CN105137285A - Power distribution network grounding fault line selection method and system - Google Patents

Abstract

The invention relates to a power distribution network grounding fault line selection method and system, and the method comprises the steps: obtaining a zero sequence voltage of a triangular winding of a secondary side opening of a bus PT of a power distribution network, and judging whether the zero sequence voltage is greater than a preset fault threshold value or not; obtaining a three-phase voltage of a bus if the zero sequence voltage is greater than the preset fault threshold value, and obtaining a fault phase according to the three-phase voltage; injecting a signal current from a corresponding phase of the secondary side of the bus PT according to the grounding fault; detecting the output current of each outgoing line of the bus, and obtaining a line where the current is greater than a preset threshold value as a fault line; detecting the zero sequence voltage of the triangular winding of the secondary side opening of the bus PT of the power distribution network, so as to judge whether a power distribution network grounding system has a grounding fault or not, and obtaining the fault phase if the power distribution network grounding system has the grounding fault; injecting the signal current from the phase, corresponding to the fault, of the secondary side of the bus PT, and detecting the current of the outgoing lines so as to determine the fault line, thereby achieving the fault line selection. The method is wide in application range, is high in accuracy of line selection, and is low in cost.

Description

Distribution net work earthing fault selection method and system

Technical field

The present invention relates to medium voltage distribution network technical field, particularly relate to a kind of distribution net work earthing fault selection method and system.

Background technology

Current domestic conventional location design can be divided into the location design based on steady-state component and the location design based on transient state component, all belongs to the route selection method of passive type.These methods all have some limitations in principle, affect a lot of because have of its route selection accuracy, the such as size etc. of CT (Currenttransformer, current transformer) imbalance, system operation mode, transition resistance.

In the system of neutral by arc extinction coil grounding, due to the compensating action of arc suppression coil, fault characteristic information is weakened further, thus make the route selection accuracy of these line selection apparatus be difficult to ensure, application in practice is also restricted.Traditional distribution net work earthing fault selection method due to disturbing factor more, there is the shortcoming that route selection accuracy is low.

Summary of the invention

Based on this, be necessary for the problems referred to above, distribution net work earthing fault selection method and system that a kind of route selection accuracy is high are provided.

A kind of distribution net work earthing fault selection method, comprises the following steps:

Obtain the residual voltage on the bus PT secondary side open-triangular winding of power distribution network, and judge whether described residual voltage is greater than default fault threshold;

If so, then obtain the three-phase voltage of bus, obtain fault phase according to described three-phase voltage;

According to the corresponding phase Injection Signal electric current of described fault phase from bus PT secondary side;

Detect the electric current that the every bar outlet of bus exports, obtain electric current and be greater than the circuit of predetermined threshold value as faulty line.

A kind of distribution net work earthing fault wire selection system, comprising:

Judge module, the residual voltage on the bus PT secondary side open-triangular winding obtaining power distribution network, and judge whether described residual voltage is greater than default fault threshold;

Processing module, for when described residual voltage is greater than described fault threshold, obtains the three-phase voltage of bus, obtains fault phase according to described three-phase voltage;

Control module, for according to the corresponding phase Injection Signal electric current of described fault phase from bus PT secondary side;

Detection module, for detecting the electric current that the every bar outlet of bus exports, obtaining electric current and being greater than the circuit of predetermined threshold value as faulty line.

Above-mentioned distribution net work earthing fault selection method and system, obtain the residual voltage on the bus PT secondary side open-triangular winding of power distribution network, and judge whether residual voltage is greater than default fault threshold; If so, then obtain the three-phase voltage of bus, obtain fault phase according to three-phase voltage.According to the corresponding phase Injection Signal electric current of fault phase from bus PT secondary side.Detect the electric current that the every bar outlet of bus exports, obtain electric current and be greater than the circuit of predetermined threshold value as faulty line.Detect power distribution network bus PT secondary side open-triangular winding on residual voltage to judge whether power distribution network earthed system earth fault occurs, if then obtain fault phase according to the three-phase voltage of bus.The phase Injection Signal electric current that bus PT secondary side is corresponding with fault phase, detect the electric current of outlet thus determine faulty line, realize failure line selection, applied widely, route selection accuracy is high and cost is low.

Accompanying drawing explanation

Fig. 1 is the process flow diagram of distribution net work earthing fault selection method in an embodiment;

Fig. 2 is the schematic diagram of injection method route selection in an embodiment;

Fig. 3 is the prejudgementing criteria analysis illustraton of model of fault phase in an embodiment;

Three-phase voltage change curve when Fig. 4 is single-phase earthing in an embodiment;

Fig. 5 is the process flow diagram obtaining fault phase in an embodiment according to three-phase voltage;

Fig. 6 is the process flow diagram obtaining fault phase in another embodiment according to three-phase voltage;

Fig. 7 is the process flow diagram of distribution net work earthing fault selection method in another embodiment;

Fig. 8 is the structural drawing of arc-extinction device in an embodiment;

Fig. 9 is the structural drawing of distribution net work earthing fault wire selection system in an embodiment;

Figure 10 is the structural drawing of processing module in an embodiment;

Figure 11 is the structural drawing of processing module in another embodiment;

Figure 12 is the structural drawing of distribution net work earthing fault wire selection system in another embodiment.

Embodiment

A kind of distribution net work earthing fault selection method, is applicable to the small current neutral grounding system of medium voltage distribution network, as shown in Figure 1, comprises the following steps:

Step S130: obtain the residual voltage on the bus PT secondary side open-triangular winding of power distribution network, and judge whether residual voltage is greater than default fault threshold.If residual voltage is greater than fault threshold, then carry out step S140, otherwise can step S130 be returned, again obtain residual voltage and judge.

The concrete value of fault threshold can adjust according to actual conditions, real-time monitoring bus PT (Potentialtransformer, voltage transformer (VT)) residual voltage on secondary side open-triangular winding, residual voltage is greater than fault threshold as the foundation judging whether to occur earth fault.Specifically as shown in Figure 2, controller can be utilized to obtain residual voltage and judge, 5 connection terminals of bus PT secondary side are received on controller, detect the residual voltage of bus.The foundation that earth fault judges detects on bus PT secondary side open-triangular winding whether have residual voltage, and its key determines fault threshold voltage U _x.As residual voltage U _lN>=U _xtime, then can think that system there occurs earth fault, then starts the evaluation algorithm to fault phase.

Under normal circumstances, due to each voltage symmetry, PT primary side voltage is: U _a=U _b=U _c, PT secondary side voltage is respectively: u _lN=0.If Single Phase Metal earth fault occurs A phase, so primary voltage becomes accordingly now PT secondary side voltage is: U _bN=U _cN=100V, U _lN=100V.

Be in the distribution system of grounding through arc at neutral grounding mode, once generation earth fault, arc suppression coil can compensate inductance current to power distribution network immediately, and the voltage now on open-triangular winding can be influenced, when system is normally run in addition, actual also can have a small amount of offset voltage.Considering certain allowance, is 120V by fault threshold voltage value in the present embodiment, is namely as residual voltage U _lN>=U _xduring=120V, think that system there occurs earth fault, start and the selection of fault phase is judged, improve judgment accuracy.

Step S140: the three-phase voltage obtaining bus, obtains fault phase according to three-phase voltage.Determine power distribution network be short-circuited fault time, measure the three-phase voltage of power distribution network median generatrix and determine fault phase, so that the corresponding Injection Signal electric current of subsequent step, selecting fault outlet rapidly by injection method.Detect the three-phase voltage of bus equally by controller, and obtain fault phase according to three-phase voltage.

When stake resistance is larger, that phase that voltage is minimum might not be fault phase, and the judgement of fault phase completes in the process of route selection most important at device, is necessary to analyze and research to the differentiation of fault phase, ensures that the judgement 100% of fault phase is correct.Suppose that singlephase earth fault occurs A phase, when fault is metallic earthing fault, resistance R=0.Set up model as shown in Figure 3.Unloaded process is done in circuit load.Be calculated as follows:

${\stackrel{\·}{I}}_N+{\stackrel{\·}{I}}_a+{\stackrel{\·}{I}}_b+{\stackrel{\·}{I}}_c=0$

${\stackrel{\·}{I}}_a=({\stackrel{\·}{U}}_N+{\stackrel{\·}{E}}_a)(jwC+\frac{1}{R})$

${\stackrel{\·}{I}}_b=({\stackrel{\·}{U}}_N+a^2{\stackrel{\·}{E}}_a)\·jwC$

${\stackrel{\·}{I}}_c=({\stackrel{\·}{U}}_N+a{\stackrel{\·}{E}}_a)\·jwC$

${\stackrel{\·}{I}}_N={\stackrel{\·}{U}}_N\·\frac{1}{jwL}$

Wherein a=e ^j120.

Calculate ${\stackrel{\·}{U}}_N=\frac{-{\stackrel{\·}{E}}_a}{1+j3wRC+\frac{R}{jwL}}$

Then ${\stackrel{\·}{U}}_A={\stackrel{\·}{U}}_N+{\stackrel{\·}{E}}_a=\frac{jR(3wC-\frac{1}{wL})}{1+jR(3wC-\frac{1}{wL})}\·{\stackrel{\·}{E}}_a$

$\left|{\stackrel{\·}{U}}_A\right|=\frac{R(3wC-\frac{1}{wL})}{\sqrt{1+R^2(3wC-\frac{1}{wL})}}\·\left|{\stackrel{\·}{E}}_a\right|$

Get θ, make $tan\frac{\mathrm{\θ}}{2}=R(3wC-\frac{1}{wL}),$ Namely be $\mathrm{\θ}=2{\mathrm{tg}}^{-1}\[R(3wC-\frac{1}{wL})\],$

Then have $\left|{\stackrel{\·}{U}}_A\right|=\sqrt{\frac{1}{2}(1-cos\mathrm{\θ})}\left|{\stackrel{\·}{E}}_a\right|$

In like manner can obtain

$\left|{\stackrel{\·}{U}}_B\right|=\sqrt{2+cos\mathrm{\θ}-\frac{\sqrt{3}}{2}sin\mathrm{\θ}}\left|{\stackrel{\·}{E}}_a\right|$

$\left|{\stackrel{\·}{U}}_C\right|=\sqrt{2+cos\mathrm{\θ}+\frac{\sqrt{3}}{2}sin\mathrm{\θ}}\left|{\stackrel{\·}{E}}_a\right|$

For isolated neutral system, inductance L gets infinity, and along with the change of resistance R, the variation range of θ is 0 to 180 degree; For neutral by arc extinction coil grounding system, system general work is in over-compensation state, and the variation range of θ is 0 to-180 degree.Get for unit length, will be plotted in a figure, as shown in Figure 4.According to Fig. 4:

During singlephase earth fault, the magnitude of voltage of fault phase changes along with the change of stake resistance between zero to load voltage value, and when wherein stake resistance is zero, faulted phase voltage is zero, is metallic earthing; When stake resistance is infinitely great, faulted phase voltage is ratings.

The magnitude of voltage of normal phase is also along with the change of stake resistance changes accordingly, and when stake resistance is zero, healthy phases voltage is rated voltage doubly, when stake resistance is infinitely great, the magnitude of voltage of healthy phases is load voltage value.

The minimum specified phase voltage being not less than 0.823 times of the magnitude of voltage of healthy phases, the highest can not higher than the specified phase voltage of 1.823 times.

Therefore, wherein in an embodiment, power distribution network is isolated neutral system, as shown in Figure 5, obtains the step of fault phase in step S140 according to three-phase voltage, comprises step S142 and step S144.

Step S142: if the phase voltage of the minimum phase of voltage is less than K times of rated voltage, then voltage is minimum is fault phase mutually.

Step S144: if three-phase voltage is all greater than K times of rated voltage, then next of the highest phase of voltage is fault phase mutually.Wherein K is less than 0.823, and in the present embodiment, K is specially 0.6.

In another embodiment, power distribution network is earth neutral system, as shown in Figure 6, obtains the step of fault phase in step S140 according to three-phase voltage, comprises step S144 and step S146.

Step S146: if the phase voltage of the minimum phase of voltage is less than K times of rated voltage, then voltage is minimum is fault phase mutually.

Step S148: if three-phase voltage is all greater than K times of rated voltage, then upper one of the highest phase of voltage is fault phase mutually.Wherein K is less than 0.823, gets 0.6 with K in sample embodiment.

Below be namely provide corresponding fault phase defining method for two kinds of different situations of power distribution network, can select according to actual conditions, improve the reliability of failure line selection and comprehensive.

Step S150: according to the corresponding phase Injection Signal electric current of fault phase from bus PT secondary side.Specifically inject the marking current of particular frequencies by controller control signal generating means from the correspondence of PT secondary side mutually, carry out acquisition so that follow-up and identify.Can induce corresponding marking current at PT primary side, most marking current can flow into earth point through the fault phase of fault outlet.

Step S160: detect the electric current that the every bar outlet of bus exports, obtains electric current and is greater than the circuit of predetermined threshold value as faulty line.Specifically all can be provided with zero sequence current mutual inductor in every bar outlet, zero sequence current mutual inductor is connected with controller, by the current delivery that collects to controller.Controller is analyzed current signal, if the marking current detected exceedes pre-set threshold value, then thinks that this circuit is faulty line.

Wherein in an embodiment, as shown in Figure 7, before step S130, distribution net work earthing fault selection method also can comprise step S110 and step S120.

Step S110: the neutral point voltage gathering power distribution network, and judge whether neutral point voltage is greater than default voltage threshold.If so, then step S120 is carried out; If not, then can return step S110, again gather neutral point voltage and judge.Specifically gather the neutral point voltage of power distribution network by arc-extinction device, and carry out follow-up crowbar operation.Be illustrated in figure 8 the structural drawing of arc-extinction device in an embodiment, arc-extinction device comprises center screen, controller and two-way arc-extinguishing circuit, and controller is arranged in the screen of center, and center screen connects two-way arc-extinguishing circuit, arc-extinguishing circuit one end, every road connects 10kV bus-tie circuit breaker cabinet, other end ground connection.

The neutral point voltage collected is received on the screen of center, judges whether to be greater than voltage threshold for controller.The concrete value of voltage threshold can adjust according to actual conditions.Arc suppression coil in native system is turn-adjusting arc-extinguishing winding, runs, full-automatic tracking compensating arc-extinguishing coil device after linked network from motion tracking.Controller in arc-extinction device also can be used as failure line selection simultaneously and controls, and realizes extinguishing arc, Line Selection, reduces costs.

Step S120: obtain extinguishing arc reference data, and according to extinguishing arc reference data, arc suppression coil is adjusted, the electric current of power distribution network earth point is down in preset range.In the present embodiment, extinguishing arc reference data comprises electric network capacitance and current, tuning-off degree and residual flow, using electric network capacitance and current, tuning-off degree and residual flow as the foundation regulating arc suppression coil compensation electric current.First tuning-off degree and residual flow are set as some scopes before putting into operation, when the tuning-off degree of system or residual flow exceed this scope, the gear of controller adjustment arc suppression coil, makes the tuning-off degree after adjustment and residual flow meet the demands.In the present embodiment, in zero sequence loop, string has damping resistance, in order to avoid there is resonance in electrical network, the threshold values (being generally set to the phase voltage of 15%) of setting is exceeded at neutral point voltage, excision damping resistance, make arc suppression coil full remuneration capacitance current, reduce the electric current of earth point, reach blow-out and ensure power system security, reliably run.

When there is earth fault, also arc eliminator is provided before carrying out failure line selection in the present embodiment, the induction reactance of arc suppression coil is regulated according to the data detected, it is made to compensate capacity current, the electric current of earth point is made to drop in certain scope, reach the object of extinguishing arc, ensure that power system security reliably runs.

Wherein in an embodiment, continue with reference to Fig. 7, after step S160, distribution net work earthing fault selection method also comprises step S170.

Step S170: detection is carried out to faulty line and obtains detection signal, and the amplitude that reduced by detection signal is greater than the position of predetermined amplitude threshold value as fault ground point.Carry out localization of fault by handheld device fault locating instrument, specifically utilize this feature of undergoing mutation of the size of marking current before and after earth point to carry out localization of fault, along faulty line detection, the point that signal weakens suddenly just thinks fault ground point.

Above-mentioned distribution net work earthing fault selection method, detect power distribution network bus PT secondary side open-triangular winding on residual voltage to judge whether power distribution network earthed system earth fault occurs, if then obtain fault phase according to the three-phase voltage of bus.The phase Injection Signal electric current that bus PT secondary side is corresponding with fault phase, detect the electric current of outlet thus determine faulty line, realize failure line selection, applied widely, route selection accuracy is high and cost is low.

Present invention also offers a kind of distribution net work earthing fault wire selection system, be applicable to the small current neutral grounding system of medium voltage distribution network, as shown in Figure 9, comprise judge module 130, processing module 140, control module 150 and detection module 160.

The residual voltage of judge module 130 on the bus PT secondary side open-triangular winding obtaining power distribution network, and judge whether residual voltage is greater than default fault threshold.The concrete value of fault threshold can adjust according to actual conditions, and the residual voltage in real time on monitoring bus PT secondary side open-triangular winding, is greater than fault threshold as the foundation judging whether to occur earth fault using residual voltage.Controller can be utilized to obtain residual voltage judging, concrete with above-mentioned distribution net work earthing fault selection method in similar, do not repeat them here.Same in the present embodiment is 120V by fault threshold voltage value, as residual voltage U _lN>=U _xduring=120V, think that system there occurs earth fault, start and the selection of fault phase is judged, improve judgment accuracy.

Processing module 140, for when residual voltage is greater than fault threshold, obtains the three-phase voltage of bus, obtains fault phase according to three-phase voltage.Determine power distribution network be short-circuited fault time, measure the three-phase voltage of power distribution network median generatrix and determine fault phase, so that the corresponding Injection Signal electric current of subsequent step, selecting fault outlet rapidly by injection method.Detect the three-phase voltage of bus equally by controller, and obtain fault phase according to three-phase voltage.Determine in the principle of fault phase and above-mentioned distribution net work earthing fault selection method similar according to three-phase voltage analysis, do not repeat them here.

Therefore, wherein in an embodiment, power distribution network is isolated neutral system, and as shown in Figure 10, processing module 140 comprises first module 142 and second unit 144.

First module 142 is for being less than K times of rated voltage in the phase voltage of the minimum phase of voltage, and choosing voltage minimum is fault phase mutually.

Second unit 144 is for being all greater than K times of rated voltage at three-phase voltage, and next choosing the highest phase of voltage is fault phase mutually.Wherein K is less than 0.823, and in the present embodiment, K is specially 0.6.

In another embodiment, power distribution network is earth neutral system, and as shown in figure 11, processing module 140 comprises the 3rd unit 146 and the 4th unit 148.

3rd unit 146 is for being less than K times of rated voltage in the phase voltage of the minimum phase of voltage, and choosing voltage minimum is fault phase mutually.

4th unit 148 is for being all greater than K times of rated voltage at three-phase voltage, and choosing upper one of the highest phase of voltage is fault phase mutually.Wherein K is less than 0.823, gets 0.6 with K in sample embodiment.

Below be namely provide corresponding fault phase defining method for two kinds of different situations of power distribution network, can select according to actual conditions, improve the reliability of failure line selection and comprehensive.

Control module 150 is for according to the corresponding phase Injection Signal electric current of fault phase from bus PT secondary side.Specifically inject the marking current of particular frequencies by controller control signal generating means from the correspondence of PT secondary side mutually, carry out acquisition so that follow-up and identify.Can induce corresponding marking current at PT primary side, most marking current can flow into earth point through the fault phase of fault outlet.

The electric current that detection module 160 exports for detecting the every bar outlet of bus, obtains electric current and is greater than the circuit of predetermined threshold value as faulty line.Specifically all can be provided with zero sequence current mutual inductor in every bar outlet, zero sequence current mutual inductor is connected with controller, by the current delivery that collects to controller.Controller is analyzed current signal, if the marking current detected exceedes pre-set threshold value, then thinks that this circuit is faulty line.

Wherein in an embodiment, as shown in figure 12, distribution net work earthing fault wire selection system also comprises acquisition module 110 and adjusting module 120.

Before the residual voltage of acquisition module 110 on the bus PT secondary side open-triangular winding obtaining power distribution network at judge module 130, gather the neutral point voltage of power distribution network, and judge whether neutral point voltage is greater than default voltage threshold.Specifically gather the neutral point voltage of power distribution network by arc-extinction device, and carry out follow-up crowbar operation.Similar in the concrete structure of arc-extinction device and above-mentioned distribution net work earthing fault selection method, do not repeat them here.

Adjusting module 120, for when neutral point voltage is greater than voltage threshold, obtains extinguishing arc reference data, and adjusts arc suppression coil according to extinguishing arc reference data, the electric current of power distribution network earth point is down in preset range.In the present embodiment, extinguishing arc reference data comprises electric network capacitance and current, tuning-off degree and residual flow, using electric network capacitance and current, tuning-off degree and residual flow as the foundation regulating arc suppression coil compensation electric current.First tuning-off degree and residual flow are set as some scopes before putting into operation, when the tuning-off degree of system or residual flow exceed this scope, the gear of controller adjustment arc suppression coil, makes the tuning-off degree after adjustment and residual flow meet the demands.

When there is earth fault, also arc eliminator is provided before carrying out failure line selection in the present embodiment, the induction reactance of arc suppression coil is regulated according to the data detected, it is made to compensate capacity current, the electric current of earth point is made to drop in certain scope, reach the object of extinguishing arc, ensure that power system security reliably runs.

Wherein in an embodiment, continue with reference to Figure 12, distribution net work earthing fault wire selection system also can comprise locating module 170, the electric current that locating module 170 exports for detecting the every bar outlet of bus at detection module 160, obtain electric current and be greater than the circuit of predetermined threshold value as after faulty line, detection is carried out to faulty line and obtains detection signal, and the amplitude that reduced by detection signal is greater than the position of predetermined amplitude threshold value as fault ground point.Carry out localization of fault by handheld device fault locating instrument, specifically utilize this feature of undergoing mutation of the size of marking current before and after earth point to carry out localization of fault, along faulty line detection, the point that signal weakens suddenly just thinks fault ground point.

Above-mentioned distribution net work earthing fault wire selection system, detect power distribution network bus PT secondary side open-triangular winding on residual voltage to judge whether power distribution network earthed system earth fault occurs, if then obtain fault phase according to the three-phase voltage of bus.The phase Injection Signal electric current that bus PT secondary side is corresponding with fault phase, detect the electric current of outlet thus determine faulty line, realize failure line selection, applied widely, route selection accuracy is high and cost is low.

Each technical characteristic of the above embodiment can combine arbitrarily, for making description succinct, the all possible combination of each technical characteristic in above-described embodiment is not all described, but, as long as the combination of these technical characteristics does not exist contradiction, be all considered to be the scope that this instructions is recorded.

The above embodiment only have expressed several embodiment of the present invention, and it describes comparatively concrete and detailed, but can not therefore be construed as limiting the scope of the patent.It should be pointed out that for the person of ordinary skill of the art, without departing from the inventive concept of the premise, can also make some distortion and improvement, these all belong to protection scope of the present invention.Therefore, the protection domain of patent of the present invention should be as the criterion with claims.

Claims (10)

1. a distribution net work earthing fault selection method, is characterized in that, comprises the following steps:

Obtain the residual voltage on the bus PT secondary side open-triangular winding of power distribution network, and judge whether described residual voltage is greater than default fault threshold;

If so, then obtain the three-phase voltage of bus, obtain fault phase according to described three-phase voltage;

According to the corresponding phase Injection Signal electric current of described fault phase from described bus PT secondary side;

Detect the electric current that the every bar outlet of bus exports, obtain electric current and be greater than the circuit of predetermined threshold value as faulty line.

2. distribution net work earthing fault selection method according to claim 1, is characterized in that, described power distribution network is isolated neutral system; Describedly obtain fault phase according to described three-phase voltage, comprise the following steps:

If the phase voltage of the minimum phase of voltage is less than K times of rated voltage, then described voltage is minimum is fault phase mutually;

If described three-phase voltage is all greater than K times of rated voltage, then next of the highest phase of voltage is fault phase mutually; Wherein K is less than 0.823.

3. distribution net work earthing fault selection method according to claim 1, is characterized in that, described power distribution network is earth neutral system; Describedly obtain fault phase according to described three-phase voltage, comprise the following steps:

If the phase voltage of the minimum phase of voltage is less than K times of rated voltage, then described voltage is minimum is fault phase mutually;

If described three-phase voltage is all greater than K times of rated voltage, then upper one of the highest phase of voltage is fault phase mutually; Wherein K is less than 0.823.

4. distribution net work earthing fault selection method according to claim 1, it is characterized in that, obtain the residual voltage on the bus PT secondary side open-triangular winding of power distribution network, and before judging whether described residual voltage is greater than default fault threshold, further comprising the steps of:

Gather the neutral point voltage of described power distribution network, and judge whether described neutral point voltage is greater than default voltage threshold;

If so, then obtain extinguishing arc reference data, and according to described extinguishing arc reference data, arc suppression coil is adjusted, the electric current of power distribution network earth point is down in preset range.

5. distribution net work earthing fault selection method according to claim 1, is characterized in that, detects the electric current that the every bar outlet of bus exports, and obtains electric current and is greater than the circuit of predetermined threshold value as after faulty line, further comprising the steps of:

Detection is carried out to faulty line and obtains detection signal, and the amplitude that reduced by detection signal is greater than the position of predetermined amplitude threshold value as fault ground point.

6. a distribution net work earthing fault wire selection system, is characterized in that, comprising:

Judge module, the residual voltage on the bus PT secondary side open-triangular winding obtaining power distribution network, and judge whether described residual voltage is greater than default fault threshold;

Processing module, for when described residual voltage is greater than described fault threshold, obtains the three-phase voltage of bus, obtains fault phase according to described three-phase voltage;

Control module, for according to the corresponding phase Injection Signal electric current of described fault phase from described bus PT secondary side;

Detection module, for detecting the electric current that the every bar outlet of bus exports, obtaining electric current and being greater than the circuit of predetermined threshold value as faulty line.

7. distribution net work earthing fault wire selection system according to claim 6, is characterized in that, described power distribution network is isolated neutral system; Described processing module comprises:

First module, for being less than K times of rated voltage in the phase voltage of the minimum phase of voltage, choosing described voltage minimum is fault phase mutually;

Second unit, for being all greater than K times of rated voltage at described three-phase voltage, next choosing the highest phase of voltage is fault phase mutually; Wherein K is less than 0.823.

8. distribution net work earthing fault wire selection system according to claim 6, is characterized in that, described power distribution network is earth neutral system; Described processing module comprises:

Unit the 3rd, for being less than K times of rated voltage in the phase voltage of the minimum phase of voltage, choosing described voltage minimum is fault phase mutually;

Unit the 4th, for being all greater than K times of rated voltage at described three-phase voltage, choosing upper one of the highest phase of voltage is fault phase mutually; Wherein K is less than 0.823.

9. distribution net work earthing fault wire selection system according to claim 6, is characterized in that, also comprise:

Acquisition module, before obtain the residual voltage on the bus PT secondary side open-triangular winding of power distribution network at judge module, gathers the neutral point voltage of described power distribution network, and judges whether described neutral point voltage is greater than default voltage threshold;

Adjusting module, for when described neutral point voltage is greater than described voltage threshold, obtains extinguishing arc reference data, and adjusts arc suppression coil according to described extinguishing arc reference data, the electric current of power distribution network earth point is down in preset range.

10. distribution net work earthing fault wire selection system according to claim 6, it is characterized in that, also comprise locating module, described locating module is used for the electric current detecting bus every bar outlet output at detection module, obtain electric current and be greater than the circuit of predetermined threshold value as after faulty line, detection is carried out to faulty line and obtains detection signal, and the amplitude that reduced by detection signal is greater than the position of predetermined amplitude threshold value as fault ground point.