CN102645613B - Transmission line malfunction positioning method based on non-contact magnetic measurement - Google Patents

Transmission line malfunction positioning method based on non-contact magnetic measurement Download PDF

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CN102645613B
CN102645613B CN201210123572.XA CN201210123572A CN102645613B CN 102645613 B CN102645613 B CN 102645613B CN 201210123572 A CN201210123572 A CN 201210123572A CN 102645613 B CN102645613 B CN 102645613B
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fault
magnetic
phase
component
module
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CN201210123572.XA
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CN102645613A (en
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黄琦
甄威
丁理杰
姚若婷
易建波
井实
张昌华
卢有亮
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电子科技大学
四川电力科学研究院
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Abstract

The invention discloses a transmission line malfunction positioning method based on non-contact magnetic measurement. The method is characterized by comprising step A, confirming a malfunction section; step B, identifying the type of the malfunction; and step C, internally positioning the malfunction section, wherein the malfunction section is confirmed by the following ways: constructing a remote terminal arranged on a transmission steel pylon, wherein the remote terminal consists of a microprocessor CPU (Central Processing Unit), a sensor, a signal regulating module, a data acquisition module DAQ (Data Acquisition), a storing module, a data communication module and a power supply module, wherein the sensor is used for measuring the three-dimensional component of the magnetic field at a three-dimensional space, and the data is transmitted to the DAQ module after passing through the signal regulating module. The invention provides a new transmission line malfunction positioning method based on the non-contact magnetic measurement. The malfunction section is positioned according to the magnetic data near the transmission line measured by a magneto-resistance magnetic field sensor with high sensibility, high band width and low cost.

Description

A kind of power transmission line fault locating method based on contactless magnetic-field measurement
Technical field
The present invention relates to a kind of transmission line malfunction location, especially a kind of power transmission line fault locating method based on contactless magnetic-field measurement.
Background technology
Overhead transmission line is widely used in the delivery of electrical energy between power generation region and receiving end electrical network.In recent years, along with the fast development of electric system, transmission line of electricity is also more and more.These circuits are because the reasons such as thunderbolt, short circuit, equipment failure, maloperation, overload easily break down.Statistics shows that transmission line malfunction is fault the most common in electric system.In the time that transmission line of electricity breaks down, detect and locate fault for patrol officer the maintenance to circuit and recovery system power supply as soon as possible significant.The time of determining line fault point is an important indicator of assessment delivery of electrical energy, is also therefore the factor that affects the whole network performance.This cognition more and more comes into one's own, and because electric power and energy market are relaxed control and the new policy of liberalization, may cause more emphasizing operation and the reliability level that reduces transmission system.For a long time, scientific research and engineering staff are devoted to the research of reliable and effective Fault Locating Method.At present, the method that can be used for physical fault location mainly contains two classes: the method based on row wave measurement and the method based on impedance measurement.In traveling wave method, catch transient pulse signal that fault causes or injected pulse signal in the line, then catch the pulse signal being reflected back.Realize localization of fault by analyzing the travelling wave signal transmission time in the line.Because the fault-signal obtaining in transmission line of electricity one end is mixed with a large amount of noises, the method (as wavelet transformation) of some modern signal processing is also referred in localization of fault.Impedance method is the method for carrying out localization of fault by the voltage-current relationship of circuit before and after measurement analysis of failure.Line parameter circuit value can obtain by computational scheme model, so just can carry out localization of fault.According to the distribution situation of receiving trap, these models can be divided into single-ended, both-end or multiterminal model.Along with the develop rapidly of relay protection, can obtain the required data of localization of fault by synchronized phasor device now.And prove that the method can improve the precision of localization of fault.
Method all can obtain rational localization of fault result in sum, and still, these methods need to directly connect measuring equipment on high voltage transmission line, have improved the cost of localization of fault.For example, the localization of fault precision of traveling wave method depends on the performance of the data acquisition system (DAS) of high price.And these methods are to be all based upon under the consistent assumed condition of transmission line parameter.Consider in reality, because transmission line of electricity is distributed in wide geographical environment, there are differences with hypothesized model.For example, wire will affect reactance in the asymmetry in space, and the difference of temperature causes the difference of impedance, and sag can have influence on electric capacity.Practical application shows that the error of such Fault Locating Method is generally the 1-2% of monitoring circuit overall length.In some cases, error can be up to 5% or more.For long distance power transmission, the accuracy of localization of fault just becomes and has been even more important, even because less Algorithm Error also will cause localization of fault to have the discrepancy of several kms, this just makes maintenance personal will spend the more time and removes looking up the fault point.Particularly in some mountain areas (such as the Chinese Liangshan Mountain), the error of may cause in the transmission line of electricity of 500KV ± 3km of this fault location system, maintainer just has to about 6 kms, could determine the particular location that fault occurs on foot in mountain area like this.And, for some impermanent faults, as arcing being caused by line-sag etc., because this kind of fault has the feature of instantaneity, that is to say that the position of breaking down has soon automatically restored to again normal condition after fault occurs, if adopt this fault location system, maintainer will spend more energy and remove the particular location of definite fault.
Summary of the invention
The object of the invention is to provides a kind of low cost, high precision, highly sensitive Fault Locating Method at this, by sensor installation on electric power pylon, then measurement data is sent to data processing unit and determines by fault analysis software the steel tower interval of guilty culprit.The magnetic field data wherein being collected by sensor also can be used for further determining of fault type and trouble spot.
The present invention is achieved in that a kind of power transmission line fault locating method based on contactless magnetic-field measurement of structure, it is characterized in that: include A: determine fault section, B, identification of defective type, C: location in fault section, wherein determine in the following manner fault section: build a remote terminal being arranged on electric power pylon, described remote terminal is by microprocessor CPU, sensor, signal condition module, data acquisition module DAQ, memory module, data communication module and power module composition, sensor is used for measuring magnetic field in three-dimensional three-dimensional component, data are sent to data acquisition module DAQ after signal condition module, the magnetic field data that CPU sends for controlling whole system continuous deal with data acquisition module DAQ, useful signal after treatment will be stored in memory module, and by data communication module, these data are sent to central station and carry out analyzing and processing, according to being changed and can determine fault section by the direction of measuring magnetic field, adjacent two measurement points interval of FR is fault section.
According to a kind of power transmission line fault locating method based on contactless magnetic-field measurement of the present invention, component input in described sensor three-dimensional magnetic field is calculated as:
????(1)
Wherein Ba, Bb, Bc is respectively the corresponding magnetic-field component producing of three-phase current ia ib ic, ix iy iz is respectively the vector of unit length of x y z axle;
Cut down Er Dingli calculating magnetic field according to Biot-Sa, Ba Bb Bc is calculated as follows:
, , ?(2)。
According to the power transmission line fault locating method based on contactless magnetic-field measurement of the present invention: it is characterized in that: identification of defective type is in the following manner: cut down Er Dingli according to Biot-Sa known, because electric current is when larger, the total magnetic field that this electric current excites is stronger, when electric current hour, the total magnetic field that this electric current excites a little less than, therefore carry out identification of defective type according to the size of total magnetic field; Be specially:
In the time of single-phase short circuit, total magnetic field is the most weak; In the time of single-phase earthing fault, measurement point magnetic-field component has following features:
(3)
In the time of three-phase shortcircuit, total magnetic field is the strongest; When line to line fault, total magnetic field falls between;
Wherein line to line fault is divided into again two phase ground short circuit and phase fault, when phase fault, has following features by the known measurement point magnetic-field component of formula (1):
(4)
When double earthfault,
(1), when AB earth fault, there is following features according to the known measurement point magnetic-field component of formula (1):
, wherein magnetic field Y-axis component while representing three-phase shortcircuit;
(2), when AC earth fault, there is following features according to the known measurement point magnetic-field component of formula (1):
, wherein magnetic field Y-axis component while representing three-phase shortcircuit;
(3), when BC earth fault, there is following features according to the known measurement point magnetic-field component of formula (1):
, wherein magnetic field Y-axis component while representing three-phase shortcircuit;
Therefore, differentiate two-phase short circuit and ground fault according to above-mentioned 3;
Set up out the feature table of comparisons of magnetic-field component under various failure conditions, just can identification of defective type according to this table of comparisons in conjunction with concrete feature.
According to the power transmission line fault locating method based on contactless magnetic-field measurement of the present invention: it is characterized in that: further the position of the localization of faults is as follows:
Concrete steps are as follows:
A, according to the data of the measuring terminals on transmission line of electricity, determine fault section;
B, according to the fault section of gained, draw faulty line length, thereby calculate short-circuit current size;
C, comparison magnetic-field measurement value and theoretical value, determine that fault type is single-phase short circuit, line to line fault, three-phase shortcircuit;
D, further determine fault type according to formula (3) (4), such as: when single-phase short circuit, draw be concrete which break down; And judging of referring to when line to line fault is that ground connection or phase fault appear in which two-phase;
The position of e, the further localization of faults after drawing concrete fault type, is specially: suppose that installation of sensors is the current i (t) in a place wire at distance fault wire, cutting down Er Dingli according to Biot-Sa has following relation:
????(5)
Wherein Bx and By are the magnetic-field components away from trouble spot place;
During due to two-phase or three-phase shortcircuit, there is the difference of phase angle in it, this simple analytic expression while therefore there is not single-phase short circuit, and for single-phase short circuit, the location in fault section can be realized by analyzing Bx or By component;
During for two-phase or three-phase phase fault, can realize the location in fault section by comparing By component.
The invention has the advantages that: the great advantage of the method proposing is herein that the maximum error of location is in a steel tower span, and do not need the conforming hypothesis of line parameter circuit value, and traditional method must be based upon on this assumed condition and error is the number percent of circuit overall length.According to the analysis of estimation of error, sag and wire binding all can not have influence on the validity of the Fault Locating Method proposing herein, and therefore the method is feasible.Compared with impedance method, method and impedance ground relation is herein little, and impedance rule is obviously subject to the impact of impedance ground.A kind of localization of fault new method based on contactless magnetic-field measurement provided by the present invention.By near the magnetic field data location fault section transmission line of electricity by high sensitivity, high bandwidth, reluctance type magnetic field sensor measurement cheaply.The magnetic field data of measuring can also be used for further determining of identification of defective type and fault section internal fault point.The typical electric power pylon parameter of overhead power transmission system and Digital Simulation.Simulation result can be different because of different structures.
Brief description of the drawings
Fig. 1 is remote monitoring terminal module diagram
The example schematic diagram that Fig. 2 typical case 500KV electric power pylon is installed magnetic field sensor
Schematic diagram is calculated in Fig. 3 measurement point magnetic field
Fig. 4 Digital Simulation System block diagram
The typical waveform schematic diagram of electric current in three phase transmission line when Fig. 5 three phase short circuit fault
Fig. 6 has shown the magnetic-field measurement value schematic diagram of each measurement point on the transmission line of electricity that links two systems
The size and Orientation in the magnetic field that two ends, Fig. 7 trouble spot are measured
Field waveform when Fig. 8 has described single-phase earthing fault
Fig. 9 has described sensor magnetic field and has measured component
Figure 10 fault section internal fault is put the distance estimations of measurement point
Figure 11 has described the Magnetic field's ratio of the measurement point nearest from trouble spot and the measurement of other measurement points
When Figure 12 considers sag, the magnetic field schematic diagram that transient state system produces.
Embodiment
Below in conjunction with appended drawings, the present invention is described in detail:
For the application of localization of fault, if location of fault can be determined in a span of adjacent two electric power pylons (such as 400m-1000m), so just enough.Once after the span that fault occurs has been determined, line maintenance personnel just can be relatively easy to find the trouble spot in this span.In this programme, we propose to install sensitive sensor on each electric power pylon (for long span, consider that this kind of measuring terminals is cheap and can, at the local work away from transmission pressure, therefore can also install extra measuring terminals in the centre of span).As shown in Figure 1-2, Fig. 2 circle represents that remote monitoring terminal is the position of sensor to the overall plan of this solution.The data that collect from remote terminal client software in conjunction with GIS(Geographic Information System) technology can graphically be shown, convenient for maintaining personnel find trouble spot rapidly.
As shown in Figure 1: remote monitoring terminal is the integrated mini-plant of a kind of PCB.Whole system is made up of microprocessor CPU and its peripherals (sensor, data acquisition DAQ module (for measurement data), memory module, communication module, signal pre-processing module and power module).Processor control whole system is also constantly carried out data acquisition.Just can extract the useful information in signal by simple data analysis (such as amplitude is calculated).Once detect in this signal and have sudden change, these data stored and send to central site processing by channel.Because this system service is in mountain area, therefore using station telecommunication (instead of communication means of dependence commerce services) is ideal communication solution.Sensor is made up of with its amplification and filtering circuit the magnetic field sensing chip that can carry out x axle y axle z axle three-dimensional measurement.Sensor adopts the design separating with main circuit, detecting unit power supply is disturbed and can not have influence on sensor.The power supply of whole system can be by being provided by the coupling of transmission pressure or providing by sun power mode, and solar-electricity source module comprises a solar panel, a charger and a battery.Sensor is used for measuring magnetic field in three-dimensional three-dimensional component, these data are sent to DAQ module after signal condition module, CPU is for controlling whole system and constantly processing the magnetic field data that DAQ module is sent, useful signal after treatment will be stored in memory module, and by communication module, these data are sent to central station and carry out analyzing and processing, according to being changed and can determine fault section by the direction of measuring magnetic field, adjacent two measurement points interval of FR is fault section.
Sensor input is calculated: the magnetic field that current-carrying transmission pressure produces can calculate by Maxwell equation.Under some assumed condition, can obtain the analytical expression that wire calculates in the magnetic field apart from its certain distance.Typical 500KV electric power pylon as shown in Figure 2, wherein, the length of supposing insulator is 4m, installation of sensors is in the centre position of steel tower (being approximately 18m apart from ground).Fig. 3 has shown the decomposition of measurement point total magnetic field, can write (supposing that wire is unlimited long straight conductor);
???(1)
Wherein Ba, Bb, Bc is respectively the corresponding magnetic-field component producing of three-phase current ia ib ic, ix iy iz is respectively the vector of unit length of x y z axle.If system is an asymmetrical system, can cut down Er Dingli calculating magnetic field according to Biot-Sa.But for simple estimation, the sag of wire is negligible, and circuit is also considered to endless wire, and therefore, Ba Bb Bc is calculated as follows:
???(2)
Calculate in Fig. 3 measurement point magnetic field, supposes that direction of current is along Z-direction and points to observer.
Localization of fault: because MR sensor can be measured magnetic field at three-dimensional 3 dimension components, therefore can be used for judging the variation of three-phase current.For a radial transmission system, only there is power supply in sending end, the position that fault occurs just can be determined in the position existing by the short-circuit current in simple judgement transmission line of electricity.The nearest measurement data of distance fault does not likely meet the hypothesis of endless wire, therefore with the data of other measurement point can be to some extent need not, can further determining for abort situation.And the data of other measurement point can be for the judgement of fault type.For two end systems, there is power supply at the two ends of transmission line of electricity, now can determine abort situation by the difference of two ends degree of short circuit.Because the method can be located fault section accurately, even therefore volatile fault is also than being easier to find out concrete trouble spot.
carry out Digital Simulation below
As shown in Figure 4, system parameter setting is as shown in table 1 for the system model of emulation experiment herein, and electric power pylon as shown in Figure 2.Suppose the load to receiving terminal of certain electric system from sending end transmission 630MW, and in 0.2s, there is fault at 0.1s in hypothesis.Next, under the prerequisite based on above-mentioned parameter configuration and hypothesis, set up distributed model, and carried out various emulation experiments herein.
Table 1 emulation transmission system parameter
Fig. 4 is Digital Simulation System block diagram (l: transmission line of electricity overall length; M: sending end electrical network is to the distance of trouble spot)
(1), location fault section
The typical fault of transmission line of electricity has single-phase short circuit, line to line fault and three-phase shortcircuit.In impedance method, must consider the impact of fault impedance and impedance ground, and these factors can not have influence on the accuracy of location in the present invention.
Wherein the waveform shown in Fig. 5 (when Fig. 5 three phase short circuit fault in three phase transmission line the typical waveform (m=100km) of electric current) is there is three phase short circuit fault in the middle of transmission line of electricity time, the current waveform that trouble spot right-hand member steel tower measurement point collects.In the time there is three-phase shortcircuit in circuit, the magnetic field of measurement also can become greatly, and the ratio of magnetic field amplification should be with the identical not considering transient of the ratio process of short-circuit current amplification.The amplification in transient state process magnetic field can be larger.
For the situation of observing whole transmission line of electricity transient process is to help the localization of faults, Fig. 6 has shown the magnetic-field measurement value (when three-phase shortcircuit along power transmission line space magnetic field distribute (m=100 km)) of each measurement point on the transmission line of electricity that links two systems.In this figure, x axle is time shaft (having described whole inaction interval, before fault, after fault and fault), and y axle represents the distribution (long to total line from 0) of transmission line of electricity, and z axle represents the measured value in magnetic field.Notice that magnetic field amplitude higher when fault starts is because the DC component of three-phase current causes.When fault, after stable magnetic field, the size of amplitude is to be determined by the short-circuit current degree of linked circuits two end systems.Magnetic field amount by simple measurement of comparison, just can know short-circuit current need not, because the difference of short-circuit current size can determine that therefore fault section contrasts magnetic field and just can locate fault section.Although the magnetic field of measuring at fault two ends can be variant, this species diversity is less.When due to component failure, while causing loss of data, can carry out failure judgement type by the data of other measurement points.
If the place that fault occurs makes the degree of two ends short-circuit current close, the amplitude in magnetic field is also close, so now can determine fault section by the direction in magnetic field.The size and Orientation in the magnetic field (steel tower M and N in Fig. 4) that two ends, trouble spot are measured is (magnetic field amplitude and direction when Fig. 7 three-phase shortcircuit (fault is that 0.2s finish time is 0.3s the zero hour, m=100 km)) as shown in Figure 7.In figure, middle small circle represents the magnetic field under normal condition, owing to being radially that Z-direction component in Fig. 3 is approximately 0, has therefore only described the value of Bx and By.In the time of fault, Bx and By are all functions of time.Can find out from Fig. 7, in the time of normal condition, the magnetic field of two measurement points of M and N is almost identical, but after fault generation, the direction in magnetic field is approximate contrary, and after trouble shooting or system recovery, the magnetic field of two measurement points is got back to again middle roundlet and punctuated.
(2), identification of defective type
The magnetic field data of measuring can not only be used for determining fault section, can also be used for identification of defective type.According to formula (1) and (2), in the time that fault occurs, can carry out identification of defective type according to the size and Orientation in magnetic field.Because short-circuit current is far longer than steady-state current, the magnetic field therefore being excited by healthy phases can be ignored.
Therefore,, when single-phase earthing fault, magnetic field meets following formula:
(3)
Field waveform when Fig. 8 has described single-phase earthing fault.Magnetic field when Fig. 8 single-phase short circuit.(a) the current waveform when short circuit of A phase.(b) the current waveform when short circuit of B phase.(c) the current waveform when short circuit of C phase.(d) field waveform when single-phase short circuit.
Fig. 9 has described sensor magnetic field and has measured component, each axial component of measuring when Fig. 9 single-phase short circuit.(the first width figure is the x axle field waveform figure measuring, and the second width figure is the y axle field waveform figure measuring; M=100 km).This shows that formula (3) is correct.
Line to line fault is divided into again two relative ground circuits and phase fault.When phase fault, have the magnetic-field component of the known measurement of formula (1) to meet following formula:
(4)
When two relative ground circuits, there is not such relational expression in magnetic-field component, but the magnetic-field component can contrast single-phase short circuit time is carried out identification of defective type.In table 2, list the feature of magnetic-field component under various failure conditions, just can identification of defective type according to this table.Step is as follows:
Step 1: according to the data of the measuring terminals on transmission line of electricity, determine fault section.
Step 2: approximate evaluation short-circuit current size
Step 3: relatively magnetic-field measurement value and theoretical value, determine fault type (single-phase short circuit, line to line fault, three-phase shortcircuit)
Step 4: further determine fault type according to formula (3) (4)
Step 5: the further position of the localization of faults.
Table 2 is according to magnetic-field measurement identification of defective type
(3), location in fault section
Above, how to locate the interval of the electric power pylon of guilty culprit.The magnetic field difference of measuring in transmission line of electricity is little, but can be different at the measurement point (M in Fig. 4 and N point) at the two ends of trouble spot.Can be by the distance of the different next further localization of faults distance measurement point of this point.Model description in Figure 10 the method for suspected fault point apart from the position of tower.Suppose that installation of sensors is the current i (t) in a place wire at distance fault wire, cutting down Er Dingli according to Biot-Sa has following relation:
?????(5)
Wherein Bx and By are the former magnetic-field components from trouble spot place.
Figure 10 fault section internal fault is put the distance estimations of measurement point:
When two-phase or three-phase shortcircuit, owing to there being the difference of phase angle, this simple analytic expression while therefore there is not single-phase short circuit.But, as long as the known type of fault, the location in fault section can be realized by analyzing Bx and By component.For example, when single-phase short circuit, Bx or By come estimated position, when two-phase or three-phase phase fault, can realize the location in fault section by comparing By component.Figure 11 has described the Magnetic field's ratio of the measurement point nearest from trouble spot and the measurement of other measurement points, can be used as interval internal fault mapping function.In the time that trouble spot distance measurement point is in 100m, recently the data of measurement point and the data of other measurement points have differently significantly, if there is no too large difference, can think that the nearest measurement point in trouble spot is again beyond 100m.So also can help patrol officer to accelerate looking up the fault.
When Figure 11 different faults occurs, the magnetic field that fault side measurement point is measured and the ratio in other measurement point magnetic fields.
Estimation of error and discussion
The localization of fault error of method proposed by the invention be mainly derived from following some: (1) device measuring error, main relevant with the characteristic of magnetoresistive transducer and circuit for signal conditioning; (2) error that transmission line of electricity sag causes; (2) in the time that the method applies to many feedback electric systems, the non-uniform Distribution of electric current will cause uncertain error, or in the time that wire bundlees, will cause the measuring error in magnetic field.Some other factor, as skin effect etc., because the position of sensor is former in transmission pressure, therefore negligible.
(1) measuring error a: advantage of magnetoresistive transducer is that this sensor is a kind of solid state sensor, therefore has the typical bandwidth of several megahertzes and tens of Gausses' resolution.Modern circuit design technique can be easier to realize the circuit for signal conditioning of number megahertz.But if only consider localization of fault, frequency is just quite reasonable in 2000Hz.Experiment demonstration, the A/D conversion chip of 12 can be limited to measuring error in 1%.
(2) sag impact: in the time will considering the sag of transmission pressure, transmission pressure varies in size with the magnetic field that straight wire produces at this point in the generation magnetic field of measurement point.The error that sag causes can be cut down Er Dingli and catenary equation solves by Biot-Sa.Identical suppose the sag of adjacent interval in this equation time, as shown in figure 12, when Figure 12 considers line-sag, the magnetic field that transient state system produces.In order to simplify calculating, two cover coordinate systems (x, y, z) and (x ', y ', z ') are adopted.For consistent with the coordinate system in Fig. 3, if (x, y, z) position that the initial point of coordinate system is placed at sensor, simultaneously in order to be consistent with the usual way of vertical chain line equation, if (x ', y ', z ') coordinate system origin is in the position of the maximum sag of the middle phase (the B phase in Figure 12) of three-phase power transmission wire.
In Figure 12, the catenary equation under (x ', y ', z ') coordinate system of B phase conductor is:
Wherein L represents the length of a steel tower span, and α represents the constant being determined by the mechanical parameter of transmission line of electricity.
Supposing the system is symmetrical, and the magnetic field that in Figure 12, A B C three-phase goes out to produce in intermediate sensor is:
Wherein, respectively x ', y ', the vector of unit length of z ' axle, the position that point (x0 ', y0 ', z0 ') is sensor in (x ', y ', z ') coordinate system, k represents spaced apart (being 11.8m in Fig. 2).
Compared with formula (2), can find out and only need to calculate definite integral.In transmission system as shown in Figure 2, if the span between steel tower is 400m, sag is 5m, and the result of calculating sag impact and not considering sag impact is as shown in table 3.Can find out that error is in 5%.
Table 3 is estimated the impact that sag effect is calculated magnetic field
3, wire binding error
For the error of estimating to produce due to the binding of wire, study typical conductors on quad bundled, its space interval is 0.3m.Here taking B mutually as example explanation, and suppose that electric current is to flow through uniformly four wires, available formula (13) is carried out the error of calculation.
The result of digital simulation demonstration, adopting parameter time error is herein only 0.01%.

Claims (1)

1. the power transmission line fault locating method based on contactless magnetic-field measurement, is characterized in that: include A: determine fault section, B, identification of defective type, C: location in fault section, wherein determine in the following manner fault section: build a remote terminal being arranged on electric power pylon, described remote terminal is by microprocessor CPU, sensor, signal condition module, data acquisition module DAQ, memory module, data communication module and power module composition, sensor is used for measuring magnetic field in three-dimensional three-dimensional component, data are sent to data acquisition module DAQ after signal condition module, the magnetic field data that CPU sends for controlling whole system continuous deal with data acquisition module DAQ, useful signal after treatment will be stored in memory module, and by data communication module, these data are sent to central station and carry out analyzing and processing, according to being changed and can determine fault section by the direction of measuring magnetic field, adjacent two measurement points interval of FR is fault section,
The component input of described sensor three-dimensional magnetic field is calculated as:
B ‾ = i ^ x B x + i ^ y B y + i ^ z B z = i ^ x ( B b + ( B a + B c ) cos θ ) + i ^ y ( ( B a - B c ) sin θ ) + i ^ z 0 - - - ( 1 )
Wherein Ba, Bb, Bc is respectively three-phase current i a, i b, i cthe corresponding magnetic-field component producing, respectively x, y, the vector of unit length of z axle;
Cut down Er Dingli calculating magnetic field according to Biot-Sa, Ba, Bb, Bc is calculated as follows:
B a = μ 0 i A 2 πr A , B b = μ 0 i B 2 π r B , B c = μ 0 i C 2 πr C - - - ( 2 ) ;
Identification of defective type is in the following manner: cut down Er Dingli according to Biot-Sa known, in the time that electric current is larger, the total magnetic field that this electric current excites is stronger, when electric current hour, the total magnetic field that this electric current excites a little less than, therefore carry out identification of defective type according to the size of total magnetic field; Be specially:
In the time of single-phase short circuit, total magnetic field is the most weak; In the time of single-phase earthing fault, measurement point magnetic-field component has following features:
In the time of three-phase shortcircuit, total magnetic field is the strongest; When line to line fault, total magnetic field falls between;
Wherein line to line fault is divided into again two phase ground short circuit and phase fault, when phase fault, has following features by the known measurement point magnetic-field component of formula (1):
When double earthfault,
When AB earth fault, there is following features according to the known measurement point magnetic-field component of formula (1):
B y ≈ B a sin θ = 1 3 B y ( 3 ) B y B x > 0 , Wherein magnetic field Y-axis component while representing three-phase shortcircuit;
When AC earth fault, there is following features according to the known measurement point magnetic-field component of formula (1):
wherein magnetic field Y-axis component while representing three-phase shortcircuit;
When BC earth fault, there is following features according to the known measurement point magnetic-field component of formula (1):
B y &ap; B a sin &theta; = 1 3 B y ( 3 ) B y B x < 0 , Wherein magnetic field Y-axis component while representing three-phase shortcircuit;
Therefore, differentiate two-phase short circuit and ground fault according to above-mentioned 3;
Set up out the feature table of comparisons of magnetic-field component under various failure conditions, just can identification of defective type according to this table of comparisons in conjunction with concrete feature;
Further the position of the localization of faults is as follows in the following manner:
Concrete steps are as follows:
A, according to the data of the measuring terminals on transmission line of electricity, determine fault section;
B, according to the fault section of gained, draw faulty line length, thereby calculate short-circuit current size;
C, comparison magnetic-field measurement value and theoretical value, determine that fault type is single-phase short circuit, line to line fault, three-phase shortcircuit;
D, further determine fault type according to formula (3) (4), when single-phase short circuit, draw be concrete which break down; And judging of referring to when line to line fault is that ground connection or phase fault appear in which two-phase;
The position of e, the further localization of faults after drawing concrete fault type, is specially: suppose that installation of sensors is the current i (t) in a place wire at distance fault wire, cutting down Er Dingli according to Biot-Sa has following relation:
B xf B x = B yf B y = 1 - cos &alpha; f 2 - - - ( 5 )
Wherein Bx and By are the magnetic-field components away from trouble spot place;
During due to two-phase or three-phase shortcircuit, there is the difference of phase angle in it, this simple analytic expression while therefore there is not single-phase short circuit, and for single-phase short circuit, the location in fault section can be realized by analyzing Bx or By component;
During for two-phase or three-phase phase fault, can realize the location in fault section by comparing By component.
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