CN104198884A - Differential principle based large-scale power grid intelligent trouble diagnosis method - Google Patents

Abstract

The invention discloses a differential principle based large-scale power grid intelligent trouble diagnosis method. The differential principle based large-scale power grid intelligent trouble diagnosis method comprises fault recording sampling, calculation of a phase current differential value with electric transmission and transformation equipment serving as a unit when the power grid normally operates, differential current calculation of primary current of the power grid equipment with power grid independent equipment serving as a calculation unit according to the fault data transmitted by a fault recorder and comparison of the differential current value and a differential current setting value to judge whether out-of-limit or not. The differential principle based large-scale power grid intelligent trouble diagnosis method has the advantages of being wide in applicable range and accurate in judgment, allowing automatic medical result push, not being influenced by factors such as a system operation mode and system oscillation and the like due to the fact that a fault position is accurately and quickly positioned according to the differential principle and a medical result is automatically pushed in a main wiring diagram.

Description

Large scale electric network intelligent failure diagnosis method based on differential principle

Technical field

The present invention relates to electrical network intelligent failure diagnosis method field, relate in particular to a kind of large scale electric network intelligent failure diagnosis method based on differential principle.

Background technology

Continuous reinforcement along with grid contact, effectively improves transmitting capacity of the electric wire netting, but simultaneously electrical network locality fault causes that the possibility that accident involves the expansion of scope improves constantly, and has increased the accurate identification difficulty of fault greatly.Therefore; in recent years; each company has all strengthened the technology support systems such as failure wave-recording networked system, relay protection information system and has built dynamics; when electrical network breaks down; all kinds of failure messages such as isolating switch action message, Fault Recorder Information, protection action sequence information can be sent to dispatching terminal in time; but operations staff is merely based on numerous discrete failure messages such as isolating switch displacement, fault oscillograph analog quantity, protective device action items; cannot be fast, accurately, intuitive judgment nature of trouble, greatly restore electricity speed and electric power netting safe running of impact.

Domestic and international many scholars are for this difficulties, propose to adopt the methods such as Petri net, rough set, multisource information fusion technology, expert diagnostic system to carry out electric network failure diagnosis, these researchs have all obtained certain effect, but required failure message is more and criterion is comparatively complicated, and practical implementation also exists larger limitation.

While there is abnormal or fault in large scale electric network; all kinds of failure messages can be sent to dispatching terminal in time; but operations staff is merely based on numerous discrete failure messages such as isolating switch displacement, fault oscillograph analog quantity, protective device action items; cannot be fast, accurately, intuitive judgment nature of trouble, greatly restore electricity speed and electric power netting safe running of impact.

Summary of the invention

Object of the present invention is exactly in order to address the above problem, a kind of large scale electric network intelligent failure diagnosis method based on differential principle has been proposed, the method can accurately be located abort situation fast, and on main wiring diagram, automatically push diagnostic result, there is applied widely, accuracy of judgement, diagnostic result pushes, is not subject to the advantages such as the factors such as system operation mode and system oscillation affect automatically, proposed the method for a kind of transmission line malfunction diagnosis, and take double bus scheme and transmission line malfunction diagnostic method has been done to specific description as example.

To achieve these goals, the present invention adopts following technical scheme:

A large scale electric network intelligent failure diagnosis method based on differential principle, comprises the following steps:

Step 1: sample with setting-up time interval automatic-calling failure wave-recording;

Step 2: when electrical network normally moves, the power transmission and transforming equipment of take carries out the calculating of phase current differential value as unit; If differential current computing value starts definite value lower than difference current, return to step 1; If differential current computing value is greater than the difference current of corresponding device, start definite value, go to step 3;

Step 3: by long-range adjustment fault oscillograph parameter, or whether all whether site inspection fault oscillograph equipment and the current return of access participation differential current computing there is multipoint earthing problem and carry out in time defect elimination, until differential current computing value starts definite value lower than difference current;

Step 4: when electrical network breaks down, the fault data transmitting according to fault oscillograph, take respectively electrical network autonomous device as computing unit, carries out the differential current computing of grid equipment phase current; Described electrical network autonomous device comprises: bus equipment, transformer equipment and transmission line of electricity;

For transmission line malfunction, first transmission line of electricity is carried out to fault primary election, filter out doubtful faulty line, then calculate the poor flow valuve of doubtful faulty line;

Step 5: difference flow valuve and poor stream setting valve are compared, if poor flow valuve is out-of-limit, judgement is broken down, and locates abort situation simultaneously and determines protection action; If poor flow valuve is not out-of-limit, judge non-fault or external area error; In two kinds of situations, all automatically push fault diagnosis report.

In described step 4, the method that transmission line of electricity carries out fault primary election comprises: branch current phase-comparison method and comprehensive directional element identification method;

Described branch current phase-comparison method is:

First determine whether doubtful bus-bar fault, if not doubtful bus-bar fault, judge the phase place of each branch current, by phase bit comparison, judge doubtful fault branch;

Described comprehensive directional element identification method is:

For asymmetry fault, according to different fault types, by judgement zero-sequence direction component and negative-sequence direction component direction, judge whether circuit is doubtful faulty line;

For symmetrical fault, adopt impedance directional element to carry out doubtful faulty line identification.

In described step 4, the method that transmission line of electricity carries out fault primary election is branch current phase-comparison method:

For circuit branch road quantity >=3, the situation of two bus paired runnings:

(1) if the poor flow valuve of bus is greater than A, and poor flow valuve/braking current value is greater than B, is bus-bar fault; Wherein, A and B are action setting valve, are setting value;

(2) if do not meet (1), be circuit branch trouble or main transformer branch trouble, doubtful fault branch judgement is as follows:

The first step: choose the branch road of fault current maximum as benchmark branch road, take its fault current as benchmark branch current;

Second step: other have the fault current of stream branch road to carry out phase bit comparison with benchmark branch current respectively:

If all branch currents and benchmark branch current phase differential all meet 120 degree～240 degree, benchmark branch road is doubtful fault branch;

If only have 1 branch road and benchmark branch road phase differential to meet 120 degree～240 degree, remain all branch roads and benchmark branch road phase differential and all meet-60 degree～60 degree left and right; Meeting 120 branch roads of spending～240 degree with benchmark branch road phase differential is doubtful fault branch.

In described step 4, the method that transmission line of electricity carries out fault primary election is branch current phase-comparison method:

For circuit branch road quantity=2, the situation of two bus paired runnings:

(1) if the poor flow valuve of bus is greater than A, and poor flow valuve/braking current value is greater than B, is bus-bar fault; Wherein, A and B are action setting valve, are setting value;

(2) if do not meet (1), be circuit branch trouble or main transformer branch trouble, doubtful fault branch judgement is as follows:

Measuring impedance is that positive circuit is doubtful fault branch, and measuring impedance is that negative circuit is non-fault line.

In described step 4, the method that transmission line of electricity carries out fault primary election is branch current phase-comparison method:

For circuit branch road quantity=1, the situation of two bus paired runnings:

(1) if the poor flow valuve of bus is greater than A, and poor flow valuve/braking current value is greater than B, is bus-bar fault; Wherein, A and B are action setting valve, are setting value;

(2) if do not meet (1), be circuit branch trouble or main transformer branch trouble, if certain circuit branch current secondary current is less than C, C is setting value, and this circuit branch road is doubtful fault branch.

In described step 4, the method that transmission line of electricity carries out fault primary election is comprehensive directional element identification method:

For asymmetry fault, concrete determination methods is:

(1) single-phase fault: zero-sequence direction component, negative-sequence direction component are positive dirction;

(2) double earthfault: zero-sequence direction component, negative-sequence direction component are positive dirction;

(3) line to line fault phase to phase fault: without zero sequence, negative-sequence direction component is positive dirction;

If certain circuit both sides directional element is all shown as positive dirction, this circuit is doubtful faulty line.

Described zero-sequence direction component is that positive dirction meets:

Described zero-sequence direction component is that positive dirction meets:

Described negative-sequence direction component is that positive dirction meets:

Wherein, for zero-sequence current, for residual voltage, for negative-sequence current, for negative sequence voltage.

In described step 4, the method that transmission line of electricity carries out fault primary election is comprehensive directional element identification method:

For symmetrical fault, concrete determination methods is:

During network system generation symmetrical fault, transmission line of electricity is without zero sequence and negative sequence component, adopt phase to phase impedance directional element to carry out faulty line identification, interphase distance relay is for judging the direction of phase to phase impedance directional element, if the polarizing voltage of interphase distance relay, operating voltage meet operating criterion equation below, prove that phase to phase impedance directional element is positive dirction; Described criterial equation is:

Wherein, for polarizing voltage, ${\stackrel{\·}{U}}_{\mathrm{\Φ\Φ}}-Z_{\mathrm{set}}{\stackrel{\·}{I}}_{\mathrm{\Φ\Φ}}$ For operating voltage, for fault voltage between phases, for fault three-phase current, Z _setfixing line taking road positive sequence impedance definite value Z _l11.2～1.5 times;

If the phase to phase impedance directional element of certain circuit both sides has all met above-mentioned corresponding actions criterion, this circuit is doubtful faulty line.

The invention has the beneficial effects as follows:

The present invention utilizes differential principle accurately to locate fast abort situation, and on main wiring diagram, automatically push diagnostic result, have applied widely, accuracy of judgement, diagnostic result pushes automatically, be not subject to the advantages such as the factors such as system operation mode and system oscillation affect, by each interval fault current, abort situation and diagnostic result push automatically, unified directly perceived displaying on main wiring diagram, for accident treatment provides the decision support of urgent need, fundamentally changed fault Artificial Diagnosis traditional mode, for accident treatment provides the decision support of urgent need, effectively promote large scale electric network controling power.

The discrimination method for line fault that the present invention proposes, principle is simple, and accuracy of judgement is not affected by rack topological structure, without voltage, accurately locates faulty line, not affected by load, vibration, power inverted orientation etc.First judge doubtful line fault, then utilize the further identification of defective circuit of differential principle, judged result accurately and reliably, has alleviated workload greatly.

Accompanying drawing explanation

Fig. 1 is the differential current computing block plan fault diagnosis principle figure of wide area Fault Recorder Information;

Fig. 2 is electric network failure diagnosis system flowchart of the present invention;

Fig. 3 is the differential wiring schematic diagram of three-winding transformer;

Fig. 4 is case 1 bus-bar fault diagnosis case of the present invention;

Fig. 5 is power system operating mode schematic diagram before case 2 faults of the present invention.

Embodiment:

Below in conjunction with accompanying drawing and embodiment, the present invention will be further described:

Fig. 1 is the differential current computing block plan fault diagnosis principle figure of wide area Fault Recorder Information; as seen from the figure its differential current computing region divide respectively with each interval differential main protection scope kissing and, utilize differential principle accuracy of judgement, be not subject to the peculiar advantages such as system operation mode, transition resistance, load current, power inverted orientation, system diagnostics accurately to locate abort situation and evaluate protection action behavior.

When electrical network normally moves, with Fixed Time Interval automatic-calling failure wave-recording, sample and carry out take the phase current differential value that power transmission and transforming equipment is unit and calculate, poor flow valuve should be almost nil.(should be load unbalanced when the out-of-limit value of poor stream of each equipment is adjusted as electrical network maximum operational mode if differential current computing value is greater than the out-of-limit value of poor stream of corresponding device, the factors such as CT error cause the maximum difference stream value that may occur), by the long-range adjustment fault oscillograph access of scheduling station septal pathways title, CT polarity and no-load voltage ratio coefficient, or whether all whether site inspection fault oscillograph equipment and the current return of access participation differential current computing there is multipoint earthing problem and carry out in time defect elimination, guarantee that the differential current computing value of all power transmission and transforming equipments when electrical network normally moves is all close to zero.

When electrical network breaks down, according to the fault data sending on fault oscillograph, take respectively electrical network autonomous device as computing unit, carry out the differential current computing of electrical network primary current; Flow valuve and the comparison of poor stream setting valve be will differ from, accurate abort situation location and the evaluation of protection action behavior realized.Its idiographic flow is illustrated in fig. 2 shown below:

This method for diagnosing faults only needs fault oscillograph data; during fault diagnosis; fault oscillograph data etc. are all the part of data acquisition of bus protection, tranformer protection, line protective devices; therefore the branch road, CT Secondary Winding type and the polarity that access fault oscillograph should meet following requirement; as space is limited, take the 220kV transformer substation bus equipment fault identification method of double bus scheme form is example:

(1) configure separately the transformer station of main transformer fault oscillograph, this station all main transformer 220kV high voltage side current analog quantity should be connected in series to our station line fault oscillograph, guarantees that same fault oscillograph of all branch road accesses of normal station median generatrix is to realize sample-synchronous.In intelligent station, all fault oscillographs are entirely stood and are adopted unified synchronous clock, and all branch roads of bus are without being connected to same fault oscillograph.

(2) the CT winding of access fault oscillograph should be selected line side CT winding (protected level).

(3) the access circuit of fault oscillograph is, Same Name of Ends of the CT of transformer branch road should be in bus bar side, and Same Name of Ends of mother CT should be in I bus bar side, and corresponding CT Secondary Winding should be Same Name of Ends outlet.If Same Name of Ends of CT of access fault oscillograph is towards contrary to the above, corresponding CT Secondary Winding should change non-same polarity outlet into, to meet polarity, requirement is set.

1. bus equipment

Large poor, the little poor computing formula of bus is as follows:

1. large spill current: I _cd=I ₁+ I ₂+ ... + I _n

2. female little spill current: the I of I _cd1=I ₁* S ₁₁+ I ₂* S ₁₂+ ... + I _n* S _1n+ I _mL* S _mL

Female little spill current: the I of II _cd2=I ₁* S ₂₁+ I ₂* S ₂₂+ ... + I _n* S _2n-I _mL* S _mL

In formula, I ₁, I ₂..., I _nrepresent each branch current vector; I _mLrepresent mother current digital amount; S ₁₁, S ₁₂..., S _1nrepresent the female disconnecting link of each branch road I position (0 represents that disconnecting link divides, and 1 represents that disconnecting link closes); S ₂₁, S ₂₂..., S _2nrepresent the female disconnecting link of each branch road II position; S _mLrepresent bus paired running state (0 represents split operation, and 1 represents paired running).

Large poor loop is the differential circuit that on the bus except bus connection switch, all the other branch currents form; Certain section of little poor loop of bus is the differential circuit that each branch current of being connected with this bus forms, comprising the bus connection switch being associated with this section of bus.

2. transformer equipment

Transformer differential electric current: be respectively the current phasor after each side of transformer is adjusted.With reference to lower Fig. 3, take Y/Y/ Δ-11 as example, the computing formula of difference current is as follows:

A differs stream:

$\begin{array}{c}\mathrm{\Δ}{\stackrel{\·}{I}}_a=({\stackrel{\·}{I}}_{\mathrm{aH}}-{\stackrel{\·}{I}}_{\mathrm{bH}})/\sqrt{3}+({\stackrel{\·}{I}}_{\mathrm{aM}}-{\stackrel{\·}{I}}_{\mathrm{bM}})\\ \×k_M\×(V_M/V_H)/(k_H\×\sqrt{3})\\ +{\stackrel{\·}{I}}_{\mathrm{aL}}\×k_L\×(V_L/V_H)/k_H\end{array}$

B differs stream:

$\begin{array}{c}\mathrm{\Δ}{\stackrel{\·}{I}}_b=({\stackrel{\·}{I}}_{\mathrm{bH}}-{\stackrel{\·}{I}}_{\mathrm{cH}})\sqrt{3}+({\stackrel{\·}{I}}_{\mathrm{bM}}-{\stackrel{\·}{I}}_{\mathrm{cM}})\\ \×k_M\×(V_M/V_H)/(k_H\×\sqrt{3})\\ +{\stackrel{\·}{I}}_{\mathrm{bL}}\×k_L\×(V_L/V_H)/k_H\end{array}$

C differs stream:

$\begin{array}{c}\mathrm{\Δ}{\stackrel{\·}{I}}_c=({\stackrel{\·}{I}}_{\mathrm{cH}}-{\stackrel{\·}{I}}_{\mathrm{aH}})/\sqrt{3}+({\stackrel{\·}{I}}_{\mathrm{cM}}-{\stackrel{\·}{I}}_{\mathrm{aM}})\\ \×k_M\×(V_M/V_H)/(k_H\×\sqrt{3})\\ +{\stackrel{\·}{I}}_{\mathrm{cL}}\×k_L\×(V_L/V_H)/k_H\end{array}$

In the above in formula, be respectively high, medium and low voltage side a, b, c phase current phasor two sub-values; k _h, k _m, k _lbe respectively the CT no-load voltage ratio of high-pressure side, medium voltage side, low-pressure side; V _h, V _m, V _lbe respectively the rated voltage of high-pressure side, medium voltage side, low-pressure side.

All fault recorder datas of the station equipment such as bus, transformer all, in same transformer station, therefore can utilize differential principle to carry out the accurate identification of fault easily.

3. transmission line of electricity

Transmission line of electricity is different from bus, transformer equipment, its fault data is stored in two different substation internal fault oscillographs, if directly adopt circuit differential principle to carry out faulty line identification, advantage is that principle is simple, accuracy of judgement, is not affected by rack topological structure, without voltage, accurately location faulty line, is not affected by load, vibration, power inverted orientation etc.But due to needs circuit offside Fault Recorder Information, the very difficult realization of whole network data unified clock at present, therefore need to manually carry out the operations such as both sides data-mapping, fault data sample-synchronous, therefore native system is preferential adopts following two kinds of methods to carry out faulty line primary election to alleviate workload, and doubtful faulty line recycling differential principle is checked, confirmed.

3.1 each branch current phase-comparison methods

The advantage of the method is that computing velocity is fast without circuit offside Fault Recorder Information, without voltage, only needs the magnitude of current can carry out identification.

(1) transformer station's (circuit branch road quantity >=3, mother co-bit) of " access main transformer branch road ":

1) the poor flow valuve of bus is greater than 400A, and poor flow valuve/braking current value is greater than 0.4, is bus-bar fault;

2) if do not meet 1), one is decided to be circuit/main transformer interval fault, judges as follows:

The first step: choose the branch road of fault current maximum (or larger), take its fault current as reference vector.

Second step: other have stream branch road (secondary current is greater than 0.4A) fault current to carry out phase bit comparison with benchmark branch current respectively.

The 3rd step, all branch currents and benchmark branch current phase differential are 180 degree left and right, for benchmark branch road is fault branch; If only have 1 branch road and benchmark branch road phase differential to be 180 degree left and right (120 degree～240 degree), other all branch roads and benchmark branch road phase differential are 0 degree (60 degree～60 degree) left and right; The branch road that is 180 about degree with benchmark branch road phase differential is fault branch.(generally should be the branch road of fault current maximum)

(2) transformer station's (circuit branch road quantity=2, mother co-bit) of " access main transformer branch road ":

1) the poor flow valuve of bus is greater than 400A, and poor flow valuve/braking current value is greater than 0.4, is bus-bar fault;

2) if do not meet 1), one is decided to be circuit/main transformer interval fault, and sampling impedance directional element is differentiated, and judges as follows:

Measuring impedance (comprising three impedance ground elements and three phase to phase impedance elements) is that positive circuit is fault branch, and measuring impedance is that negative circuit is non-fault line.

(3) transformer station's (circuit branch road quantity=1, mother co-bit) of " access main transformer branch road ":

1) the poor flow valuve of bus is greater than 400A, and poor flow valuve/braking current value is greater than 0.4, is bus-bar fault;

2) if do not meet 1), one is decided to be circuit/main transformer interval fault, and circuit branch current secondary current is less than 0.4A, and fault branch is this circuit branch road.

3.2 comprehensive directional element identification methods

The advantage of the method is not affected by rack topological structure, without offside Fault Recorder Information, only need this side electric current and voltage amount can carry out identification.

(1) asymmetry fault

1) single-phase fault: zero sequence direction, negative-sequence direction component should be positive dirction

2) double earthfault: zero sequence direction, negative-sequence direction component should be positive dirction

3) line to line fault phase to phase fault, without zero sequence, negative sequence direction should be positive dirction

Empirical data shows, for 220kV and above system, zero sequence, negative phase-sequence primary current are greater than 300A, and asymmetry fault has occurred electrical network, and then utilizes zero negative sequence directional element to carry out faulty line identification.

Zero sequence positive dirction element:

In formula, zero-sequence current and residual voltage are all self-produced, by A, B, C three-phase current, the voltage collecting, automatically calculate acquisition, rather than directly collect after outside input.

Negative phase-sequence positive dirction element:

In formula, negative-sequence current and negative sequence voltage are all self-produced.

(2) symmetrical fault (three-phase shortcircuit)

During network system generation symmetrical fault, all without zero negative sequence component, therefore only can adopt impedance directional element to carry out faulty line identification, Z _aB, Z _aC, Z _bCall should meet criterion is below positive dirction.

Interphase distance relay adopts the ohm relay with offset characteristic.Operating criterion is

for memory voltage before fault.

Z _setcan fixedly get " circuit positive sequence impedance definite value " z _l11.2～1.5 times.

After directional element has calculated, all positive dirction circuits are identified at main wiring diagram.If circuit both sides are all shown as positive dirction, this circuit is doubtful faulty line, the poor flow valuve of manual calculations circuit both sides fault current again, as poor flow valuve is greater than poor stream setting valve, this circuit is faulty line, and line fault point location can adopt the hybrid ranging methods such as single end distance measurement, both-end impedance range finding, travelling wave ranging to carry out trouble spot and accurately locate.

Concrete example:

Case 1: somewhere thunderstorm weather, A station: 220kV bus bar differential prptection operation, 220kV mother 200A switch, this side II line 213 switch breakings, offside B station: II line 213 switch breakings.

During fault analysis, can independently select relevant range, differential algorithm startup value and the percentage differential element acting characteristic curve of differential current computing.By Fig. 4, can obviously be found out, during this fault, bus differential current computing value drops in active region, can accurately judge that bus A phase ground connection occurs and is converted to A, C double earthfault; Circuit non-fault, femalely sends out after differential jumping order tripping circuit offside switch far away.

Case 2: somewhere thunderstorm weather, before fault, as shown in Figure 5, wherein the D of circuit L8 transformer station side isolating switch is in a minute position for the method for operation.When electrical network breaks down, isolating switch three-phase tripping operation in circuit L4 both sides does not overlap, the #1 main transformer high-pressure side of the C of transformer station and the tripping operation of bus three-phase.

Utilize above-mentioned diagnostic method, according to the fault recorder data of delivering to dispatching terminal on after fault, carry out computational analysis, calculate the fault direction of the poor flow valuve of bus equipment and tripping operation circuit both sides first respectively, can obtain as calculated, the A of transformer station, B, C tri-station buses, the equal non-fault of transformer equipment, circuit L4, L7, L8 are doubtful faulty line, then calculate one by one the poor flow valuve (referring to table 1) of doubtful faulty line, by table 1, can accurately judge that this electric network fault is as A phase earth fault in circuit L8 generating region.

The doubtful faulty line differential current computing of table 1 value

Through site inspection; this fault is that circuit L8 end the A phase earth fault Qie Gai circuit C of transformer station side isolating switch occurs because of operating mechanism fault isolated fault in time point; its breaker fail protection is through setting deferred action tripping #1 main transformer high-pressure side and bus connection switch, and L4 circuit is misoperation jumping offside isolating switch far away when miscarrying charging overcurrent protection causes external area error during because of normal operation.

During electric network fault, operations staff is merely based on numerous discrete failure messages such as isolating switch displacement, fault oscillograph analog quantity, protective device action items, cannot be fast, accurate, intuitive judgment nature of trouble.For this key issue of quick and precisely identification of fault; novelty proposes a kind of large scale electric network intelligent failure diagnosis method based on differential principle herein; utilize differential principle accuracy of judgement, be not subject to the peculiar advantages such as system operation mode, transition resistance, load current, power inverted orientation, system diagnostics accurately to locate abort situation and evaluate protection action behavior; and by each interval fault current, abort situation and diagnostic result unified directly perceived displaying on main wiring diagram, for accident treatment provides the decision support of urgent need.This system is accurate failure judgement position in a lot of electric network faults are processed, and for fast recovery of power supply provides the decision support of being badly in need of, has stronger engineering using value.

Although above-mentioned, by reference to the accompanying drawings the specific embodiment of the present invention is described; but be not limiting the scope of the invention; one of ordinary skill in the art should be understood that; on the basis of technical scheme of the present invention, those skilled in the art do not need to pay various modifications that creative work can make or distortion still in protection scope of the present invention.

Claims (8)

1. the large scale electric network intelligent failure diagnosis method based on differential principle, is characterized in that, comprises the following steps:

Step 1: sample with setting-up time interval automatic-calling failure wave-recording;

Step 2: when electrical network normally moves, the power transmission and transforming equipment of take carries out the calculating of phase current differential value as unit; If differential current computing value starts definite value lower than difference current, return to step 1; If differential current computing value is greater than the difference current of corresponding device, start definite value, go to step 3;

Step 3: by long-range adjustment fault oscillograph parameter, or whether all whether site inspection fault oscillograph equipment and the current return of access participation differential current computing there is multipoint earthing problem and carry out in time defect elimination, until differential current computing value starts definite value lower than difference current;

Step 4: when electrical network breaks down, the fault data transmitting according to fault oscillograph, take respectively electrical network autonomous device as computing unit, carries out the differential current computing of grid equipment phase current; Described electrical network autonomous device comprises: bus equipment, transformer equipment and transmission line of electricity;

For transmission line malfunction, first transmission line of electricity is carried out to fault primary election, filter out doubtful faulty line, then calculate the poor flow valuve of doubtful faulty line;

Step 5: difference flow valuve and poor stream setting valve are compared, if poor flow valuve is out-of-limit, judgement is broken down, and locates abort situation simultaneously and determines protection action; If poor flow valuve is not out-of-limit, judge non-fault or external area error; In two kinds of situations, all automatically push fault diagnosis report.

2. a kind of large scale electric network intelligent failure diagnosis method based on differential principle as claimed in claim 1, is characterized in that, in described step 4, the method that transmission line of electricity carries out fault primary election comprises: branch current phase-comparison method and comprehensive directional element identification method;

Described branch current phase-comparison method is:

First determine whether doubtful bus-bar fault, if not doubtful bus-bar fault, judge the phase place of each branch current, by phase bit comparison, judge doubtful fault branch;

Described comprehensive directional element identification method is:

For asymmetry fault, according to different fault types, by judgement zero-sequence direction component and negative-sequence direction component direction, judge whether circuit is doubtful faulty line;

For symmetrical fault, adopt impedance directional element to carry out doubtful faulty line identification.

3. a kind of large scale electric network intelligent failure diagnosis method based on differential principle as claimed in claim 1 or 2, is characterized in that, in described step 4, the method that transmission line of electricity carries out fault primary election is branch current phase-comparison method:

For circuit branch road quantity >=3, the situation of two bus paired runnings:

(1) if the poor flow valuve of bus is greater than A, and poor flow valuve/braking current value is greater than B, is bus-bar fault; Wherein, A and B are action setting valve, are setting value;

(2) if do not meet (1), be circuit branch trouble or main transformer branch trouble, doubtful fault branch judgement is as follows:

The first step: choose the branch road of fault current maximum as benchmark branch road, take its fault current as benchmark branch current;

Second step: other have the fault current of stream branch road to carry out phase bit comparison with benchmark branch current respectively:

If all branch currents and benchmark branch current phase differential all meet 120 degree～240 degree, benchmark branch road is doubtful fault branch;

If only have 1 branch road and benchmark branch road phase differential to meet 120 degree～240 degree, remain all branch roads and benchmark branch road phase differential and all meet-60 degree～60 degree left and right; Meeting 120 branch roads of spending～240 degree with benchmark branch road phase differential is doubtful fault branch.

4. a kind of large scale electric network intelligent failure diagnosis method based on differential principle as claimed in claim 1 or 2, is characterized in that, in described step 4, the method that transmission line of electricity carries out fault primary election is branch current phase-comparison method:

For circuit branch road quantity=2, the situation of two bus paired runnings:

(1) if the poor flow valuve of bus is greater than A, and poor flow valuve/braking current value is greater than B, is bus-bar fault; Wherein, A and B are action setting valve, are setting value;

(2) if do not meet (1), be circuit branch trouble or main transformer branch trouble, doubtful fault branch judgement is as follows:

Measuring impedance is that positive circuit is doubtful fault branch, and measuring impedance is that negative circuit is non-fault line.

5. a kind of large scale electric network intelligent failure diagnosis method based on differential principle as claimed in claim 1 or 2, is characterized in that, in described step 4, the method that transmission line of electricity carries out fault primary election is branch current phase-comparison method:

For circuit branch road quantity=1, the situation of two bus paired runnings:

(1) if the poor flow valuve of bus is greater than A, and poor flow valuve/braking current value is greater than B, is bus-bar fault; Wherein, A and B are action setting valve, are setting value;

(2) if do not meet (1), be circuit branch trouble or main transformer branch trouble, if certain circuit branch current secondary current is less than C, C is setting value, and this circuit branch road is doubtful fault branch.

6. a kind of large scale electric network intelligent failure diagnosis method based on differential principle as claimed in claim 1 or 2, is characterized in that, in described step 4, the method that transmission line of electricity carries out fault primary election is comprehensive directional element identification method:

For asymmetry fault, concrete determination methods is:

(1) single-phase fault: zero-sequence direction component, negative-sequence direction component are positive dirction;

(2) double earthfault: zero-sequence direction component, negative-sequence direction component are positive dirction;

(3) line to line fault phase to phase fault: without zero sequence, negative-sequence direction component is positive dirction;

If certain circuit both sides directional element is all shown as positive dirction, this circuit is doubtful faulty line.

7. a kind of large scale electric network intelligent failure diagnosis method based on differential principle as claimed in claim 6, is characterized in that, described zero-sequence direction component is that positive dirction meets:

Described zero-sequence direction component is that positive dirction meets:

Described negative-sequence direction component is that positive dirction meets:

Wherein, for zero-sequence current, for residual voltage, for negative-sequence current, for negative sequence voltage.

8. a kind of large scale electric network intelligent failure diagnosis method based on differential principle as claimed in claim 1 or 2, is characterized in that, in described step 4, the method that transmission line of electricity carries out fault primary election is comprehensive directional element identification method:

During network system generation symmetrical fault, transmission line of electricity is without zero sequence and negative sequence component, adopt phase to phase impedance directional element to carry out faulty line identification, interphase distance relay is for judging the direction of phase to phase impedance directional element, if the polarizing voltage of interphase distance relay, operating voltage meet operating criterion equation below, prove that phase to phase impedance directional element is positive dirction; Described criterial equation is:

Wherein, for polarizing voltage, ${\stackrel{\·}{U}}_{\mathrm{\Φ\Φ}}-Z_{\mathrm{set}}{\stackrel{\·}{I}}_{\mathrm{\Φ\Φ}}$ For operating voltage, for fault voltage between phases, for fault three-phase current, Z _setfixing line taking road positive sequence impedance definite value Z _l11.2～1.5 times;

If the phase to phase impedance directional element of certain circuit both sides has all met above-mentioned corresponding actions criterion, this circuit is doubtful faulty line.