CN108872799B - Active power distribution network fault section positioning method and system based on positive sequence current fault component - Google Patents
Active power distribution network fault section positioning method and system based on positive sequence current fault component Download PDFInfo
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- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G01R31/08—Locating faults in cables, transmission lines, or networks
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- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
- Y04S10/52—Outage or fault management, e.g. fault detection or location
Abstract
The invention discloses a positive sequence current fault component-based active power distribution network fault section positioning method and system, which comprise the following steps: collecting three-phase current flowing through switches on two sides of a protected feeder line in real time; after a feeder line is detected to have a fault, calculating to obtain the amplitude and the phase of positive sequence current fault components on two sides of the protected feeder line; calculating a starting amount and a braking threshold value; and when the starting quantity of n continuous sampling points of a certain section of line is greater than the braking threshold value, judging that the section is a fault section. Simulation analysis shows that for power distribution networks containing DGs of different types, when faults of different types occur at different positions, the fault section can be correctly identified, and the method has the advantages of strong transition resistance tolerance capability, high sensitivity, strong reliability and the like. In addition, the invention does not need fault line selection and voltage information, and has good economy.
Description
Technical Field
The invention relates to the technical field of active power distribution network fault section positioning, in particular to an active power distribution network fault section positioning method and system based on a positive sequence current fault component.
Background
With the exhaustion of global fossil energy, the enhancement of environmental awareness of various countries, and the development of distributed power generation technology and power electronic technology, Distributed Generation (DG) based on clean energy is connected to a power distribution network in large quantities. The concept of an active power distribution network (ADN) is proposed in 2008 international large power grid Conference (CIGRE), that is, a distributed power source is locally connected to a power distribution network, which is considered as a direction for developing a future power distribution network. The DG power supply has the advantages of low energy consumption, less investment, flexibility, reliability and the like, but the access of the DG power supply changes the grid structure of the traditional power distribution network, so that the traditional single-end power supply radiation type network is changed into a double-end or multi-end power supply complex network, the network structure, the operation mode and the trend direction of the DG power supply network are changed, and the traditional three-section type current protection of the power distribution network is not applicable any more.
Distributed power sources in the active power distribution network are various in types and are influenced by control modes, and fault characteristics of different types of distributed power sources after faults are different. According to different grid connection modes, the DG can be divided into a motor type power supply (RTDG) capable of being directly connected with the grid and an inverter type power supply (IIDG) which needs inversion and grid connection after boosting. Compared with the motor DG, the inverter DG has more complex characteristics after the fault. The current grid connection regulation requires that the IIDG should preferentially output reactive power to support system voltage when the distribution network is in fault, so that current output by the IIDG is influenced by the voltage of a grid connection point, and the current has high randomness, so that the conventional current protection is difficult to determine a proper setting value, and the reliability and sensitivity of protection are influenced. Therefore, it has become an important issue for active power distribution network protection to propose a method for locating fault sections of a power distribution network containing various types of DGs.
The positive, negative and zero sequence components generated when the power system fails contain a large amount of fault information, and the characteristics of the electric quantities can be used for positioning fault sections of the active power distribution network. At present, scholars at home and abroad carry out a series of researches on control strategies of each electrical sequence component and DG during fault, and provide fault section positioning methods suitable for active power distribution networks.
The prior art provides a pilot protection scheme based on positive sequence current phase angular salient variable directions, the change directions of current phase angles before and after a fault are compared at each protection installation position, 1 is output when the current phase angle difference is a positive value, 1 is output when the current phase angle difference is a negative value, the protection output results at two ends are the same and are external faults, and the protection output results at two ends are the internal faults when the protection output results are opposite. The scheme has low requirement on a communication channel and does not need voltage information, but is only suitable for an active power distribution network containing a motor type DG.
The prior art provides an active power distribution network pilot protection scheme using current amplitudes at two ends of a protection circuit. The scheme only utilizes current amplitude information, has a simple principle and higher sensitivity, has more limiting conditions when in application, and is only suitable for an active power distribution network with lower DG permeability and IIDG.
In the prior art, based on the analysis of the IIDG fault characteristics, an active power distribution network protection scheme for identifying faults by using the amplitude difference of positive sequence differential impedance at two ends of a line when the faults occur inside and outside a region is provided. The protection scheme is not influenced by the fault characteristics of the backside IIDG and does not need synchronous sampling of data at two ends, but a voltage transformer needs to be installed at each protection installation position, so that the cost is high, and the protection scheme does not have the condition of application in the existing power distribution network.
The method reasonably avoids the influence of the synchronous error on the protection braking characteristic, but does not consider the influence of the low voltage ride through characteristic and the transition resistance on the fault current output by the IIDG.
The prior art proposes a hierarchical protection scheme based on a specific network structure of an active power distribution network. The scheme is fast and reliable, but has limitations and is effective only for specific network structures.
In the prior art, a self-adaptive positive sequence current quick-break protection scheme suitable for a power distribution network containing an IIDG is constructed by utilizing the relationship between the positive sequence voltage at the protection installation position and the positive sequence current flowing through the protection when two-phase interphase short-circuit faults and three-phase short-circuit faults occur at different positions. The scheme enlarges the effective protection range of the existing protection and improves the selectivity and the sensitivity of the original protection scheme. But the proposal adds a protective element, and has poor economy; the scheme is complicated to set, influences of transition resistance are ignored, and reliability is difficult to guarantee when fault transition resistance is large.
The prior art researches the phase relation between positive sequence current flowing through protection and voltage before fault at a protection installation position when a positive direction and a negative direction of a power distribution network are in fault, and provides a new principle of a direction element based on phase information of the positive sequence fault current and the voltage before fault. The principle improves the reliability of directional elements, avoids the problem of voltage dead zones of the traditional power elements, but needs to additionally install a voltage transformer at each protection position, and neglects the influence of the passing current on fault phases.
Therefore, the existing active power distribution network fault section positioning and protecting schemes do not have reliable schemes which only utilize current information and are not influenced by factors such as transition resistance, DG permeability, DG type and the like.
Disclosure of Invention
In order to solve the problems, the invention provides a positive sequence current fault component-based active power distribution network fault section positioning method and system. Compared with other active power distribution network fault positioning methods, the method only utilizes positive sequence current information, does not need to install a voltage transformer, and does not need fault phase selection; the method is applicable to power distribution networks containing inverter DGs and motor DGs; the method has the advantages of high sensitivity, high action speed, capability of reflecting all fault types, no load influence, strong transition resistance tolerance and the like.
In order to achieve the purpose, the invention adopts the following technical scheme:
disclosed in some embodiments is a positive sequence current fault component-based active power distribution network fault section locating method, comprising:
collecting three-phase current flowing through switches at two ends of a protected feeder line in real time;
after the feeder line is detected to have a fault, respectively calculating the amplitude and the phase of the positive sequence current at the two ends of the protected feeder line by fast Fourier transform, and further obtaining the amplitude and the phase of the positive sequence current fault component at the two ends of the protected feeder line;
transmitting positive sequence current fault component amplitude and phase information and sampling moment information which are respectively obtained at two ends of a protected feeder line to an opposite end through an optical fiber channel;
calculating the starting amount according to the amplitude information of the positive sequence current fault components at the two ends of the protected feeder line;
calculating a braking threshold value according to phase information of positive sequence current fault components at two ends of a protected feeder line;
when the starting quantity of n continuous sampling points of a certain section of feeder line is greater than a braking threshold value, judging that the section is a fault section; wherein n is a set value.
Further, the amplitude and the phase of the positive sequence current fault component at the two ends of the protected feeder line are obtained, specifically:
the amplitude of the positive sequence current fault component at the two ends of the protected feeder line is equal to the difference between the positive sequence current amplitude at the current moment and the positive sequence current amplitude before a power frequency period;
the phase of the positive sequence current fault component at the two ends of the protected feeder line is equal to the difference between the positive sequence current phase at the current moment and the positive sequence current phase before a power frequency period.
Further, calculating a starting amount according to amplitude information of positive sequence current fault components at two ends of a protected feeder line, specifically: the starting amount is equal to the ratio of the absolute value of the amplitude of the positive sequence current fault component at the two ends of the protected feeder line.
Further, a braking threshold is calculated according to phase information of positive sequence current fault components at two ends of the protected feeder line, specifically:
wherein, | θmn1And | is the absolute value of the phase difference of the positive sequence current fault components at the two ends of the protected feeder line.
Further, the value range of n is 5-10, and the larger the value of n is, the higher the protection reliability is, but the action time is increased at the same time.
An active power distribution network fault section locating system based on positive sequence current fault components disclosed in some embodiments includes a server including a memory, a processor, and a computer program stored on the memory and executable on the processor, the processor implementing the method when executing the program.
A computer-readable storage medium is disclosed in some embodiments having a computer program stored thereon which, when executed by a processor, performs the above-described method.
Compared with the prior art, the invention has the beneficial effects that:
(1) the fault section can be positioned only by utilizing current information, a voltage transformer does not need to be additionally arranged at a protection installation position, and fault phase selection is also not needed, so that the method has higher economical efficiency;
(2) the method fully reflects the excellent performance of the positive-sequence fault current in relay protection, can reliably and quickly locate various types of faults, is not influenced by fault positions, load current and DG capacity, has strong transition resistance tolerance capability and has higher sensitivity;
(3) the method is applicable to both power distribution networks containing inverter type distributed power supplies and motor type distributed power supplies, and has good adaptability;
(4) the identification method has the advantages of simple and clear principle, accurate identification and easy engineering realization.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.
Fig. 1 is a schematic diagram of a simple active power distribution network;
fig. 2(a) is a positive sequence network diagram when an active power distribution network fails;
fig. 2(b) is a positive sequence network diagram before a fault occurs in the active distribution network;
fig. 2(c) is a positive sequence network diagram of a fault attachment state of the active power distribution network;
FIG. 3 is a positive sequence network diagram of an additional fault state of an active power distribution network including an IIDG;
FIG. 4 is a positive sequence network diagram of a fault additional state during an out-of-area fault of an active power distribution network including an IIDG;
FIG. 5 is a schematic diagram of a simulation model of an active power distribution network;
fig. 6(a) is a change curve of the braking threshold value to current amplitude ratio when a two-phase short circuit occurs at point f 1;
fig. 6(b) is a variation curve of the braking threshold value to current amplitude ratio when a three-phase short circuit occurs at point f 1;
fig. 6(c) is a change curve of the braking threshold value to current amplitude ratio when a two-phase ground short circuit occurs at point f 1;
fig. 6(d) is a change curve of the braking threshold value to current amplitude ratio when a two-phase ground short circuit with 10 Ω transition resistance occurs at point f 1;
FIG. 7 is a flowchart of a method for locating a fault section.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The invention discloses an active power distribution network fault section positioning method based on positive sequence current fault components, which comprises the following steps of:
(1) collecting three-phase currents of a, b and c flowing through switches at two ends of a protected feeder line in real time;
(2) when the phase current in the feeder line is detected to be suddenly changed, the feeder line is regarded as a fault, the amplitude and the phase of the positive sequence current at two ends of the line of the protected feeder line are respectively calculated through fast Fourier transform, and the amplitude and the phase of the fault component of the positive sequence current at the two ends are further obtained;
(3) transmitting the positive sequence current fault component amplitude and phase information and sampling moment information obtained at two ends of the feeder line to the opposite end through an optical fiber channel;
(4) calculating the starting amount according to the amplitude information of the positive sequence current fault components at the two ends of the protected feeder line obtained in the step (3);
(5) calculating a braking threshold value according to the phase information of the positive sequence current fault components at the two ends of the protected feeder line obtained in the step (3);
(6) and (3) comparing the starting amount obtained in the step (4) with the braking threshold value obtained in the step (5) at the same moment, and when the starting amount of n continuous sampling points of a certain section of line is greater than the braking threshold value, judging that the section is a fault section.
In the step (4), the principle of calculating the protection starting amount based on the amplitude information of the positive sequence current fault components at the two ends of the line is as follows:
taking the active power distribution network shown in fig. 1 as an example, when a fault occurs in the feeder MN, considering that the voltage and frequency adjustment processes of the system are constrained by time constants, the system in a short time can be equivalent to a linear system, and the positive sequence composite sequence network after the fault can be divided into a network before the fault occurs and a fault additional network by the superposition theorem. If the DG in the distribution network is a motor type DG, the post-fault positive sequence network, the pre-fault positive sequence network, and the positive sequence fault additional network are shown in fig. 2(a), fig. 2(b), and fig. 2(c), respectively.
In the drawings
Respectively system and DGm1、Zn1、Zmf1、Znf1Respectively are positive sequence equivalent impedances of the left side of the M end, the right side of the N end, the M end to a fault point and the fault point to the N end,
is the voltage at the fault point before the fault occurs,
the current positive sequence fault components of the M end and the N end are respectively, the delta Z is fault additional impedance, and the value is determined by the fault type.
When the distributed power supply is the IIDG, the IIDG cannot be equivalent to a voltage source connected in series with an impedance in consideration of the randomness of the output of the IIDG after a fault. Since the fault current output by the IIDG is related to the drop degree of the voltage at the grid-connected point, it is mostly equivalent to a voltage control type current source in the existing research.
An additional sequence network for positive sequence fault of an active power distribution network with IIDG distributed power supply is shown in figure 3
Is the positive sequence fault component of the IIDG output current. The current in the detection points at the two ends of the protection section can be divided into two parts by the superposition theorem: one part is generated by the fault additional potential and one part is generated by the equivalent current source of the IIDG. The positive sequence fault component of the two-terminal current can be expressed as
In the formula, Zms1＝Zm1+Zmf1，
Providing a positive sequence fault component of current, K, for an additional potentialdgIs composed of
The current distribution coefficient of (1).
Due to the influence of the control strategy, the short-circuit current provided by the inverter type DG after the fault does not usually exceed twice its rated current, and when the fault occurs at the upstream of the DG, the short-circuit current provided by the DG is much smaller than that provided by the system side,
relative to the size of
And can be ignored. At the moment, the positive sequence current fault component amplitude value flowing through the M end of the protection circuit
Far larger than the fault component amplitude of the positive sequence current flowing through the N end of the line
Therefore, the fault section can be positioned by constructing a positive sequence fault component amplitude criterion of the current at two ends of the line. Defining the protection starting amount as the amplitude ratio I of the positive sequence current fault components at two ends of the liner
For the fault section, the fault current at two ends of the line is respectively provided by a system power supply and an IIDG, the amplitude difference is large, and IrAnd is also larger.
For the non-fault section, as shown in FIG. 4, the fault current at both ends of the line is provided by the system power supply or IIDG, with small amplitude difference, IrIs close to 1.
By combining the analysis, the positive sequence fault current amplitude ratio of the fault section and the non-fault section in the power distribution network containing the IIDG has obvious difference, so that the method is used as the protection starting amount. However, for a power distribution network with a motor type dg (rtdg), the fault section cannot be accurately located under various conditions by using only the current amplitude, and current phase information needs to be introduced.
In the step (5), the principle of calculating the protective braking threshold value based on the phase information of the positive sequence current fault components at the two ends of the line is as follows:
as shown in fig. 2(c), when a fault occurs in the active power distribution network region, the directions of positive sequence current fault components at two ends of the line are both from the line to the bus, the phase difference is only determined by the impedance angles of the lines at the two ends, and the value of the phase difference is close to 0; when the fault occurs outside the area, the directions of the positive sequence current fault components at the two ends of the line are opposite, and the phase difference is close to 180 degrees. The method utilizes the characteristic to construct a braking threshold value, and the braking threshold value is set to be Kset
Wherein, | θmn1And | is the absolute value of the phase difference of the positive sequence current fault components at the two ends.
For a motor type DG, | θ of the fault sectionmn1I is approximately equal to 0, when cos (| 180-theta)mn1|)≈-1，KsetThe brake threshold is extremely small and the sensitivity of protection in case of a fault in the area can be effectively improved by approximately 0; of non-faulted section | θmn1|≈180°，cos(|180-θmn1|)≈1，KsetAnd the brake threshold is extremely large due to the fact that the brake is approximately equal to + ∞, and the safety of protection during an out-of-range fault can be effectively improved.
For the power distribution network containing the IIDG, due to the randomness of the IIDG output after the fault, the theta of the fault sectionmn1And (3) the value range of | is large, the fault section is difficult to accurately position only by depending on the current phase, and the current amplitude information obtained in the step (4) needs to be introduced.
In the step (6), the principle of positioning the fault section by using the amplitude of the positive sequence current fault component is as follows:
in order to increase the reliability of protection, when the starting quantity met by n continuous sampling points of a certain section is set to be greater than a braking threshold value, the section is judged to be a fault section. The criterion of the protective action is
Ir＞Kset
For a motor type DG, when a fault point is located at the upstream of the DG and is close to the DG, the starting amount is small, but the braking threshold value of a fault section is close to 0 at the moment, so that the accuracy of fault positioning can be still ensured.
For the inverter type DG, because of uncertainty of output after the fault, the situation that the braking threshold value of the fault section is slightly larger can occur, but because the starting amount of the fault section is larger at the moment, the accuracy of fault positioning can still be ensured.
The method comprises the following steps of (1) constructing a power distribution network simulation model containing DGs of different types by utilizing PSCAD, and performing simulation verification on a fault section positioning method:
1) modeling
The structure of the simulation model is shown in FIG. 2. The system reference voltage is 10.5kV, and the equivalent internal resistance Z of the systemsJ0.14 Ω, line parameter r1＝0.13Ω/km，x10.402 Ω/km. The DG rated power is 4MW, and the impedance per unit length of the line is as follows: r is 0.13 omega/km, X is 0.402 omega/km, and the lengths of lines AB, BC, CD and DE are 3km, 2 km and 3km respectively; the rated power of each load on the feeder is 4MVA, and the power factor is 0.9. Corresponding protection is configured at the circuit breaker CBi. The fault points f1, f2 are located in the feeders BC, DE, respectively, and f3 is located on the other feeder.
2) Exemplary Fault simulation
a) Power distribution network fault simulation containing IIDG
When a two-phase short circuit, a three-phase short circuit, a two-phase ground short circuit, and a two-phase ground short circuit through a 10 Ω transition resistance occur at point f1, the changes in the braking threshold value to the current amplitude ratio before and after the occurrence of the fault are shown in fig. 6(a), 6(b), 6(c), and 6(d), respectively. Faults occur when the set time is 0.2s, and the time of one cycle is observed before and after.
As can be seen from fig. 6(a) - (d), no matter two-phase short circuit, three-phase short circuit or two-phase ground short circuit occurs, the braking threshold value rapidly decreases to 0 within 5ms after the fault occurs, and at the same time, the current positive sequence fault component amplitude ratio rapidly increases. When the fault is a metallic fault, the current amplitude ratio exceeds the braking threshold value in the 3 rd ms after the fault occurs, and is 4ms when the 10 omega transition resistance is included, so that the method can act quickly under various conditions and has strong transition resistance tolerance capability.
Various types of faults are respectively set at f1, f2 and f3, wherein the f1 and f2 faults take into account the fact that the faults are located at the head end and the tail end of the line. The simulation results are shown in tables 1-3, wherein each item of data is taken from the 10 th ms after the fault.
TABLE 1 simulation results for a failure point of f1
TABLE 2 simulation results for failure point f2
TABLE 3 simulation results for failure point f3
From the simulation results of table 1, table 2 and table 3, no matter what type of fault occurs at the head end or the tail end of the line, the positive sequence current fault component in the fault section has a larger amplitude value, the braking threshold value is smaller, and the starting amount is larger than the braking threshold value; and the conditions that the amplitude of the positive sequence current fault component is smaller, the braking threshold value is larger and the starting amount is smaller than the braking threshold value exist in the non-fault section. It is worth noting that the positive sequence current fault component amplitude of the fault section is smaller when a fault occurs at the tail end of the line compared with the head end of the line, but the starting amount can still be ensured to be larger than the braking threshold value; in addition, when the ground is short-circuited through the 10 Ω transition resistor, the situation that the braking threshold value is increased due to the fact that the phase difference of the positive sequence current fault components is large occurs in the fault section, and the braking threshold value can still be guaranteed to be smaller than the starting amount. Therefore, for the power distribution network containing the IIDG, the fault section positioning method based on the positive sequence current fault component can accurately position the fault section.
b) Fault simulation method for power distribution network comprising RTDG
Setting DG as RTDG, and setting various types of faults at f1, f2 and f3 respectively, wherein the faults at f1 and f2 are considered to be at the head end and the tail end of the line. The simulation results are shown in tables 4-6, wherein the data are all taken from the 10 th ms after the fault.
Table 4 simulation results with failure point f1
TABLE 5 simulation results for failure point f2
TABLE 6 simulation results for failure point f3
From the simulation results of table 4, table 5 and table 6, no matter what type of fault occurs at the head end or the tail end of the line, the positive sequence current fault component in the fault section has a larger amplitude value, the braking threshold value is smaller, and the starting amount is larger than the braking threshold value; and the conditions that the amplitude of the positive sequence current fault component is smaller, the braking threshold value is larger and the starting amount is smaller than the braking threshold value exist in the non-fault section. It is noted that when the fault point f1 is located at the end of the line, the fault point is close to the downstream DG, the positive sequence current fault component amplitude ratio of the fault section is smaller than that of the non-fault section, but since the braking thresholds of the fault section and the non-fault section are close to 0 and extremely large, respectively, it is still ensured that the activation amount of the fault section is greater than the braking threshold, and not that of the fault section is less than the braking threshold. Therefore, for a power distribution network containing the RTDG, the fault location method based on the positive sequence current fault component pilot can accurately locate the fault section.
According to the simulation results, the fault section positioning method based on the positive sequence current fault component can be suitable for power distribution networks containing various types of DGs, is not influenced by fault types, and has strong transition resistance tolerance capability and high reliability and sensitivity.
The method utilizes the characteristics of the amplitude and the phase of the positive sequence current fault components at the two ends of the feeder line, firstly utilizes the amplitude information of the positive sequence current fault components to construct the starting amount, utilizes the phase difference of the positive sequence current fault components to construct the braking threshold value, and then compares the starting amount and the braking threshold value in each section to position the fault section. PSCAD simulation results show that the method can correctly position the fault section within 10ms under various fault conditions, has strong transition resistance tolerance capability, and greatly improves the reliability and sensitivity of the method by adding the braking threshold value. In addition, the method only utilizes the positive sequence current fault component information, does not need fault phase selection, does not need to additionally install a voltage transformer at a protection installation position, and has good economical efficiency.
In other embodiments, the present invention further discloses an active power distribution network fault section locating system based on positive sequence current fault components, including: a server comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, the processor implementing the steps when executing the program:
collecting three-phase current flowing through switches at two ends of a protected feeder line in real time;
after the feeder line is detected to have a fault, respectively calculating the amplitude and the phase of the positive sequence current at the two ends of the protected feeder line by fast Fourier transform, and further obtaining the amplitude and the phase of the positive sequence current fault component at the two ends of the protected feeder line;
transmitting positive sequence current fault component amplitude and phase information and sampling moment information which are respectively obtained at two ends of a protected feeder line to an opposite end through an optical fiber channel;
calculating the starting amount according to the amplitude information of the positive sequence current fault components at the two ends of the protected feeder line;
calculating a braking threshold value according to phase information of positive sequence current fault components at two ends of a protected feeder line;
when the starting quantity of n continuous sampling points of a certain section of feeder line is greater than a braking threshold value, judging that the section is a fault section; wherein n is a set value.
The amplitude of the positive sequence current fault component at two ends of the protected feeder line is equal to the difference between the positive sequence current amplitude at the current moment and the positive sequence current amplitude before one power frequency period;
the phase of the positive sequence current fault component at the two ends of the protected feeder line is equal to the difference between the positive sequence current phase at the current moment and the positive sequence current phase before a power frequency period.
The starting amount is equal to the ratio of the absolute value of the amplitude of the positive sequence current fault component at the two ends of the protected feeder line.
Braking threshold
Wherein, | θmn1And | is the absolute value of the phase difference of the positive sequence current fault components at the two ends of the protected feeder line.
In still other embodiments, the present invention further discloses a computer readable storage medium having a computer program stored thereon, the program being executed by a processor to perform the steps of:
collecting three-phase current flowing through switches at two ends of a protected feeder line in real time;
after the feeder line is detected to have a fault, respectively calculating the amplitude and the phase of the positive sequence current at the two ends of the protected feeder line by fast Fourier transform, and further obtaining the amplitude and the phase of the positive sequence current fault component at the two ends of the protected feeder line;
transmitting positive sequence current fault component amplitude and phase information and sampling moment information which are respectively obtained at two ends of a protected feeder line to an opposite end through an optical fiber channel;
calculating the starting amount according to the amplitude information of the positive sequence current fault components at the two ends of the protected feeder line;
calculating a braking threshold value according to phase information of positive sequence current fault components at two ends of a protected feeder line;
when the starting quantity of n continuous sampling points of a certain section of feeder line is greater than a braking threshold value, judging that the section is a fault section; wherein n is a set value.
The amplitude of the positive sequence current fault component at two ends of the protected feeder line is equal to the difference between the positive sequence current amplitude at the current moment and the positive sequence current amplitude before one power frequency period;
the phase of the positive sequence current fault component at the two ends of the protected feeder line is equal to the difference between the positive sequence current phase at the current moment and the positive sequence current phase before a power frequency period.
The starting amount is equal to the ratio of the absolute value of the amplitude of the positive sequence current fault component at the two ends of the protected feeder line.
Braking threshold
Wherein, | θmn1And | is the absolute value of the phase difference of the positive sequence current fault components at the two ends of the protected feeder line.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.
Claims (6)
1. A method for positioning a fault section of an active power distribution network based on a positive sequence current fault component is characterized by comprising the following steps:
collecting three-phase current flowing through switches at two ends of a protected feeder line in real time;
after the feeder line is detected to have a fault, respectively calculating the amplitude and the phase of the positive sequence current at the two ends of the protected feeder line by fast Fourier transform, and further obtaining the amplitude and the phase of the positive sequence current fault component at the two ends of the protected feeder line;
transmitting positive sequence current fault component amplitude and phase information and sampling moment information which are respectively obtained at two ends of a protected feeder line to an opposite end through an optical fiber channel;
calculating the starting amount according to the amplitude information of the positive sequence current fault components at the two ends of the protected feeder line;
calculating a braking threshold value according to phase information of positive sequence current fault components at two ends of a protected feeder line, specifically:
wherein, | θmn1I is the absolute value of the phase difference of the positive sequence current fault components at the two ends of the protected feeder line;
when the starting quantity of n continuous sampling points of a certain section of feeder line is greater than a braking threshold value, judging that the section is a fault section; wherein n is a set value.
2. The active power distribution network fault section positioning method based on the positive sequence current fault component as claimed in claim 1, wherein the amplitude and phase of the positive sequence current fault component at two ends of the protected feeder line are obtained, specifically:
the amplitude of the positive sequence current fault component at the two ends of the protected feeder line is equal to the difference between the positive sequence current amplitude at the current moment and the positive sequence current amplitude before a power frequency period;
the phase of the positive sequence current fault component at the two ends of the protected feeder line is equal to the difference between the positive sequence current phase at the current moment and the positive sequence current phase before a power frequency period.
3. The method for locating the fault section of the active power distribution network based on the positive sequence current fault component as claimed in claim 1, wherein the starting amount is calculated according to the amplitude information of the positive sequence current fault component at the two ends of the protected feeder line, specifically: the starting amount is equal to the ratio of the absolute value of the amplitude of the positive sequence current fault component at the two ends of the protected feeder line.
4. The active power distribution network fault section positioning method based on the positive sequence current fault component as claimed in claim 1, wherein the value range of n is 5-10, and the larger the value of n is, the higher the protection reliability is, but the action time is increased at the same time.
5. Active power distribution network fault section location system based on positive sequence current fault components, characterized in that it comprises a server comprising a memory, a processor and a computer program stored on the memory and executable on the processor, which when executing the program implements the method according to any of claims 1-3.
6. A computer-readable storage medium, on which a computer program is stored, which program, when being executed by a processor, is adapted to carry out the method of any one of claims 1-3.
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| CN109613398B (en) * | 2018-12-12 | 2021-11-09 | 国网山东省电力公司电力科学研究院 | Fault direction discrimination method and discrimination element for high-voltage alternating current-direct current hybrid power grid |
| CN109613383A (en) * | 2018-12-27 | 2019-04-12 | 中国电力科学研究院有限公司 | Meter and the alternating current circuit fault judgment method and system of direct current access |
| CN111900704A (en) * | 2020-08-04 | 2020-11-06 | 国网山东省电力公司聊城供电公司 | Active power distribution network current differential protection method and device without strict data synchronization |
| CN113009280B (en) * | 2021-03-08 | 2022-05-06 | 长沙学院 | Micro-grid fault positioning method based on fault characteristic active construction |
| CN113281615B (en) * | 2021-05-28 | 2023-05-23 | 广西电网有限责任公司电力科学研究院 | Active power distribution network line fault characteristic analysis method and storage medium |
| CN113659548B (en) * | 2021-08-23 | 2022-05-27 | 山东大学 | Power distribution network pilot protection method and system based on positive sequence fault component energy direction |
| CN116381417A (en) * | 2023-06-01 | 2023-07-04 | 中国南方电网有限责任公司超高压输电公司广州局 | Intelligent analysis method and device for power transmission equipment, computer equipment and storage medium |
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