CN108776283B - Power distribution network single-phase disconnection fault judgment method and system under incomplete CT configuration - Google Patents
Power distribution network single-phase disconnection fault judgment method and system under incomplete CT configuration Download PDFInfo
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- CN108776283B CN108776283B CN201810304509.3A CN201810304509A CN108776283B CN 108776283 B CN108776283 B CN 108776283B CN 201810304509 A CN201810304509 A CN 201810304509A CN 108776283 B CN108776283 B CN 108776283B
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Abstract
The invention discloses a method and a system for judging single-phase disconnection faults of a power distribution network under incomplete CT configuration, wherein the judging method comprises a fault starting criterion and a disconnection fault detection criterion; the judging system consists of a current/voltage conversion module, a voltage/voltage change module, a working power supply module, a digital-to-analog conversion module, a data calculation processing module, a control module, a switching value input and output module, a communication interface module and a human-computer interaction module; the invention introduces the voltage quantity and the current quantity to jointly form the disconnection fault criterion, can comprehensively consider the change conditions of each phase current and voltage, can judge the disconnection fault under the condition of incomplete configuration of the CT, can reliably and accurately distinguish the disconnection fault and the conditions of CT disconnection, asymmetric load and the like, and ensures the reliability of the disconnection fault protection criterion.
Description
Technical Field
The invention relates to the technical field of power equipment detection, in particular to a method and a system for judging a single-phase disconnection fault of a power distribution network under incomplete CT configuration.
Background
The frequent occurrence of open faults of distribution lines has gradually attracted attention. Several documents exist at home and abroad, which carry out theoretical analysis on the change of the electrical quantity caused by the disconnection fault of the distribution line, particularly the change characteristics of each sequence component, and summarize the change rule of the related electrical quantity; a method for judging and positioning a disconnection fault based on a negative sequence current component is proposed in the literature, but the situation of incomplete configuration of CT generally exists in a power distribution network, and the acquisition and calculation of the negative sequence component have great limitations; the document proposes a method for judging and positioning the disconnection fault based on wavelet transformation, but the method has higher requirements on data sampling frequency and calculation processing precision, and is not suitable for large-area popularization and application in a power distribution network.
No special disconnection fault protection device is equipped in the current distribution network. After a line break fault occurs, the change rule of line current and bus voltage is greatly different from that of a short-circuit fault, the traditional short-circuit protection principle and device for reflecting current increase and voltage reduction can not provide a sensitive and reliable protection function for the line break fault, and when the line break fault occurs, corresponding protection measures are not provided, so that the power grid has the risk of operation with faults. In addition, considering that the current power distribution network cannot provide complete three-phase current under the condition that the CT is incompletely configured, generally A, C two-phase configured CT and the B-phase is not configured with CT, if an A-phase disconnection fault occurs, the A-phase current is reduced from normal load current to 0, and if the branch of the power distribution network is considered, the A-phase current cannot be reduced to 0 but can be obviously reduced. The C-phase current will also be reduced, but not significantly, to the minimum of the normal load current
And (4) doubling. If C phase disconnection occurs, the obtained current change rule is similar to that of A phase disconnection. In this case, the reliability of the fault detection cannot be ensured by merely forming a criterion on the current flow, since, for example, a fault detection is carried outIf the conditions of load asymmetry, A-phase or C-phase CT disconnection fault and the like occur, the change rules of the current magnitude are similar, and the conditions are easily judged as single-phase disconnection fault by mistake. Therefore, it is necessary to provide a system and a method for judging a single-phase disconnection fault of a power distribution network in consideration of incomplete configuration of CT, so as to provide a sensitive and reliable disconnection fault protection function for the power distribution network.
Disclosure of Invention
In order to solve the above problems, the present invention provides a method and a system for determining a single-phase disconnection fault of a power distribution network under incomplete CT configuration.
In order to achieve the purpose, the invention is realized by the following technical scheme:
a method for judging a single-phase disconnection fault of a power distribution network under incomplete CT configuration comprises a fault starting criterion and a disconnection fault detection criterion;
wherein the fault starting criterion is
In the formula,. DELTA.iφIs the variation of the sampled values of the a-phase or C-phase current,
and
the current sampling values of the A phase or the C phase equivalent previous time and the N power frequency periods previous time,
to k consecutive
Summation, 1<k≤N/2，INFor effective value of rated current of line, ksetTo set the threshold coefficient, ksetThe value of (A) is 0.1 to 0.2; n is a natural number;
the disconnection fault detection criterion comprises a B-phase disconnection fault criterion and an A-phase or C-phase disconnection fault criterion;
wherein the criterion of the disconnection fault of the B phase is
Wherein the content of the first and second substances,
the larger amplitude of the A-phase current and the C-phase current is taken;
the smaller amplitude of the A-phase current and the C-phase current is taken;
a phase difference between the A-phase current and the C-phase current;
the smaller amplitude of the A phase voltage and the C phase voltage is taken;
the criterion of the disconnection fault of the A phase or the C phase is
Wherein the content of the first and second substances,
the larger amplitude of the A-phase current and the C-phase current is taken;
the smaller amplitude of the A-phase current and the C-phase current is taken;
the larger amplitude of the A phase voltage and the C phase voltage is taken;
the smaller amplitude of the A-phase voltage, the B-phase voltage and the C-phase voltage is taken as the representation.
The preferable method for judging the single-phase disconnection fault of the power distribution network under the incomplete CT configuration comprises the following steps:
①, the disconnection protection device continuously detects the A phase current and the C phase current when in normal operation, when the sampling amount of either phase current meets the fault starting criterion, the disconnection protection is started, and the step is entered into step ②;
② judging the magnitude of phase A and phase C current, then using the larger value of the two to compare with the smaller value, judging whether the ratio is larger than 1.2, if so, entering step ③, otherwise entering step ④;
③ if the phase A current is larger than the phase C current, using the voltage amplitude of the phase C voltage smaller than the voltage amplitudes of the phase A and the phase B to judge whether the ratio is larger than 1.2, if so, it is indicated that the phase C power failure occurs, otherwise, it is not the line break failure, and the process is ended, similarly, if the phase C current is larger than the phase A current, using the voltage amplitude of the phase A voltage smaller than the voltage amplitudes of the phase B and the phase C to judge whether the ratio is larger than 1.2, if so, it is indicated that the phase A power failure occurs, otherwise, it is not the line break failure, and the process is ended;
④ judging whether the phase angle difference between the A phase current and the C phase current is between [130 DEG, 180 DEG ], then judging whether the ratio is larger than 1.2 by the voltage amplitude of the B phase which is smaller than the voltage amplitude of the A phase and the C phase, if the above conditions are satisfied at the same time, indicating that the B phase has broken line fault, otherwise, ending the process.
Preferably, k issetThe value of (A) is 0.15.
The invention also comprises a power distribution network single-phase line break fault judgment system under incomplete CT configuration, which consists of a current/voltage conversion module, a voltage/voltage change module, a working power supply module, a digital-to-analog conversion module, a data calculation processing module, a control module, a switching value input/output module, a communication interface module and a man-machine interaction module, wherein the digital-to-analog conversion module is respectively connected with the current/voltage conversion module, the voltage/voltage change module and the data calculation processing module, and the control module is respectively connected with the data calculation processing module, the man-machine interaction module, the communication interface module and the switching value input/output module.
Preferably, the input current signal only has phase A and phase C current, the input voltage information is A, B, C three-phase voltage, the current signal is converted into weak voltage signal suitable for the work and processing of the microcomputer system through the current/voltage conversion module and the voltage signal through the voltage/voltage conversion module, and the peak value is +/-5V to +/-15V; the weak voltage signal is converted into a discrete digital signal after being processed by the digital-to-analog conversion module, and then the discrete digital signal is calculated and processed by the data calculation processing module to finish the calculation of the amplitude and the phase of the voltage and the current;
the control module carries out logic comparison and judgment on the calculation result from the data calculation processing module and judges whether the current electrical quantity relation meets the criterion or not; if the judgment is met, the line is broken, the switching value is controlled to be input into the output module to send a tripping command, and the circuit breaker is controlled to trip; if the judgment is not met, the disconnection protection device does not act, and the disconnection fault does not occur on the protected line;
the switching value input and output module is acted by the control module and can send a tripping command and an alarm signal; the circuit breaker position state signal or other switching value information from the outside can be received;
the working power supply module provides direct current working voltages with different amplitudes for the whole protection device;
the human-computer interaction module comprises a keyboard and a liquid crystal display and is used for completing basic human-computer interaction functions;
the communication interface module is used for completing the information interaction function between the disconnection protection device and the substation automation system, and the disconnection protection device needs to upload measurement, calculation and criterion results to the substation automation system and also needs to receive various remote control instructions from the substation automation system.
Preferably, the peak to peak value is ± 10V.
Preferably, the data calculation processing module is a DSP chip of TMS320 series.
Preferably, the control module is an STM32F type single chip microcomputer chip.
Preferably, the DC operating voltages of different magnitudes are 220V, + -12V, 5V and 3.3V.
Compared with the prior art, the invention has the following advantages:
the invention has clear principle, easy realization, no need of additional equipment, low cost and no increase of operation and maintenance workload, and divides the line break fault protection basis into a fault starting criterion and a line break fault detection criterion, wherein the fault starting criterion has high enough sensitivity to allow the starting criterion to act when the line break fault is not caused, but not allow the line break fault to be started. The invention introduces the voltage quantity and the current quantity to jointly form the disconnection fault criterion, can comprehensively consider the change conditions of each phase current and voltage, can judge the disconnection fault under the condition of incomplete CT configuration, can reliably and accurately distinguish the disconnection fault, the CT disconnection, load asymmetry and other conditions, and ensures the reliability of the disconnection fault protection criterion.
Drawings
FIG. 1 is a flow chart of a method for judging a single-phase disconnection fault of a power distribution network under incomplete CT configuration;
FIG. 2 is a schematic diagram of a typical 10kV system power distribution network structure;
FIG. 3 is a schematic diagram showing the change law of the current of each phase before and after the fault under incomplete CT configuration;
FIG. 4 is a schematic view of a voltage variation curve at A;
FIG. 5 is a schematic view of a voltage variation curve at B;
fig. 6 is a schematic structural connection diagram of a power distribution network single-phase disconnection fault judgment system under incomplete CT configuration.
Detailed Description
The invention aims to provide a method and a system for judging a single-phase disconnection fault of a power distribution network under incomplete CT configuration, which are realized by the following technical scheme:
the incomplete configuration of the CT of the power distribution network means that the a-phase and C-phase are equipped with the CT, and the B-phase is not equipped with the CT, so that only the current of the a-phase and C-phase can be obtained for secondary equipment such as a protection device, and the B-phase current cannot be obtained. For the busbar PT, a three-phase five-column type PT is generally provided, which can provide complete A, B, C three-phase voltage and zero-sequence voltage. The invention provides corresponding single-phase disconnection protection criterion based on the mutual inductor configuration condition and corresponding electric quantity.
Assuming that an a-phase disconnection fault occurs, the a-phase current is reduced from the normal load current to 0, and if the distribution network branch is considered, the a-phase current is not reduced to 0, but is significantly reduced. The C-phase current will also be reduced, but not significantly, to the minimum of the normal load current
And (4) doubling. If C phase disconnection occurs, the obtained current change rule is similar to that of A phase disconnection. At the moment, the reliability of judging the line breaking fault cannot be ensured only by depending on the current quantity forming criterion, because if the conditions of load asymmetry, A-phase or C-phase CT line breaking fault and the like occur, the change rules of the current quantities are similar, and the conditions are easily judged as single-phase line breaking fault by mistake. In order to improve the reliability of judging the disconnection fault under incomplete CT configuration, the invention introduces a voltage quantity to form the disconnection fault criterion together with a current quantity.
When the A-phase line break fault occurs, the change rule of the voltage quantity shows that the A-phase voltage can be obviously increased, the other two non-fault phase voltages can be reduced, and the zero-sequence voltage with a certain amplitude value appears in the system. When the A-phase CT disconnection fault occurs, the three-phase voltage of the system is basically symmetrical, and the zero-sequence voltage amplitude value is not very large; when the three-phase load is asymmetric, although zero-sequence voltage with a certain amplitude exists, the amplitude is still not very large, and the three-phase voltage of the system is basically in a symmetric state. Therefore, the change conditions of the phase currents and the voltages of all phases are comprehensively considered, the disconnection fault can be judged under the condition that the CT is not completely configured, the disconnection fault and the conditions of CT disconnection, asymmetric load and the like can be reliably and accurately distinguished, and the reliability of the disconnection fault protection criterion is ensured.
When a phase-C disconnection fault occurs, the corresponding electrical quantities are different except for the phase, and the change rules are the same, so that the description is omitted.
When a B-phase disconnection fault occurs, the currents of the A-phase and the C-phase are slightly reduced, but the phase difference is increased; at least one phase (fault phase) of the three-phase voltage can be obviously increased, the other two phases can be reduced, and zero-sequence voltage with a certain amplitude value can be generated.
To sum up: when the non-B-phase line is broken, the current of the fault phase can be obviously reduced, and the current of the other phase can be slightly reduced; when the B-phase is broken, the currents of the two phases are slightly reduced, but the phase difference is increased. No matter which phase is broken, the broken phase of the three-phase voltage is obviously increased, the other two phases are slightly reduced, and zero-sequence voltage with certain amplitude can appear.
The disconnection fault protection criterion comprises two parts: the first part is fault initiation criteria and the second part is disconnection fault detection criteria. The fault starting criterion is required to have high sensitivity enough to allow the starting criterion to act when the fault is not broken, but not to start when the fault is broken. The fault starting criterion acts and then enters the disconnection fault detection criterion, the requirement on the criterion is high reliability, and disconnection faults and non-disconnection faults can be reliably distinguished.
Starting criterion:
in the formula (I), the compound is shown in the specification,
is the variation of the sampled values of the a-phase or C-phase current,
and
the current sampling values of the A phase or the C phase equivalent previous time and the N power frequency periods previous time,
to k consecutive
Summation, 1<k≤N/2，INFor effective value of rated current of line, ksetIn order to set the threshold value coefficient, 0.1-0.2 can be selected according to an empirical value; n is a natural number.
The first condition in the starting criterion expression is that the reaction current is reduced, the second condition requires that the amplitude of the reduction of the current is required to meet a certain requirement, and the disconnection protection is started after the two conditions are met.
For the starting criterion, it is important to ensure sufficient sensitivity, so that the starting condition of the disconnection protection is met as long as the current value is reduced, and the specific situations such as whether the disconnection fault really occurs and the comparison of the disconnection fault occur need to be further distinguished by the disconnection fault detection criterion.
Line break fault detection criterion:
for the B-phase disconnection fault, the criterion is as follows:
in the formula (I), the compound is shown in the specification,
the larger amplitude of the A-phase current and the C-phase current is taken;
the smaller amplitude of the A-phase current and the C-phase current is taken;
a phase difference between the A-phase current and the C-phase current;
the smaller amplitude of the A-phase voltage and the C-phase voltage is taken as the representation. The threshold value of the ratio 1.2 is determined empirically, and the ranges of 130 ° and 180 ° are determined jointly from theoretical analysis and calculation results.
When the B-phase disconnection fault occurs, A, C two-phase current is reduced, so that the disconnection protection starting criterion can be reliably started. At this time A, C the two-phase current amplitudes are basically equivalent, thus meeting the first current amplitude ratio criterion; A. the phase difference of the current of the two phases C is increased and is at most 180 degrees, so that the second current phase difference criterion can be met; the B-phase voltage will increase and A, C the voltage of at least one of the two phases will decrease, thus satisfying a third voltage magnitude ratio criterion.
For the disconnection of the A phase or the C phase, the criterion is as follows:
in the formula (I), the compound is shown in the specification,
the larger amplitude of the A-phase current and the C-phase current is taken;
the smaller amplitude of the A-phase current and the C-phase current is taken;
the larger amplitude of the A phase voltage and the C phase voltage is taken;
the smaller amplitude of the A-phase voltage, the B-phase voltage and the C-phase voltage is taken as the representation. The threshold value of the ratio 1.2 is determined empirically.
When the A-phase or C-phase disconnection fault occurs, the current of the fault phase can be obviously reduced, so that the disconnection protection starting criterion can be reliably started. At the moment, the non-fault phase current is larger than the fault current, so the amplitude ratio of the non-fault phase current to the fault current is also larger, and the first current amplitude ratio criterion is met; at the moment, the fault phase voltage is increased, at least one of the other two non-fault phase voltages is reduced, so that the ratio of the fault phase voltage to the minimum value of the non-fault phase voltages is larger, and a second amplitude voltage ratio criterion is met.
Analyzing the influence of the abnormal operation state on the criterion:
1) CT disconnection: the electrical quantity change characteristics of the secondary side when the CT is disconnected are similar to the line disconnection fault, but obvious differences exist. When the CT is disconnected, the phase current of the disconnected line is obviously reduced or changed into 0, the starting criterion of the disconnection fault can be met, the ratio criterion of the current amplitude can also be met, but the amplitude and the phase difference of the non-fault phase current are not changed at the moment, and the three-phase voltage is basically in a symmetrical state, so that the phase angle difference criterion of the non-fault phase current cannot be met, the voltage amplitude ratio criterion cannot be met, and the CT disconnection and line disconnection faults can be reliably distinguished. In addition, when a line disconnection fault occurs, similar changes of currents of a plurality of measuring points generally occur at the same time, and the current of a certain point is changed only due to the CT disconnection, so that the CT disconnection and the line disconnection fault in an incomplete connection mode can be further distinguished.
2) Non-full phase operation: in power distribution networks, the non-full phase operation of the line, except for a disconnection fault, is mostly caused by switching operations. The switch of the distribution network is basically three-phase operation, and a long-time non-full-phase operation state generally cannot occur. If the line does not operate in full phase for a long time due to switch faults and the like, the line is regarded as a broken line fault. For the short-time non-full-phase operation state, proper action delay can be set to avoid the wire breakage protection misjudgment possibly caused by the short-time non-full-phase operation.
3) Asymmetric load: the load asymmetry is caused by single-phase electricity utilization, and is easy to appear on a load branch line. When the three-phase load asymmetry reaches a certain degree, the characteristics similar to the line break fault can appear in the three-phase current, but the three-phase voltage of the system is still basically symmetrical when the load asymmetry appears, and the voltage amplitude ratio criterion cannot be met, so that the asymmetrical load operation and the single-phase line break fault can be distinguished.
The invention is further described with reference to specific examples.
Example 1
Fig. 1 shows a flowchart of a method for determining a single-phase disconnection fault of a power distribution network under incomplete CT configuration, which includes the following steps:
①, the disconnection protection device continuously detects the A phase current and the C phase current when in normal operation, when the sampling amount of either phase current meets the fault starting criterion, the disconnection protection is started, and the step ② is entered into the disconnection fault judgment flow;
② judging the magnitude of phase A and phase C current, then using the larger value of the two to compare with the smaller value, judging whether the ratio is larger than 1.2, if so, entering step ③, otherwise entering step ④;
③ if the phase A current is larger than the phase C current, using the voltage amplitude of the phase C voltage smaller than the voltage amplitudes of the phase A and the phase B to judge whether the ratio is larger than 1.2, if so, it is indicated that the phase C power failure occurs, otherwise, it is not the line break failure, and the process is ended, similarly, if the phase C current is larger than the phase A current, using the voltage amplitude of the phase A voltage smaller than the voltage amplitudes of the phase B and the phase C to judge whether the ratio is larger than 1.2, if so, it is indicated that the phase A power failure occurs, otherwise, it is not the line break failure, and the process is ended;
④ judging whether the phase angle difference between the A phase current and the C phase current is between [130 DEG, 180 DEG ], then judging whether the ratio is larger than 1.2 by the voltage amplitude of the B phase which is smaller than the voltage amplitude of the A phase and the C phase, if the above conditions are satisfied at the same time, indicating that the B phase has broken line fault, otherwise, ending the process.
Example 2
As shown in fig. 2, which is a schematic diagram of a typical power distribution network structure, a 10kV system adopts a neutral ungrounded operation mode and a single-power-supply radial network structure. The bus is provided with n outgoing lines (L1-Ln), and each outgoing line comprises a plurality of load branches. With L1 as the object of study, the branching situation is shown in the figure, where the rectangular box represents the breaker, the dots represent the sectionalizing switches, the arrows represent the loads, and the remaining lines L2-Ln adopt a simplified equivalent structure.
Taking a single-phase disconnection fault occurring on a main feeder of a line L1 as an example, assuming that a disconnection fault point is located between a breaker A and a sectionalizing switch C in the diagram, the change rule of each phase current before and after the fault is as shown in FIG. 3, and the diagram has no B-phase current curve because CT is not completely configured;
after the phase A is disconnected, the phase A and the phase C are both reduced, wherein the phase A of the fault is most obvious, the change amplitude reaches 71.42%, the requirement of starting criteria is met, the disconnection protection is reliably started, and the ratio of the amplitude of the phase C to the amplitude of the phase A is about 3.2 and is more than 1.2.
At this time, the voltage at the position A represents the voltage of each measuring point between the fault point and the power supply, the voltage at the position C represents the voltage of each measuring point between the fault point and the load, the voltage change curve at the position A is shown in figure 4, the voltage change curve at the position B is shown in figure 5, the voltage amplitude of the phase A of the fault phase is the highest and is about 7.5kV, the voltage amplitude of the phase A of the two non-fault phases is basically equal and is about 5.5kV, and the ratio of the two phases is about 1.38 and is more than 1.2.
By combining the change rules of the current and the voltage, the phase current of the fault is obviously reduced when the A-phase disconnection fault occurs, and the disconnection protection can be reliably started; the ratio of the amplitude of the non-fault phase current to the amplitude of the fault phase current is larger than 1.2, the ratio of the amplitude of the fault phase voltage to the amplitude of the non-fault phase voltage is also larger than 1.2, and the A-phase disconnection fault can be reliably judged. And for the C-phase disconnection fault, the rule is similar, and the description is omitted.
When a phase-B open-circuit fault occurs, the phase-B current cannot be obtained because the phase-B is not equipped with a CT. At the moment, two non-fault phase currents are also reduced, and the disconnection protection can be reliably started due to the fact that the starting criterion has high sensitivity. At the moment, the amplitudes of the A-phase current and the C-phase current are almost the same, so that the amplitude ratio of the A-phase current to the C-phase current is not larger than 1.2, the phase difference between the A-phase current and the C-phase current is increased to about 145 degrees, the phase voltage B is obviously increased, the amplitude ratio of the phase voltage B to the phase voltage A or the phase voltage C is about 1.4 and is larger than 1.2, and therefore the criterion of the disconnection fault. Therefore, when the phase B is lack of CT, the phase B can still be judged to be broken by means of the non-fault phase current and the change rule of the three-phase voltage.
Example 3
Fig. 6 is a schematic structural connection diagram of a power distribution network single-phase disconnection fault judgment system under incomplete CT configuration, where the power distribution network single-phase disconnection fault judgment system under incomplete CT configuration is composed of a current/voltage conversion module, a voltage/voltage change module, a working power supply module, a digital-to-analog conversion module, a data calculation processing module, a control module, a switching value input/output module, a communication interface module and a human-computer interaction module, where the digital-to-analog conversion module is respectively connected with the current/voltage conversion module, the voltage/voltage change module and the data calculation processing module, and the control module is respectively connected with the data calculation processing module, the human-computer interaction module, the communication interface module and the switching value input/output module;
because CT is not completely configured, the input current signal only has A-phase current and C-phase current, and the input voltage information is A, B, C three-phase voltage. The current signal is converted into a weak voltage signal suitable for the work and the processing of a microcomputer system through a current/voltage conversion module and a voltage signal through a voltage/voltage conversion module, and the peak value is +/-5V- +/-15V; the specific numerical value depends on the adopted digital-to-analog conversion chip; the weak voltage signal is converted into a discrete digital signal after being processed by the digital-to-analog conversion module, and then the discrete digital signal is calculated and processed by the data calculation processing module to finish the calculation of the amplitude and the phase of the voltage and the current; the data calculation processing module generally adopts a DSP chip, and is typically TMS320 series;
the control module logically compares and judges the calculation result from the data calculation processing module, judges whether the current electrical quantity relation meets the criterion, and adopts a single chip microcomputer chip, such as an STM32F single chip microcomputer chip. If the judgment is met, the line is broken, the switching value is controlled to be input into the output module to send a tripping command, and the circuit breaker is controlled to trip; if the judgment is not met, the disconnection protection device does not act, and the disconnection fault does not occur on the protected line;
the switching value input and output module is acted by the control module and can send a tripping command and an alarm signal; the circuit breaker position state signal or other switching value information from the outside can be received;
the working power supply module provides direct current working voltages with different amplitudes, including 220V, plus or minus 12V, 5V, 3.3V and the like, for the whole protection device;
the human-computer interaction module comprises a keyboard and a liquid crystal display and is used for completing basic human-computer interaction functions; the communication interface module is used for completing the information interaction function between the disconnection protection device and the substation automation system, and the disconnection protection device needs to upload measurement, calculation and criterion results to the substation automation system and also needs to receive various remote control instructions from the substation automation system.
Claims (3)
1. A single-phase disconnection fault judgment method for a power distribution network under incomplete CT configuration is characterized by comprising the following steps: the method comprises the following steps of (1) judging a fault starting criterion and a disconnection fault detection criterion;
wherein the fault starting criterion is
In the formula,. DELTA.iφIs the variation of sampled values of phase A or C current, iφ(n) and iφ(N-N) is the current sampling value of the A phase or the C phase equivalent previous time and the N power frequency periods previous time,
to k consecutive
Summation, 1<k≤N/2，INFor effective value of rated current of line, ksetTo set the threshold coefficient, ksetThe value of (A) is 0.1 to 0.2; n is a natural number;
the disconnection fault detection criterion comprises a B-phase disconnection fault criterion and an A-phase or C-phase disconnection fault criterion;
wherein the criterion of the disconnection fault of the B phase is
Wherein the content of the first and second substances,
the larger amplitude of the A-phase current and the C-phase current is taken;
the smaller amplitude of the A-phase current and the C-phase current is taken;
a phase difference between the A-phase current and the C-phase current;
the smaller amplitude of the A phase voltage and the C phase voltage is taken;
the criterion of the disconnection fault of the A phase or the C phase is
Wherein the content of the first and second substances,
the larger amplitude of the A-phase current and the C-phase current is taken;
the smaller amplitude of the A-phase current and the C-phase current is taken;
the larger amplitude of the A phase voltage and the C phase voltage is taken;
the smaller amplitude of the A-phase voltage, the B-phase voltage and the C-phase voltage is taken as the representation.
2. The method for judging the single-phase disconnection fault of the power distribution network under the incomplete CT configuration according to claim 1, wherein the method comprises the following steps: the method comprises the following steps:
①, the disconnection protection device continuously detects the A phase current and the C phase current when in normal operation, when the sampling amount of either phase current meets the fault starting criterion, the disconnection protection is started, and the step is entered into step ②;
② judging the magnitude of phase A and phase C current, then using the larger value of the two to compare with the smaller value, judging whether the ratio is larger than 1.2, if so, entering step ③, otherwise entering step ④;
③ if the phase A current is larger than the phase C current, using the voltage amplitude of the phase C voltage smaller than the voltage amplitudes of the phase A and the phase B to judge whether the ratio is larger than 1.2, if so, it is indicated that the phase C power failure occurs, otherwise, it is not the line break failure, and the process is ended, similarly, if the phase C current is larger than the phase A current, using the voltage amplitude of the phase A voltage smaller than the voltage amplitudes of the phase B and the phase C to judge whether the ratio is larger than 1.2, if so, it is indicated that the phase A power failure occurs, otherwise, it is not the line break failure, and the process is ended;
④ judging whether the phase angle difference between the A phase current and the C phase current is between [130 DEG, 180 DEG ], then judging whether the ratio is larger than 1.2 by the voltage amplitude of the B phase which is smaller than the voltage amplitude of the A phase and the C phase, if the above conditions are satisfied at the same time, indicating that the B phase has broken line fault, otherwise, ending the process.
3. The method for judging the single-phase disconnection fault of the power distribution network under the incomplete CT configuration according to claim 1, wherein the method comprises the following steps: k is a radical ofsetThe value of (A) is 0.15.
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| CN109444666B (en) * | 2018-12-17 | 2020-12-25 | 国网山东省电力公司电力科学研究院 | Power distribution network single-phase high-blocking line fault identification method and device |
| CN111007355A (en) * | 2019-12-11 | 2020-04-14 | 苏州银蕨电力科技有限公司 | Disconnection fault detection method based on wide-area synchronous intelligent sensor |
| CN111579927B (en) * | 2020-05-22 | 2022-03-29 | 南京南瑞继保电气有限公司 | Disconnection protection judgment method and device suitable for single-side power transmission line |
| CN112014686B (en) * | 2020-08-14 | 2022-07-05 | 国网河南省电力公司封丘县供电公司 | Low-voltage distribution network fault positioning method based on shortest path of adjacency matrix |
| CN112098898A (en) * | 2020-09-22 | 2020-12-18 | 国网四川省电力公司眉山供电公司 | Disconnection fault judgment method and device and regulation and control system |
| CN112345977B (en) * | 2020-10-21 | 2023-11-24 | 河南华润电力首阳山有限公司 | Electrical equipment and PT secondary circuit disconnection judging method, system and device thereof |
| CN113013880A (en) * | 2021-04-20 | 2021-06-22 | 西安兴汇电力科技有限公司 | Fault processing method based on 5G communication module distribution line |
| CN114640093B (en) * | 2022-02-23 | 2023-03-24 | 北京天能继保电力科技有限公司 | Method and device for protecting broken line of distributed power transmission and distribution line |
| CN114938074B (en) * | 2022-03-22 | 2023-05-09 | 国网黑龙江省电力有限公司齐齐哈尔供电公司 | Automation system applied to district power distribution |
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