CN107979076B - Power transmission line protection method and system based on transient component frequency spectrum characteristics - Google Patents
Power transmission line protection method and system based on transient component frequency spectrum characteristics Download PDFInfo
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- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
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Abstract
A power transmission line protection method and system based on transient component frequency spectrum characteristics comprises the following steps: acquiring three-phase currents on two sides of a line after a fault, and calculating beta mode currents with the three phases as references; when the beta mode currents of the three phases are not 0, a phase-to-phase fault occurs, and the type of the phase-to-phase fault is judged by adopting a preset phase-to-phase fault protection criterion; when the inter-phase fault type is an intra-area fault, the protection acts rapidly; when the interphase fault type is an external fault, no protection action is carried out; the preset interphase fault protection criterion comprises the following steps: and determining the faults inside and outside the area according to the frequency spectrum and the frequency spectrum difference of the beta mode current at the two sides of the line. The technical scheme of the invention has strong criterion adaptability, and is not only suitable for ultra-high and extra-high voltage transmission lines with large distributed capacitance, but also for series compensation lines and transmission lines provided with shunt reactors.
Description
Technical Field
The invention relates to the technical field of electricity, in particular to a power transmission line protection method and system based on transient component frequency spectrum characteristics.
Background
For high-voltage lines, especially ultra-high voltage and ultra-high voltage transmission lines, due to the fact that distributed capacitance of the lines is large, capacitance current after a fault affects the action performance of power frequency quantity protection, and at present, the capacitance current is compensated by a conventional method. However, when a fault occurs in a region, the line model is changed due to the existence of the fault point, so that the action current and the fault point current are different after the compensation measure is taken, and when the line length reaches a certain degree, protection can be rejected. The effective resistance of a large-capacity generator and a power transmission line with split conductors is very small, the attenuation time constant of a network is very large, so that the transient components of current and voltage are attenuated very slowly during short circuit, the transient transition process lasts for a long period of time, the waveform and the phase of power frequency electric quantity can be seriously influenced, and further protection misoperation can be caused.
At present, the protection research based on the transient component mainly focuses on the utilization of the time domain feature, and the protection principle using the frequency domain feature of the transient component is few.
Disclosure of Invention
In order to solve the above-mentioned deficiencies in the prior art, the present invention provides a power transmission line protection method and system based on transient component spectrum characteristics.
A power transmission line protection method based on transient component frequency spectrum characteristics comprises the following steps:
acquiring three-phase currents on two sides of a line after a fault, and calculating beta mode currents with the three phases as references;
when the beta mode currents of the three phases are not 0, a phase-to-phase fault occurs, and the type of the phase-to-phase fault is judged by adopting a preset phase-to-phase fault protection criterion;
when the inter-phase fault type is an intra-area fault, protecting the rapid action;
when the interphase fault type is an out-of-area fault, no protection action is performed;
the preset interphase fault protection criterion comprises: and determining the faults inside and outside the area according to the frequency spectrum and the frequency spectrum difference of the beta mode current at the two sides of the line.
Preferably, the preset inter-phase fault protection criterion includes:
calculating the frequency spectrum of the beta mode current according to a Fourier algorithm model;
carrying out difference operation pretreatment on the frequency spectrum signal of the beta-mode current according to a set threshold value;
calculating the frequency spectrum difference of beta mode currents on two sides of the line according to the result after pretreatment;
And determining the faults inside and outside the area according to the frequency spectrum and the frequency spectrum difference of the beta mode current at the two sides of the line.
Preferably, acquiring three-phase currents on two sides of the line after the fault, and calculating beta mode currents with the three phases as a reference, includes:
and (4) collecting three-phase currents on two sides of the line after the fault, and respectively calculating beta mode currents with A, B, C phases as references.
Preferably, the calculating a frequency spectrum of the β -mode current according to a fourier algorithm model includes:
calculating the frequency spectrum of the beta-mode current as follows
In the formula, I (f)N) Represents: the current amplitude; n represents the frequency spectrum times; i.e. iβRepresents: current beta modulus; n represents: and (6) sampling values.
Preferably, the preprocessing of the differential operation on the frequency spectrum signal of the β -mode current according to a set threshold value includes:
carrying out zero setting processing on frequency values of which the amplitude values are smaller than the threshold value in the current frequency spectrum;
otherwise, setting the frequency spectrum value to be 1A for processing;
the threshold value is the frequency value of Iset.
Preferably, calculating a frequency spectrum difference of the beta mode currents on two sides of the line according to the preprocessed result, wherein the frequency spectrum difference comprises the following steps:
and calculating the frequency difference between two frequencies with the amplitude value of 1A in the beta mode current spectrum on one side, and sending the frequency difference to the opposite side of the line for the same processing.
Preferably, determining the in-zone fault and the out-zone fault according to the frequency spectrum and the frequency spectrum difference of the beta mode current on two sides of the line comprises the following steps:
Comparing the frequency difference of the beta mode current frequency spectrums on the two sides of the line;
when the absolute value of the frequency difference of the beta mode current frequency spectrums on the two sides is smaller than a fixed value Ifset, the fault is judged to be out-of-range fault,
otherwise, judging as the fault in the area.
Preferably, the determining the in-zone fault and the out-zone fault according to the frequency spectrum and the frequency spectrum difference of the beta mode current on two sides of the line further comprises:
when no frequency value with the amplitude value larger than the threshold Iset exists in the beta mode current frequency spectrum on one side of two sides of the circuit, and a frequency value with the amplitude value larger than the threshold Iset exists in the beta mode current frequency spectrum on the other side of the circuit, the circuit is judged to be an in-zone fault;
and when the frequency values with the amplitude values larger than the threshold value Iset do not exist in the beta mode current frequency spectrums on the two sides of the circuit, the protection criterion exits.
Another objective of the present invention is to provide a power transmission line protection system based on transient component spectrum characteristics, including: the fault diagnosis device comprises an acquisition calculation module, a fault judgment module, a fault processing module and a criterion module;
the acquisition and calculation module is used for acquiring three-phase currents on two sides of the line after the fault occurs and calculating beta mode currents with the three phases as the reference;
the fault judgment module is used for judging that an inter-phase fault occurs when the beta mode currents of the three phases are not 0, and judging the type of the inter-phase fault by adopting a preset inter-phase fault protection criterion;
The fault processing module is used for protecting quick action when the interphase fault type is an intra-area fault; when the interphase fault type is an out-of-range fault, no protection action is performed;
and the criterion module is used for determining the faults inside and outside the area according to the frequency spectrum and the frequency spectrum difference of the beta mode current on the two sides of the line.
Preferably, the criterion module includes: the device comprises a calculation submodule, a preprocessing submodule, a calculation frequency spectrum difference submodule and a determination submodule;
the calculation submodule is used for calculating the frequency spectrum of the beta mode current according to a Fourier algorithm model;
the preprocessing submodule is used for carrying out differential operation preprocessing on the frequency spectrum signal of the beta-mode current according to a set threshold value;
the frequency spectrum difference calculating submodule is used for calculating the frequency spectrum difference of beta mode currents on two sides of the line according to the preprocessed result;
and the determining submodule is used for determining the faults inside and outside the area according to the frequency spectrum and the frequency spectrum difference of the beta mode current at two sides of the line.
Preferably, the calculation submodule includes: a Fourier algorithm model;
calculating the frequency spectrum of the beta mode current according to the following formula through the Fourier algorithm model
In the formula, I (f)N) Represents: the current amplitude; n represents the frequency spectrum times; i.e. i βRepresents: current beta modulus; n represents: and (6) sampling values.
Preferably, the fault processing module, the first processing submodule and the second processing submodule;
the first processing submodule is used for judging the frequency difference of beta mode current frequency spectrums on two sides of the line and the magnitude of a fixed value Ifset;
when the absolute value of the frequency difference of the beta mode current frequency spectrums on the two sides is smaller than a fixed value Ifset, judging that the fault is out of range;
otherwise, judging as an intra-area fault;
the second processing submodule is used for judging the amplitude of the beta mode current frequency spectrum at two sides of the line and the magnitude of the threshold value Iset;
when no frequency value with the amplitude value larger than the threshold Iset exists in the beta mode current frequency spectrum on one side of two sides of the circuit, and a frequency value with the amplitude value larger than the threshold Iset exists in the beta mode current frequency spectrum on the other side of the circuit, the circuit is judged to be an in-zone fault;
and when the frequency values with the amplitude values larger than the threshold value Iset do not exist in the beta mode current frequency spectrums on the two sides of the circuit, the protection criterion exits.
Compared with the prior art, the invention has the beneficial effects that:
the technical scheme of the invention is that a rapid protection action is made based on the protection criterion of the current transient component frequency spectrum characteristic; when a fault occurs, acquiring three-phase currents on two sides of the line, calculating beta mode currents with the three phases as references, when the beta mode currents of the three phases are not 0, generating an interphase fault, and judging the interphase fault type by adopting a preset interphase fault protection criterion; and determining the faults inside and outside the area according to the frequency spectrum and the frequency spectrum difference of the beta mode current at two sides of the line, and protecting the fast action when the faults inside the area occur and protecting the misoperation when the faults outside the area occur.
The protection criterion of the technical scheme of the invention does not need synchronous sampling of the electric quantities at two ends of the line, and is not influenced by the system operation mode, load current, transition resistance, fault time, PT and CT disconnection and system oscillation; the method has strong criterion adaptability, and is not only suitable for ultra-high voltage and ultra-high voltage transmission lines with large distributed capacitance, but also for series compensation lines and transmission lines provided with shunt reactors.
The technical scheme of the invention only needs to calculate the current frequency spectrum, has low requirement on the sampling rate, and uses the Fourier algorithm to calculate the frequency spectrum, so that the calculated amount is small.
Drawings
FIG. 1 is a flow chart of the method of the present invention;
fig. 2 is a schematic diagram of a transmission line fault according to the present invention;
FIG. 3 is a frequency spectrum of beta mode current on two sides of a line when F1 of the present invention fails;
FIG. 4 is a spectrum of beta mode current after preprocessing of data at both sides of a line when F1 fails according to the present invention;
FIG. 5 is a frequency spectrum of beta mode current on two sides of a line when F2 of the present invention fails;
fig. 6 is a beta mode current frequency spectrum after data preprocessing at both sides of a line when F2 fails according to the present invention;
in fig. 1, F2 is an intra-zone fault point, and F1 is an extra-zone fault point.
Detailed Description
For a better understanding of the present invention, reference is made to the following description taken in conjunction with the accompanying drawings and examples.
The invention utilizes the transient component frequency spectrum after the transmission line fault to distinguish the inter-phase fault inside and outside the region. Because mutual inductance exists between the transmission conductors, three-phase electric quantities can influence each other after a fault, the electric quantities can be decoupled through the conversion matrix, the mutual inductance influence is eliminated, and the mutually independent electric quantities are obtained. The decoupled electrical quantity can be divided into line-mode components
And zero modulus component
Two kinds. When the phase-to-phase short circuit occurs, only the line mode component exists, and no zero mode component exists. The interphase fault comprises an interphase short circuit and an interphase grounding fault, the interphase short circuit fault is divided into a three-phase short circuit and a two-phase short circuit, when the three-phase short circuit occurs in a line, a system is separated from the short circuit, and transient components on two sides of a fault point are independent; when two phases are short-circuited, the short-circuit additional components in the two fault phases are equal in size and opposite in direction, and the sum of electromotive forces induced by the two fault phases in a healthy phase is zero, so that transient components on two sides of a short-circuit point are not influenced by each other; when two phases are grounded, the beta modulus is transmitted between two fault phases and is not influenced by a zero-mode component and a transient component on the other side of a fault point. When the line has an interphase fault (interphase short circuit and two-phase grounding), the transient current beta moduli on the two sides of the fault point are mutually independent. The identification of faults inside and outside the zone can be realized by utilizing the frequency spectrum difference in the beta modulus.
The power transmission line protection method based on the transient component spectrum characteristics as shown in fig. 1 includes:
acquiring three-phase currents on two sides of a line after a fault, and calculating beta mode currents with the three phases as references;
when the beta mode currents of the three phases are not 0, a phase-to-phase fault occurs, and the type of the phase-to-phase fault is judged by adopting a preset phase-to-phase fault protection criterion;
when the inter-phase fault type is an intra-area fault, protecting the rapid action;
when the interphase fault type is an out-of-area fault, no protection action is performed;
the preset interphase fault protection criterion comprises the following steps: and determining the faults inside and outside the area according to the frequency spectrum and the frequency spectrum difference of the beta mode current at the two sides of the line.
The preset interphase fault protection criterion comprises the following steps:
calculating the frequency spectrum of the beta mode current according to a Fourier algorithm model;
carrying out differential operation pretreatment on the frequency spectrum signal of the beta-mode current according to a set threshold value;
calculating the frequency spectrum difference of the beta mode currents on the two sides of the line according to the result after pretreatment;
and determining the faults inside and outside the area according to the frequency spectrum and the frequency spectrum difference of the beta mode current at the two sides of the line.
The method for acquiring three-phase currents on two sides of a line after a fault and calculating beta mode currents with the three phases as references comprises the following steps: and (4) collecting three-phase currents on two sides of the line after the fault, and respectively calculating beta mode currents with A, B, C phases as references.
The calculating the frequency spectrum of the beta mode current according to a Fourier algorithm model comprises the following steps:
calculating the frequency spectrum of the beta-mode current as follows
In the formula, I (f)N) Represents: the current amplitude; n represents the frequency spectrum times; i.e. iβRepresents: current beta modulus; n represents: and (6) sampling values.
And carrying out differential operation pretreatment on the frequency spectrum signal of the beta mode current according to a set threshold value, wherein the differential operation pretreatment comprises the following steps:
carrying out zero setting processing on frequency values of which the amplitude values are smaller than the threshold value in the current frequency spectrum;
otherwise, setting the frequency spectrum value to be 1A for processing;
the threshold value is the frequency value of Iset.
Calculating the frequency spectrum difference of the beta mode currents on two sides of the line according to the preprocessed result, wherein the frequency spectrum difference comprises the following steps:
and calculating the frequency difference between two frequencies with the amplitude value of 1A in the beta mode current spectrum on one side, and sending the frequency difference to the opposite side of the line for the same processing.
Determining the faults inside and outside the area according to the frequency spectrum and the frequency spectrum difference of the beta mode current at two sides of the line, wherein the fault comprises the following steps:
comparing the frequency difference of beta mode current frequency spectrums on two sides of the line;
when the absolute value of the frequency difference of the beta mode current frequency spectrums on the two sides is smaller than a fixed value Ifset, the fault is judged to be out-of-range fault,
otherwise, the fault is judged to be in-zone fault.
Determining the faults inside and outside the area according to the frequency spectrum and the frequency spectrum difference of the beta mode current at two sides of the line, and further comprising the following steps:
When no frequency value with the amplitude value larger than the threshold Iset exists in the beta mode current frequency spectrum on one side of two sides of the circuit, and a frequency value with the amplitude value larger than the threshold Iset exists in the beta mode current frequency spectrum on the other side of the circuit, the circuit is judged to be an in-zone fault;
and when the frequency values with the amplitude values larger than the threshold value Iset do not exist in the beta mode current frequency spectrums on the two sides of the circuit, the protection criterion exits.
Example 1: system F1 out-of-site fault shown in FIG. 2
(1) Collecting three-phase current on two sides of power transmission line
Calculating the beta-mode component of the current at two sides of the line by the formula
The beta mode current spectrum (shown in fig. 3) is calculated using fourier algorithm.
Calculated by the following formula
In the formula, I (f)N) Represents: the current amplitude; n represents the frequency spectrum times; i.e. iβRepresents: current beta modulus; n represents: and (6) sampling values.
(2) And carrying out differential operation on the frequency spectrum signal, setting a threshold value Iset, and setting a frequency value with the amplitude value smaller than Iset in the current frequency spectrum to be zero. The frequency values with amplitudes greater than Iset in the frequency spectrum are retained, the amplitude values are set to be 1A, the rest are set to be 0, and the processed frequency spectrum is shown in figure 4.
(3) Calculating the frequency difference delta f at protection 11Transmitted to the protection 2, with a frequency difference Δ f at the protection 22And Δ f2-Δf2If fset is less, the fault is judged to be an out-of-area fault.
Example 2: system F2 point-to-point fault shown in fig. 2
(1) Collecting three-phase current on two sides of power transmission line
Calculating the beta-mode component of the current at two sides of the line by the formula
The beta mode current spectrum (shown in fig. 5) is calculated.
(2) And carrying out differential operation on the frequency spectrum signal, setting a threshold value Iset, and setting a frequency value with the amplitude value smaller than Iset in the current frequency spectrum to be zero. The frequency value with amplitude greater than Iset in the spectrum is retained, and the amplitude is set to 1A, and the processed spectrum is shown in FIG. 6.
(3) Calculating the frequency difference delta f at protection 11Transmitted to the protection 2, with a frequency difference Δ f at the protection 22And Δ f2-Δf2And if the signal is larger than fset, judging the signal to be an intra-area fault.
The invention provides a power transmission line protection system based on transient component frequency spectrum characteristics, the principle is the same as a power transmission line protection method based on the transient component frequency spectrum characteristics, and the modules of the system are further explained as follows:
the method comprises the following steps: the fault diagnosis device comprises a calculation module, a fault judgment module, a fault processing module and a criterion module;
the acquisition and calculation module is used for acquiring three-phase currents on two sides of the line after the fault occurs and calculating beta mode currents with the three phases as the reference;
the fault judgment module is used for judging that an inter-phase fault occurs when the beta mode currents of the three phases are not 0 and judging the type of the inter-phase fault by adopting a preset inter-phase fault protection criterion;
The fault processing module is used for protecting quick action when the interphase fault type is an intra-area fault; when the interphase fault type is an out-of-range fault, no protection action is performed;
and the criterion module is used for determining the faults inside and outside the area according to the frequency spectrum and the frequency spectrum difference of the beta mode current on the two sides of the line.
The criterion module comprises: the device comprises a calculation submodule, a preprocessing submodule, a calculation frequency spectrum difference submodule and a determination submodule;
the calculation submodule is used for calculating the frequency spectrum of the beta mode current according to a Fourier algorithm model;
the preprocessing submodule is used for carrying out differential operation preprocessing on the frequency spectrum signal of the beta-mode current according to a set threshold value;
the frequency spectrum difference calculating submodule is used for calculating the frequency spectrum difference of beta mode currents on two sides of the line according to the preprocessed result;
the determining submodule is used for determining the faults inside and outside the area according to the frequency spectrum and the frequency spectrum difference of the beta mode current at the two sides of the line;
a computation submodule, comprising: a Fourier algorithm model;
calculating the frequency spectrum of the beta mode current according to the following formula through the Fourier algorithm model
In the formula, I (f)N) Represents: the current amplitude; n represents the frequency spectrum times; i.e. iβRepresents: current beta modulus; n represents: and (6) sampling values.
The fault processing module comprises a first processing submodule and a second processing submodule;
the first processing submodule is used for judging the frequency difference of beta mode current frequency spectrums on two sides of the line and the magnitude of a fixed value Ifset;
when the absolute value of the frequency difference of the beta mode current frequency spectrums on the two sides is smaller than a fixed value Ifset, judging that the fault is out of range;
otherwise, judging as an intra-area fault;
the second processing submodule is used for judging the amplitude of the beta mode current frequency spectrums on the two sides of the line and the magnitude of the threshold value Iset;
when no frequency value with the amplitude value larger than the threshold Iset exists in the beta mode current frequency spectrum on one side of two sides of the circuit, and a frequency value with the amplitude value larger than the threshold Iset exists in the beta mode current frequency spectrum on the other side of the circuit, the circuit is judged to be an in-zone fault;
and when the frequency values with the amplitude values larger than the threshold value Iset do not exist in the beta mode current frequency spectrums on the two sides of the circuit, the protection criterion exits.
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 flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams 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.
The present invention is not limited to the above embodiments, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention are included in the scope of the claims of the present invention which are filed as the application.
Claims (10)
1. A power transmission line protection method based on transient component frequency spectrum characteristics is characterized by comprising the following steps:
acquiring three-phase currents on two sides of a line after a fault, and calculating beta mode currents with the three phases as references;
when the beta mode currents of the three phases are not 0, a phase-to-phase fault occurs, and the type of the phase-to-phase fault is judged by adopting a preset phase-to-phase fault protection criterion;
when the inter-phase fault type is an intra-area fault, protecting rapid action;
when the interphase fault type is an out-of-area fault, no protection action is performed;
The preset interphase fault protection criterion comprises: determining the faults inside and outside the area according to the frequency spectrum and the frequency spectrum difference of the beta mode current at the two sides of the line;
the preset interphase fault protection criterion comprises:
calculating the frequency spectrum of the beta mode current according to a Fourier algorithm model;
carrying out differential operation pretreatment on the frequency spectrum signal of the beta-mode current according to a set threshold value;
calculating the frequency spectrum difference of the beta mode currents on the two sides of the line according to the result after pretreatment;
and determining the faults inside and outside the area according to the frequency spectrum and the frequency spectrum difference of the beta mode current at the two sides of the line.
2. The power transmission line protection method based on transient component frequency spectrum characteristics according to claim 1, wherein three-phase currents on two sides of a line after a fault are obtained, and a beta mode current based on the three phases is calculated, and the method comprises the following steps: and (4) collecting three-phase currents on two sides of the line after the fault, and respectively calculating beta mode currents with A, B, C phases as references.
3. The method for protecting power transmission line based on transient component spectrum characteristics according to claim 1, wherein said calculating the spectrum of the beta mode current according to a fourier algorithm model comprises:
calculating the frequency spectrum of the beta-mode current as follows
In the formula, I (f) N) Represents: the current amplitude; n represents: the frequency spectrum times; i.e. iβRepresents: current beta modulus; n represents: and (6) sampling values.
4. The power transmission line protection method based on the transient component spectrum feature of claim 2, wherein the preprocessing of the differential operation of the spectrum signal of the beta-mode current according to the set threshold value comprises: carrying out zero setting processing on the frequency value amplitude of which the amplitude is smaller than the threshold value in the current frequency spectrum; otherwise, setting the frequency value amplitude to be 1A; the threshold value is the frequency value of Iset.
5. The power transmission line protection method based on the transient component frequency spectrum characteristics as claimed in claim 4, wherein calculating the beta mode current frequency spectrum difference on two sides of the line according to the preprocessed result comprises:
and calculating the frequency difference between two frequencies with the amplitude value of 1A in the beta mode current spectrum on one side, and sending the frequency difference to the opposite side of the line for the same processing.
6. The method of claim 5, wherein determining the in-zone and out-of-zone faults based on the spectrum difference and the spectrum difference of the beta mode current at the two sides of the line comprises:
comparing the frequency difference of beta mode current frequency spectrums on two sides of the line;
When the absolute value of the difference value of the frequency difference of the beta mode current frequency spectrums on the two sides is smaller than a fixed value Ifset, the fault is judged to be out-of-range fault,
otherwise, the fault is judged to be in-zone fault.
7. The method of claim 6, wherein the determining of the in-zone fault and the out-of-zone fault is based on the spectrum difference and the spectrum difference of the beta mode current at two sides of the line, further comprising: when no frequency value with the amplitude value larger than the threshold Iset exists in the beta mode current frequency spectrum on one side of two sides of the circuit, and a frequency value with the amplitude value larger than the threshold Iset exists in the beta mode current frequency spectrum on the other side of the circuit, the circuit is judged to be an in-zone fault; and when the frequency values with the amplitude values larger than the threshold value Iset do not exist in the beta mode current frequency spectrums on the two sides of the circuit, the protection criterion exits.
8. A transmission line protection system based on transient component frequency spectrum characteristics is characterized by comprising: the fault diagnosis device comprises an acquisition calculation module, a fault judgment module, a fault processing module and a criterion module;
the acquisition and calculation module is used for acquiring three-phase currents on two sides of the line after the fault occurs and calculating beta mode currents with the three phases as the reference;
the fault judgment module is used for judging that an inter-phase fault occurs when the beta mode currents of the three phases are not 0, and judging the type of the inter-phase fault by adopting a preset inter-phase fault protection criterion;
The fault processing module is used for protecting rapid action when the inter-phase fault type is an intra-area fault; when the interphase fault type is an out-of-area fault, no protection action is performed;
the criterion module is used for determining the faults inside and outside the area according to the frequency spectrum and the frequency spectrum difference of the beta mode current at the two sides of the line;
the criterion module comprises: the device comprises a calculation submodule, a preprocessing submodule, a calculation frequency spectrum difference submodule and a determination submodule;
the calculating submodule is used for calculating the frequency spectrum of the beta mode current according to a Fourier algorithm model;
the preprocessing submodule is used for carrying out differential operation preprocessing on the frequency spectrum signal of the beta-mode current according to a set threshold value;
the frequency spectrum difference calculating submodule is used for calculating the frequency spectrum difference of beta mode currents on two sides of the line according to the preprocessed result;
and the determining submodule is used for determining the faults inside and outside the area according to the frequency spectrum and the frequency spectrum difference of the beta mode current at two sides of the line.
9. The power transmission line protection system based on transient component spectral characteristics of claim 8, wherein the calculation submodule comprises: a Fourier algorithm model;
calculating the frequency spectrum of the beta mode current according to the following formula through the Fourier algorithm model
In the formula, I (f)N) Represents: the current amplitude; n represents: frequency spectrum times; i.e. iβRepresents: current beta modulus; n represents: and (6) sampling values.
10. The power transmission line protection system based on transient component spectral characteristics of claim 8, wherein the fault processing module, the first processing submodule and the second processing submodule;
the first processing submodule is used for judging the magnitude of the absolute value of the difference value of the frequency spectrum difference of the beta mode current frequency spectrums on the two sides of the line and the fixed value Ifset;
when the absolute value of the difference value of the frequency spectrum difference of the beta mode current frequency spectrums on the two sides is smaller than a fixed value Ifset, judging that the fault is out of range;
otherwise, judging as an intra-area fault;
the second processing submodule is used for judging the amplitude of the beta mode current frequency spectrums on the two sides of the line and the magnitude of the threshold value Iset;
when no spectrum difference with the amplitude value larger than the threshold Iset exists in the beta mode current spectrum on one side of the two sides of the circuit, and the spectrum difference with the amplitude value larger than the threshold Iset exists in the beta mode current spectrum on the other side of the circuit, the fault in the area is judged; and when no frequency spectrum difference with the amplitude value larger than the Iset threshold value exists in the beta mode current frequency spectrums on the two sides of the line, the protection criterion exits.
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