CN101369727A - Route selection method aiming at electric arc ground fault - Google Patents

Abstract

A wire selection method for arcing ground failure uses zero sequence voltage amplitude as a selection-judged starting signal. After the zero sequence voltage amplitude is more than a threshold value, a zero sequence voltage of each feeding wire being sampled, then 50Hz fundamental wave treatment is implemented to the sampling signals to obtain zero sequence transient state currents, further five to six feeding wires with maximum amplitude of zero sequence transient state current are selected as ''doubtful true'' failure feeding wires, from which a feeding wire with maximum amplitude is selected as a quantity ib(k) of standard feeding wire, and the ib(k) is multiplied with the zero sequence transient state currents of the other ''doubtful true'' feeding wires point by point separately, and an algebraic average of a period of time is calculated as failure predication quantity Wj. If only one Wj of the all Wj is negative, the corresponding feeding wire is the failure feeding wire; if all Wj are negative, the standard feeding wire is the failure feeding wire; if all Wj are positive, the busbar is fault.

Description

A kind of selection method at the arcing ground fault

Technical field

The present invention relates to a kind of electricity grid substation small current earthing wire-selecting method, be applicable to the electrical network of any neutral ground, effective especially to the arcing ground fault.Belong to the power automation technical field.

Background technology

Experiment and on-the-spot electrical network recorder data all prove: because the complexity of single phase ground fault during some single phase ground fault, has only stable state in the feeder line zero-sequence current; Has only transient state during some single phase ground fault; Both have concurrently during some single phase ground fault.The laboratory physical simulation experiment also proves: under considerable arcing ground condition, steady-state current is very little or almost nil in the fault current, and transient current is then very high, causes the route selection effect all not really desirable, falsely drops, the probability of selective reject is than higher.On-the-spot operational data proves, is the arcing ground fault more than 50% in the earth fault.As seen, carry out at arcing ground fault, significant to the accuracy that improves route selection based on the research of the small current earthing wire-selecting method of transient analysis.Existing many scholars have explored when utilizing single phase ground fault, and the abundant information of transient state component is come the method for failure judgement feeder line in the zero-sequence current.But, still be not suitable for and use the microcomputer development line selection apparatus because calculation of complex is calculated length consuming time.The present invention has provided a kind of fault line selection method for single-phase-to-ground fault new, can realize and satisfy online in real time route selection calculating needs on single-chip microcomputer.

Summary of the invention

Technical problem: the purpose of this invention is to provide a kind of selection method at the arcing ground fault, its route selection principle is simple, very easy-to-use chip microcontroller, used expense is low, be not subjected to the influence of zero sequential potential transformer and zero sequence current mutual inductor angle error, be not subjected to the influence of the dispersiveness of zero sequence current mutual inductor characteristic when weak excitation (little electric current) yet.

Technical scheme: the present invention was not lost efficacy to there being the very low earth fault of transient process or transient state component (as high resistance earthing fault) route selection in the zero-sequence current, and therefore, suggestion is used with various selection methods based on steady-state analysis.

The present invention is directed to the selection method of arcing ground fault, it is characterized in that this method adopts following steps:

A. the residual voltage of sampling calculates and judges also whether residual voltage surpasses the threshold value of adjusting, and then illustrates that electrical network has single phase ground fault if surpass, and then, carry out following 5 steps route selections judgement,

B. the zero-sequence current of each feeder line of synchronized sampling, then to sampled signal carry out 50Hz first-harmonic trap handle the zero sequence transient current sampled value of each feeder line,

C. seek feeder line conduct " being suspected to be " fault feeder of 5～6 zero sequence transient current amplitude maximums,

D. the sampled value of feeder line of selecting a zero sequence transient current amplitude maximum in " being suspected to be " fault feeder is as the sampling quantity i of benchmark feeder line _b(k),

E. the sampling quantity i of benchmark feeder line _b(k) " be suspected to be " with all the other that the fault feeder sampled value is point-to-point respectively and multiply each other, and ask 1/4 cycle to a cycle, promptly the algebraic mean value of the time of 5 ~ 20ms is as fault judgement amount W _j,

F. according to this fault judgement amount W _jPositive and negative definite fault feeder, if fault judgement amount W _jA unique W is arranged _jValue is for negative, and then corresponding feeder line is a fault feeder; If fault judgement amount W _jAll be negative, then the benchmark feeder line is a fault feeder; If fault judgement amount W _jJust all being, then is busbar fault.

Beneficial effect: the invention provides a kind of small current earthing wire-selecting new method that is applicable to any neutral ground electrical network at the arcing ground fault, its route selection principle is simple, very easy-to-use chip microcontroller, used expense is low, be not subjected to the influence of zero sequential potential transformer and zero sequence current mutual inductor angle error, be not subjected to the influence of the dispersiveness of zero sequence current mutual inductor characteristic when weak excitation (little electric current) yet, effective especially to the arcing ground fault, route selection accuracy rate height.

Description of drawings

Fig. 1 constitutes logical construction of the present invention.

Embodiment

To achieve these goals, the present invention takes following technical scheme to realize:

Be applicable to the special route selection new method at the arcing ground fault of various neutral non-effective grounding electrical networks, it comprises:

1. the residual voltage of sampling calculates and judges also whether residual voltage surpasses the threshold value of adjusting, and then illustrates that electrical network has single phase ground fault if surpass, and then, carry out following 5 steps route selections judgement.

2. the zero-sequence current of each feeder line of synchronized sampling, and with the zero-sequence current sampled value i of each feeder line _0j(k) carry out 50Hz first-harmonic trap and handle, to obtain the zero sequence transient current sampled value of each feeder line

3. know by document [1], the zero sequence transient current of fault feeder is the summation of the zero sequence transient current of all non-fault feeders, therefore, the zero sequence transient current of fault feeder is always greater than the zero sequence transient current of non-fault feeder, for this reason, can seek the feeder line of 5 ~ 6 zero sequence transient current amplitude maximums as " being suspected to be " fault feeder.

4. the sampled value of feeder line of selecting a zero sequence transient current amplitude maximum in " being suspected to be " fault feeder is as the sampling quantity i of benchmark feeder line _b(k), obviously, the benchmark feeder line is the possibility maximum of fault feeder line.

5. the sampling quantity i of benchmark feeder line _b(k) " be suspected to be " with all the other that the fault feeder sampled value is point-to-point respectively and multiply each other, and (be generally 1/4 cycle to a cycle, promptly 5 ~ 20ms) algebraic mean value is as the fault judgement amount to ask a period of time $W_j=\frac{1}{N}\underset{k=0}{\overset{N}{\mathrm{\Σ}}}{i}_{0j}^{\′}\left(k\right)i_b\left(k\right),$ In the formula: N is the sampling number of a period of time.

6. according to this fault judgement amount W _jPositive and negative definite fault feeder, if fault judgement amount W _jA unique W is arranged _jValue is for negative, and then respective feed connection is a fault feeder; If fault judgement amount W _jAll be negative, then the benchmark feeder line is a fault feeder; If fault judgement amount W _jJust all being, then is busbar fault.

Enforcement of the present invention needs and is used for the zero sequential potential transformer (PT) that residual voltage measures and the zero sequence current mutual inductor of each feeder line zero sequence current measurement.According to list of references [1]: 1. during arcing ground, every starting the arc once all has transient state component to occur.The frequency of transient state component is relevant with multiple factors such as electric network composition, transformer parameter, fault point resistance with rate of decay characteristic, but irrelevant with neutral grounding mode.These characteristics are identical in a definite electric network composition, electrical network parameter and definite fault point, are uncertain values at different electrical networks, but faulty line are identical with the characteristic of non-fault line.Power-to-ground capacitance, alternate electric capacity, transformer and the line inductance big frequency that heals is lower; Fault point resistance is healed high attenuation speed sooner.2. the size of non-fault line zero sequence transient measuring electric current and this line mutual-ground capacitor is big or small proportional, and faulty line zero sequence transient measuring electric current equals all non-fault line zero sequence transient measuring electric current sums, and direction is opposite.In conjunction with Fig. 1 specific implementation process of the present invention is made the following instructions:

1, the zero-sequence current of real-time synchronized sampling residual voltage and each feeder line, respectively: u ₀(k) and i _0j(k).Because the present invention judges fault feeder according to the size and Orientation of zero sequence transient current, the frequency height of transient current requires sample frequency also high, implements sample frequency of the present invention and can not be lower than 6400Hz.

2, calculate the residual voltage instantaneous amplitude, and judge according to it whether electrical network single phase ground fault takes place.

3, after judgement has single phase ground fault, with the zero-sequence current sampled value i of each feeder line _0j(k) carry out 50Hz first-harmonic trap and handle, get the zero sequence transient current sampled value of each feeder line

4, seek the feeder line of 5 ~ 6 zero sequence transient current amplitude maximums as " being suspected to be " fault feeder.

5, in " being suspected to be " fault feeder, select the sampled value of feeder line of a zero sequence transient current amplitude maximum as the sampling quantity i of benchmark feeder line _b(k).

6, the sampling quantity i of benchmark feeder line _b(k) " be suspected to be " with all the other that the fault feeder sampled value is point-to-point respectively and multiply each other, and (be generally 1/4 cycle to a cycle, promptly 5 ~ 20ms) algebraic mean value is as fault judgement amount W to ask a period of time _j

7, according to positive and negative definite fault feeder of this fault judgement amount Wj, if fault judgement amount W _jA unique W is arranged _jValue is for negative, and then respective feed connection is a fault feeder; If fault judgement amount W _jAll be negative, then the benchmark feeder line is a fault feeder; If fault judgement amount W _jJust all being, then is busbar fault.

8, show fault feeder.

The present invention constitutes line selection apparatus with the Intel296 microcomputer chip, also can constitute its basic structure such as figure below with other microcomputer chips.

Claims (1)

1. selection method at the arcing ground fault is characterized in that this method adopts following steps:

A. the residual voltage of sampling calculates and judges also whether residual voltage surpasses the threshold value of adjusting, and then illustrates that electrical network has single phase ground fault if surpass, and then, carry out following 5 steps route selections judgement,

B. the zero-sequence current of each feeder line of synchronized sampling, then to sampled signal carry out 50Hz first-harmonic trap handle the zero sequence transient current sampled value of each feeder line,

C. seek feeder line conduct " being suspected to be " fault feeder of 5～6 zero sequence transient current amplitude maximums,

D. the sampled value of feeder line of selecting a zero sequence transient current amplitude maximum in " being suspected to be " fault feeder is as the sampling quantity i of benchmark feeder line _b(k),

E. the sampling quantity i of benchmark feeder line _b(k) " be suspected to be " with all the other that the fault feeder sampled value is point-to-point respectively and multiply each other, and ask 1/4 cycle to a cycle, promptly the algebraic mean value of the time of 5 ~ 20ms is as fault judgement amount W _j,

F. according to this fault judgement amount W _jPositive and negative definite fault feeder, if fault judgement amount W _jA unique W is arranged _jValue is for negative, and then corresponding feeder line is a fault feeder; If fault judgement amount W _jAll be negative, then the benchmark feeder line is a fault feeder; If fault judgement amount W _jJust all being, then is busbar fault.

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