CN115291032A - Power distribution network single-phase earth fault line selection method, device, system and storage medium - Google Patents
Power distribution network single-phase earth fault line selection method, device, system and storage medium Download PDFInfo
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Abstract
The invention discloses a method, a device, a system and a storage medium for single-phase earth fault line selection of a power distribution network, wherein the method comprises the following steps: acquiring zero-sequence current of each feeder line in the process of reducing the zero-sequence voltage of the system step by step; calculating a zero sequence current proportion coefficient of each feeder line after voltage regulation by taking the initially measured zero sequence current as a reference, wherein the feeder line with the zero sequence current proportion coefficient larger than a preset proportion coefficient threshold value is a fault feeder line; if no feeder line is satisfied, calculating the nonlinear distortion degree of the zero sequence current of each feeder line in the voltage regulating process, wherein the feeder line with the maximum nonlinear distortion degree is the fault feeder line. By actively regulating and controlling the zero sequence voltage of the system, the fault characteristic component is amplified, and the problem of difficult line selection when the resonant grounding system has a high-resistance grounding fault is effectively solved. The two criteria are adopted to fuse the line selection method, and the line selection accuracy is improved.
Description
Technical Field
The invention relates to the field of fault line selection of a power distribution network, in particular to a single-phase earth fault line selection method, a single-phase earth fault line selection device, a single-phase earth fault line selection system and a single-phase earth fault line selection storage medium of the power distribution network.
Background
The neutral points of the distribution network in China mostly adopt a grounding mode of arc suppression coils, the grounding mode can obviously reduce the capacitance current of a fault point, but the detection and line selection of signals are difficult because the amplitude of the fault current is small and the direction is uncertain. The high-resistance grounding fault has the characteristics of large transition resistance, unstable fault point, intermittent arc at the fault point and the like, so that the fault electrical quantity characteristic is extremely unobvious, and the conventional protection is difficult to operate reliably. When the resonant grounding system has a high resistance fault, the fault detection and line selection problems are more difficult. If the fault point can not be found and processed in time, it is very easy to cause serious accidents such as electric shock casualties of human bodies, mountain fire induction and the like. Therefore, after the resonant grounding system generates a high-resistance grounding fault, the fault feeder line can be quickly and effectively identified, and the method has great significance for maintaining the stability of equipment, protecting personal safety and guaranteeing national life.
The existing line selection methods can be divided into two categories, namely a passive method and an active method according to the source of the used signal. The passive line selection method realizes fault line selection according to fault information characteristics generated by the ground fault, and comprises a steady state line selection method and a transient state line selection method. The steady state line selection method is to select lines by utilizing steady state signals which continuously exist in the grounding period, and because the zero sequence current polarity of a fault line of the resonance grounding system is uncertain, and when a high resistance fault occurs, the contents of steady state components such as power frequency current, active components, negative sequence current and the like are low, the detection effect of the steady state line selection method on the high resistance fault is poor. The transient state line selection method utilizes transient state signals generated in the initial stage of a fault to select lines, and has the main advantages that the fault transient state signals are obvious and can reach dozens of times of steady state signals, and the fault transient state signals are basically not influenced by a neutral point grounding mode, but the components have instability, uncertainty and instantaneity, so that the difficulty of characteristic quantity extraction and protection fixed value setting is caused, and higher requirements are provided for the sampling frequency of the device. The active line selection method carries out fault line selection through information characteristics generated by an additional device, and comprises an injection signal method, a medium resistance method, a residual current increment method, a small disturbance method and the like. The method has the advantages that the characteristics and the strength of signals for line selection are controllable, and the method has the defects that expensive signal injection equipment is needed, the investment is high, the selection requirement on the injected signals is high, and the amplitude and the phase of initial injection current can seriously influence the line selection effect.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a method, a device, a system and a storage medium for selecting a single-phase earth fault line of a power distribution network.
In a first aspect, a method for selecting a single-phase earth fault line of a power distribution network is provided, which includes:
s1: obtaining zero sequence current of each feeder line in the process of reducing the zero sequence voltage of the system step by step;
s2: calculating a zero sequence current proportion coefficient of each feeder line after voltage regulation by taking the initially measured zero sequence current as a reference, wherein the feeder line with the zero sequence current proportion coefficient larger than a preset proportion coefficient threshold value is a fault feeder line; if no feeder is satisfied, entering step S3; s3: and calculating the nonlinear distortion degree of the zero sequence current of each feeder line in the voltage regulating process, wherein the feeder line with the maximum nonlinear distortion degree is the fault feeder line.
In the process of reducing the zero sequence voltage of the system step by step, the zero sequence voltage of the system is reduced, and the fault phase voltage is increased. When the transition resistance of the fault point is far smaller than the zero sequence capacitive reactance of the line, the zero sequence current of the non-fault feeder line is in direct proportion to the zero sequence voltage of the system (descending), the zero sequence current of the fault feeder line is in direct proportion to the voltage of the fault phase (ascending), and the zero sequence current increase and decrease difference of each feeder line in the voltage regulation process is reduced to perform line selection. When the transition resistance of a fault point is large, the line selection cannot be accurately carried out by using the increase and decrease difference of the zero sequence current of each feeder line, but the zero sequence current of the non-fault feeder line is in direct proportion to the zero sequence voltage (linear decrease), the zero sequence current of the fault feeder line is generated by the combined action of the zero sequence voltage and the fault phase voltage and presents a nonlinear change trend, and the line selection is assisted by using the nonlinear distortion degree of the zero sequence current of each feeder line in the downshift voltage regulation process. The problem of difficult line selection when a high-resistance grounding fault occurs in the resonant grounding system is effectively solved by amplifying the fault characteristic component step by step; two criteria are adopted to fuse the line selection method, tens of kilohms of ground fault feeder lines are effectively identified, and the accuracy rate of line selection is improved.
Further, before obtaining zero sequence current of each feeder line in the process of reducing the zero sequence voltage of the system step by step, the method further comprises the following steps:
and judging whether the power distribution network has single-phase earth faults or not, and if so, carrying out single-phase earth fault line selection on the power distribution network.
And judging whether the power distribution network has single-phase earth faults or not in real time, if the power distribution network has single-phase earth faults, performing fault line selection, and if the power distribution network does not have single-phase earth faults, circularly judging whether the power distribution network has single-phase earth faults or not according to a preset time interval.
Further, the judging whether the power distribution network has the single-phase earth fault specifically includes:
and if the zero-sequence voltage of the system is greater than the first phase voltage threshold value or the zero-sequence voltage variation of the system is greater than the second phase voltage threshold value, judging that the single-phase earth fault occurs in the power distribution network.
When the power distribution network has a single-phase earth fault, the zero-sequence voltage of the system is larger than a certain proportion of the phase voltage, and the change quantity of the zero-sequence voltage of the system is also larger than a certain proportion of the phase voltage.
Further, the step-by-step reduction of the zero sequence voltage of the system is realized by the following method:
a plurality of tapping taps are uniformly arranged on a primary side winding tap of the transformer to form a plurality of gears;
when single-phase earth fault occurs, the initial gear of the fault phase tapping tap is regulated and controlled to be grounded, and after time delay, the grounding gear of the tapping tap is gradually reduced to the lowest gear.
A plurality of tap taps are uniformly arranged on each winding on the primary side of the transformer to form a plurality of gears. When the power distribution network system normally operates, all the phase tapping joints are in a disconnected state; once single-phase earth fault occurs, the initial gear set by the fault phase tapping is quickly regulated and controlled to be grounded, and after preset time delay, the grounding gear of the tapping is gradually reduced to the lowest gear. The process of reducing the tap grounding gear is essentially the process of reducing the zero sequence voltage of the system and increasing the fault phase voltage.
Further, the zero sequence current proportionality coefficient is defined as follows:
in the formula, alpha in For the zero sequence current proportionality coefficient of the ith feeder line when the zero sequence voltage of the system is reduced to n level 0ix Is zero-sequence current of ith feeder line under the initial level x of the zero-sequence voltage of the system, I 0in Reducing the zero sequence voltage of the system to be zero sequence current of the ith feeder line after n levels; wherein n =1,2,3, x-1.
Further, the preset scaling factor threshold is
Wherein K rel The value is 1.1-1.2 for the reliability coefficient.
In the process of reducing the zero sequence voltage of the system step by step, the zero sequence current of the non-fault feeder line is reduced, so the proportionality coefficient value of the zero sequence current of the fault feeder line does not exceed 1, the zero sequence current of the fault feeder line is improved, the proportionality coefficient of the zero sequence current of the fault feeder line is larger than 1, based on the situation, a preset proportionality coefficient threshold value is set, and the fault feeder line can be judged by comparing the proportionality coefficient of the zero sequence current of each feeder line with the proportionality coefficient of the zero sequence current of the feeder line.
Further, the nonlinear distortion degree of the zero-sequence current of each feeder line is defined by the slope variance of the zero-sequence current of each feeder line:
in the formula, S 2 [I 0i ]The slope variance of the zero sequence current of the ith feeder line is obtained; x is the initial level of the zero sequence voltage of the system; k 0in For reducing the zero sequence voltage of the system to n level, the slope of the zero sequence current, K 0in ＝I 0in -I 0in-1 (n≥2)；
The slope average value of the corresponding zero sequence current in the process of reducing the zero sequence voltage level for the ith feeder line,
in the process of reducing the zero sequence voltage of the system step by step, the zero sequence current of the non-fault feeder line still has a linear change trend, and when the zero sequence current of the fault feeder line has a nonlinear change trend. Based on the method, the nonlinear distortion degree of the zero-sequence current of each feeder line is reflected by the slope variance of the zero-sequence current of each feeder line, and the feeder line with the largest slope variance of the zero-sequence current is the fault feeder line.
In a second aspect, a single-phase earth fault line selection device for a power distribution network is provided, which includes:
the data acquisition module is used for acquiring zero-sequence current of each feeder line in the process of reducing the zero-sequence voltage of the system step by step;
the line selection judging module is used for selecting lines by adopting the following two line selection criteria:
calculating a zero sequence current proportion coefficient of each feeder line after voltage regulation by taking the initially measured zero sequence current as a reference, wherein the feeder line with the zero sequence current proportion coefficient larger than a preset proportion coefficient threshold value is a fault feeder line; if no feeder line is satisfied, calculating the nonlinear distortion degree of the zero sequence current of each feeder line in the voltage regulating process, wherein the feeder line with the maximum nonlinear distortion degree is the fault feeder line.
In a third aspect, a single-phase earth fault line selection system for a power distribution network is provided, which includes:
the system zero sequence voltage control module is used for performing step-by-step reduction control on the system zero sequence voltage;
the data acquisition module is used for acquiring zero-sequence current of each feeder line in the process of reducing the zero-sequence voltage of the system step by the system zero-sequence voltage control module;
the line selection module is used for acquiring zero sequence current of each feeder line in the process of reducing the zero sequence voltage of the system step by step, and performing line selection by adopting the following two line selection criteria:
calculating a zero-sequence current proportionality coefficient of each feeder line after voltage regulation by taking the primarily measured zero-sequence current as a reference, wherein the feeder line with the zero-sequence current proportionality coefficient larger than a preset proportionality coefficient threshold value is a fault feeder line; if no feeder line is satisfied, calculating the nonlinear distortion degree of the zero sequence current of each feeder line in the voltage regulating process, wherein the feeder line with the maximum nonlinear distortion degree is the fault feeder line.
In a fourth aspect, a computer-readable storage medium stores a computer program which, when loaded by a processor, implements a single-phase ground fault line selection method for a power distribution network as described above.
Advantageous effects
The invention provides a method, a device, a system and a storage medium for selecting a single-phase earth fault line of a power distribution network. Two criteria are adopted to fuse the line selection method, and the zero sequence current proportionality coefficient of each feeder line in the voltage regulation process is utilized to select the line when the medium and low resistance ground fault occurs; when a high-resistance grounding fault occurs, the nonlinear distortion degree of zero-sequence current of each feeder line in the voltage regulation process is utilized to assist line selection, so that tens of kilohms of grounding fault feeder lines can be effectively identified, and the fault line selection accuracy of the resonant grounding system is greatly improved. In addition, the line selection method provided by the invention does not need to newly add a line selection device, the transformer is the existing transformer substation, and only the tapping tap is added to enable the winding to be grounded, so that the cost is greatly reduced, and the economical efficiency is very high.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a flowchart of a single-phase earth fault line selection method for a power distribution network according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a transformer stepped-ground voltage regulation according to an embodiment of the present invention;
FIG. 3 is a vector diagram for stepped voltage regulation provided by embodiments of the present invention;
FIG. 4 is a zero sequence network diagram of a feeder equivalent of a resonant grounding system provided by an embodiment of the present invention;
FIG. 5 is a simulation model diagram of a single-phase earth fault of a 10kv distribution network provided by the embodiment of the invention;
fig. 6 is a diagram of a change situation of zero sequence current proportionality coefficients of each feeder line according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It should be apparent that the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to solve the problem of low accuracy of high-resistance ground fault line selection in a resonant grounding system, the invention provides a line selection scheme for judging a fault feeder line by identifying the increase and decrease of zero-sequence current of each feeder line along with the regulation and control of neutral point voltage from the viewpoint of actively regulating and controlling the neutral point voltage of the system. The scheme of the present invention is specifically illustrated by the following examples.
Example 1
As shown in fig. 1, this embodiment provides a method for selecting a single-phase earth fault of a power distribution network, which is applied when a single-phase earth fault occurs in the power distribution network, and specifically includes:
s1: and obtaining zero sequence current of each feeder line in the process of reducing the zero sequence voltage of the system step by step. As shown in fig. 2, in implementation, the step-by-step reduction of the zero sequence voltage of the system can be implemented by the following method:
at the primary side A of the transformer Y 、B Y 、C Y A plurality of tapping taps are uniformly arranged on the three winding taps to form a plurality of gears, and the gears are numbered according to a mode that the neutral point is gradually increased to the outlet of the feeder line from 1 to K;
when the power distribution network system normally operates, all phase tapping joints are in a disconnected state; once single-phase earth fault happens, the initial gear of the fault phase tapping tap is rapidly regulated and controlled to be grounded. At this time, the step voltage regulation phasor diagram is shown in fig. 3, where N is a system neutral point, and O is a zero potential point when an earth fault occurs, and the following voltage relationship exists:
wherein
Is a zero-sequence voltage of a neutral point,
in order to be a faulty phase voltage,
and n is a tap grounding gear for a fault phase power supply electromotive force.
As explained below for the selection of the initial gear, since the transient fault arc can be extinguished by itself, and no additional line selection operation is required, the tap initial gear x is selected based on the transient fault reliable arc extinction, that is, the following formula is satisfied:
in the formula of U r For the fault arc reignition voltage, K is the total number of taps (i.e., total number of gears).
After a short time delay, the grounding gear of the tap is gradually reduced to the lowest gear. The process of reducing the tap grounding gear is essentially the process of reducing the zero sequence voltage of the system and increasing the fault phase voltage.
S2: calculating a zero sequence current proportion coefficient of each feeder line after voltage regulation by taking the initially measured zero sequence current as a reference, wherein the feeder line with the zero sequence current proportion coefficient larger than a preset proportion coefficient threshold value is a fault feeder line; if not (i.e. no feeder meets the criterion), step S3 is performed. The specific realization principle is as follows:
it can be known from the equivalent zero sequence network diagram of the feeder of the resonant grounding system shown in fig. 4 that:
when the system has single-phase earth fault, the zero-sequence current of the non-fault feeder line
For line-to-ground capacitive currents
Namely, the zero-sequence current of the non-fault feeder line is in direct proportion to the zero-sequence voltage of the system; wherein the content of the first and second substances,
is a three-phase voltage at the bus, C 0i For non-faulted feeder i three-phase to ground capacitance (assuming the three line to ground capacitances are approximately balanced), j represents an imaginary number and ω represents angular velocity.
Zero sequence current of fault feeder
Should be line-to-ground capacitive current
And fault earth current
And (c) the sum, i.e.:
wherein, C 0k For fault feeder three-phase to ground capacitance, R f Is a fault feeder line transition resistance.
Under the condition of low-impedance grounding fault, the zero-sequence capacitive reactance of the line is far larger than the ground resistance of the fault point, and the zero-sequence current of the fault feeder line can be approximately considered to be in direct proportion to the fault phase voltage. The process of reducing the tap grounding gear is essentially the process of reducing the zero sequence current of the non-fault feeder line and improving the zero sequence current of the fault feeder line.
In order to improve the line selection precision, zero-sequence current corresponding to the tap at the initial gear x is taken as reference current, and a zero-sequence current proportionality coefficient is defined
Wherein alpha is in Is the zero sequence current proportionality coefficient when the zero sequence voltage of the system is reduced to n level (namely, the grounding gear is the gear n) of the ith feeder line, I 0ix Is zero-sequence current of ith feeder line under the initial level x of the zero-sequence voltage of the system, I 0in For the zero sequence voltage of the system to be reduced to the zero sequence current of the ith feeder line after n levels (namely, the grounding gear is the gear n), n =1,2,3.
The zero sequence current proportionality coefficient of the non-fault feeder line meets
The zero sequence current proportion coefficient of the fault line meets
Wherein, U 0n Corresponding to the zero sequence voltage of the system when the gear n is grounded, U 0x Corresponding to the zero sequence voltage, U, of the system when the initial gear x is grounded fn Corresponding to the fault phase voltage, U, when gear n is grounded fx The voltage is corresponding to the fault phase when the initial gear x is grounded. Accordingly, the preset scaling factor threshold is set as
Wherein K rel The value is 1.1-1.2 for reliable coefficient, and zero sequence current proportional coefficient criterion is further constructed
If the zero sequence current proportionality coefficient of the feeder line exists, the zero sequence current proportionality coefficient is satisfied
Then the feeder can be determined to be a faulty feeder.
S3: and calculating the nonlinear distortion degree of the zero sequence current of each feeder line in the voltage regulating process, wherein the feeder line with the maximum nonlinear distortion degree is the fault feeder line.
And when the fault transition resistance value is larger, the accuracy of the fault line selection method in the step S2 is reduced, and based on the accuracy, the fault line selection is carried out by utilizing the nonlinear distortion degree of the zero-sequence current of each feeder line. When the fault transition resistance value is large, the formula
The effect of the capacitance current to the ground cannot be ignored, and the fault feeder line has a nonlinear variation trend along with the reduction of the gear, while the non-fault feeder line still has a linear variation trend. Therefore, a zero sequence current nonlinear distortion degree criterion is constructed. In this embodiment, the non-linear distortion degree of the zero-sequence current of each feeder line is defined by a slope variance of the zero-sequence current of each feeder line:
in the formula, S 2 [I 0i ]The slope variance of the zero sequence current of the ith feeder line is obtained; x is the initial level of the zero sequence voltage of the system; k 0in For reducing the zero sequence voltage of the system to n level (i.e. the grounding gear is the gear n), the zero sequence current slope, K 0in ＝I 0in -I 0in-1 (n≥2)；
The slope average value of the corresponding zero sequence current in the process of reducing the zero sequence voltage level for the ith feeder line,
and screening the zero sequence current slope variance of each feeder line, wherein the feeder line with the maximum zero sequence current slope variance is the fault feeder line.
During implementation, before the single-phase earth fault line selection of the power distribution network, whether the single-phase earth fault occurs in the power distribution network needs to be judged, and if the single-phase earth fault occurs, the single-phase earth fault line selection of the power distribution network is carried out. If not, judging whether the power distribution network has the single-phase earth fault according to preset time interval circulation.
Specifically, if the zero-sequence voltage of the system is greater than the first phase voltage threshold value or the change of the zero-sequence voltage of the system is greater than the second phase voltage threshold value, it is determined that the single-phase ground fault occurs in the power distribution network. When a single-phase earth fault occurs in the power distribution network, the zero-sequence voltage of the system is larger than a certain proportion of the phase voltage, such as 15% of the phase voltage; the change quantity of the zero sequence voltage of the system is larger than a certain proportion of the phase voltage, such as 3 percent of the phase voltage; based on the method, whether the single-phase earth fault occurs can be judged by judging whether the system zero-sequence voltage or the system zero-sequence voltage variation exceeds a certain threshold value.
The zero sequence voltage of the system is reduced, and the fault phase voltage is increased. When the transition resistance of the fault point is far smaller than the zero sequence capacitive reactance of the line, the zero sequence current of the non-fault feeder line is in direct proportion to the zero sequence voltage of the system (descending), the zero sequence current of the fault feeder line is in direct proportion to the voltage of the fault phase (ascending), and the zero sequence current increase and decrease difference of each feeder line in the voltage regulation process is reduced to perform line selection. When the transition resistance of a fault point is large, the line selection cannot be accurately carried out by using the increase and decrease difference of the zero sequence current of each feeder line, but the zero sequence current of the non-fault feeder line is in direct proportion to the zero sequence voltage (linear decrease), the zero sequence current of the fault feeder line is generated by the combined action of the zero sequence voltage and the fault phase voltage and presents a nonlinear change trend, and the line selection is assisted by using the nonlinear distortion degree of the zero sequence current of each feeder line in the downshift voltage regulation process. The problem of difficult line selection when a resonant grounding system has a high-resistance grounding fault is effectively solved by amplifying the fault characteristic components step by step; the two criteria are adopted to fuse the line selection method, so that the accuracy of line selection is improved.
Of course, it should be understood that, when a low-resistance ground fault occurs, the fault line selection can be realized by adopting the steps S1 and S2; and under the condition that the fault transition resistance value is large, fault line selection can be realized by adopting the steps S1 and S3.
Example 2
This embodiment provides a distribution network single-phase earth fault route selection device, includes:
the data acquisition module is used for acquiring zero-sequence current of each feeder line in the process of reducing the zero-sequence voltage of the system step by step;
the line selection judging module is used for selecting lines by adopting the following two line selection criteria:
calculating a zero sequence current proportion coefficient of each feeder line after voltage regulation by taking the initially measured zero sequence current as a reference, wherein the feeder line with the zero sequence current proportion coefficient larger than a preset proportion coefficient threshold value is a fault feeder line; if no feeder line meets the requirement, calculating the nonlinear distortion degree of the zero sequence current of each feeder line in the voltage regulating process, wherein the feeder line with the maximum nonlinear distortion degree is the fault feeder line.
For other specific implementation processes in this embodiment, refer to embodiment 1, which is not described herein again.
Example 3
The embodiment provides a single-phase earth fault line selection system of a power distribution network, which comprises a system zero sequence voltage control module, a data acquisition module and a line selection module;
the system zero sequence voltage control module is used for performing step-by-step reduction control on the system zero sequence voltage; specifically, the system zero sequence voltage control module comprises a grounding branch and a tapping tap arranged on a primary side winding of the transformer;
and the data acquisition module is used for acquiring the zero sequence current of each feeder line in the process of reducing the zero sequence voltage of the system step by the zero sequence voltage control module of the system.
The line selection module is used for acquiring zero sequence current of each feeder line in the process of reducing the zero sequence voltage of the system step by step, and adopts the following two line selection criteria for line selection:
calculating a zero-sequence current proportionality coefficient of each feeder line after voltage regulation by taking the primarily measured zero-sequence current as a reference, wherein the feeder line with the zero-sequence current proportionality coefficient larger than a preset proportionality coefficient threshold value is a fault feeder line; if no feeder line is satisfied, calculating the nonlinear distortion degree of the zero sequence current of each feeder line in the voltage regulating process, wherein the feeder line with the maximum nonlinear distortion degree is the fault feeder line.
In specific implementation, a control module for controlling the action of the zero sequence voltage control module of the system and a line selection module can be integrated in one processor for realization.
Example 4
The present embodiment is a computer-readable storage medium, which stores a computer program, and the computer program, when being loaded by a processor, implements the single-phase ground fault line selection method for a power distribution network according to the foregoing embodiments.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
It is understood that the same or similar parts in the above embodiments may be mutually referred to, and the same or similar parts in other embodiments may be referred to for the content which is not described in detail in some embodiments.
Any process or method descriptions in flow charts or otherwise described herein may be understood as representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps in the process, and alternate implementations are included within the scope of the preferred embodiment of the present invention in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the present invention.
In the embodiment, the zero sequence voltage of the system is actively regulated, namely, the zero sequence voltage of the system is reduced step by step, in the process, the zero sequence voltage of the system and the zero sequence current of a non-fault feeder line are reduced, but the fault phase voltage and the zero sequence current of a fault feeder line are improved, so that the fault characteristic component is amplified step by step, and the problem of difficult line selection when the high-resistance ground fault occurs in the resonant grounding system is effectively solved. Adopting two criteria fusion line selection methods, when the ground resistance of the fault point is far less than the zero sequence capacitive reactance of the line, using the zero sequence current proportionality coefficient of each feeder line in the voltage regulation process to select the line; under the condition of large transition resistance, the zero-sequence current nonlinear distortion degree of each feeder line in the voltage regulation process is used for assisting line selection, so that tens of kilohms of ground fault feeder lines can be effectively identified. The scheme of the invention only needs to install the tapping tap and the corresponding grounding branch on the transformer winding, does not need to increase corresponding line selection equipment, greatly reduces the investment cost and has strong economy.
In order to further understand the technical solution of the present invention, the following further describes the technical solution of the present invention with reference to a specific simulation experiment.
Simulation experiment:
in order to verify the feasibility of the scheme provided by the invention, a power distribution network single-phase earth fault model is built in PSCAD/EMTDC, and as shown in FIG. 5, each phase of a high-voltage side winding is provided with 10 gears. R occurs in the circuit L4 under the simulated resonance grounding operation mode f The permanent ground faults of 200 Ω, 1000 Ω and 2000 Ω, the shift positions of the regulated grounding transformer are sequentially from X =8 (initial shift position) to X =6 to X =4 (for improving accuracy, the shift positions at both ends are not used for grounding during the regulation), and the change of the zero-sequence current of each feeder line is monitored as shown in fig. 6. The dotted line in the figure is the criterion 1 (zero sequence current proportionality coefficient criterion) mentioned in the text at K rel And the upper half part of a dotted line is a protection action range along with the change of the gear when the gear is 1.2. As can be seen, R occurs systematically f Permanent ground fault of =200 Ω, due to R f The zero sequence current of the fault feeder line is approximately considered to be in direct proportion to the fault phase voltage, so that the fault feeder line is in a linear increasing trend and the non-fault feeder line is in a linear decreasing trend in the downshift process, the criterion 1 effectively acts at the moment, and the criterion 2 (the criterion of the zero sequence current nonlinear distortion degree) cannot act. Phylogenetic R f Permanent earth fault of =1000 Ω, because of R f The current is large, the capacitance current to ground of the fault feeder line cannot be ignored, but the fault grounding current still occupies the dominant position at the moment, the total zero sequence current of the line is in a nonlinear increasing trend along with the reduction of gears, and both the criterion 1 and the criterion 2 can normally act at the moment. Continuing to increase the transition resistance value when R f When the zero-sequence capacitance current is in a dominant position when the zero-sequence capacitance current is 2000 omega, the total zero-sequence current of the line is in a nonlinear reduction trend along with the reduction of the gears, at the moment, the criterion 1 can still correctly act at a low-gear position, and when the high-gear position has a failure condition, the line selection operation needs to be carried out by depending on the criterion 2.
In order to verify the accuracy of line selection under the condition of high-resistance grounding fault of the criterion 2 provided by the invention, R occurs under the simulated resonance grounding mode f ＝3000Ω、R f And (3) regulating and controlling a tap of the transformer from an initial gear to a lowest gear by a permanent ground fault when the voltage is not less than 5000 omega, and observing zero sequence current of each feeder line in the downshift processChange the situation and record the slope variance of the zero sequence current as table 1. As can be seen from the table, the zero sequence current variance of the feeder line L4 is the largest, so that the feeder line L4 can be judged to be a fault feeder line and is consistent with a fault feeder line which is actually simulated, and the feasibility of the method provided by the invention is proved.
TABLE 1
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (10)
1. A single-phase earth fault line selection method for a power distribution network is characterized by comprising the following steps:
s1: obtaining zero sequence current of each feeder line in the process of reducing the zero sequence voltage of the system step by step;
s2: calculating a zero sequence current proportion coefficient of each feeder line after voltage regulation by taking the initially measured zero sequence current as a reference, wherein the feeder line with the zero sequence current proportion coefficient larger than a preset proportion coefficient threshold value is a fault feeder line; if no feeder is satisfied, entering step S3;
s3: and calculating the nonlinear distortion degree of the zero sequence current of each feeder line in the voltage regulating process, wherein the feeder line with the maximum nonlinear distortion degree is the fault feeder line.
2. The method for selecting the single-phase earth fault line of the power distribution network according to claim 1, wherein before obtaining the zero sequence current of each feeder line in the process of reducing the zero sequence voltage of the system step by step, the method further comprises:
and judging whether the power distribution network has single-phase earth faults or not, and if so, carrying out single-phase earth fault line selection on the power distribution network.
3. The method for selecting the single-phase earth fault line of the power distribution network according to claim 2, wherein the step of judging whether the single-phase earth fault occurs to the power distribution network specifically comprises the following steps:
and if the zero-sequence voltage of the system is greater than the first phase voltage threshold value or the zero-sequence voltage variation of the system is greater than the second phase voltage threshold value, judging that the single-phase earth fault occurs in the power distribution network.
4. The single-phase earth fault line selection method for the power distribution network according to claim 1, wherein the step-by-step reduction of the zero sequence voltage of the system is realized by the following steps:
a plurality of tapping taps are uniformly arranged on a primary side winding tap of the transformer to form a plurality of gears;
when single-phase earth fault occurs, the initial gear of the fault phase tapping tap is regulated and controlled to be grounded, and after time delay, the grounding gear of the tapping tap is gradually reduced to the lowest gear.
5. The method for single-phase earth fault line selection of the power distribution network according to any one of claims 1 to 4, wherein the zero-sequence current proportionality coefficient is defined as follows:
in the formula, alpha in For the zero sequence current proportionality coefficient of the ith feeder line when the zero sequence voltage of the system is reduced to n level 0ix Is the zero sequence current of the ith feeder line under the initial level x of the zero sequence voltage of the system, I 0in Reducing the zero sequence voltage of the system to be the zero sequence current of the ith feeder line after n levels; wherein n =1,2,3.., x-1.
6. The single-phase earth fault line selection method for the power distribution network according to claim 5, wherein the preset scaling factor threshold is
Wherein K rel The value is 1.1-1.2 for the reliability coefficient.
7. The method according to any one of claims 1 to 4, wherein the degree of nonlinear distortion of the zero-sequence current of each feeder line is defined by a slope variance of the zero-sequence current of each feeder line:
in the formula, S 2 [I 0i ]The slope variance of the zero sequence current of the ith feeder line is obtained; x is the initial level of the zero sequence voltage of the system; k 0in For reducing the zero sequence voltage of the system to n level, the slope of the zero sequence current, K 0in ＝I 0in -I 0in-1 (n≥2)；
The slope average value of the corresponding zero sequence current in the process of reducing the zero sequence voltage level for the ith feeder line,
8. the utility model provides a distribution network single-phase earth fault route selection device which characterized in that includes:
the data acquisition module is used for acquiring zero-sequence current of each feeder line in the process of reducing the zero-sequence voltage of the system step by step;
the line selection judging module is used for selecting lines by adopting the following two line selection criteria:
calculating a zero-sequence current proportionality coefficient of each feeder line after voltage regulation by taking the primarily measured zero-sequence current as a reference, wherein the feeder line with the zero-sequence current proportionality coefficient larger than a preset proportionality coefficient threshold value is a fault feeder line; if no feeder line is satisfied, calculating the nonlinear distortion degree of the zero sequence current of each feeder line in the voltage regulating process, wherein the feeder line with the maximum nonlinear distortion degree is the fault feeder line.
9. The utility model provides a distribution network single-phase earth fault route selection system which characterized in that includes:
the system zero sequence voltage control module is used for controlling the zero sequence voltage of the system to be reduced step by step;
the data acquisition module is used for acquiring zero-sequence current of each feeder line in the process that the zero-sequence voltage control module of the system reduces the zero-sequence voltage of the system step by step;
the line selection module is used for acquiring zero sequence current of each feeder line in the process of reducing the zero sequence voltage of the system step by step, and performing line selection by adopting the following two line selection criteria:
calculating a zero sequence current proportion coefficient of each feeder line after voltage regulation by taking the initially measured zero sequence current as a reference, wherein the feeder line with the zero sequence current proportion coefficient larger than a preset proportion coefficient threshold value is a fault feeder line; if no feeder line is satisfied, calculating the nonlinear distortion degree of the zero sequence current of each feeder line in the voltage regulating process, wherein the feeder line with the maximum nonlinear distortion degree is the fault feeder line.
10. A computer-readable storage medium, storing a computer program, wherein the computer program, when being loaded by a processor, is adapted to carry out a method according to any one of claims 1 to 7 for single-phase earth fault line selection in a power distribution network.
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| CN117555238A (en) * | 2023-12-21 | 2024-02-13 | 北京嘉海鼎盛科技有限公司 | Dynamic disturbance compensation-based fault-tolerant control method for fault-phase failure of dynamometer |
| CN117706278A (en) * | 2024-02-04 | 2024-03-15 | 昆明理工大学 | Fault line selection method and system for power distribution network and readable storage medium |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117555238A (en) * | 2023-12-21 | 2024-02-13 | 北京嘉海鼎盛科技有限公司 | Dynamic disturbance compensation-based fault-tolerant control method for fault-phase failure of dynamometer |
| CN117706278A (en) * | 2024-02-04 | 2024-03-15 | 昆明理工大学 | Fault line selection method and system for power distribution network and readable storage medium |
| CN117706278B (en) * | 2024-02-04 | 2024-06-07 | 昆明理工大学 | Fault line selection method and system for power distribution network and readable storage medium |
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