CN109975657A - Single-phase ground fault line selecting method of small-electric current grounding system based on differential characteristic value - Google Patents

Single-phase ground fault line selecting method of small-electric current grounding system based on differential characteristic value Download PDF

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CN109975657A
CN109975657A CN201910271280.2A CN201910271280A CN109975657A CN 109975657 A CN109975657 A CN 109975657A CN 201910271280 A CN201910271280 A CN 201910271280A CN 109975657 A CN109975657 A CN 109975657A
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electricity
line
transmission line
zero
compensating element
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张美金
才志君
郐育
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Liaoning Technical University
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Liaoning Technical University
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08Locating faults in cables, transmission lines, or networks
    • G01R31/081Locating faults in cables, transmission lines, or networks according to type of conductors
    • G01R31/086Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors

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Abstract

The present invention proposes the single-phase ground fault line selecting method of small-electric current grounding system based on differential characteristic value, comprising: construction differential type topological structure;Zero sequence current mutual inductor is respectively set before and after each compensation branch of transmission line of electricity L1, L2, L3 respectively;It calculates and works as route LiWhen singlephase earth fault occurs, the zero-sequence current I of earth fault is flowed throughog, i.e., the sum of each branch zero-sequence current;Calculate the differential characteristic value of each branch;If differential characteristic value less than zero, determines the transmission line of electricity for faulty line;If differential characteristic value is greater than zero, determine the transmission line of electricity for non-fault line;The present invention studies a kind of differential type fault line selection method for single-phase-to-ground fault, the criterion has adaptable to electric system, different Contact patch and different scales power grid, high sensitivity, selective good feature are able to satisfy, can be played a significant role in terms of improving single-phase grounded malfunction in grounded system of low current route selection reliability.

Description

Single-phase ground fault line selecting method of small-electric current grounding system based on differential characteristic value
Technical field
The invention belongs to distribution network failure detection technique fields, and in particular to a kind of low current based on differential characteristic value connects Ground system single-phase earth fault route selecting method.
Background technique
It is transformed and accelerates with urban construction, urban distribution network cable run is more and more, and route overall length is continuously increased, and is transported Capable device intelligence degree remains in out initial stage level, and since equipment is outmoded, run unit is difficult to grasp cable run Operation conditions, parameters can not be implemented to grasp, and cause run unit that cannot grasp route existing defects in time, and cable run goes out Since equipment can not be intelligent out of service after existing failure, operations staff searches fault point difficulty, and search procedure also follows old side Method, not only artificial intensity is big, also will cause equipment damage, and time-consuming, influences power supply reliability, due to being now applied to power supply system The protective device technology of system is not mature enough, malfunctions phenomenon frequent occurrence, cannot play the role of protection well.
Currently, there are many small current neutral grounding power supply system fault line selection method for single-phase-to-ground fault, but due to being transported by system neutral The influence of the factors such as line mode, system scale and line form and quality, reliability and sensitivity tend not to meet the requirements, Refused action and malfunction happen occasionally.Therefore, the small current neutral grounding power supply system list of a kind of high reliability and high sensitivity is studied Phase ground fault line selecting method influences on failure is reduced, improves power supply quality, reduces breakdown loss and is of great significance.
The single-phase earthing or leak current fault route selection problem of small current neutral grounding system are the important interior of relay protection of power system One of hold, the great attention by domestic and international power industry.Influence of the earthing mode of neutral point in electric power system to route selection criterion Greatly, and the neutral operation method of various countries' electric system there are larger differences, therefore, research of the country variant in the field It emphasizes particularly on different fields.German electric system uses neutral by arc extinction coil grounding mode more, focuses under study for action temporary to failure process The research of state parameter.France currently replaces pervious resistance grounded system with arc suppression coil earthing system, in the field Research mainly uses zero sequence admittance route selection method.Research of the Japan in the field mainly uses fundamental wave reactive power direction power method.Norway Then identify the phase relation of residual voltage and zero-sequence current using the phase in space electric field and magnetic field, realizes failure line selection.
In short, research of the country variant in the field is all based on the expansion of its neutral point in electric power system method of operation, altogether No matter being power system operation mode with putting, the starting point of research is all post-fault system residual voltage and zero-sequence current Changing rule.
The leak current fault route selection criterion that develops of early stage have zero sequence active power route selection method, zero sequence reactive power route selection method, Zero sequence admittance route selection method, current injection method, quintuple harmonics route selection method etc..It generally speaking, is all special using the stable state of leak current fault It levies parameter and transient fault characteristic parameter carries out failure line selection.
Currently, the research of transient fault parameter is increasingly taken seriously, first half wave parameter route selection method, traveling wave route selection method, benefit Preferable research achievement is achieved with the wavelet transformation line selection algorithm of Parameters of Time-frequency Field and S-transformation route selection method etc..But transient state event It is short there are the time to hinder parameter, requires signal capture high, nonlinear load generates in practical applications harmonic wave and system operatio The harmonic wave etc. that process generates, may have an impact the reliability of criterion, constrain the application of criterion.
With Computer Control Technology application, the detection algorithm and control algolithm of some complexity can be achieved, There are also research, neural networks principles and fuzzy control theories to be applied to single-phase earth fault line selection in terms of intelligent route selection, By the fusion of multiple faults characteristic parameter, faulty line is identified.New method in recent years can be mainly divided into down on the whole Column four direction:
1, based on the selection method of steady-state quantity
(1) zero-sequence current is than width method
The location design that this method utilizes is that the capacitive earth current of faulty line is maximum, is equivalent to all regular links pair The sum of ground capacitance current, the amplitude for being mainly characterized by zero-sequence current of faulty line are greater than the zero-sequence current width of all regular links Value.Zero-sequence current is simpler than width method location design, but since collection in worksite zero sequence current signal can have interference signal, and Larger by influence factors such as line lengths, route selection accuracy is not high in actual application, can not be applied in practice.
(2) zero sequence admittance method
Zero sequence admittance method is a kind of improved zero-sequence current selection method, and this method route selection is led according to the zero sequence measured The size received and direction.Since the size of the zero sequence admittance measured not will receive the shadow that ground resistance variation in fault point generates It rings, so sensitivity is higher.But the selection method is influenced by zero sequence transformer characteristic, usually in isolated neutral and low Route selection accuracy rate is higher when resistance ground connection, but under high resistance ground state, zero sequence measurement admittance value can be made to become too small, influenced The accuracy rate of failure line selection.
(3) colony amplitude comparison phase comparing method
The thinking of this method is that the amplitude size of the zero-sequence current first each route compares, and it is big to filter out amplitude Former lines treat as suspected malfunctions line, then the phase of the electric current of suspected malfunctions line is compared, the direction of phase and other Several line Phases it is reversed be exactly faulty line, if the zero-sequence current phase of all routes is all the same, then it is assumed that be that bus is deposited In failure.Influence this approach reduce ground resistance, system operation mode and voltage level to route selection result, accuracy rate are opposite It is higher.But after high resistance earthing fault occurs for electric system, the zero-sequence current of each route can all become smaller, so that just The zero-sequence current difference of normal route and faulty line becomes smaller, and is just likely to that route selection mistake occurs at this time or leaks showing for choosing As.And this method is not suitable for neutral by arc extinction coil grounding mode, and there are certain restrictions in application range.
(4) quintuple harmonics method
Since inductive current has compensation effect to zero-sequence current under arc suppression coil mode, so zero-sequence current direction method cannot It is suitable in the system of neutral by arc extinction coil grounding.And harmonic wave cannot be fully compensated in arc suppression coil, and contains five in harmonic wave Subharmonic is most, therefore can select faulty line by comparing the size and Orientation of quintuple harmonics, and here it is the choosings of quintuple harmonics Line principle.But the harmonic content due to containing in each power grid is different, in the small power grid of harmonic content, quintuple harmonics method is lost Effect.
2, based on the selection method of transient
(1) first half-wave method
This method is put forward by German researchers at first, this selection method assumes initially that ground fault appears in phase Voltage is near maximum value.When it is maximum value that failure, which comes across phase voltage, the direct-to-ground capacitance of non-faulting phase can be in charging State, and the direct-to-ground capacitance of failure phase can then be in discharge condition.First half period after failure generation, first half-wave method Faulty line and regular link are distinguished according to the direction of transient zero-sequence current.The transient zero-sequence current of faulty line and regular link Flow direction be inconsistent, although the direction route selection using transient zero-sequence current is not influenced by arc suppression coil, due to Polar relationship is very short there are the time, so the sensitivity requirement to measuring cell is high, is not easy to realize.And this method is by short circuit Phase angle and electrical network parameter are affected, and generate falsely drop phenomenon sometimes.
(2) wavelet analysis method
Wavelet analysis is all widely used at many aspects such as pattern analysis, Audio Signal Processing, computer vision.By The characteristic preferably to localize is owned by time domain and frequency domain in wavelet method, and treatment effect will be substantially better than in traditional Fu Leaf transformation, and by the flexible of video window, translational motion, wavelet transformation can apply in the analysis of non-stationary signal, so It is widely used in the signal analysis of power distribution network.The route selection of wavelet method is that electric current can occur to change suddenly when being generated using failure The principle of change carries out route selection, and the method for taking Wavelet Singularity to detect, using wavelet transformation, finds out the very big of mould to fault-signal It is worth point, and the polarity and size of the modulus maximum of each route wavelet conversion coefficient is compared, to selects failure Route.
Compared with Fourier transformation, wavelet transformation is due to that by the flexible of window function and can translate more to signal progress Scale Decomposition has a clear superiority in terms of extracting signal effective information so compensating for the deficiency of many Fourier transformation. In terms of failure line selection, the isolated neutral system that Wavelet Transformation Algorithm can be applied not only to neutral point can also be applied to neutral point In the system for selling arc coil ground connection, applied widely, recognition capability is strong, shows very big advantage in small current system In single-phase earth fault line selection, wavelet transformation has filled up the defect that route selection is carried out with steady-state quantity, can well adapt to complexity Situation.Wavelet transformation can be applied in the biggish route selection situation of the transient state components such as intermittent electric arc, for being mutated to transient state The feature extraction of signal can check that transient state is mutated, greatly enhance the agility of failure line selection.But due to small Wave conversion interference resistance is poor, and when handling the route selection problem of high resistance earthing fault, the sudden change amount of transient current can be bright It is aobvious to weaken, the accuracy rate of route selection can be made to lower significantly.
(3) wavelet packet analysis method
The energy value of transient state component is larger when the principle that the analysis method of wavelet packet utilizes is due to generating failure, and use is small Details coefficients of the Wave Decomposition after the detail coefficients or reconstruct on a certain scale, form the variant projects of location of some energy values. Since the locating polarity that wavelet packet analysis method is concerned with wavelet packet coefficient is not associated with the size of amplitude, therefore will not receive Cross the interference of resistance variation, this method uses frequency is high in transient current ingredient to realize failure line selection, especially when When the initial phase angle of failure is bigger, the accuracy of route selection is very high.But wavelet packet analysis method is affected by the initial phase angle of failure, When initial phase angle becomes very little, the accuracy of route selection will be lower.
(4) transient energy method
Similar to steady state energy method, transient state energy value method is also to annotate entire route selection process with the visual angle of energy.Think After power distribution network breaks down, the energy function value of faulty line is negative value, but the energy function value of regular link is bigger than zero Positive, and the energy function absolute value of faulty line will be equal to other each route energy function absolute values summation. This selection method is especially suitable in pin arc coil earthed system, due to the energy exchange between line capacitance and inductance, energy Have that the time is longer in systems, is conducive to the feature extraction of signal in this way.But when analysis is through high resistance ground system, because The resistance value of transition resistance is larger, and residual voltage amplitude can be reduced accordingly, and zero-sequence current also becomes smaller, and route selection susceptibility reduces at this time, It is easy to appear and falsely drops phenomenon.
3, the extraneous route selection method exerted one's influence
Injection method
The location design of injection method is failure phase determining first, then by a special direct current signal injection ground connection transformation One end of device neutral point, since the direct current signal of external world's input only flows in the route that ground fault occurs, so in the presence of Special direct current Injection Signal can be detected inside the route of failure, and Injection Signal is not present in normal route.It detects The route of special DC signal is the route for generating failure.The method of operation of distribution network system will not influence injecting signal Route selection is as a result, applied widely.But since Injection Current is affected by ground resistance, when high resistance ground, Injection Signal It is very small, in fact it could happen that the case where route selection is failed.And the equipment that must have input signal increases the complexity of power distribution network Degree and economic cost.
4, criterion route selection method is merged
Neural network
Neural network is by imitating the method for operation of animal nerve network come the mathematics of distributed variable-frequencypump information Method.The algorithm possesses powerful self-learning ability, while having stronger fault-tolerance.When carrying out failure line selection, neural network The result of several single criterions would generally be integrated consideration by method, finally select failure according to the fault measurement value size of definition Route.But the algorithm needs a learning process, a large amount of measured data is needed in learning process, and be easy by operation side The influence of formula, it is also necessary to further perfect.
In summary existing selection method there are the problem of it is as follows
1, the poor universality of failure line selection criterion, same criterion is in different systems in application, quality discrepancy is very big;
2, sensitivity is affected by system parameter, and when scale is applied compared with mini system, sensitivity cannot be met the requirements;
3, poor robustness, reliability vulnerable to such environmental effects, especially using transient state parameter as route selection criterion when it is more prominent Out.
Summary of the invention
Based on the above technical problem, the present invention proposes a kind of single-phase earthing of small current earthing system based on differential characteristic value Fault-line selecting method, the specific steps are as follows:
Step 1: construction differential type topological structure, it is specific as follows: in the equivalent insulation against ground resistance of source side connection line r0With distribution capacity c0, the insulation against ground resistance r of source side line equivalent0With distribution capacity c0It is connected in parallel, one end connects after parallel connection Source side is connect, the other end is connected with ground wire;The equivalent insulation against ground resistance r of transmission line of electricity L1 connection line1, distribution capacity c1, Transmission line of electricity L1 equivalent insulation against ground resistance r1, distribution capacity c1It is connected in parallel, one end connects transmission line of electricity L1 after parallel connection, separately One end is connected with ground wire;Transmission line of electricity L1 is connected with first compensation branch one end, the first compensation branch other end and ground wire It is connected, the first compensation branch includes the first compensation inductance SK1With the first compensating element, LK1, the first compensation inductance SK1One End is connected with transmission line of electricity L1, the other end and the first compensating element, LK1It is connected, the first compensating element, LK1It is connected with ground wire It connects;The equivalent insulation against ground resistance r of transmission line of electricity L2 connection line2, distribution capacity c2, transmission line of electricity L2 line equivalent is over the ground Insulation resistance r2, distribution capacity c2It is connected in parallel, one end connects transmission line of electricity L2 after parallel connection, and the other end is connected with ground wire;Transmission of electricity Route L2 is connected with second compensation branch one end, and the second compensation branch other end is connected with ground wire, the second compensation branch Road includes the second compensation inductance SK2With the second compensating element, LK2, the second compensation inductance SK2One end is connected with transmission line of electricity L2, The other end and the second compensating element, LK2It is connected, the second compensating element, LK2It is connected with ground wire;Transmission line of electricity L3 connection line etc. The insulation against ground resistance r of effect3, distribution capacity c3, the insulation against ground resistance r of transmission line of electricity L3 line equivalent3, distribution capacity c3And Connection connection, one end connects transmission line of electricity L3 after parallel connection, and the other end is connected with ground wire;Transmission line of electricity L3 and third compensate branch one End is connected, and the third compensation branch other end is connected with ground wire, and the third compensation branch includes third compensation inductance SK3With Third compensating element, LK3, third compensation inductance SK3One end is connected with transmission line of electricity L3, the other end and third compensating element, LK3 It is connected, third compensating element, LK3It is connected with ground wire;
Step 2: zero sequence current mutual inductor is respectively set before and after each compensation branch of transmission line of electricity L1, L2, L3 respectively, institute It states front and back zero sequence current mutual inductor measured value and is respectively as follows: HAnd H;Wherein, HFor zero sequence current mutual inductor before the i-th transmission line of electricity Measured value, HFor zero sequence current mutual inductor measured value after the i-th transmission line of electricity, i=1,2,3;
Step 3: calculating and work as route LiWhen singlephase earth fault occurs, the zero-sequence current I of earth fault is flowed throughog, i.e., respectively The sum of branch zero-sequence current;
Step 4: calculating the differential characteristic value of each branch: △ Iiαβ=H-H, wherein i=1,2,3;
Step 5: if differential characteristic value less than zero, determines the transmission line of electricity for faulty line;If differential characteristic value is greater than Zero, then determine the transmission line of electricity for non-fault line;
Advantageous effects:
For the low problem of single-phase grounded malfunction in grounded system of low current route selection poor reliability, sensitivity, a kind of difference is studied Dynamic formula fault line selection method for single-phase-to-ground fault.The criterion have to electric system it is adaptable, be able to satisfy different Contact patch and The good feature of different scales power grid, high sensitivity, selectivity can improve single-phase grounded malfunction in grounded system of low current route selection It plays a significant role in terms of reliability.It can efficiently solve and be deposited in current small grounding current system single phase grounding fault line selection technology Technical problem.
Detailed description of the invention
Fig. 1 is the single-phase ground fault line selecting method of small-electric current grounding system based on differential characteristic value of the embodiment of the present invention Flow chart;
Fig. 2 is the differential type topological structure schematic diagram of the embodiment of the present invention;
Vectogram is obtained according to each branch zero-sequence current value when Fig. 3 is the LK capacitive compensation of the embodiment of the present invention;
Vectogram is obtained according to each branch zero-sequence current value when Fig. 4 is the LK resistive compensation of the embodiment of the present invention;
Fig. 5 is that LK inductive compensation-full remuneration of the embodiment of the present invention obtains vectogram according to each branch zero-sequence current value;
Fig. 6 is that LK inductive compensation-undercompensation of the embodiment of the present invention obtains vectogram according to each branch zero-sequence current value;
Fig. 7 is that LK inductive compensation-overcompensation of the embodiment of the present invention obtains vectogram according to each branch zero-sequence current value;
Fig. 8 is the Matlab simulation model figure of the embodiment of the present invention;
Fig. 9 is three kinds of differential characteristic values of each branch of compensation way of the embodiment of the present invention, wherein Fig. 9 (a) is LK capacitive benefit The differential characteristic value of each branch is repaid, Fig. 9 (b) is the resistive each differential characteristic value of branch of compensation of LK, and Fig. 9 (c) is LK inductive compensation each The differential characteristic value in road.
Specific embodiment
Invention is described further with specific implementation example with reference to the accompanying drawing, the present invention is a kind of to be based on differential characteristic value Single-phase ground fault line selecting method of small-electric current grounding system, as shown in Figure 1, the specific steps are as follows:
Step 1: construction differential type topological structure, it is specific as follows: in the equivalent insulation against ground resistance of source side connection line r0With distribution capacity c0, the insulation against ground resistance r of source side line equivalent0With distribution capacity c0It is connected in parallel, one end connects after parallel connection Source side is connect, the other end is connected with ground wire;The equivalent insulation against ground resistance r of transmission line of electricity L1 connection line1, distribution capacity c1, Transmission line of electricity L1 equivalent insulation against ground resistance r1, distribution capacity c1It is connected in parallel, one end connects transmission line of electricity L1 after parallel connection, separately One end is connected with ground wire;Transmission line of electricity L1 is connected with first compensation branch one end, the first compensation branch other end and ground wire It is connected, the first compensation branch includes the first compensation inductance SK1With the first compensating element, LK1, the first compensation inductance SK1One End is connected with transmission line of electricity L1, the other end and the first compensating element, LK1It is connected, the first compensating element, LK1It is connected with ground wire It connects;The equivalent insulation against ground resistance r of transmission line of electricity L2 connection line2, distribution capacity c2, transmission line of electricity L2 line equivalent is over the ground Insulation resistance r2, distribution capacity c2It is connected in parallel, one end connects transmission line of electricity L2 after parallel connection, and the other end is connected with ground wire;Transmission of electricity Route L2 is connected with second compensation branch one end, and the second compensation branch other end is connected with ground wire, the second compensation branch Road includes the second compensation inductance SK2With the second compensating element, LK2, the second compensation inductance SK2One end is connected with transmission line of electricity L2, The other end and the second compensating element, LK2It is connected, the second compensating element, LK2It is connected with ground wire;Transmission line of electricity L3 connection line etc. The insulation against ground resistance r of effect3, distribution capacity c3, the insulation against ground resistance r of transmission line of electricity L3 line equivalent3, distribution capacity c3And Connection connection, one end connects transmission line of electricity L3 after parallel connection, and the other end is connected with ground wire;Transmission line of electricity L3 and third compensate branch one End is connected, and the third compensation branch other end is connected with ground wire, and the third compensation branch includes third compensation inductance SK3With Third compensating element, LK3, third compensation inductance SK3One end is connected with transmission line of electricity L3, the other end and third compensating element, LK3 It is connected, third compensating element, LK3It is connected with ground wire;
110kv following level high-voltage fence in China uses isolated neutral or grounding through arc mode, i.e. low current Earthed system.Single-phase earthing is the multiple failure in electric system, and probability of happening accounts for 80% or more of failure in system.For Meet the requirement of requirement of the power consumer to power supply reliability, especially first order load user and two stage load users, specification rule Small current neutral grounding system is scheduled on when singlephase earth fault occurs, can be operated with failure 2 hours, it in special circumstances can be with event Barrier operation 8 hours, it is therefore an objective to which realization can search fault point under conditions of operation.Quickly identification faulty line is quick lookup event Hinder the necessary condition of point, therefore, single-phase grounded malfunction in grounded system of low current route selection is the weight of Relay Protection Technology in Power System Want one of content.
In the power supply system of some special industries such as coal mine, to guarantee safety in production and personal safety, generally use small Current grounding system, to limit single-phase earth fault current.Since the singlephase earth fault in Coal Mine Power Distribution System can cause electricity Force system overvoltage, and fault electric arc is generated in leakage point of electricity, there are actuation gas and coal dust, the danger for leading to person electric shock, electric leakage The above earth potential distribution that fault current generates, there is the danger for igniting electric cap in advance.Therefore, event single-phase to power supply system in coal mine The requirement for hindering protection is higher, when phase conductor insulation against ground is reduced to certain value, that is, thinks that leak current fault has occurred, necessary at this time Implement protection, cuts off the power.But the loads such as the ventilation and draining of underground coal mine are very high to the reliability requirement of power supply, it is desirable that protecting When protection unit cuts off faulty line, the normal work of non-fault line cannot be influenced, i.e., claimed device should have good Selectivity.
The low reliability of single-phase grounded malfunction in grounded system of low current route selection is always the protrusion for perplexing failure line selection Problem, domestic and foreign scholars have made a large amount of research work to this, also achieve many valuable achievements, but these achievements are being answered Used time has limitation more, and good technical performance is shown in particular system, in the system of another structure or scale Reliability, sensitivity and selectivity cannot all be met the requirements, and malfunction can be also generated under individual cases and causes fault incidence Expansion, influence power supply reliability.
Differential type single-phase grounded malfunction in grounded system of low current route selection technology is a kind of difference after being based on ground fault generation The fault-line selecting method of sampled point metastable state signal difference needs to be added one in major loop to guarantee that the difference has identifiability Quantitative compensation original part constructs as shown in Figure 2 by 3 transmission line of electricity L1、L2、L3The topological structure of composition, the structure is at every The compensation branch being made of SK and LK, r is added in the head end of distribution network transmission lineiAnd ciWhat is indicated is the insulated electro of line-to-ground Resistance and distribution capacity, respectively install a zero sequence current mutual inductor H before and after compensating branchAnd H, realize zero before and after compensation branch Sequence current measurement value generates difference, realizes the identification to failure according to the feature of difference.Due to the difference of two mutual inductors output electric current It is different to be determined completely by compensating parameter, therefore, it can be achieved that fault identification accuracy rate up to 100%.
Step 2: zero sequence current mutual inductor is respectively set before and after each compensation branch of transmission line of electricity L1, L2, L3 respectively, institute It states front and back zero sequence current mutual inductor measured value and is respectively as follows: HAnd H;Wherein, HFor zero sequence current mutual inductor before the i-th transmission line of electricity Measured value, HFor zero sequence current mutual inductor measured value after the i-th transmission line of electricity, i=1,2,3;
Step 3: calculating and work as route LiWhen singlephase earth fault occurs, the zero-sequence current I of earth fault is flowed throughog, i.e., respectively The sum of branch zero-sequence current;
In the present embodiment, as route L3When singlephase earth fault occurs, according to zero-sequence current feature it is found that flowing through ground connection event Hinder the zero-sequence current I of pointogIt is the sum of each branch zero-sequence current, i.e. Iog=I1LK+IO1N+I2LK+IO2N+I3LK+IO3N;I1LK、I2LK、 I3LKIt is route L respectively1、L2、L3The zero-sequence current flowed through through artificial neutral point, IO1N、IO2N、IO3NIt is route L respectively1、L2、L3Stream Cross the sum of insulation against ground resistance and capacitance current.Each branch zero sequence current mutual inductor HijCurrent measured value is as shown in table 1, I is transmission line of electricity serial number.
1 zero sequence current mutual inductor measured value of table
Step 4: calculating the differential characteristic value of each branch: △ Iiαβ=H-H, wherein i=1,2,3;
Obtain leak current fault electric current i at each zero sequence current mutual inductor1And i2Changing rule, pass through i=i1-i2, it is poor to analyze The changing rule of dynamic fault current.
The difference of adjacent current mutual inductor measuring magnitude is defined as zero sequence current differential protection characteristic value, is indicated with △ I.Each branch is differential Characteristic value is as shown in table 2.
The 2 differential characteristic value of each branch of table
It is analyzed according to Tables 1 and 2 it is found that in non-fault line, the electric current that each zero sequence current mutual inductor flows through is thereafter The sum of side line road zero-sequence current, when singlephase earth fault occurs for route section, each zero sequence current mutual inductor institute before fault point Surveying current value will change, and the current value of zero sequence current mutual inductor at adjacent two be made the difference, faulty line and non-fault line Difference is different, it can selects faulty line.
Step 5: if differential characteristic value less than zero, determines the transmission line of electricity for faulty line;If differential characteristic value is greater than Zero, then determine the transmission line of electricity for non-fault line;
1) by changing the property (R, L, C) and size of compensating element, LK, under the conditions of analyzing various compensating parameters, i1And i2 Changing rule and current in the fault point i feature.
According to the difference of compensation branch property, it is divided into capacitive compensation, resistive compensation and three kinds of compensation ways of inductive compensation, In the case of middle inductive compensation, and exists and be fully compensated, three kinds of states of undercompensation and overcompensation.Using vector diagram analysis method, divide Analysing compensation branch of different nature has He Yitong to faulty line and the differential characteristic value influence of non-fault line, obtains different choosings Line criterion.
(1)LKiWhen for capacitive compensation, IiLKIt is capacitive, IOiNIt is capacitance-resistance, IONIt is capacitance-resistance, IOiIt is IiLKAnd IOiNThe sum of, So IOiIt is also capacitance-resistance, the vectogram such as Fig. 3 is obtained according to each branch zero-sequence current value.
Criterion 1:
When LK is capacitive compensation, faulty line L3Differential characteristic value △ I3< 0, non-fault line L1、L2Differential characteristic value △ Ii >0。
(2)LKiWhen for resistive compensation, IiLKIt is resistive, IOiNIt is capacitance-resistance, IONIt is capacitance-resistance, IOiIt is IiLKAnd IOiNThe sum of, So IOiIt is also capacitance-resistance.The vectogram such as Fig. 4 is obtained according to each branch zero-sequence current value.
Criterion 2:
LKiWhen for resistive compensation, faulty line L3Differential characteristic value △ I3< 0, non-fault line L1、L2Differential characteristic value △ Ii>0。
(3)LKiWhen for inductive compensation, full remuneration can be divided into according to offset size, undercompensation and three kinds of overcompensation Situation.
When a) being fully compensated, IiLKIt is perception, IOiNIt is capacitance-resistance, IONIt is capacitance-resistance, IOiIt is IiLKAnd IOiNThe sum of, because complete Full compensation, i.e. perception are offset with capacitive, so IOiBe it is resistive, the vectogram such as Fig. 5 is obtained according to each branch zero-sequence current value.
B) when undercompensation, IiLKIt is perception, IOiNIt is capacitance-resistance, IONIt is capacitance-resistance, IOiIt is IiLKAnd IOiNThe sum of, because of underfill It repays, so IOiIt is capacitance-resistance, the vectogram such as Fig. 6 is obtained according to each branch zero-sequence current value.
C) when overcompensation, IiLKIt is perception, IOiNIt is capacitance-resistance, IONIt is capacitance-resistance, IOiIt is IiLKAnd IOiNThe sum of, because of overfill It repays, so IOiIt is resistance sense capacitive, the vectogram such as Fig. 7 is obtained according to each branch zero-sequence current value.
Criterion 3:
LKiWhen for inductive compensation, no matter in being fully compensated, undercompensation or overcompensation state, faulty line L3It is differential Characteristic value △ I3< 0, non-fault line L1、L2Differential characteristic value △ Ii>0。
5) neutral point in electric power system isolated neutral system simulation model is built using Matlab/Simulink, verifies differential choosing Line principle feasibility, simulation model are as shown in Figure 8.
Successively by LKiIt is arranged to three kinds of compensation ways to be emulated, obtains differential characteristic value simulation result shown in Fig. 9.
By simulation result it is found that the differential characteristic value of non-fault line is all larger than 0 under three kinds of compensation ways, faulty line is differential Characteristic value is consistent less than 0 with criterion, can determine faulty line and non-fault line.In physical fault, abort situation, Ground resistance, line parameter circuit value can have an impact route selection result, therefore influence to carry out simulating, verifying to various failures.Emulate route selection As the result is shown can correct decision be out of order route.
Different compensation ways are different to the influence for flowing into current in the fault point, and inflow current in the fault point is excessive, will increase personnel The risk of electric shock also results in restriking for ground-fault arc, generates power supply system transient effect, may especially cause system System resonance, generates higher overvoltage, simulates different compensating parameters using simulation model, analyzes to power supply system safety shadow It rings, the results are shown in Table 3 for partial simulation:
3 compensating parameter of table and simulation result
To meet power system security, capacitive compensation parameter should be less than 23uF, and resistive compensating parameter should be greater than 52 Ω, sense Property compensating parameter should be greater than 0.265H, while be also contemplated that economy in the premise for meeting safety.
6) electric system of neutral-piont earth free model is built, as shown in Figure 2.
With capacitance simulation line-to-ground distribution capacity.With the ground resistance of resistance simulation singlephase earth fault;Construction is artificial Neutral point accesses compensating element, LK in neutral pointi, zero sequence current mutual inductor is added in neutral point front and back;Adjust compensating element, LKi's Parameter observes the influence of compensating element,;It adjusts distribution parameter (C), observes the influence of power grid scale;Regulated ground resistance sizes (zero to specified value) observes the influence of ground connection degree, surveys zero-sequence current I before and after artificial neutral point repeatedly1And I2Changing rule. Can analysis accurately determine faulty line and non-fault line.It is as shown in table 4 to record some experimental data.
4 experimental data of table
According to analysis of experimental data, no matter which kind of compensation way regardless of compensating parameter is all satisfied non-faulting line The differential characteristic value in road is greater than 0, and the differential characteristic value of faulty line is identical as theory analysis and simulation analysis result less than 0, therefore this Single-phase ground fault line selecting method of small-electric current grounding system of the kind based on differential characteristic value can accurately select faulty line.

Claims (3)

1. a kind of single-phase ground fault line selecting method of small-electric current grounding system based on differential characteristic value, which is characterized in that specific Steps are as follows:
Step 1: construction differential type topological structure, it is specific as follows: in the equivalent insulation against ground resistance r of source side connection line0With point Cloth capacitor c0, the insulation against ground resistance r of source side line equivalent0With distribution capacity c0It is connected in parallel, one end connects power supply after parallel connection Side, the other end are connected with ground wire;The equivalent insulation against ground resistance r of transmission line of electricity L1 connection line1, distribution capacity c1, power transmission line Road L1 equivalent insulation against ground resistance r1, distribution capacity c1Be connected in parallel, it is in parallel after one end connect transmission line of electricity L1, the other end with Ground wire is connected;Transmission line of electricity L1 is connected with first compensation branch one end, and the first compensation branch other end is connected with ground wire, The first compensation branch includes the first compensation inductance SK1With the first compensating element, LK1, the first compensation inductance SK1One end and transmission of electricity Route L1 is connected, the other end and the first compensating element, LK1It is connected, the first compensating element, LK1It is connected with ground wire;Power transmission line The equivalent insulation against ground resistance r of road L2 connection line2, distribution capacity c2, the insulation against ground resistance of transmission line of electricity L2 line equivalent r2, distribution capacity c2It is connected in parallel, one end connects transmission line of electricity L2 after parallel connection, and the other end is connected with ground wire;Transmission line of electricity L2 with Second compensation branch one end is connected, and the second compensation branch other end is connected with ground wire, and the second compensation branch includes the Two compensation inductance SK2With the second compensating element, LK2, the second compensation inductance SK2One end is connected with transmission line of electricity L2, the other end with Second compensating element, LK2It is connected, the second compensating element, LK2It is connected with ground wire;Transmission line of electricity L3 connection line is equivalent over the ground Insulation resistance r3, distribution capacity c3, the insulation against ground resistance r of transmission line of electricity L3 line equivalent3, distribution capacity c3It is connected in parallel, and One end connects transmission line of electricity L3 after connection, and the other end is connected with ground wire;Transmission line of electricity L3 is connected with third compensation branch one end, The third compensation branch other end is connected with ground wire, and the third compensation branch includes third compensation inductance SK3It is compensated with third Element LK3, third compensation inductance SK3One end is connected with transmission line of electricity L3, the other end and third compensating element, LK3It is connected, the Three compensating element, LK3It is connected with ground wire;
Step 2: zero sequence current mutual inductor is respectively set before and after each compensation branch of transmission line of electricity L1, L2, L3 respectively, before described Zero sequence current mutual inductor measured value is respectively as follows: H afterwardsAnd H;Wherein, HIt is measured for zero sequence current mutual inductor before the i-th transmission line of electricity Value, HFor zero sequence current mutual inductor measured value after the i-th transmission line of electricity, i=1,2,3;
Step 3: calculating and work as route LiWhen singlephase earth fault occurs, the zero-sequence current I of earth fault is flowed throughog, i.e., each branch The sum of zero-sequence current;
Step 4: calculating the differential characteristic value of each branch: △ Iiαβ=H-H, wherein i=1,2,3;
Step 5: if differential characteristic value less than zero, determines the transmission line of electricity for faulty line;If differential characteristic value is greater than zero, Determine the transmission line of electricity for non-fault line.
2. the single-phase ground fault line selecting method of small-electric current grounding system according to claim 1 based on differential characteristic value, It is characterized in that, the step 5 specifically: first compensating element, the second compensating element, and third compensating element, are capacitive When compensation, if differential characteristic value less than zero, determines the transmission line of electricity for faulty line;If differential characteristic value is greater than zero, sentence The fixed transmission line of electricity is non-fault line;
When first compensating element, the second compensating element, and third compensating element, are resistive compensation, if differential characteristic value is small In zero, then determine the transmission line of electricity for faulty line;If differential characteristic value is greater than zero, determine the transmission line of electricity for non-faulting line Road;
When first compensating element, the second compensating element, and third compensating element, are capacitive compensation, if differential characteristic value is small In zero, then determine the transmission line of electricity for faulty line;If differential characteristic value is greater than zero, determine the transmission line of electricity for non-faulting line Road;
When first compensating element, the second compensating element, and third compensating element, are inductive compensation, if differential characteristic value is small In zero, then determine the transmission line of electricity for faulty line;If differential characteristic value is greater than zero, determine the transmission line of electricity for non-faulting line Road.
3. the single-phase ground fault line selecting method of small-electric current grounding system according to claim 2 based on differential characteristic value, It is characterized in that, when first compensating element, the second compensating element, and third compensating element, are inductive compensation, specifically: the One compensating element, the second compensating element, and third compensating element, are inductive compensation and are when being fully compensated, if differential characteristic value Less than zero, then determine the transmission line of electricity for faulty line;If differential characteristic value is greater than zero, determine the transmission line of electricity for non-faulting Route;
When first compensating element, the second compensating element, and third compensating element, are inductive compensation and are undercompensation, if differential spy Value indicative then determines the transmission line of electricity for faulty line less than zero;If differential characteristic value is greater than zero, determine that the transmission line of electricity is non- Faulty line;
When first compensating element, the second compensating element, and third compensating element, are inductive compensation and are overcompensation, if differential spy Value indicative then determines the transmission line of electricity for faulty line less than zero;If differential characteristic value is greater than zero, determine that the transmission line of electricity is non- Faulty line.
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