CN103809080A - Double-end high frequency impedance type fault ranging method suitable for comprehensive power distribution system - Google Patents

Abstract

The invention discloses a double-end high frequency impedance type fault ranging method suitable for comprehensive power distribution system, and the method belongs to the field of the power system relay protection. The method concretely comprises two steps, step 1, ignoring the mutual inductance of the line and counting the line impedance between the power supply and the fault point by using following formula; step 2, confirming the concrete fault position by using following formula. The method can count based on the line impedance without the fault resistance of the short circuit point, the wave shape of transient state component and the impedance of the system, the method is simple, fast and effective to be easily realized in the actual power system; the synchronization service of the global positioning system (GPS) is not required and the method is very effective in the direct current transmission system; the method is also suitable for the line with distribution load and keeps the high precision while the running condition changes greatly.

Description

A kind of both-end high-frequency resistance formula fault distance-finding method that is applicable to overall power distribution system

Technical field

The invention belongs to field of relay protection in power, particularly a kind of both-end high-frequency resistance formula fault distance-finding method that is applicable to overall power distribution system.

Background technology

In a comprehensive electric system, (comprise distribution network, isolated power system), have increasing isolated power system, for example train, steamer, aircraft etc., in these systems, all there is no exposed distribution line, if can not judge in advance abort situation, will be difficult to excision and repair fault, therefore fast accurate localization of fault for restoring electricity rapidly and to improve the reliability of electric system most important.Meanwhile, localization of fault can also improve the stability of electric system fast, guarantees to reconfigure rapidly, and can reduce the harm that fault is brought.

The Fault Locating Method that carrys out the accurate location of the localization of faults in distribution line by measuring impedance is divided into two classes conventionally: single-ended method and both-end method.The one-end fault localization method proposing is at present to realize by the parameter before measuring fault and after fault, do not need special communication port, but the distribution line that the accuracy of result can for example be can't harm, do not have fault current and flow to load end, fault and do not occur in the impact of the desirable hypothesis such as isolating switch place.At present do not need synchronous both-end Fault Locating Method in addition, be by utilizing the stable state information before fault to realize, thereby avoided the error of bringing due to stationary problem.But this method will lose efficacy in the situation that there is no before fault information, so be difficult to really be used in actual electric system.Document (I.Zamora in addition, J.F.Minambres, A.J.Mazon, R.Alvarez-lsasi and J.Lazaro, " Fault location on two-terminal transmission lines based on voltages ", IEE Proceedings Generation, Transmission and Distribution, vol.143, pp.1-6, Jan1996) algorithm proposing is considered the saturation problem of fault initial period current transformer, the voltage measurement information of an operational failure point.But this method needs the relevant information of system impedance, and may be subject to fault impedance impact, therefore limit the application of the method.

In sum, be necessary to seek a kind of Novel double end formula fault localization scheme that can really effectively also can be applicable to practical power systems.

Summary of the invention

The problem existing for above-mentioned prior art, the present invention proposes a kind of both-end high-frequency resistance formula fault distance-finding method that is applicable to overall power distribution system, it is characterized in that, and the method is specially:

Step 1: ignore the mutual inductance of circuit, adopt following formula to calculate the line impedance between power supply and trouble spot:

$Z_X=\left[\begin{array}{c}{Z}_{\mathrm{xaa}}\\ Z_{\mathrm{xbb}}\\ Z_{\mathrm{xcc}}\end{array}\right]=\left[\begin{array}{c}\frac{V_{2a}-V_{1a}+I_{2a}{Z}_{\mathrm{taa}}}{I_{1a}+I_{2a}}\\ \frac{V_{2b}-V_{1b}+I_{2b}{Z}_{\mathrm{tbb}}}{I_{1b}+I_{2b}}\\ \frac{V_{2c}-V_{1c}+I_{2c}{Z}_{\mathrm{tcc}}}{I_{1c}+I_{2c}}\end{array}\right]$

Wherein, Z _xaa, Z _xbb, Z _xccrepresent respectively the self-induction impedance between power supply and the trouble spot of A phase, B phase, C phase circuit, V _1a, V _1b, V _1c, I _1a, I _1b, I _1cand V _2a, V _2b, V _2c, I _2a, I _2b, I _2cmagnitude of voltage and the current value of two trouble spots in the A phase, B phase, C phase circuit that represents respectively to record;

Adopt following formula to calculate the resulting impedance Z of circuit between power supply and load _t:

$Z_t=Z_x+Z_{t-x}=\left[\begin{array}{ccc}{\mathrm{<figure-callout\; id="0"\; label="Z\; xaa"\; filenames="HDA0000466616550000021.png,HDA0000466616550000041.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{\mathrm{xaa}}& 0& 0\\ 0& {\mathrm{<figure-callout\; id="0"\; label="Z\; xbb"\; filenames="HDA0000466616550000021.png,HDA0000466616550000041.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{\mathrm{xbb}}& 0\\ 0& 0& Z_{\mathrm{xcc}}\end{array}\right]+\left[\begin{array}{ccc}{Z}_{t-\mathrm{<figure-callout\; id="0"\; label="xaa"\; filenames="HDA0000466616550000021.png,HDA0000466616550000041.png"\; state="\{\{state\}\}">xaa</figure-callout>}}& 0& 0\\ 0& Z_{t-\mathrm{<figure-callout\; id="0"\; label="xbb"\; filenames="HDA0000466616550000021.png,HDA0000466616550000041.png"\; state="\{\{state\}\}">xbb</figure-callout>}}& 0\\ 0& 0& Z_{t-\mathrm{xcc}}\end{array}\right]$

$=\left[\begin{array}{ccc}{Z}_{\mathrm{<figure-callout\; id="0"\; label="taa"\; filenames="HDA0000466616550000021.png,HDA0000466616550000041.png"\; state="\{\{state\}\}">taa</figure-callout>}}& 0& 0\\ 0& {\mathrm{<figure-callout\; id="0"\; label="Z\; tbb"\; filenames="HDA0000466616550000021.png,HDA0000466616550000041.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{\mathrm{tbb}}& 0\\ 0& 0& Z_{\mathrm{tcc}}\end{array}\right]$

Wherein, t represents the total length of circuit, Z _xrepresent the impedance of circuit between power supply and trouble spot, x represents the distance of measurement point to trouble spot, Z _t-xrepresent the impedance of residue circuit, t-x represents to remain the length of circuit, Z _t-xaa, Z _t-xbb, Z _t-xccrepresent that respectively A phase, B phase, C remain the self-induction impedance of circuit, Z mutually _taa, Z _tbb, Z _tccrepresent respectively the self-induction impedance of circuit between the power supply of A phase, B phase, C phase and load;

Step 2: adopt following formula to determine the particular location of fault:

Wherein, Z ₀for known quantity, represent the resistance value of circuit unit length.

The beneficial effect of the invention is: (1) the inventive method is directly used the wideband fault transient component within the scope of traditional sensors, do not need to know fault resstance, the waveform of transient state component and the impedance of system of short dot, only need to know that the impedance of circuit just can calculate; For the phase fault in three-phase system and ground short circuit, the position that the information that only need to know fault phase just can the localization of faults; (2) compare with row wave technology with traditional power frequency technology, the inventive method more fast, accurately, can be used under various fault types, fault condition, fault resstance and system condition; In the time of service condition generation great variety, still can be applicable to the circuit with distribution load, keep its high precision; Easily accomplished in practical power systems, and do not need that GPS's is synchronous; (3), by utilizing from the high-frequency signal (reaching as high as 3kHz) of fault transient process, can be reduced to positioning time within later 4ms occurs fault, within positioning precision can reach 1m.

Accompanying drawing explanation

Fig. 1 is the single-phase circuit figure with earth fault;

Fig. 2 is the Thevenin equivalent circuit of non-fundamental frequency signal;

Fig. 3 is experimental facilities figure;

Wherein, 1-Chroma voltage source, 2-direct voltage source, 3-FPGA unit, 4-three phase rectifier, 5-three-phase resistance device, 6-trouble unit, 7-cable;

Fig. 4 (a) is mains side three-phase voltage value while there is ground short circuit;

Fig. 4 (b) is mains side three-phase electricity flow valuve while there is ground short circuit;

Fig. 4 (c) is load-side three-phase voltage value while there is ground short circuit;

Fig. 4 (d) is load-side three-phase electricity flow valuve while there is ground short circuit;

Fig. 5 (a) is mains side three-phase voltage value while there is phase fault;

Fig. 5 (b) is mains side three-phase electricity flow valuve while there is phase fault;

Fig. 5 (c) is load-side three-phase voltage value while there is phase fault;

Fig. 5 (d) is load-side three-phase electricity flow valuve while there is phase fault;

Fig. 6 is fault positioning experiment circuit diagram;

Fig. 7 (a) is magnitude of voltage and the current value that while there is jumping characteristic fault, mains side is measured;

Fig. 7 (b) is magnitude of voltage and the current value that while there is jumping characteristic fault, load-side is measured;

Fig. 8 (a) is magnitude of voltage and the current value of measuring with the mains side of the phase fault of 1 Ω resistance;

Fig. 8 (b) is magnitude of voltage and the current value of measuring with the load-side of the phase fault of 1 Ω resistance;

Fig. 8 (c) is with measuring circuit reactance value and actual value comparative result under the different faults of the phase fault of 1 Ω resistance;

Fig. 9 (a) is by magnitude of voltage and current value that after the simulation of IGBT switch, mains side is measured;

Fig. 9 (b) is magnitude of voltage and the current value of measuring by IGBT switch simulation back loading side;

Figure 10 (a) is measuring circuit reactance value and actual value comparative result under the different faults with 1 Ω fault resstance;

Figure 10 (b) is measuring circuit reactance value and actual value comparative result under the different faults with 3 Ω fault resstances.

Embodiment

With specific embodiment, the inventive method is further described with reference to the accompanying drawings below.

The ultimate principle of the inventive method can be introduced by a three-phase circuit figure with short trouble, as shown in Figure 1.Wherein V _sthe alternating-current voltage source of expression system, Z _a-S, Z _b-S, Z _c-Srepresent respectively the internal impedance of A phase, B phase, C phase line system, Z _a-Load, Z _b-Load, Z _c-Loadrepresent respectively the impedance of A phase, B phase, C phase line load, Z _trepresent the resulting impedance of circuit between power supply and load, Z _ax, Z _bx, Z _cxrepresent respectively the impedance of circuit between the power supply of A phase, B phase, C phase and trouble spot, Z _at-x, Z _bt-x, Z _ct-xrepresent respectively the impedance of the residue circuit of A phase, B phase, C phase, F represents trouble spot.

Short trouble can be regarded as the transient state process of the voltage and current being caused by the transient voltage source of trouble spot, wherein contains the very wide signal of frequency range.The Thevenin equivalent circuit of non-fundamental frequency signal as shown in Figure 2.

In Fig. 2, by fault transient power supply V _fprovide non-fundamental frequency transient voltage component, R _frepresent fault resstance.Wherein on every electricity mutually, there are two measurement points, lay respectively at power end and load side.Under failure condition, the electric current of each measurement point and magnitude of voltage can record.With reference to the circuit of figure 2, can be released by Kirchhoff's current law (KCL):

$\left[\begin{array}{c}{V}_{1a}\\ V_{1b}\\ V_{1c}\end{array}\right]+\left[\begin{array}{c}{I}_{1a}\\ I_{1b}\\ I_{1c}\end{array}\right]\left[\begin{array}{ccc}{Z}_{\mathrm{xaa}}& Z_{\mathrm{xab}}& Z_{\mathrm{xac}}\\ Z_{\mathrm{xba}}& Z_{\mathrm{xbb}}& Z_{\mathrm{xbc}}\\ Z_{\mathrm{xca}}& Z_{\mathrm{xcb}}& Z_{\mathrm{xcc}}\end{array}\right]=\left[\begin{array}{c}{V}_{2a}\\ V_{2b}\\ V_{2c}\end{array}\right]+\left[\begin{array}{c}{I}_{2a}\\ I_{2b}\\ I_{2c}\end{array}\right]\left[\begin{array}{ccc}{Z}_{t-\mathrm{xaa}}& Z_{t-\mathrm{xab}}& Z_{t-\mathrm{xac}}\\ Z_{t-\mathrm{xba}}& Z_{t-\mathrm{xbb}}& Z_{t-\mathrm{xbc}}\\ Z_{t-\mathrm{xca}}& Z_{t-\mathrm{xcb}}& Z_{t-\mathrm{xcc}}\end{array}\right]---\left(1\right)$

Wherein, V _1a, V _1b, V _1c, I _1a, I _1b, I _1cand V _2a, V _2b, V _2c, I _2a, I _2b, I _2cmagnitude of voltage and the current value of two trouble spots in the A phase, B phase, C phase circuit that represents respectively to record; Z _xaa, Z _xbb, Z _xccrepresent respectively the self-induction impedance between power supply and the trouble spot of A phase, B phase, C phase circuit; Z _xab, Z _xacrepresent respectively the mutual inductive impedance between power supply and the trouble spot of A phase and B phase, A phase and C phase circuit, Z _xba, Z _xbcrepresent respectively the mutual inductive impedance between power supply and the trouble spot of B phase and A phase, B phase and C phase circuit, Z _xca, Z _xcbrepresent respectively the mutual inductive impedance between power supply and the trouble spot of C phase and A phase, C phase and B phase circuit; Z _t-xaa, Z _t-xbb, Z _t-xccrepresent that respectively A phase, B phase, C remain the self-induction impedance of circuit mutually; Z _t-xab, Z _t-xacrepresent that respectively A phase and B phase, A phase and C remain the mutual inductive impedance of circuit, Z mutually _t-xba, Z _t-xbcrepresent that respectively B phase and A phase, B phase and C remain the mutual inductive impedance of circuit, Z mutually _t-xca, Z _t-xcbrepresent that respectively C phase and A phase, C phase and B remain the mutual inductive impedance of circuit mutually.Because compared with the self-induction of circuit, the mutual inductance between circuit is very little, so in analytic process, can ignore the mutual inductance of circuit, only needs the numerical value of self-impedance just can obtain accurate result.So formula (1) can abbreviation be:

$\left[\begin{array}{c}{V}_{1a}\\ V_{1b}\\ V_{1c}\end{array}\right]+\left[\begin{array}{c}{I}_{1a}\\ I_{1b}\\ I_{1\mathrm{<figure-callout\; id="0"\; label="c\; Z\; xaa"\; filenames="HDA0000466616550000021.png,HDA0000466616550000041.png"\; state="\{\{state\}\}">c</figure-callout>}}& \\ \end{array},\right]\left[\begin{array}{c}{Z}_{\mathrm{xaa}}\end{array}\right]\left[\begin{array}{ccc}{}_{}& 0& 0\\ 0& {\mathrm{<figure-callout\; id="0"\; label="Z\; xbb"\; filenames="HDA0000466616550000021.png,HDA0000466616550000041.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{\mathrm{xbb}}& 0\\ 0& 0& Z_{\mathrm{xcc}}\end{array}\right]=\left[\begin{array}{c}{V}_{2a}\\ V_{2b}\\ V_{2c}\end{array}\right]+\left[\begin{array}{c}{I}_{2a}\\ I_{2b}\\ I_{2c}\end{array}\right]\left[\begin{array}{ccc}{Z}_{t-\mathrm{<figure-callout\; id="0"\; label="xaa"\; filenames="HDA0000466616550000021.png,HDA0000466616550000041.png"\; state="\{\{state\}\}">xaa</figure-callout>}}& 0& 0\\ 0& Z_{t-\mathrm{<figure-callout\; id="0"\; label="xbb"\; filenames="HDA0000466616550000021.png,HDA0000466616550000041.png"\; state="\{\{state\}\}">xbb</figure-callout>}}& 0\\ 0& 0& Z_{t-\mathrm{xcc}}\end{array}\right]---\left(2\right)$

The resulting impedance of circuit:

$Z_t=Z_x+Z_{t-x}=\left[\begin{array}{ccc}{\mathrm{<figure-callout\; id="0"\; label="Z\; xaa"\; filenames="HDA0000466616550000021.png,HDA0000466616550000041.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{\mathrm{xaa}}& 0& 0\\ 0& {\mathrm{<figure-callout\; id="0"\; label="Z\; xbb"\; filenames="HDA0000466616550000021.png,HDA0000466616550000041.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{\mathrm{xbb}}& 0\\ 0& 0& Z_{\mathrm{xcc}}\end{array}\right]+\left[\begin{array}{ccc}{Z}_{t-\mathrm{<figure-callout\; id="0"\; label="xaa"\; filenames="HDA0000466616550000021.png,HDA0000466616550000041.png"\; state="\{\{state\}\}">xaa</figure-callout>}}& 0& 0\\ 0& Z_{t-\mathrm{<figure-callout\; id="0"\; label="xbb"\; filenames="HDA0000466616550000021.png,HDA0000466616550000041.png"\; state="\{\{state\}\}">xbb</figure-callout>}}& 0\\ 0& 0& Z_{t-\mathrm{xcc}}\end{array}\right]---\left(3\right)$

$=\left[\begin{array}{ccc}{Z}_{\mathrm{<figure-callout\; id="0"\; label="taa"\; filenames="HDA0000466616550000021.png,HDA0000466616550000041.png"\; state="\{\{state\}\}">taa</figure-callout>}}& 0& 0\\ 0& {\mathrm{<figure-callout\; id="0"\; label="Z\; tbb"\; filenames="HDA0000466616550000021.png,HDA0000466616550000041.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{\mathrm{tbb}}& 0\\ 0& 0& Z_{\mathrm{tcc}}\end{array}\right]$

Wherein, t represents the total length of circuit, Z _xrepresent the impedance of circuit between power supply and trouble spot, x represents the distance of measurement point to trouble spot, Z _t-xrepresent the impedance of residue circuit, t-x represents to remain the length of circuit, Z _taa, Z _tbb, Z _tccrepresent respectively the self-induction impedance of circuit between the power supply of A phase, B phase, C phase and load;

Matrix is calculated, can draw the line impedance between power supply and trouble spot:

$Z_x=\left[\begin{array}{c}{Z}_{\mathrm{xaa}}\\ Z_{\mathrm{xbb}}\\ Z_{\mathrm{xcc}}\end{array}\right]={\left(\begin{array}{c}\left[\begin{array}{c}{V}_{2a}\\ V_{2b}\\ V_{2c}\end{array}\right]-\left[\begin{array}{c}{V}_{1a}\\ V_{1b}\\ V_{1c}\end{array}\right]+\left[\begin{array}{c}{I}_{2a}\\ I_{2b}\\ I_{2c}\end{array}\right]\left[\begin{array}{ccc}{Z}_{t-\mathrm{<figure-callout\; id="0"\; label="xaa"\; filenames="HDA0000466616550000021.png,HDA0000466616550000041.png"\; state="\{\{state\}\}">xaa</figure-callout>}}& 0& 0\\ 0& Z_{t-\mathrm{<figure-callout\; id="0"\; label="xbb"\; filenames="HDA0000466616550000021.png,HDA0000466616550000041.png"\; state="\{\{state\}\}">xbb</figure-callout>}}& 0\\ 0& 0& Z_{t-\mathrm{xcc}}\end{array}\right]\left)\right(\left[\begin{array}{c}{I}_{1a}\\ I_{1b}\\ I_{1c}\end{array}\right]+\left[\begin{array}{c}{I}_{2a}\\ I_{2b}\\ I_{2c}\end{array}\right]\end{array}\right)}^{-1}$

$=\left[\begin{array}{c}\frac{V_{2a}-V_{1a}+I_{2a}{Z}_{\mathrm{taa}}}{I_{1a}+I_{2a}}\\ \frac{V_{2b}-V_{1b}+I_{2b}{Z}_{\mathrm{tbb}}}{I_{1b}+I_{2b}}\\ \frac{V_{2c}-V_{1c}+I_{2c}{Z}_{\mathrm{tcc}}}{I_{1c}+I_{2c}}\end{array}\right]---\left(4\right)$

Adopt following formula to determine the particular location of fault:

Wherein, Z ₀represent the resistance value of circuit unit length, Z ₀must just know before out abort situation is estimated, this can be by measuring.

As shown in Figure 3, this confirmatory experiment equipment is by Chroma voltage source 1 for the confirmatory experiment equipment of this method, direct voltage source 2, and FPGA unit 3, three phase rectifier 4, three-phase resistance device 5, trouble unit 6, test forms with cable 7.Three-phase electrical power system adopts the Chroma voltage source 1 of 50Hz to realize, and Chroma voltage source 1 is as AC power, and voltage magnitude is 50V(peak-to-peak value), to guarantee that fault current (exchanges 25A, direct current 10A) in the allowed band of Chroma voltage source 1.There is the direct voltage source 2 of high electric current output (40A) for testing the method for straight-flow system.FPGA unit 3 is for sending the initialization of fault tripping signal and data collector.Be connected to the three phase rectifier 4 of cooling fan for generation of nonlinear-load.The gelled three-phase resistance device 5 of tool serves as passive type load.Trouble unit 6 can produce variable fault resstance.Test is placed in cable duct with cable 7, comprises the SY type cable (having similar impedance ranges to the feeder cable using in aircraft) of two 10m and a 1m.

Experiment fault test comprises phase-to phase fault and earth fault, and mains side three-phase voltage, electric current and load-side three-phase voltage under these two kinds of faults, current measurement data are as Fig. 4 (a)～4(d), Fig. 5 (a)～5(d) as shown in.

According to formula (2),, only need to know the data of fault phase when the location.In ensuing result, will provide the measurement data of two measurement points under phase-to phase fault and ground fault condition.According to the difference of test-types, can the short trouble that have short-circuit resistance be added in system by IGBT switch or mechanical switch.

1) jumping characteristic fault

The short trouble of electric system is regarded as the catastrophic failure applying suddenly conventionally, can cause that the step of measuring voltage changes, and this fault accesses short trouble to introduce jumping characteristic fault component by mechanical switch.

First step test adopts Chroma voltage source 1 and resistive load, phase fault and the short trouble mutually and between neutral point are carried in respectively to distance measurement point 0m, 10m, 20m and 21m place, be trouble spot F1, F2, F3, F4 place, to produce the short trouble at diverse location place on circuit, by laying respectively at the F1 of circuit head end and end and the measurement mechanism at F4 place records voltage and the magnitude of current, as shown in Figure 6.System is connected to the resistive load (every phase 6.8 Ω) of Y-connection at distribution line end.

With 1 Ω fault resstance in the situation that (in the scope allowing at power supply for fault current limiting), the magnitude of voltage recording from measurement point 1 and measurement point 2 and the transient state component of current value are as Fig. 7 (a) with 7(b).

The magnitude of voltage recording and current value are brought in formula (2), calculated the impedance between measurement point 1 and trouble spot.Obtain as Fig. 8 (a) and magnitude of voltage and the current value 8(b); Fig. 8 (c) is measuring circuit reactance value and actual value comparative result under different faults, and wherein the line reactance value of the calculating of different faults position is solid line, and the data that calibration obtains are dotted lines.As expection, the reactance calculated value of circuit increases along with the increase of fault distance.After compared with calibration value, find that calculated value shows very high accuracy, can well distinguish fault, the distance of error between 5%(F3 and F4) in.Along with the increase of fault resstance, the transient state component of fault reduces, and can make in this case the error of calculated value slightly increase.System is in the time of original research, and it is 5% of 20m line, i.e. 1m that degree of accuracy requires.Accuracy corresponding to most abort situation is about 1%.

2) catastrophic failure

Conventionally, the short trouble of cable can cause that the step of voltage waveform and current waveform changes.This situation can be simulated by IGBT switch.The magnitude of voltage recording from measurement point 1 and measurement point 2 and the transient state component of current value are as Fig. 9 (a) with 9(b).

By Fig. 9 (a), 9(b) with 7(a), 7(b) in the transient state component of jumping characteristic fault compare, the transient being caused by IGBT switch is a step.The transient of this catastrophic failure also can produce the useful signal that can reach 3kHz, and this is enough to accurately locate abort situation.For the situation of jumping characteristic fault, respectively in the time of 1 Ω fault resstance and 3 Ω fault resstance the calculated value of 4 diverse locations as Figure 10 (a) with 10(b).

Therefore,, for AC system, the Two-terminal Fault Location scheme based on the flat failure message of height that is applicable to overall power distribution system can both find abort situation quickly and accurately.This Fault Locating Method can allow fault resstance to change in the larger context (approximately from 0 to load resistance).Do not need to know fault resstance, the waveform of transient state component and the impedance of system of short dot, only need to know that the impedance of circuit just can calculate, applied widely in engineering, can be generalized in overhead transmission line and transmission system.

The above; only for preferably embodiment of the present invention, but protection scope of the present invention is not limited to this, is anyly familiar with in technical scope that those skilled in the art disclose in the present invention; the variation that can expect easily or replacement, within all should being encompassed in protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection domain of claim.

Claims (1)

1. a both-end high-frequency resistance formula fault distance-finding method that is applicable to overall power distribution system, is characterized in that, the method is specially:

Step 1: ignore the mutual inductance of circuit, adopt following formula to calculate the line impedance between power supply and trouble spot:

$Z_X=\left[\begin{array}{c}{Z}_{\mathrm{xaa}}\\ Z_{\mathrm{xbb}}\\ Z_{\mathrm{xcc}}\end{array}\right]=\left[\begin{array}{c}\frac{V_{2a}-V_{1a}+I_{2a}{Z}_{\mathrm{taa}}}{I_{1a}+I_{2a}}\\ \frac{V_{2b}-V_{1b}+I_{2b}{Z}_{\mathrm{tbb}}}{I_{1b}+I_{2b}}\\ \frac{V_{2c}-V_{1c}+I_{2c}{Z}_{\mathrm{tcc}}}{I_{1c}+I_{2c}}\end{array}\right]$

Wherein, Z _xaa, Z _xbb, Z _xccrepresent respectively the self-induction impedance between power supply and the trouble spot of A phase, B phase, C phase circuit, V _1a, V _1b, V _1c, I _1a, I _1b, I _1cand V _2a, V _2b, V _2c, I _2a, I _2b, I _2cmagnitude of voltage and the current value of two trouble spots in the A phase, B phase, C phase circuit that represents respectively to record;

Adopt following formula to calculate the resulting impedance Z of circuit between power supply and load _t:

$Z_t=Z_x+Z_{t-x}=\left[\begin{array}{ccc}{Z}_{\mathrm{xaa}}& 0& 0\\ 0& Z_{\mathrm{xbb}}& 0\\ 0& 0& Z_{\mathrm{xcc}}\end{array}\right]+\left[\begin{array}{ccc}{Z}_{t-\mathrm{xaa}}& 0& 0\\ 0& Z_{t-\mathrm{xbb}}& 0\\ 0& 0& Z_{t-\mathrm{xcc}}\end{array}\right]$

$=\left[\begin{array}{ccc}{Z}_{\mathrm{taa}}& 0& 0\\ 0& Z_{\mathrm{tbb}}& 0\\ 0& 0& Z_{\mathrm{tcc}}\end{array}\right]$

Wherein, t represents the total length of circuit, Z _xrepresent the impedance of circuit between power supply and trouble spot, x represents the distance of measurement point to trouble spot, Z _t-xrepresent the impedance of residue circuit, t-x represents to remain the length of circuit, Z _t-xaa, Z _t-xbb, Z _t-xccrepresent that respectively A phase, B phase, C remain the self-induction impedance of circuit, Z mutually _taa, Z _tbb, Z _tccrepresent respectively the self-induction impedance of circuit between the power supply of A phase, B phase, C phase and load;

Step 2: adopt following formula to determine the particular location of fault:

Wherein, Z ₀for known quantity, represent the resistance value of circuit unit length.

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