequence current, utilizes the method for transient zero-sequence current not to be subjected to the influence of load variations yet.During the flashing fault, it is constantly breakdown to be accompanied by the trouble spot, and transient signal constantly produces, and therefore utilizes the method for transient zero-sequence current that the flashing fault is had stronger applicability.
Utilizing this method not need as utilizing power current must be reference with the residual voltage signal, goes for obtaining the circuit of residual voltage.
Do not have reactance load over the ground no matter have on the circuit, the regularity of distribution of transient zero-sequence current is all identical on the faulty line.Therefore, utilize the Changing Pattern of transient zero-sequence current to carry out the fault segmentation, be not subjected to system earth mode, line reactance effects of load, can produce more transient information during the flashing fault, widely applicable; Transient signal is big than the steady-state signal amplitude, detection sensitivity, reliability height.
Realize content of the present invention, whole system should be made up of three parts: be distributed in the pick-up unit of each check point of circuit, be positioned at the main website and the communication system of transformer station.The course of work is the variation that pick-up unit is responsible for real-time Monitoring Line residual voltage electric current, calculates transient zero-sequence current amplitude and initial polarity after the fault, and result of calculation is reported main website.Main website determines fault section and sends alerting signal after receiving the information that each terminal device reports.By artificial or automatic remote control respective switch fault isolation and recovery are perfected the power supply of circuit again.The specific implementation step is as follows:
Line detection apparatus:
1) according to the variation of residual voltage or zero-sequence current entry condition as singlephase earth fault:
In small current neutral grounding system, when the metallicity singlephase earth fault took place, the ground connection phase voltage was reduced to 0, and two perfect phase voltage raise for line voltage be phase voltage
Figure C0114554000071
Doubly.Simultaneously, residual voltage on the circuit and zero-sequence current all can increase, the phase voltage when wherein the residual voltage amplitude equals operate as normal.Therefore, can utilize residual voltage or zero-sequence current to surmount the entry condition of certain threshold as singlephase earth fault:
S 0>S 0d
Used residual voltage, zero-sequence current can be that the result who directly measures calculates by three-phase voltage or electric current:
S 0 ( t ) = 1 3 ( S A ( t ) + S B ( t ) + S C ( t ) )
S has represented voltage or electric current in above-mentioned two formulas.
When there was transition resistance in earth point, residual voltage reduced along with the increase of transition resistance.The influence of unbalance voltage when overcoming operate as normal simultaneously, the threshold of residual voltage generally is taken as 30% of phase voltage.
The power frequency effective value of residual voltage, zero-sequence current or instantaneous value can be as the fault initiating conditions.
2) the initial moment of trouble-shooting:
Because transient signal is only of short duration in initial moment appearance of fault and duration in direct earth fault.The transient state process of simultaneous faults point both sides only with line construction, the relating to parameters of this side, promptly form might not be identical for the transient zero-sequence current frequency of both sides, so the polar relationship of both sides is only set up fully at instant of failure.Therefore, must be fully, the transient state process of record trouble exactly, and search initial moment of fault exactly, promptly represent first measurement point of this transient state process.
After singlephase earth fault starts, start previous power frequency cycle in the time range that starts a back power frequency cycle, seeking the moment that transient zero-sequence current sudden change flow control once surmounts a set threshold, can think the initial moment of fault.
Threshold can be measured instantaneous maximal value according to transient zero-sequence current sudden change in this scope and determines, as its 20%.
3) amplitude of calculating transient zero-sequence current:
The transient zero-sequence current amplitude is calculated can adopt formula I f = 1 T 0 ∫ 0 T 0 i 0 2 ( t ) dt , If but T 0That chooses excessively then is subject to the influence of arc suppression coil or reactance load, and too small then transient information can not utilize fully.Therefore, must guarantee T 0Choose reservation transient signal as much as possible and try one's best the reservation power frequency component few, generally choose T 0Greater than 1/8 less than 1/2 power frequency cycle.
Also can adopt alternate manner to calculate the transient zero-sequence current amplitude, but method should be unified on every circuit.
4) calculate the initial polarity of transient zero-sequence current in the initial moment of fault:
If the scene can obtain residual voltage, zero sequence current signal simultaneously, then the electric current initial polarity is defined as the variation tendency of instant of failure transient zero-sequence current with respect to the transient state residual voltage.Trend just is all mutually, otherwise for negative.Judge transient state residual voltage U 0, electric current I 0Whether variation tendency is identical can adopt following formula:
P = ∫ 0 T 1 u 0 ( t ) i 0 ( t ) dt
If the scene can only obtain zero sequence current signal and can not obtain the residual voltage signal, then the electric current initial polarity is defined as the polarity of instant of failure transient zero-sequence current itself, promptly calculates:
P = ∫ 0 T 1 i 0 ( t ) dt
T wherein 1Make P the time of first extreme value occur for being carved into when initial from fault.If P>0 then transient zero-sequence current initial polarity are for just, otherwise P<0 is for negative.Second formula is equally applicable under the condition of residual voltage signal.
5) report failure message:
Line detection apparatus reports the failure message of main website except transient zero-sequence current amplitude and initial polarity, also should comprise supplementarys such as fault-time, residual voltage amplitude.
Main website:
Determine the fault section position according to the failure message that each check point of circuit reports:
Select the plurality of detection point of transient zero-sequence current amplitude maximum to compare its initial polarity.If certain section both sides transient current initial polarity on the contrary then this section is a fault section, if all participations check point initial polarity relatively is all identical and its transient zero-sequence current amplitude is monotone variation trend with circuit, the check point of amplitude maximum must be positioned at all and participate in the relatively end of check point, and then fault section does not participate in the relatively section of a side for there is check point near it.
Communication system:
Different communication system differences mainly are the speed that information is transmitted.Because singlephase earth fault can charging operation by rules, to detect, the timeliness of segmentation requires and not really high, therefore various communication systems can both be finished task of the presently claimed invention.
Description of drawings
Fig. 1 is a specific implementation system architecture synoptic diagram;
Fig. 2 is the trouble spot rear side zero-sequence current waveform of a physical record;
Fig. 3 is front side, the trouble spot zero-sequence current waveform with the same fault of Fig. 2;
Fig. 4 is the regularity of distribution figure on transient zero-sequence current road along the line during singlephase earth fault in the attached system shown in Figure 1.
Wherein: CB outlet isolating switch S1-S6 on-pole switch FTU1-FTU6 feeder automation terminal unit RTU is that the terminal device Tf of transformer station is fault moment I-VIII track section f trouble spot
Embodiment
If a whole set of detection system is made up of isolated plant during specific implementation, then must cause the waste of equipment and fund.Therefore a best implementation is: and feed line automatization system or the shared hardware and software platform of railway signal power supply monitoring system, with FTU, RTU as line detection apparatus, and shared main website and communication system, only need corresponding software of increase and a small amount of hardware to get final product.
Accompanying drawing 1-4 is one embodiment of the present of invention, below in conjunction with the structure and the course of work of illustrative system.
As shown in Figure 1, a whole set of detection system is made up of three parts: the feeder automation terminal unit FTU1-FTU6, the terminal device RTU of transformer station that are distributed in each check point of circuit are as line detection apparatus, be positioned at the main website of transformer station, get in touch the communication system of each pick-up unit and main website.The specific implementation step is as follows:
If between switch S 4, the S5 singlephase earth fault takes place, then the detected zero-sequence current variation of the pick-up unit of trouble spot rear side (from the trouble spot to the power supply) will be as shown in Figure 2, and the detected zero-sequence current of the pick-up unit of front side, trouble spot will be as shown in Figure 3.Though the detected zero-sequence current amplitude of each check point will along with its to the distance of trouble spot and change, wherein the variation of power frequency component will be with the position of the having or not of arc suppression coil, reactance load and is different.But the transient zero-sequence current characteristic of instant of failure is fixed: the initial polarity of each side is unified, and amplitude with to the trouble spot apart from becoming contravariant to concern.Whole piece circuit and the detected transient zero-sequence current amplitude of each check point and polar relationship are as shown in Figure 4.
Among Fig. 1 on the circuit each pick-up unit detected transient zero-sequence current amplitude and polarity are reported main website by communication system.Main website determines fault section according to transient zero-sequence current amplitude and polarity that each check point of faulty line reports.
The plurality of detection point that main website selection amplitude is bigger compares polarity and determines fault section.If the amplitude threshold is lower, as select the check point of five amplitude maximums to be respectively relatively initial polarity of FTU1~FTU5 participation.Then FTU1~FTU4 initial polarity is identical and all opposite with the FTU5 initial polarity, then can failure judgement be positioned at section VI.If the amplitude threshold is higher, as only selecting relatively initial polarity of three check point FTU2~FTU4, then all identical and amplitude of its initial polarity is increase trend, therefore can failure judgement be positioned at the opposite side near the maximum check point FTU4 of amplitude, promptly is positioned section VI equally.
After determining fault section, ground connection information can be reported with various forms by main website, and automatic or manual machine in due course instruction cut-off switch S4, S5, and the isolated fault section overhauls, and does not influence the power supply that perfects section simultaneously.

Claims (3)

1, sectional detection method of small current earthing fault of power system by pressing pick-up unit, main website and the communication system cooperation realization that section is installed on the circuit, is characterized in that detailed process is: line detection apparatus:
A according to the variation of line zero sequence voltage or zero-sequence current as the fault initiating condition;
B is according to the variation search initial moment of fault of transient zero-sequence current;
C calculates fault segmentation information needed: the segmentation information needed comprises the amplitude of the transient zero-sequence current that fault produces and the initial polarity of transient zero-sequence current, and the formula that wherein is used for calculating the transient zero-sequence current amplitude is: I f = 1 T 0 ∫ 0 T 0 i 0 2 ( t ) dt , I fBe the transient zero-sequence current amplitude, i 0Be transient zero-sequence current, T 0Be the delay time of transient zero-sequence current, T 0Choose reservation transient signal that must be as much as possible and try one's best the reservation power frequency component few, and wherein calculate the initial polarity of transient zero-sequence current as follows, if the scene can obtain residual voltage, zero sequence current signal simultaneously, then the electric current initial polarity defines according to the variation tendency of instant of failure transient zero-sequence current with respect to the transient state residual voltage, if the scene can only obtain zero sequence current signal, then initial polarity defines according to the variation tendency of instant of failure transient zero-sequence current itself.
Main website:
D determines fault section according to the amplitude and the initial polarity of the transient zero-sequence current that each pick-up unit of faulty line reports.
2, method according to claim 1, it is characterized in that, the method that transient zero-sequence current amplitude that main website reports according to each pick-up unit of faulty line in the steps d and initial polarity are determined fault section is as follows: its initial polarity of plurality of detection point comparison of selecting transient zero-sequence current amplitude maximum, if certain section both sides transient zero-sequence current initial polarity on the contrary then this section is the guilty culprit section, if all participations check point initial polarity relatively is all identical and the transient zero-sequence current amplitude is monotone variation trend with circuit, the check point of amplitude maximum must be positioned at all and participate in the relatively end of check point, and then fault section does not participate in the relatively section of a side for there is check point near it.
3, method according to claim 1 and 2, it is characterized in that, adopt following method to determine the initial polarity of transient zero-sequence current: if the scene can obtain residual voltage, zero sequence current signal simultaneously, the polarity of then initial transient zero-sequence current defines according to the variation tendency of instant of failure transient zero-sequence current with respect to the transient state residual voltage, the initial polarity of the identical then transient zero-sequence current of this trend is for just, the initial polarity of the opposite then transient zero-sequence current of this trend is judged transient state residual voltage u for negative 0, transient zero-sequence current i 0Variation tendency whether identically can adopt first formula:
P = ∫ 0 T 1 u 0 ( t ) i 0 ( t ) dt
If the scene can only obtain zero sequence current signal and can not obtain the residual voltage signal, then the electric current initial polarity defines according to the variation tendency of instant of failure transient zero-sequence current itself, can adopt second formula:
P = ∫ 0 T 1 i 0 ( t ) dt
If wherein in first and second formula T1 be carved into time P>0 that makes P first extreme value occur when initial from fault the initial polarity of transient zero-sequence current for just, otherwise the initial polarity of P<0 transient zero-sequence current is for negative, and second formula is equally applicable under the condition of residual voltage signal.
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CN110865278B (en) * 2019-12-05 2022-07-29 南京四方亿能电力自动化有限公司 Ground fault positioning method based on transient mutation energy capturing method
CN112485715B (en) * 2020-11-30 2022-09-27 云南电网有限责任公司电力科学研究院 Reliable line selection method and device based on current zero-rest transient characteristics
CN112485716B (en) * 2020-11-30 2023-01-20 云南电网有限责任公司电力科学研究院 Line selection method based on zero-rest transient characteristic signal of ground fault arc current

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