CN110045232B - Method for identifying ground fault phase of neutral point non-effective grounding system - Google Patents
Method for identifying ground fault phase of neutral point non-effective grounding system Download PDFInfo
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Abstract
The invention discloses a method for identifying a ground fault phase of a neutral point non-effective grounding system, which specifically comprises the following steps: (1) obtaining corresponding voltage amplitude and phase by performing FFT calculation on the three-phase voltage signal sampled in real time; (2) taking the number of fixed sampling points, and carrying out mean value smoothing treatment on the three-phase voltage amplitude and the three-phase voltage phase; (3) obtaining single-change state values of three-phase voltage amplitude and phase by adopting a special synchronization mechanism; (4) the fault phase can be determined by comprehensively judging the amplitude of the three-phase voltage to earth and the single-time change state value of the phase, so that the accuracy and the real-time performance of fault phase detection are greatly improved. The invention relates to the technical field of power distribution network systems, solves the problems of influence and misjudgment on fault phase detection caused by oscillation of three-phase voltage to earth due to the change of earth resistance at the moment of earthing of a fault phase and in the process of earthing, and can quickly and accurately judge the fault phase under any earthing impedance and three-phase unbalanced state.
Description
Technical Field
The invention relates to the technical field of power distribution systems, in particular to a method for identifying a ground fault phase of a neutral point non-effective grounding system.
Background
The voltage class of the power distribution network above 6kV is more than 95 percent and all the power distribution network operates in a neutral point non-effective grounding mode, most of power failure faults are caused by grounding, the loss is thousands of billions of yuan each year, the accuracy and the sensitivity of system ground fault phase identification are greatly influenced by grounding resistance, the change range of the grounding resistance is large and ranges from dozens of ohms to dozens of kiloohms, the existing ground fault phase identification technology is difficult to adapt to the grounding resistance which changes in such a large range, particularly, the sensing is difficult and misjudgment is easy to generate under the conditions that the ground parameters of a power grid are unbalanced and high-resistance grounding faults, the high-efficiency and accurate fault phase identification is difficult to realize, if the ground fault phase cannot be accurately judged in time, the ground fault cannot be processed in the first time, the insulation breakdown is caused for a long time, the arc overvoltage is generated, the phase short circuit is caused, and, even the accidents of 'fire burning and continuous operation' are caused.
Referring to chinese patent publication No. CN109085450A, a method and an apparatus for selecting a phase of a small current grounding system fault are disclosed, which provide a method and an apparatus for selecting a phase of a small current grounding system fault by obtaining a zero sequence voltage and each phase-to-ground voltage of the small current grounding system, and obtaining a state of the small current grounding system according to the zero sequence voltage, determining a sequence of voltage step change information values according to each phase-to-ground voltage when the state of the small current grounding system is in a ground fault state, and finally determining a phase of a ground fault according to the sequence of voltage step change information values, specifically obtaining a neutral grounding mode information value when only one phase information value in the sequence of step change information values is a second value (represented by 1), and obtaining a second value (represented by 1) obtained by the step change of each phase-to-ground voltage when the neutral grounding mode information value is the first value (represented by 0); when the neutral point grounding mode information value is a second numerical value (represented by 1), the right phase of the corresponding line of the second numerical value (represented by 1) obtained according to the sudden change of the relative ground voltage is a ground fault phase, the neutral point grounding mode information value is determined according to the grounding mode of the system, and when the grounding mode of the system is a neutral point ungrounded mode or an arc suppression coil is in under-compensated grounding, the neutral point grounding mode information value is the second numerical value (represented by 1); when the grounding mode of the system is arc suppression coil overcompensation grounding, the information value of the neutral point grounding mode is a first value (indicated by 0), and the patent has the following defects through analysis:
(1) in addition, after the fault is grounded, the grounding resistance can be broken down and recovered along with insulation, and the burning condition of an electric arc randomly changes, so that the three-phase voltage can oscillate in the process, the wrong voltage mutation information value sequence is easily obtained, and the fault phase identification error is caused, therefore, the patent adopts the method for obtaining the voltage mutation information value sequence for multiple times to prevent misjudgment, and the process is as follows: when the system is still in a ground fault state, acquiring a voltage mutation information value sequence at intervals, for example: the period of time may be 0.5 second, and then the consecutive occurrence times of the same voltage mutation amount information value sequence are obtained, and when the voltage mutation amount information value sequences obtained by the consecutive preset times are the same, it indicates that the obtained voltage mutation amount information value sequence is a stable sequence, and may be used as a basis for determining a fault phase, for example: the preset times can be five, when the continuous occurrence times of the voltage mutation quantity information value sequence is five, the voltage mutation quantity information value sequence is considered to be a stable sequence, otherwise, the voltage mutation quantity information value sequence is obtained again and counted again, so that the fault phase identification method has great time delay, after the ground resistor is required to be stabilized, the three-phase ground voltage must not oscillate in the sampling period of the continuous 5-time (0.5 second each time) voltage mutation information value sequence to judge the fault phase, and in the actual fault grounding process, particularly in the arc burning process, the ground resistor is possibly in a changing state all the time, so that the three-phase ground voltage is in an oscillating state for a long time, and under the condition, the fault phase identification method disclosed by the patent can be invalid;
(2) the method only uses three-phase voltage-to-ground information as a basis for judging the fault phase, the information quantity is insufficient, and misjudgment is easily caused under the states of sudden change of a line load and sudden change of three-phase imbalance.
Referring to Chinese patent publication No. CN108957223A, it is disclosed that the identification of the ground phase of the under-compensated single-phase high-voltage earth fault of the power distribution network is illegal, by comparing the amplitude and phase of the zero-sequence voltage of the single-phase earth fault of the power distribution network with the amplitude and phase of the zero-sequence voltage during normal operation, the amplitude-phase change characteristic of the zero-sequence voltage during fault is obtained, and then the amplitude-phase change characteristic is compared with the amplitude-phase change law of the zero-sequence voltage during the single-phase earth fault of A, B, C three-phase, and the single-phase earth fault phase is identified based on the zero-sequence voltage change law when the fault characteristic satisfies the ground fault of a certain phase.
Disclosure of Invention
Technical problem to be solved
Aiming at the defects of the prior art, the invention provides a method for identifying a ground fault phase of a neutral point non-effective grounding system, which solves the problems that the existing method has poor real-time performance of fault phase identification, is easy to misjudge and is difficult to realize efficient and accurate fault phase identification under the conditions of ground resistance change, sudden change of line load and three-phase imbalance during fault.
(II) technical scheme
In order to achieve the purpose, the invention is realized by the following technical scheme: a method for identifying a ground fault phase of a neutral point non-effective grounding system specifically comprises the following steps:
s1, obtaining corresponding voltage amplitudes Uat, Ubt and Uct and phases theta at, theta bt and theta ct after FFT calculation;
s2, taking fixed sampling points, carrying out mean value smoothing processing on three-phase voltage amplitudes Uat, Ubt and Uct and phases theta at, theta bt and theta ct, and storing the mean values as Uar, Ubr, Ucr, theta ar, theta br and theta cr in real time;
s3, when the absolute values of the differences between the instantaneous three-phase voltage amplitude Uat, Ubt, Uct and the phase position theta at, theta bt, theta ct and the mean value Uar, Ubr, Ucr and the difference between the mean value theta ar, theta br, theta cr stored in the last step S2 are respectively larger than the set values, delta is calculated1And1setting the last mean value as the voltage amplitude Ua0, Ub0 and Uc0 and the phase theta a0, theta b0 and theta c0 before the fault, and setting the flag bits group U and group theta to be 1;
s4, when the absolute values of the differences between the current instantaneous three-phase voltage amplitude Uat, Ubt, Uct and the phase position theta at, theta bt, theta ct and the mean value Uar, Ubr, Ucr and the difference between the mean value theta ar, theta br and theta cr stored in the last step S2 are respectively smaller than the set numerical value, delta2And2and when the flag bits group U and group theta are 1, setting the flag bits GNDU and GND theta to 1, and simultaneously judging whether the three-phase voltage and phase mean values Uar, Ubr, Ucr and theta ar, theta br and theta cr are respectively greater than the voltage amplitude and the phases before the fault Ua0, Ub0, Uc0 and theta 0Theta a0, theta B0 and theta C0, if the amplitude flags are larger than the phase flags, the corresponding amplitude flags Au, Bu and Cu and the corresponding phase flags A theta, B theta and C theta are set to be 1, and if the amplitude flags are not larger than the phase flags, the phase flags A theta, B theta and C theta are set to be 0;
s5, when GNDU and GND θ are 1:
when Au is equal to 0, Bu is equal to 1 and Cu is equal to 1, judging that the fault phase is an A phase;
when Au is 1, Bu is 0 and Cu is 0, judging the fault phase as B phase;
and when Au is equal to 1, Bu is equal to 1 and Cu is equal to 0, judging that the fault phase is the C phase.
Preferably, in step S1, the system only needs to sample the three-phase voltages Ua, Ub, Uc, and the three-phase voltages Ua, Ub, Uc may be represented as follows:
preferably, the flag bits group u and group θ in step S3 are used for logic synchronization.
Preferably, in step S5, the failed phase is determined to be the a phase when Au is 0, Bu is 0, and Cu is 1, if a θ is 1, B θ is 0, and C θ is 0, the failed phase is determined to be the B phase if a θ is 0, B θ is 1, and C θ is 0, the failed phase is determined to be the a phase when a θ, B θ, and C θ are in other states, the failed phase is determined to be the a phase when Uat < Ubt, and the failed phase is determined to be the B phase when Ubt < Uat.
Preferably, in step S5, the failed phase is determined to be the B-phase when Au is equal to 1, Bu is equal to 0, and Cu is equal to 0, if a θ is equal to 0, B θ is equal to 1, and C θ is equal to 0, the failed phase is determined to be the C-phase if a θ is equal to 0, B θ is equal to 0, and C θ is equal to 1, and the failed phase is determined to be the B-phase when Ubt < Uct and the failed phase is determined to be the C-phase when Uct < Ubt.
Preferably, in step S5, the failed phase is determined to be the a phase when Au is 0, Bu is 1, and Cu is 0, if a θ is 1, B θ is 0, and C θ is 0, the failed phase is determined to be the C phase if a θ is 0, B θ is 0, and C θ is 1, the failed phase is determined to be the a phase when a θ, B θ, and C θ are in other states, the failed phase is determined to be the a phase when Uat < Uct, and the failed phase is determined to be the C phase when Uct < Uat.
(III) advantageous effects
The invention provides a method for identifying a ground fault phase of a neutral point non-effective grounding system. Compared with the prior art, the method has the following beneficial effects:
(1) the method for identifying the ground fault phase of the neutral point non-effective grounding system comprises the following steps: s1, obtaining corresponding voltage amplitudes Uat, Ubt, Uct and phases theta at, theta bt, theta ct after FFT calculation, S2, taking fixed sampling points, carrying out averaging smoothing treatment on the three-phase voltage amplitudes Uat, Ubt, Uct and phases theta at, theta bt, theta ct, and storing the average values as Uar, Ubr, Ucr, theta ar, theta br, theta cr in real time, S3, when detecting that the instantaneous three-phase voltage amplitudes Uat, Ubt, Uct and phases theta at, theta bt, theta ct values and the average values Uar, Ubr, Ucr and theta ar, theta br, theta cr stored in the last step S2 are respectively greater than set values delta 1 and 1, setting the average value of the last time as the voltage before fault Ua0, Ub0, Uc0 and phases theta a0, theta b 2 c, theta 0, theta 23, theta rd, theta # 493, theta rd, theta # 4 and theta r, and the instantaneous three-phase voltage amplitudes before fault are detected, theta at, theta b # 3 and theta rd, theta # 1 and theta # 4, When absolute values of differences between θ bt and θ ct and the mean values Uar, Ubr, Ucr and θ ar, θ br and θ cr stored in the previous step S2 are respectively smaller than set values δ 2 and 2, and when flag bits group u and group θ are 1, setting flag bits GNDU and GND θ to 1, and simultaneously determining whether the three-phase voltage and phase mean values Uar, Ubr, Ucr and θ ar, θ br and θ cr are respectively larger than voltage amplitude before failure and phases Ua0, Ub0, Uc0, θ a0, θ B0 and θ C0, if so, setting corresponding amplitude flags Au, Bu, Cu and phase flags a θ, B θ and C θ to 1, otherwise, setting 0, S5, when GNDU and θ are 1: when Au is equal to 0, Bu is equal to 1 and Cu is equal to 1, the fault phase is judged to be an A phase, when Au is equal to 1, Bu is equal to 0 and Cu is equal to 0, the fault phase is judged to be a B phase, when Au is equal to 1, Bu is equal to 1 and Cu is equal to 0, the fault phase is judged to be a C phase, and the problems that the fault phase is connected to the ground instantly and in the grounding process, the three phases oscillate to the ground voltage due to the change of the ground resistance, the three phases are unbalanced due to the sudden change of the single-phase load in the power grid, and the influence and the misjudgment on the fault phase detection can be well solved.
(2) According to the method for identifying the ground fault phase of the neutral point non-effective grounding system, a special synchronization mechanism is adopted to obtain the single change state values of the three-phase voltage amplitude and the phase, the fault phase can be determined only by comprehensively judging the single change state values of the three-phase voltage amplitude and the phase, the accuracy and the real-time performance of fault phase detection are greatly improved, and the fault phase can be rapidly and accurately judged under any grounding impedance and three-phase unbalanced state.
Drawings
FIG. 1 is a circuit diagram of an electrical power system according to the present invention;
FIG. 2 is a flow chart of the present invention;
FIG. 3 is a data table diagram for determining a fault phase according to three phase-to-ground voltage amplitude and phase information flag bits Au, Bu, Cu, and A θ, B θ, and C θ;
FIG. 4 is a flow chart of the working conditions of the amplitude marks Au, Bu, Cu and the phase marks A theta, B theta, C theta of the present invention;
FIG. 5 is a simulation experiment statistical chart of instantaneous three-phase voltage amplitudes Uat, Ubt and Uct, mean values Uar, Ubr and Ucr and amplitude marks Au, Bu and Cu when the grounding resistance is set to 10 ohms;
FIG. 6 is a statistical chart of simulation experiments of instantaneous phases θ at, θ bt, θ ct when the ground resistance of the present invention is set to 10 ohms;
FIG. 7 is an experimental simulation diagram of the influence of three-phase unbalance on three-phase voltage-to-ground amplitudes caused by sudden changes of single-phase loads of the power grid according to the invention;
fig. 8 is an experimental simulation diagram of the influence of three-phase unbalance on three-phase voltage-to-ground voltage phases caused by sudden change of single-phase load of the power grid.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1 to 8, an embodiment of the present invention provides a technical solution: a method for identifying a ground fault phase of a neutral point non-effective grounding system specifically comprises the following steps:
s1, obtaining corresponding voltage amplitudes Uat, Ubt, Uct and phases theta at, theta bt, theta ct after FFT calculation, wherein the system only needs to sample three-phase ground voltages Ua, Ub, Uc, and the three-phase ground voltages Ua, Ub, Uc can be expressed as follows:
s2, taking fixed sampling points, carrying out mean value smoothing processing on three-phase voltage amplitudes Uat, Ubt and Uct and phases theta at, theta bt and theta ct, and storing the mean values as Uar, Ubr, Ucr, theta ar, theta br and theta cr in real time;
s3, when the absolute values of the differences between the instantaneous three-phase voltage amplitude Uat, Ubt, Uct and the phase position theta at, theta bt, theta ct and the mean value Uar, Ubr, Ucr and the difference between the mean value theta ar, theta br, theta cr stored in the last step S2 are respectively larger than the set values, delta is calculated1And1when the voltage is in fault, setting the last mean value as the voltage amplitude Ua0, Ub0, Uc0 and the phase theta a0, theta b0 and theta c0 before the fault, setting the flag bits group U and group theta to be 1, and using the flag bits group U and group theta for logic synchronization;
s4, when the absolute values of the differences between the current instantaneous three-phase voltage amplitude Uat, Ubt, Uct and the phase position theta at, theta bt, theta ct and the mean value Uar, Ubr, Ucr and the difference between the mean value theta ar, theta br and theta cr stored in the last step S2 are respectively smaller than the set numerical value, delta2And2when the flag bits group U and group theta are 1, setting the flag bits GNDU and GND theta to 1, simultaneously judging whether the three-phase voltage and phase mean values Uar, Ubr, Ucr and theta ar, theta br and theta cr are respectively greater than the voltage amplitude and the phases Ua0, Ub0, Uc0 and theta a0, theta B0 and theta C0 before the fault, if so, setting the corresponding amplitude flags Au, Bu and Cu and the phase flags A theta, B theta and C theta to 1, otherwise, setting 0;
s5, when GNDU and GND θ are 1:
when Au is equal to 0, Bu is equal to 1 and Cu is equal to 1, judging that the fault phase is an A phase;
when Au is 1, Bu is 0 and Cu is 0, judging the fault phase as B phase;
when Au is equal to 1, Bu is equal to 1, Cu is equal to 0, the failed phase is determined to be a C-phase, when Au is equal to 0, Bu is equal to 0, and Cu is equal to 1, if a θ is equal to 1, B θ is equal to 0, and C θ is equal to 0, the failed phase is determined to be a-phase, if a θ is equal to 0, B θ is equal to 1, and C θ is equal to 0, the failed phase is determined to be a B-phase, when a θ, B θ, and C θ are in other states, when Uat < Ubt, the failed phase is determined to be a-phase, when Ubt < Uat, the failed phase is determined to be B-phase, when Au is equal to 1, Bu is equal to 0, Cu is equal to 0, if a θ is equal to 0, B θ is equal to 1, C θ is equal to 0, the failed phase is determined to be B-phase, if a θ is equal to 0, B θ is equal to 0, when a θ is equal to 0, the failed phase is determined to B630, when a θ is equal to 0, the failed phase is equal to B3, the C is equal to 3, the failed phase is determined to be a-phase, the C is equal to be B-phase, the C-phase is determined to be B-phase, the failed phase is equal to 3, the failed phase is equal to be B-phase, the C-phase is equal to 0, the C-phase, the failed phase is determined to be B-phase, the failed phase is equal to be B-phase, the C-phase is equal to 3, the C-phase is equal to be B-phase, the failed phase, the C-phase is equal to 0, the failed phase, the C-phase is equal to be a-phase is determined to 0, the C-phase is determined to be a-phase, and the failed phase is determined to be B-phase, the failed phase is equal to be B-phase, the failed phase is equal to 3, the failed phase is equal to be B-phase, the failed phase, and the failed phase is equal to 0, the failed phase is equal to the C-phase is equal to the failed phase is equal to be B-phase is equal to be the failed phase, and the failed phase is equal to be the failed phase, and the phase is equal to be the failed phase, the fault state of Uct, the fault state of, Bu is 1, Cu is 0, if A theta is 1, B theta is 0, C theta is 0, the fault phase is judged to be A phase, if A theta is 0, B theta is 0, C theta is 1, the fault phase is C phase, if A theta, B theta and C theta are in other states, Uat is < Uct, the fault phase is A phase, and Uct is < Uat, the fault phase is C phase. Simulation of experiment
As can be seen from fig. 5 and fig. 6, the method of the present invention simulates setting a Phase fault at 0.4s, setting the Ground resistance to 10 ohms, seeing that at the Ground moment, A, B, C the amplitudes Uat, Ubt, Uct and phases thetaat, thetabt, thetact of the three phases to the Ground voltage have obvious oscillation, obtaining Uar, Ubr, Ucr and thetar, thetabr, thetacr by averaging smooth filtering, thereby eliminating the influence of signal oscillation, synchronously triggering the three phases to the Ground voltage amplitude and Phase information flags Au, Bu, Cu and a theta, C theta by using the synchronization technique, avoiding the erroneous outputs of Phase selection results a _ Phase _ group, B _ Phase _ group, C _ Phase _ group caused by the signals, wherein three signals a _ Phase _ group, B _ Phase _ group, C _ Phase _ group represent the fault state of A, B, C, and the output result is 1 Phase fault state of the three phases representing A, B, C Phase fault state, a value of 0 indicates that the phase is a non-fault phase, and in a low grounding resistance (10 ohms) state, only 0.04 second is needed from the start of fault grounding to the completion of fault phase selection, and the phase selection can be successfully completed only by once judgment.
According to the simulation result of the method, an A-Phase fault is set at 0.4s, the Ground resistance is set to 10 kilo-ohms, the amplitudes Uat, Ubt and Uct and the phases theta at, theta bt and theta ct of A, B, C three-Phase Ground voltage oscillate more violently in a high Ground resistance state, the influence of signal oscillation can be eliminated well through mean value smoothing filtering, and the fault Phase discrimination results of A _ Phase _ group being 1, B _ Phase _ group being 0 and C _ Phase _ group being 0 are successfully realized by integrating the amplitudes and Phase information flag bits Au, Bu, Cu, A theta, B theta and C theta of the three-Phase Ground voltage.
The table of fig. 3 shows how to judge the fault phase according to the amplitude and phase information flag bits Au, Bu, Cu of the three-phase voltage-to-ground voltage and a θ, B θ, and C θ, where the symbol indicates either 0 or 1.
As can be seen from fig. 7 and 8, according to the influence of three-phase imbalance caused by sudden change of the single-phase load of the power grid on the amplitude and phase of the three-phase voltage to ground, it can be seen that, when the single-phase load of the power grid suddenly changes (so that the load of the C phase suddenly increases), B, C both changes the amplitude and phase of the two phases, but the amplitude and phase of the a phase are not affected, whereas the six conditions of | Uat-Uar | > δ 1, | Ubt-Ubr | > δ 1, | Uct-Ucr | > δ 1, | θ at- θ ar | > δ 1, | θ bt- θ br | > δ 1, | θ ct- θ cr | > δ 1 must be satisfied at the same time to determine that a ground fault occurs, so that the anti-interference capability of the fault phase identification system is greatly enhanced by the present invention.
As can be seen from the simulation results, even under such severe conditions, the phase selection can be performed rapidly and correctly, only 0.358 seconds is needed from the start of the fault grounding to the completion of the fault phase selection, and the phase selection can be successfully performed only by one judgment2And2the phase selection sensitivity is set by parameters, the lower the two parameters are set, the longer the phase selection time is, and conversely, the larger the parameters are set, the higher the sensitivity is, and the shorter the phase selection time is.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (6)
1. A method for identifying a ground fault phase of a neutral point non-effective grounding system is characterized by comprising the following steps: the method specifically comprises the following steps:
s1, obtaining corresponding voltage amplitudes Uat, Ubt and Uct and phases theta at, theta bt and theta ct after FFT calculation;
s2, taking fixed sampling points, carrying out mean value smoothing processing on three-phase voltage amplitudes Uat, Ubt and Uct and phases theta at, theta bt and theta ct, and storing the mean values as Uar, Ubr, Ucr, theta ar, theta br and theta cr in real time;
s3, when the absolute values of the differences between the instantaneous three-phase voltage amplitude Uat, Ubt, Uct and the phase position theta at, theta bt, theta ct and the mean value Uar, Ubr, Ucr and the difference between the mean value theta ar, theta br, theta cr stored in the last step S2 are respectively larger than the set values, delta is calculated1And λ1Setting the last mean value as the voltage amplitude Ua0, Ub0 and Uc0 and the phase theta a0, theta b0 and theta c0 before the fault, and setting the flag bits group U and group theta to be 1;
s4, when the absolute values of the differences between the current instantaneous three-phase voltage amplitude Uat, Ubt, Uct and the phase position theta at, theta bt, theta ct and the mean value Uar, Ubr, Ucr and the difference between the mean value theta ar, theta br and theta cr stored in the last step S2 are respectively smaller than the set numerical value, delta2And λ2And is markedWhen the flag bits Ground U and Ground theta are 1, setting the flag bits GNDU and GND theta to 1, simultaneously judging whether the three-phase voltages and the phase mean values Uar, Ubr, Ucr and theta ar, theta br and theta cr are respectively greater than the voltage amplitude and the phases Ua0, Ub0, Uc0 and theta a0, theta B0 and theta C0 before the fault, if so, setting the corresponding amplitude flags Au, Bu and Cu and the phase flags A theta, B theta and C theta to 1, otherwise, setting 0;
s5, when GNDU and GND θ are 1:
when Au is equal to 0, Bu is equal to 1 and Cu is equal to 1, judging that the fault phase is an A phase;
when Au is equal to 1, Bu is equal to 0 and Cu is equal to 1, judging that the fault phase is the B phase;
and when Au is equal to 1, Bu is equal to 1 and Cu is equal to 0, judging that the fault phase is the C phase.
2. The method for identifying the ground fault phase of the neutral point non-effective grounding system according to claim 1, wherein: in step S1, the system only needs to sample the three-phase voltage to earth Ua, Ub, Uc, which can be expressed as follows:
3. the method for identifying the ground fault phase of the neutral point non-effective grounding system according to claim 1, wherein: the flag bits group u and group θ in step S3 are used for logic synchronization.
4. The method for identifying the ground fault phase of the neutral point non-effective grounding system according to claim 1, wherein: in step S5, when Au is 0, Bu is 0, and Cu is 1, the failed phase is determined to be the a phase if a θ is 1, B θ is 0, and C θ is 0, the failed phase is determined to be the B phase if a θ is 0, B θ is 1, and C θ is 0, the failed phase is determined to be the a phase if a θ, B θ, and C θ are in other states, the failed phase is determined to be the a phase if Uat < Ubt, and the failed phase is determined to be the B phase if Ubt < Uat.
5. The method for identifying the ground fault phase of the neutral point non-effective grounding system according to claim 1, wherein: in step S5, when Au is 1, Bu is 0, and Cu is 1, if a θ is 0, B θ is 1, and C θ is 0, the failed phase is determined as B-phase, if a θ is 0, B θ is 0, and C θ is 1, the failed phase is determined as C-phase, if a θ, B θ, and C θ are in other states, the failed phase is determined as B-phase when Ubt < Uct, and the failed phase is determined as C-phase when Uct < Ubt.
6. The method for identifying the ground fault phase of the neutral point non-effective grounding system according to claim 1, wherein: in step S5, when Au is 0, Bu is 1, and Cu is 0, if a θ is 1, B θ is 0, and C θ is 0, the failed phase is determined to be the a phase, if a θ is 0, B θ is 0, and C θ is 1, the failed phase is determined to be the C phase, if a θ, B θ, and C θ are in other states, Uat < Uct indicates that the failed phase is the a phase, and if Uct < Uat indicates that the failed phase is the C phase.
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| CN201910404320.6A CN110045232B (en) | 2019-05-16 | 2019-05-16 | Method for identifying ground fault phase of neutral point non-effective grounding system |
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| CN112526405B (en) * | 2020-12-03 | 2022-02-15 | 广东电网有限责任公司电力科学研究院 | Fault diagnosis method and related device for capacitor switching-out system |
| CN113325268B (en) * | 2021-05-27 | 2022-07-05 | 长沙理工大学 | Asymmetric power grid single-phase high-resistance earth fault phase identification method considering line impedance |
| CN114123183B (en) * | 2021-11-24 | 2024-04-19 | 山东大学 | Flexible grounding system applied to power distribution network ungrounded system and control method thereof |
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