CN113805010A - A method and system for judging single-phase grounding fault in distribution network - Google Patents
A method and system for judging single-phase grounding fault in distribution network Download PDFInfo
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Abstract
本发明公开一种配电网单相接地故障的研判方法及系统，本发明涉及配电网故障研判领域，本发明提供的研判系统采用实时监视电网故障分量突变量变化的启动算法，启动后，计算故障瞬间第一阶段暂态量的相关参数和故障稳定后第二阶段稳态量的相关参数，进行多判据研判后，通过综合融合后，实现单相接地就地可靠研判，该方法算法简单可靠，计算速度快，实现了就地快速研判。
The invention discloses a method and a system for judging and judging a single-phase grounding fault in a distribution network. The invention relates to the field of judging and judging distribution network faults. Calculate the relevant parameters of the transient quantity in the first stage at the moment of the fault and the relevant parameters of the steady state quantity in the second stage after the fault is stabilized. After multi-criteria research and judgment, after comprehensive fusion, the single-phase grounding can be reliably judged on site. This method algorithm Simple and reliable, the calculation speed is fast, and the on-site rapid research and judgment is realized.
Description
Technical Field
The invention relates to the field of power distribution network fault study and judgment, in particular to a study and judgment method and a study and judgment system for single-phase earth faults of a power distribution network.
Background
In a power distribution network, the most types of faults are single-phase earth faults, and the current method for solving the single-phase earth fault line selection positioning generally adopts a centralized mode (such as a small-current earth line selection device installed on a transformer substation) or a distributed mode (such as a transient recording type fault indicator installed on a line), and both of the modes rely on global information (outlet zero-sequence current information of the whole transformer substation or recording information of all fault indicators on the whole line) to perform single-phase earth fault line selection judgment after large data analysis, but cannot realize the function of performing single-phase earth fault on-site study and judgment through self-parameter identification and calculation by installing simple and convenient equipment in a protection interval like a conventional microcomputer protection device and through a reliable on-site study and judgment algorithm after the single-phase earth fault occurs.
Disclosure of Invention
In order to solve the problems of the prior art, the invention provides a method for studying and judging a single-phase earth fault of a power distribution network, which comprises the following steps,
s1, collecting a fault component of power distribution equipment to obtain a fundamental wave effective value of the fault component;
s2, setting a fault fixed value, judging whether a fundamental wave effective value is greater than or equal to the fault fixed value, if so, entering the next step, and if not, entering S1;
s3, collecting 4 cycles of data before the fault and 8 cycles of data after the fault is started to temporarily store fault recording waveforms, judging whether the fault is an instantaneous fault or a false ground fault according to the effective values of the three-phase voltage and the zero-sequence voltage fundamental wave of the 8 th cycle of the data after the fault is started, if so, entering S1 and storing the fault recording data, and if not, entering the next step;
s4, subtracting the data of the 1 st cycle corresponding point from the data of the 2 nd to 12 th cycle corresponding points, constructing a fault oscillogram, and searching a fault starting point by a mutation quantity difference value calculation method;
and S5, acquiring three-phase current fault components, zero-sequence voltage fault components and zero-sequence current fault components of the fault starting point in different transient states based on the fault starting point, carrying out multi-criterion research and calculation, and judging whether the grounding fault exists below the power distribution equipment or not after comprehensive fusion.
Preferably, in the process of acquiring the fault component of the power distribution equipment, the zero-sequence voltage fault component and the three-phase current fault component of the power distribution equipment are calculated in real time to obtain the fault component, wherein the fault component is obtained by subtracting a corresponding sampling point before 5 cycles from a sampling point of the current cycle to calculate a difference value.
Preferably, S2 includes setting a voltage fault setpoint and a current fault setpoint;
if the zero sequence voltage fault component is greater than or equal to the real-time voltage fault fixed value and/or the three-phase current fault component is greater than or equal to the current fault fixed value, the process goes to S3.
Preferably, S5 includes the steps of:
s5.1, acquiring a first study variable in a first half cycle of a first-stage transient state after a fault, wherein the first study variable comprises a first-stage transient state zero-sequence voltage fault component initial angle, a first-stage transient state zero-sequence voltage fault component derivative and zero-sequence current fault component correlation coefficient, a first-stage transient state zero-sequence voltage fault component and zero-sequence current fault component correlation coefficient, a first-stage transient state zero-sequence current fault component effective value and an attenuation direct current component of a first-stage transient state zero-sequence current fault component;
s5.2, acquiring second study variables of the 5 th cycle of the second-stage steady state after the fault, wherein the second study variables comprise a second-stage steady-state zero-sequence current fault component effective value, a second-stage steady-state negative-sequence current fault component effective value and an included angle between the second-stage steady-state zero-sequence voltage fault component and the zero-sequence current fault component;
and S5.3, judging the ground fault according to the numerical relationship between the first studying and judging variable and the second studying and judging variable.
Preferably, in the process of judging the ground fault, the fault diagnosis for the ungrounded system includes: the numerical relationship comprises at least 4 numerical relationships, and when the earth fault is judged according to at least 2 numerical relationships, the earth fault is finally judged.
Preferably, in the process of determining the ground fault, the fault analysis for the system with the neutral point grounded through the arc suppression coil includes: the numerical relationship comprises at least 4 numerical relationships, and when the earth fault is judged according to at least 2 numerical relationships, the earth fault is finally judged.
Preferably, in the process of determining the ground fault, when the numerical relationship includes a transient attenuation dc relationship, the determination is performed according to 5 numerical relationships, and when the ground fault is determined according to at least 3 numerical relationships, the ground fault is finally determined.
Preferably, the judging method further comprises the following steps:
and S6, storing wave recording data according to the judgment result of S5, and returning fault detection according to the drop value of the voltage component of the fault component, wherein when the voltage component is lower than 50% of the starting value, returning to S1.
A system for studying and judging single-phase earth fault of a power distribution network comprises,
the data processing module is used for acquiring the fault component of the power distribution equipment and acquiring a fundamental wave effective value of the fault component;
the data analysis module is used for judging whether the fundamental wave effective value is greater than or equal to the fault constant value or not by setting the fault constant value, entering the next module if the fundamental wave effective value is greater than or equal to the fault constant value, and continuing to analyze if the fundamental wave effective value is smaller than the fault constant value;
the first fault studying and judging module is in data interaction with the data analysis module and is used for temporarily storing fault recording waveforms by collecting 4 cycles of data before a fault and 8 cycles of data after the fault is started, judging whether the fault recording waveforms are transient faults or false ground faults or not according to the effective values of three-phase voltage and zero sequence voltage fundamental waves of 8 th cycle of the fault after the fault is started, if so, returning to the data analysis module and storing the fault recording data, and if not, entering the next module;
the fault point construction module is in data interaction with the first fault study and judgment module and is used for subtracting the data of the 1 st cycle corresponding point from the data of the 2 nd to 12 th cycle corresponding points, constructing a fault oscillogram and searching a fault starting point by a mutation quantity difference value calculation method;
and the second fault studying and judging module is in data interaction with the fault point constructing module and is used for acquiring three-phase current fault components, zero-sequence voltage fault components and zero-sequence current fault components of the fault starting point in different transient stages based on the fault starting point, carrying out multi-criterion studying and judging calculation, and judging whether the grounding fault exists below the power distribution equipment or not after comprehensive fusion.
Preferably, the judging system further comprises a high-precision phase current measuring system for data acquisition, and the high-precision phase current measuring system is electrically connected with the data analysis module through a high-precision open-type phase current transformer;
the judging system also comprises a judging and returning module, the judging and returning module performs data interaction with the second fault judging module, and is used for storing wave recording data according to the judging result of the second fault judging module and performing fault detection and return according to the drop value of the voltage component of the fault component, wherein when the voltage component is lower than 50% of the starting value, the data returning module returns to the data analysis module;
the high-precision open-type phase current transformer at least comprises three 0.05 SS-level high-precision open-type phase current transformers.
The invention discloses the following technical effects:
the method has the advantages that the on-site study and judgment protection device adopts a starting algorithm for monitoring the change of the fault component break variable of the power grid in real time, after starting, the related parameters of the transient state quantity of the first stage at the moment of the fault and the related parameters of the steady state quantity of the second stage after the fault is stabilized are calculated, multi-criterion study and judgment calculation is carried out, and after comprehensive fusion, the on-site reliable study and judgment of the single-phase grounding is realized.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a block diagram of a system of devices according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an exemplary structure of a current measurement channel according to an embodiment of the invention;
FIG. 3 is a flow chart of a method according to the present invention.
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.
As shown in fig. 1-3, the present invention provides a method for studying and judging single-phase earth fault of a power distribution network, comprising the following steps,
s1, acquiring a fault component of power distribution equipment through a high-precision phase current measuring system and a voltage acquisition system to obtain a fundamental wave effective value of the fault component;
s2, fault starting and studying and judging, namely judging whether the fundamental wave effective value of the fault component is greater than or equal to a fault fixed value or not, if the fundamental wave fault component effective value is greater than or equal to the fault fixed value, carrying out high-precision fault recording, entering the next step, and if the fundamental wave effective value is smaller than the fault fixed value, entering S1;
s3, collecting 4 cycles of data before the fault and 8 cycles of data after the fault is started to temporarily store fault recording waveforms, judging whether the fault is an instantaneous fault or a false ground fault according to the effective values of the three-phase voltage and the zero-sequence voltage fundamental wave of the 8 th cycle of the data after the fault is started, if so, entering S1 and storing the fault recording data, and if not, entering the next step;
s4, subtracting the data of the 1 st cycle corresponding point from the data of the 2 nd to 12 th cycle corresponding points, constructing a fault oscillogram, and searching a fault starting point by a mutation quantity difference value calculation method;
and S5, acquiring three-phase current fault components, zero-sequence voltage fault components and zero-sequence current fault components of the fault starting point in different transient states based on the fault starting point, carrying out multi-criterion research and calculation, and judging whether the grounding fault exists below the power distribution equipment or not after comprehensive fusion.
Further, in the process of acquiring the fault components of the power distribution equipment, the zero-sequence voltage fault components and the three-phase current fault components of the power distribution equipment are calculated in real time to obtain the fault components, wherein the fault components are obtained by subtracting the corresponding sampling points before 5 cycles from the sampling points of the current cycles to calculate the difference.
Further, S2 includes setting a voltage fault setpoint and a current fault setpoint;
if the zero sequence voltage fault component is greater than or equal to the real-time voltage fault fixed value and/or the three-phase current fault component is greater than or equal to the current fault fixed value, the process goes to S3.
Further, S5 includes the steps of:
s5.1, acquiring a first study variable in a first half cycle of a first-stage transient state after a fault, wherein the first study variable comprises a first-stage transient state zero-sequence voltage fault component initial angle, a first-stage transient state zero-sequence voltage fault component derivative and zero-sequence current fault component correlation coefficient, a first-stage transient state zero-sequence voltage fault component and zero-sequence current fault component correlation coefficient, a first-stage transient state zero-sequence current fault component effective value and an attenuation direct current component of a first-stage transient state zero-sequence current fault component;
s5.2, acquiring second study variables of the 5 th cycle of the second-stage steady state after the fault, wherein the second study variables comprise a second-stage steady-state zero-sequence current fault component effective value, a second-stage steady-state negative-sequence current fault component effective value and an included angle between the second-stage steady-state zero-sequence voltage fault component and the zero-sequence current fault component;
and S5.3, judging the ground fault according to the numerical relationship between the first studying and judging variable and the second studying and judging variable.
Further, in the process of determining the ground fault, the fault study and determination for the ungrounded system includes: the numerical relationship comprises at least 4 numerical relationships, and when the earth fault is judged according to at least 2 numerical relationships, the earth fault is finally judged.
Further, in the process of judging the ground fault, the fault research and judgment of the system with the neutral point grounded through the arc suppression coil comprises the following steps: and when the numerical relation comprises at least 4 numerical relations, and the earth fault is judged according to at least 2 numerical relations, the earth fault is finally judged.
Further, in the process of determining a ground fault, in the process of determining the ground fault, if a numerical relationship includes a transient-attenuated direct-current relationship, the determination is performed according to the above 5 numerical relationships, and when the ground fault is determined according to at least 3 numerical relationships, the ground fault is finally determined.
Further, the judging method further comprises the following steps:
and S6, storing wave recording data according to the judgment result of S5, and returning fault detection according to the drop value of the voltage component of the fault component, wherein when the voltage component is lower than 50% of the starting value, returning to S1.
A system for studying and judging single-phase earth fault of a power distribution network comprises,
the data processing module is used for acquiring the fault component of the power distribution equipment and acquiring a fundamental wave effective value of the fault component;
the data analysis module is used for judging whether the fundamental wave effective value is greater than or equal to the fault constant value or not by setting the fault constant value, entering the next module if the fundamental wave effective value is greater than or equal to the fault constant value, and continuing to analyze if the fundamental wave effective value is smaller than the fault constant value;
the first fault studying and judging module is in data interaction with the data analysis module and is used for temporarily storing fault recording waveforms by collecting 4 cycles of data before a fault and 8 cycles of data after the fault is started, judging whether the fault recording waveforms are transient faults or false ground faults or not according to the effective values of three-phase voltage and zero sequence voltage fundamental waves of 8 th cycle of the fault after the fault is started, if so, returning to the data analysis module and storing the fault recording data, and if not, entering the next module;
the fault point construction module is in data interaction with the first fault study and judgment module and is used for subtracting the data of the 1 st cycle corresponding point from the data of the 2 nd to 12 th cycle corresponding points, constructing a fault oscillogram and searching a fault starting point by a mutation quantity difference value calculation method;
and the second fault studying and judging module is in data interaction with the fault point constructing module and is used for acquiring three-phase current fault components, zero-sequence voltage fault components and zero-sequence current fault components of the fault starting point in different transient stages based on the fault starting point, carrying out multi-criterion studying and judging calculation, and judging whether the grounding fault exists below the power distribution equipment or not after comprehensive fusion.
Further, the air conditioner is provided with a fan,
the studying and judging system also comprises a high-precision phase current measuring system for data acquisition, wherein the high-precision phase current measuring system is electrically connected with the data analysis module through a high-precision open-type phase current transformer;
the judging system also comprises a judging and returning module, the judging and returning module performs data interaction with the second fault judging module, and is used for storing wave recording data according to the judging result of the second fault judging module and performing fault detection and return according to the drop value of the voltage component of the fault component, wherein when the voltage component is lower than 50% of the starting value, the data returning module returns to the data analysis module;
the high-precision open-type phase current transformer at least comprises three 0.05 SS-level high-precision open-type phase current transformers.
Example 1: the in-situ study and judgment equipment comprises:
the device consists of three '0.05 SS-level high-precision open-type phase current transformers' and a 'local study and judgment protection device';
typical parameters of the high-precision open-type phase current transformer are as follows:
transformation ratio: 600A/1A, accurate grade: 0.05SS (the prior art has international leading level when the accurate level reaches 0.05 SS), and the load is 0.1 omega;
namely, the ratio difference of 5 percent In, 20 percent In, 100 percent In and 120 percent In is less than or equal to 0.05 percent, and the phase difference is less than or equal to 2';
the specific value difference of 1% In is less than or equal to +/-0.1%, and the phase difference is less than or equal to +/-4'.
The high-precision open-type phase current transformer adopts a special passive compensation principle and a secondary light load design.
A. B, C three high-precision open-type phase current transformers ensure that the current sampling phase consistency of the three phase current transformers is controlled to be less than or equal to +/-4' due to extremely small phase difference errors, and the technical requirements of synthesizing zero-sequence current are met.
The high-precision current converter design method is realized by adopting a small current transformer and an IV current converter. Specifically, the transformation ratio of the small current transformer is 1A/0.01A, and the accurate level is as follows: 0.01SS level (the prior art has international leading level when the accurate level reaches 0.01SS level), namely, the ratio difference is less than or equal to 0.01 percent and the phase difference is less than or equal to 0.3 percent when 5 percent In, 20 percent In, 100 percent In and 120 percent In are contained, and the ratio difference is less than or equal to 0.02 percent and the phase difference is less than or equal to 0.6 percent when 1 percent In is contained.
The IV current converter adopts a zero load impedance conversion method, and the converter is secondarily connected with a required resistor (the typical value is 353 ohms) to realize rated 3.53V voltage output.
The high-precision AD converter typically adopts an independent 16-bit true double-stage low-power consumption 8-channel high-precision AD converter (model: AD7606), and the sampling frequency is typically 12.8k (256 points/cycle).
DSP systems typically employ 32-bit floating-point DSPs for fast digital signal processing and ground algorithm development.
Three high-precision open-type phase current transformers are adopted, zero sequence current and negative sequence current can be accurately synthesized, and basic current data are provided for a grounding research and judgment algorithm.
The in-situ judging protector has 3 current simulating channels (I)a、Ib、Ic) And 4 voltage analog channels (U)a、Ub、Uc、3U0) Three-phase power of input and device acquisition systemAnd after the phase current information of the voltage and zero sequence voltage and 3 matched high-precision open-type phase current transformers is judged by a DSP system starting algorithm and researched by a grounding algorithm, alarm opening or trip opening is executed, and in-situ fault identification is completed.
The designed 3 current simulation channels select the filter capacitor with good capacitance value consistency or directly remove the filter capacitor on the circuit, so as to ensure the phase consistency of the three-phase current simulation channels.
An independent 16-bit true double-stage low-power-consumption 8-channel high-precision AD converter is selected, so that the phase consistency during three-phase current analog-to-digital conversion is ensured.
232/485 communication interfaces are configured to realize remote communication, small wireless interface modules are reserved for near field communication networking, the summary of all data in the transformer substation is realized, and the centralized data remote transmission is convenient.
1. Monitoring fault components in real time under normal conditions:
monitoring system fault components in real time: if the zero sequence voltage fault component and the negative sequence current fault component exceed a fixed value, a grounding research and judgment starting algorithm is started, and the equipment adopts a fault starting algorithm of zero sequence voltage and negative sequence current combined starting, and the specific implementation method is as follows:
a) the equipment calculates the zero-sequence voltage fault component and the three-phase current fault component in real time, and the calculation formula is as follows:
ΔU0k＝Uk-Uk-5*N
ΔIak＝Iak-Iak-5*N
ΔIbk＝Ibk-Ibk-5*N
ΔIck＝Ick-Ick-5*N
and the fault component is calculated by subtracting the corresponding sampling point before 5 cycles from the sampling point of the current cycle.
Typically 256 points are sampled per cycle, i.e., N256.
b) And calculating fundamental effective values of the zero sequence voltage fault component and the negative sequence current fault component every 10mS, namely data of fault conditions of delta U0 and delta I2, and judging whether the set value is exceeded or not.
ΔU0 therefore≥ΔU0SET
Or Δ I2 therefore≥ΔI2SET
If the value exceeds the predetermined value, the single-phase grounding judgment process is performed. And if the fixed value is not exceeded, continuing to periodically monitor a new cycle of system fault component tasks.
ΔU0SETAnd (5) selecting min {15V, 5 times of the maximum historical unbalanced voltage value }.
ΔI2SETAnd selecting min {1A, 10 times of the maximum historical unbalanced negative sequence current }.
ΔU0SETThe zero sequence voltage fixed value is selected by adopting a fixed value and according to the maximum value of the maximum unbalanced voltage.
ΔI2SETThe negative sequence current fixed value is selected by adopting a fixed value and according to the negative sequence current which avoids the maximum unbalance.
2. After grounding study and judgment are started, recording waves after a fault is carried out for 160ms, and then carrying out waveform temporary storage on 4-cycle data before the fault and 8-cycle data after the fault is started, specifically (I)a、Ib、Ic、Ua、Ub、Uc、3U0In total 7 analog channels)
The grounding study and judgment process is as follows:
1) and calculating the three-phase voltage of the 8 th cycle after the fault and the zero sequence voltage fundamental wave effective value, and judging whether the fault is an instantaneous fault or a false ground fault. And if the fault is an instantaneous fault or a false ground fault, returning the ground studying and judging flow and simultaneously storing fault recording data.
2) Calculate Δ 3U0And the wave curve is obtained by subtracting the data of the 1 st cycle corresponding point from the data of the 2 nd to 12 th cycle corresponding points.
3) Finding fault starting point
According to Delta 3U0The starting point is searched by adopting a mutation quantity difference value calculation method.
4) And calculating the fault components of the three-phase current, the zero-sequence voltage and the zero-sequence current in the transient state (the transient first half cycle) in the first stage after the fault according to the determined fault starting point.
ΔUTemporary 0k＝U0k-U0k-N
ΔITemporary ak＝Iak-Iak-N
ΔITemporary bk＝Ibk-Ibk-N
ΔITemporary ck＝Ick-Ick-N
ΔITemporary 0k＝ΔITemporary ak+ΔITemporary bk+ΔITemporary ck
The value of k starts from the point of failure and goes 1 cycle after the failure.
4) The first half cycle of the transient state in the first stage (i.e. 1/8 cycles after failure) is calculated as follows:
starting angle of fault component of transient zero-sequence voltage in the first stage: alpha is alphaInitial angle；
Correlation coefficient of the first-stage transient zero-sequence voltage fault component derivative and the zero-sequence current fault component: rho1；
Correlation coefficient of transient zero-sequence voltage fault component and zero-sequence current fault component of the first stage: rho2；
The first-stage transient zero-sequence current fault component effective value is as follows: delta I0 first stage effective value；
Attenuation direct-current component of first-stage transient zero-sequence current fault component: delta I0DC；
The calculation method of the related parameters comprises the following steps:
a)αinitial angleThe calculation method comprises the steps of extracting the 5 th cycle wave whole cycle wave zero-sequence voltage waveform of the determined fault starting point, and calculating the initial phase angle alpha through Fourier transformationInitial angle N-5The initial phase angle is approximately equal to alphaInitial angle。
b) The transient zero sequence voltage fault component derivative calculation method adopts a zero sequence voltage fault difference method to calculate, namely
dU(k)＝U(k)-U(k-1)
c) The correlation coefficient calculation method has the following formula:
when only the calculation correlation coefficient in the first half wave is calculated, N is taken to be 32
d)ΔI0 first stage effective valueThe calculation adopts a root mean square method
Because only the correlation coefficient in the first half wave is calculated, N is taken to be 32
e)ΔI0DCCalculation method
The attenuated direct current component is calculated according to a cycle wave data value after the first half-wave impact component is avoided
5) And calculating the fault components of the three-phase current of the 5 th cycle after the second stage steady-state fault after the fault, the fault components of the zero-sequence voltage and the fault components of the zero-sequence current according to the determined fault starting point.
ΔUSteady 0k＝U0k+5N-U0k-N
ΔIStabilizing ak＝Iak+5N-Iak-N
ΔIStable bk＝Ibk+5N-Ibk-N
ΔISteady ck＝Ick+5N-Ick-N
ΔISteady 0k＝ΔIStabilizing ak+ΔIStable bk+ΔISteady ck
Second-stage steady-state zero-sequence current fault component effective value delta I0 second stage effective value；
Second-stage steady-state negative-sequence current fault component effective value delta I2 second stage significance value；
Second stage steady state zero sequence voltage fault component and zero sequence current fault component included angle alphaU0-I0。
The calculation method of the related parameters comprises the following steps:
a)ΔI0 second stage effective valueThe calculation adopts a root mean square method
x (n) is selected as a discrete sampling point of the fault component of the 5 th cycle zero-sequence current;
the second stage is a stabilization stage, and N is generally selected to be 256.
b)ΔI2 second stage significance valueCalculation method
Extracting the waveform data of the three-phase current fault components in the 5 th cycle after the fault;
respectively obtaining real parts and imaginary parts of three-phase currents by a fundamental wave Fourier algorithm, namely
Ra、Xa、Rb、Xb、Rc、Xc
Calculating the real and imaginary parts of the negative sequence current according to the following formula
Finally calculating the amplitude of the negative sequence current
c)αU0-I0Calculation method
Extracting fault component waveform data of zero-sequence voltage and zero-sequence current in the 5 th cycle after the fault;
respectively obtaining fundamental wave initial phase angles alpha of voltage and current by a fundamental wave Fourier algorithmU0、αI0；
αU0-I0＝αU0-αI0；
6) The in-situ study and judgment process adopts the following convenient, simple and reliable in-situ study and judgment method to realize rapid fault in-situ identification and study and judgment.
The transient intensity variable is calculated and,
and (3) an ungrounded system, and respectively calculating fault results by adopting the following algorithm:
a) if BB is greater than 2, the transient process is obvious, and a transient zero sequence voltage derivative current polarity discrimination method is executed:
if ρ1＜ρ1SETIf the grounding is judged to be grounding, if the grounding is not met, the judgment is not made;
b) if BB is less than or equal to 2, the transient process is not obvious, and a transient zero-sequence voltage and current polarity discrimination method is executed:
if ρ2＜ρ2SETIf the grounding is judged to be grounding, if the grounding is not met, the judgment is not made;
c) method for judging negative sequence current of steady-state fault
If Δ I2＞ΔI2SETIf the grounding is judged to be grounding, if the grounding is not met, the judgment is not made;
d) judging the angle of the steady-state zero-sequence voltage and current:
if α isU0-I0E, judging the grounding state if the state is within 65-115 degrees, and judging the grounding state if the state is not satisfied;
e) and (4) fusing the results: in the above algorithm results, as long as at least 2 results are satisfied and the result is judged to be grounded, the result is finally judged to be grounded, otherwise, the result is considered to be non-fault.
And a system for grounding the neutral point through the arc suppression coil respectively calculates fault results by adopting the following algorithm:
a) if α isInitial angleBelongs to (-15 degrees), and executes a transient attenuation direct current discrimination method:
ΔIDC≥ΔIDCSET；
b) if BB is greater than 2, the transient process is obvious, and the transient zero sequence voltage derivative current polarity discrimination method comprises the following steps:
if ρ1＜ρ1SETIf yes, grounding is performed, otherwise, judging is not performed;
c) if BB is less than or equal to 2, the transient process is not obvious, and the transient zero-sequence voltage and current polarity discrimination method comprises the following steps:
if ρ2＜ρ2SETIf yes, grounding is performed, otherwise, judging is not performed;
d) method for judging negative sequence current of steady-state fault
If Δ I2＞ΔI2SETIf the grounding is judged to be grounding, if the grounding is not met, the judgment is not made;
e) judging the angle of the steady-state zero-sequence voltage and current:
if α isU0-I0E (250-265 deg), grounding, otherwise, not judging;
f) and (4) fusing the results: in the above algorithm results, if at least 2 results are satisfied (if the transient attenuation dc discrimination method can determine, at least 3 results are required) and it is determined as grounding, it is finally determined as grounding, otherwise, it is determined as non-fault.
7) On-site study and judgment fault recovery process
After the fault is researched and judged, the 3U is monitored in real time0When 3U is used0And when the voltage drops to be lower than the starting value by 50 percent, delaying for 1 second to carry out fault monitoring and returning, and carrying out real-time variable monitoring again under the normal condition.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus once an item is defined in one figure, it need not be further defined and explained in subsequent figures, and moreover, the terms "first", "second", "third", etc. are used merely to distinguish one description from another and are not to be construed as indicating or implying relative importance.
Finally, it should be noted that: the above-mentioned embodiments are only specific embodiments of the present invention, which are used for illustrating the technical solutions of the present invention and not for limiting the same, and the protection scope of the present invention is not limited thereto, although the present invention is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: any person skilled in the art can modify or easily conceive the technical solutions described in the foregoing embodiments or equivalent substitutes for some technical features within the technical scope of the present disclosure; such modifications, changes or substitutions do not depart from the spirit and scope of the present invention in its spirit and scope. Are intended to be covered by the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
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