CN107979076A - A transmission line protection method and system based on transient component spectrum characteristics - Google Patents

Abstract

A power transmission line protection method and system based on transient component frequency spectrum characteristics includes obtaining three-phase currents on two sides of a line after fault, calculating β mode currents with the three phases as reference, judging phase-to-phase fault types by adopting a preset phase-to-phase fault protection criterion when the β mode currents of the three phases are not 0, protecting fast action when the phase-to-phase fault types are in-zone faults, and not performing protection action when the phase-to-phase fault types are out-of-zone faults, wherein the preset phase-to-phase fault protection criterion includes that in-zone faults and out-of-zone faults are determined according to β mode current frequency spectrums and frequency spectrum differences on two sides of the line.

Description

A transmission line protection method and system based on transient component spectrum characteristics

technical field

The invention relates to the field of electrical technology, in particular to a transmission line protection method and system based on transient component spectrum characteristics.

Background technique

For high-voltage lines, especially EHV and UHV transmission lines, due to the large distributed capacitance of the line, the capacitive current after a fault will affect the action performance of power frequency protection. The current conventional method is to compensate the capacitive current. However, when there is a fault in the zone, the line model will change due to the existence of the fault point, so that the operating current after taking compensation measures is different from the current at the fault point. When the line length reaches a certain level, the protection may refuse to operate. Since the effective resistance of large-capacity generators and transmission lines with split conductors is very small, the decay time constant of the network is very large, so that the transient components of current and voltage decay very slowly during short circuit, so the transient transition process will last for a long time For a period of time, it will seriously affect the waveform and phase of the power frequency electrical quantity, which may cause protection malfunction. The current measure is to use a filter to filter it out, but the transient component contains a lot of useful fault information. Through effective The action performance of protection can be improved by utilizing the information of transient components.

At present, the protection research based on transient components mainly focuses on the utilization of time-domain characteristics, and there are few protection principles based on the frequency-domain characteristics of transient components.

Contents of the invention

In order to solve the above-mentioned deficiencies in the prior art, the present invention provides a transmission line protection method and system based on the spectral characteristics of transient components.

A transmission line protection method based on the spectral characteristics of transient components, comprising:

Obtain the three-phase current on both sides of the line after the fault, and calculate the β-mode current based on the three phases;

When none of the β-mode currents of the three phases is 0, a phase-to-phase fault occurs, and a preset phase-to-phase fault protection criterion is used to determine the type of the phase-to-phase fault;

When the phase-to-phase fault type is an internal fault, the protection acts quickly;

When the phase-to-phase fault type is an external fault, no protection action is performed;

The preset phase-to-phase fault protection criterion includes: determining internal and external faults according to the β-mode current spectrum and spectrum difference on both sides of the line.

Preferably, the preset phase-to-phase fault protection criteria include:

Calculate the frequency spectrum of the β-mode current according to the Fourier algorithm model;

Perform differential calculation preprocessing on the spectrum signal of the β-mode current according to the set threshold value;

Calculate the spectrum difference of the β-mode current on both sides of the line according to the preprocessed results;

In-area and out-of-area faults are determined according to the β-mode current spectrum and spectrum difference on both sides of the line.

Preferably, the three-phase current on both sides of the line after the fault is obtained, and the β-mode current based on the three phases is calculated, including:

The three-phase currents on both sides of the line after the fault are collected, and the β-mode currents based on phases A, B, and C are calculated respectively.

Preferably, the calculation of the spectrum of the β-mode current according to the Fourier algorithm model includes:

Calculate the frequency spectrum of the β-mode current by the following formula

In the formula, I(f _N ) means: current amplitude; N means: frequency spectrum; i _β means: current β modulus; n means: sampling value.

Preferably, differential operation preprocessing is performed on the spectrum signal of the β-mode current according to the set threshold value, including:

performing zero-setting processing on frequency values whose amplitudes are smaller than the threshold value in the current spectrum;

Otherwise, set the spectrum value to 1A;

The threshold value is the frequency value of Iset.

Preferably, the spectrum difference between the β-mode currents on both sides of the line is calculated according to the preprocessed results, including:

Calculate the frequency difference between two frequencies with an amplitude of 1A in the β-mode current spectrum on one side, and send it to the opposite side of the line for the same processing.

Preferably, determining in-area and out-of-area faults according to the β-mode current spectrum and spectrum difference on both sides of the line includes:

Compare the frequency difference of the β-mode current spectrum on both sides of the line;

When the absolute value of the frequency difference of the β-mode current spectrum on both sides is less than the fixed value Ifset, it is determined as an external fault,

Otherwise, it is judged as an internal fault.

Preferably, determining in-area and out-of-area faults according to the β-mode current spectrum and spectrum difference on both sides of the line also includes:

When there is no frequency value with an amplitude greater than the threshold value Iset in the β-mode current spectrum on one side of the line on both sides of the line, and there is a frequency value with an amplitude greater than the threshold value Iset in the other side spectrum β-mode current spectrum, it is judged as an area Internal failure;

When there is no frequency value whose amplitude is greater than the threshold value Iset in the spectrum of the β-mode current on both sides of the line, the protection criterion exits.

Another object of the present invention is to propose a transmission line protection system based on the spectral characteristics of transient components, including: an acquisition calculation module, a fault judgment module, a fault processing module and a criterion module;

The obtaining calculation module is used to obtain the three-phase current on both sides of the line after the fault, and calculate the β-mode current based on the three phases;

The fault judging module is used for judging the occurrence of a phase-to-phase fault when the β-mode currents of the three phases are all zero, and using a preset phase-to-phase fault protection criterion to judge the type of the phase-to-phase fault;

The fault processing module is used to perform protection action quickly when the phase-to-phase fault type is an internal fault; when the phase-to-phase fault type is an external fault, no protection action is performed;

The criterion module is used for determining faults inside and outside the zone according to the β-mode current spectrum and spectrum difference on both sides of the line.

Preferably, the criterion module includes: a calculation submodule, a preprocessing submodule, a spectrum difference calculation submodule and a determination submodule;

The calculation submodule is used to calculate the frequency spectrum of the β-mode current according to the Fourier algorithm model;

The preprocessing sub-module is used to perform differential operation preprocessing on the spectrum signal of the β-mode current according to a set threshold value;

The calculation spectrum difference sub-module is used to calculate the spectrum difference of the β-mode current on both sides of the line according to the preprocessed result;

The determination sub-module is used to determine the internal and external faults according to the β-mode current spectrum and spectrum difference on both sides of the line.

Preferably, the calculation sub-module includes: a Fourier algorithm model;

Through the Fourier algorithm model, the spectrum of the β-mode current is calculated as follows

In the formula, I(f _N ) means: current amplitude; N means: frequency spectrum; i _β means: current β modulus; n means: sampling value.

Preferably, the fault processing module includes a first processing sub-module and a second processing sub-module;

The first processing sub-module is used to judge the frequency difference of the β-mode current spectrum on both sides of the line and the size of the fixed value Ifset;

When the absolute value of the frequency difference of the β-mode current spectrum on both sides is less than the fixed value Ifset, it is determined to be an external fault;

Otherwise, it is judged as an internal fault;

The second processing sub-module is used to judge the amplitude of the β-mode current spectrum on both sides of the line and the size of the threshold value Iset;

When there is no frequency value with an amplitude greater than the threshold value Iset in the β-mode current spectrum on one side of the line on both sides of the line, and there is a frequency value with an amplitude greater than the threshold value Iset in the other side spectrum β-mode current spectrum, it is judged as an area Internal failure;

When there is no frequency value whose amplitude is greater than the threshold value Iset in the spectrum of the β-mode current on both sides of the line, the protection criterion exits.

Compared with prior art, the beneficial effect of the present invention is:

The technical solution of the present invention is based on the protection criterion of the current transient component spectrum characteristics to make a fast protection action; after a fault occurs, the three-phase current on both sides of the line is obtained, and the β-mode current based on the three phases is calculated. The β-mode current of the three phases is not 0, and a phase-to-phase fault occurs, and the type of the phase-to-phase fault is judged by using the preset phase-to-phase fault protection criterion; the internal and external faults are determined according to the β-mode current spectrum and spectrum difference on both sides of the line , when there is a fault in the zone, the protection will act quickly, and when there is a fault outside the zone, the protection will not malfunction.

The protection criterion of the technical solution of the present invention does not require synchronous sampling of electrical quantities at both ends of the line, and is not affected by system operation mode, load current, transition resistance, fault time, PT and CT disconnection, and system oscillation; and the criterion has strong adaptability, It 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 installed with shunt reactors.

The technical scheme of the present invention only needs to calculate the current spectrum, and has low requirements on the sampling rate, and uses the Fourier algorithm to calculate the spectrum, so the calculation amount is small.

Description of drawings

Fig. 1 is method flowchart of the present invention;

Fig. 2 is a fault schematic diagram of the transmission line of the present invention;

Fig. 3 is the β mode current spectrum of line both sides when F1 fault of the present invention;

Fig. 4 is the β-mode current spectrum after data preprocessing on both sides of the line when F1 fault of the present invention;

Fig. 5 is the β-mode current spectrum of line both sides when F2 fault of the present invention;

Fig. 6 is the β-mode current spectrum after data preprocessing on both sides of the line when F2 fault of the present invention;

Among them, F2 in Figure 1 is the fault point inside the zone, and F1 is the fault point outside the zone.

Detailed ways

In order to better understand the present invention, the content of the present invention will be further described below in conjunction with the accompanying drawings and examples.

The invention utilizes the frequency spectrum of the transient component after the fault of the transmission line to distinguish the internal and external phase faults. Due to the mutual inductance between the transmission wires, the three-phase electrical quantities will affect each other after a fault. The electrical quantities can be decoupled through the conversion matrix to eliminate the influence of mutual inductance and obtain mutually independent electrical quantities. The decoupled electrical quantities can be divided into line-mode components and the zero-mode component two kinds. In phase-to-phase short circuit, there are only line-mode components and no zero-mode components. Phase-to-phase faults include phase-to-phase short-circuit and phase-to-phase-to-ground faults. Phase-to-phase short-circuit faults are divided into three-phase short-circuit and two-phase short-circuit. When a three-phase short-circuit occurs on a line, the system is separated from the short-circuit, and the transient components on both sides of the fault point are independent; When the phases are short-circuited, the short-circuit additional components in the two faulty phases are equal in size and opposite in direction, and the sum of their induced electromotive forces in the sound phase is zero, so the transient components on both sides of the short-circuit point do not affect each other; when the two phases are grounded, The β modulus propagates between the two faulted phases and is unaffected by the zero-mode component and the transient component on the other side of the fault point. When a phase-to-phase fault (phase-to-phase short-circuit and two-phase-to-ground) occurs on the line, the transient current β moduli on both sides of the fault point are independent of each other. Using the spectrum difference in the β modulus can realize the fault identification inside and outside the zone.

A kind of transmission line protection method based on transient component spectrum characteristics as shown in Figure 1, comprising:

Obtain the three-phase current on both sides of the line after the fault, and calculate the β-mode current based on the three phases;

When none of the β-mode currents of the three phases is 0, a phase-to-phase fault occurs, and a preset phase-to-phase fault protection criterion is used to determine the type of the phase-to-phase fault;

When the phase-to-phase fault type is an internal fault, the protection acts quickly;

When the phase-to-phase fault type is an external fault, no protection action is performed;

The pre-set phase-to-phase fault protection criterion includes: determining the internal and external faults according to the β-mode current spectrum and spectrum difference on both sides of the line.

Pre-set phase-to-phase fault protection criteria include:

Calculate the frequency spectrum of the β-mode current according to the Fourier algorithm model;

Perform differential calculation preprocessing on the spectrum signal of the β-mode current according to the set threshold value;

Calculate the spectrum difference of the β-mode current on both sides of the line according to the preprocessed results;

In-area and out-of-area faults are determined according to the β-mode current spectrum and spectrum difference on both sides of the line.

Obtain the three-phase current on both sides of the line after the fault, and calculate the β-mode current based on the three phases, including: collect the three-phase current on both sides of the line after the fault, and calculate the β-mode current based on phase A, B, and C respectively .

The described calculation of the spectrum of the β-mode current according to the Fourier algorithm model includes:

Calculate the frequency spectrum of the β-mode current by the following formula

In the formula, I(f _N ) means: current amplitude; N means: frequency spectrum; i _β means: current β modulus; n means: sampling value.

Perform differential calculation preprocessing on the spectrum signal of the β-mode current according to the set threshold value, including:

performing zero-setting processing on frequency values whose amplitudes are smaller than the threshold value in the current spectrum;

Otherwise, set the spectrum value to 1A;

The threshold value is the frequency value of Iset.

Calculate the β-mode current spectrum difference on both sides of the line according to the preprocessed results, including:

Calculate the frequency difference between two frequencies with an amplitude of 1A in the β-mode current spectrum on one side, and send it to the opposite side of the line for the same processing.

According to the β-mode current spectrum and spectrum difference on both sides of the line to determine the internal and external faults, including:

Compare the frequency difference of the β-mode current spectrum on both sides of the line;

When the absolute value of the frequency difference of the β-mode current spectrum on both sides is less than the fixed value Ifset, it is determined as an external fault,

Otherwise, it is judged as an internal fault.

Determining internal and external faults according to the β-mode current spectrum and spectrum difference on both sides of the line, including:

When there is no frequency value whose amplitude is greater than the threshold value Iset in the β-mode current spectrum on one side of the line on both sides of the line, and there is a frequency value whose amplitude is greater than the threshold value Iset in the other side spectrum β-mode current spectrum, it is judged as an area Internal failure;

When there is no frequency value whose amplitude is greater than the threshold value Iset in the spectrum of the β-mode current on both sides of the line, the protection criterion exits.

Example 1: Out-of-area fault at point F1 of the system shown in Figure 2

(1) Collect the three-phase current on both sides of the transmission line Calculate the β mode component of the current on both sides of the line, the calculation formula is Using the Fourier algorithm to calculate the β-mode current spectrum (shown in Figure 3).

Calculate according to the formula

In the formula, I(f _N ) means: current amplitude; N means: frequency spectrum; i _β means: current β modulus; n means: sampling value.

(2) Carry out differential calculation on the spectrum signal, set the threshold value Iset, and set the frequency value whose amplitude is smaller than Iset in the current spectrum to zero. The frequency value whose amplitude is greater than Iset in the spectrum is reserved, and its amplitude is set to 1A, and the rest are set to 0. The processed spectrum is shown in Figure 4.

(3) Calculate the frequency difference Δf ₁ at protection 1, and transmit it to protection 2. If the frequency difference at protection 2 is Δf ₂ , and Δf ₂ -Δf ₂ <fset, it is judged as an external fault.

Embodiment 2: Faults in the F2 point of the system shown in Fig. 2

(1) Collect the three-phase current on both sides of the transmission line Calculate the β mode component of the current on both sides of the line, the calculation formula is Calculate the β-mode current spectrum (shown in Figure 5).

(2) Carry out differential calculation on the spectrum signal, set the threshold value Iset, and set the frequency value whose amplitude is smaller than Iset in the current spectrum to zero. The frequency value whose amplitude is greater than Iset in the spectrum is reserved, and its amplitude is set to 1A. The processed spectrum is shown in Figure 6.

(3) Calculate the frequency difference Δf ₁ at protection 1 and transmit it to protection 2. If the frequency difference at protection 2 is Δf ₂ , and Δf ₂ -Δf ₂ >fset, it is judged as an internal fault.

The present invention proposes a transmission line protection system based on the spectral characteristics of transient components. This principle is the same as a transmission line protection method based on the spectral characteristics of transient components. The modules of the system are further described below:

Including: acquisition calculation module, fault judgment module, fault processing module and criterion module;

Obtaining a calculation module, which is used to obtain the three-phase current on both sides of the line after the fault, and calculate the β-mode current based on the three phases;

A fault judging module, configured to judge the occurrence of a phase-to-phase fault when the β-mode currents of the three phases are all zero, and use a preset phase-to-phase fault protection criterion to judge the type of the phase-to-phase fault;

The fault processing module is used to perform quick protection action when the phase-to-phase fault type is an internal fault; when the phase-to-phase fault type is an external fault, no protection action is performed;

The criterion module is used to determine the faults inside and outside the zone according to the β-mode current spectrum and spectrum difference on both sides of the line.

A criterion module, including: a calculation submodule, a preprocessing submodule, a calculation spectrum difference submodule and a determination submodule;

Calculation sub-module, used to calculate the frequency spectrum of the β-mode current according to the Fourier algorithm model;

A preprocessing sub-module, configured to perform differential calculation preprocessing on the spectrum signal of the β-mode current according to a set threshold value;

The calculation spectrum difference sub-module is used to calculate the spectrum difference of the β-mode current on both sides of the line according to the preprocessed results;

A determination sub-module is used to determine in-area and out-of-area faults according to the β-mode current spectrum and spectrum difference on both sides of the line;

Calculation sub-module, including: Fourier algorithm model;

Through the Fourier algorithm model, the spectrum of the β-mode current is calculated as follows

In the formula, I(f _N ) means: current amplitude; N means: frequency spectrum; i _β means: current β modulus; n means: sampling value.

A fault processing module, a first processing sub-module and a second processing sub-module;

The first processing sub-module is used to judge the frequency difference of the β-mode current spectrum on both sides of the line and the size of the fixed value Ifset;

When the absolute value of the frequency difference of the β-mode current spectrum on both sides is less than the fixed value Ifset, it is determined to be an external fault;

Otherwise, it is judged as an internal fault;

The second processing sub-module is used to judge the amplitude of the β-mode current spectrum on both sides of the line and the size of the threshold value Iset;

When there is no frequency value whose amplitude is greater than the threshold value Iset in the β-mode current spectrum on one side of the line on both sides of the line, and there is a frequency value whose amplitude is greater than the threshold value Iset in the other side spectrum β-mode current spectrum, it is judged as an area Internal failure;

When there is no frequency value whose amplitude is greater than the threshold value Iset in the spectrum of the β-mode current on both sides of the line, the protection criterion exits.

Those skilled in the art should understand that the embodiments of the present application may be provided as methods, systems, or computer program products. 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, etc.) having computer-usable program code embodied therein.

The present application is described with reference to flowcharts and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It should be understood that each procedure and/or block in the flowchart and/or block diagram, and a combination of procedures and/or blocks in the flowchart and/or block diagram can be realized by computer program instructions. These computer program instructions may be provided to a general purpose computer, special purpose computer, embedded processor, or processor of other programmable data processing equipment to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing equipment produce a An apparatus for realizing the functions specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to operate in a specific manner, such that the instructions stored in the computer-readable memory produce an article of manufacture comprising instruction means, the instructions The device realizes the function specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions can also be loaded onto a computer or other programmable data processing device, causing a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process, thereby The instructions provide steps for implementing the functions specified in the flow diagram procedure or procedures and/or block diagram procedures or blocks.

The above are only embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention are included in the pending application of the present invention. within the scope of the claims.

Claims (12)

1. A kind of 1. line protection method based on transient state component spectrum signature, it is characterised in that including：

   The circuit both sides three-phase current after failure is obtained, and calculates the β mould electric currents on the basis of three-phase；

   When the β moulds electric current of three-phase is not 0, generation phase-to phase fault, is sentenced using phase-to phase fault Protection criteria set in advance The disconnected phase-to phase fault type；

   When the phase-to phase fault type is troubles inside the sample space, quick acting is protected；

   When the phase-to phase fault type is external area error, without protection act；

   The phase-to phase fault Protection criteria set in advance includes：It is true according to the circuit both sides β moulds current spectrum and spectral difference Determine in area and external area error.
2. 2. the line protection method based on transient state component spectrum signature as claimed in claim 1, it is characterised in that described Phase-to phase fault Protection criteria set in advance includes：

   The frequency spectrum of the β moulds electric current is calculated according to fourier algorithm model；

   Calculus of differences pretreatment is carried out to the spectrum signal of the β moulds electric current according to the threshold value of setting；

   It is poor that circuit both sides β mould current spectrums are calculated according to pretreated result；

   According to the circuit both sides β moulds current spectrum and spectral difference determines in area and external area error.
3. 3. the line protection method based on transient state component spectrum signature as claimed in claim 1, it is characterised in that obtain Circuit both sides three-phase current after failure, and the β mould electric currents on the basis of three-phase are calculated, including：

   Circuit both sides three-phase current after collection failure, calculates the β mould electric currents on the basis of A, B, C phase respectively.
4. 4. the line protection method based on transient state component spectrum signature as claimed in claim 2, it is characterised in that described The frequency spectrum of the β moulds electric current is calculated according to fourier algorithm model, including:

   The frequency spectrum of the β moulds electric current is calculated as follows

   <mrow> <mi>I</mi> <mrow> <mo>(</mo> <msub> <mi>f</mi> <mi>N</mi> </msub> <mo>)</mo> </mrow> <mo>=</mo> <munderover> <mo>&amp;Sigma;</mo> <mrow> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow> <mi>N</mi> <mo>-</mo> <mn>1</mn> </mrow> </munderover> <msub> <mi>i</mi> <mi>&amp;beta;</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&amp;pi;</mi> </mrow> <mi>N</mi> </mfrac> </mrow> </msup> <mo>,</mo> <mi>N</mi> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mn>1</mn> <mo>,</mo> <mn>...</mn> <mo>,</mo> <mi>N</mi> <mo>-</mo> <mn>1</mn> </mrow>

   In formula, I (f_N) represent：Current amplitude；N is represented:Frequency spectrum number；i_βRepresent：Current beta modulus value；N is represented：Sampled value.
5. 5. the line protection method based on transient state component spectrum signature as claimed in claim 2, it is characterised in that according to The threshold value of setting carries out calculus of differences pretreatment to the spectrum signal of the β moulds electric current, including：

   The frequency values that amplitude in the current spectrum is less than to the threshold value carry out zero setting processing；

   Otherwise, spectrum value is carried out putting 1A processing；

   The threshold value is the frequency values of Iset.
6. 6. the line protection method based on transient state component spectrum signature as claimed in claim 2, it is characterised in that according to Pretreated result calculating circuit both sides β mould current spectrums are poor, including：

   Difference on the frequency of two amplitudes between 1A frequencies in the β mould current spectrums of side is calculated, and sends to circuit offside and carries out phase With processing.
7. 7. the line protection method based on transient state component spectrum signature as claimed in claim 2, it is characterised in that according to The circuit both sides β moulds current spectrum and spectral difference determines in area and external area error, including：

   The difference on the frequency size of alternative route both sides β mould current spectrums；

   When the absolute value of the difference on the frequency of the both sides β mould current spectrums is less than definite value Ifset, it is determined as external area error,

   Otherwise, it is determined that it is troubles inside the sample space.
8. 8. the line protection method based on transient state component spectrum signature as claimed in claim 7, it is characterised in that according to The circuit both sides β moulds current spectrum and spectral difference determines in area and external area error, further includes：

   As the frequency values for being more than the threshold value Iset in β mould current spectrums in side in circuit both sides without amplitude, opposite side frequency spectrum β The frequency values for having amplitude to be more than the threshold value Iset in mould current spectrum, are judged as troubles inside the sample space；

   When the frequency values for being more than the threshold value Iset in β moulds current spectrum in circuit both sides without amplitude, Protection criteria exits.
9. A kind of 9. transmission line protection system based on transient state component spectrum signature, it is characterised in that including：Obtain and calculate mould Block, breakdown judge module, fault processing module and criterion module；

   The acquisition computing module, for obtaining the circuit both sides three-phase current after failure, and calculates the β moulds on the basis of three-phase Electric current；

   The breakdown judge module, is not 0 for the β moulds electric current when three-phase, judges phase-to phase fault occurs, and using pre- The phase-to phase fault Protection criteria first set judges the phase-to phase fault type；

   The fault processing module, for when the phase-to phase fault type is troubles inside the sample space, protecting quick acting；When the phase Between fault type when being external area error, without protection act；

   The criterion module, for according to the circuit both sides β moulds current spectrum and spectral difference determines in area and external area error.
10. 10. the transmission line protection system as claimed in claim 9 based on transient state component spectrum signature, it is characterised in that institute Criterion module is stated, including：Calculating sub module, pretreatment submodule, calculate spectral difference submodule and determination sub-module；

    The calculating sub module, for calculating the frequency spectrum of the β moulds electric current according to fourier algorithm model；

    The pretreatment submodule, calculus of differences is carried out for the threshold value according to setting to the spectrum signal of the β moulds electric current Pretreatment；

    The calculating spectral difference submodule, it is poor for calculating circuit both sides β mould current spectrums according to pretreated result；

    The determination sub-module, for according to the circuit both sides β moulds current spectrum and spectral difference determines in area and external area error.
11. 11. the transmission line protection system as claimed in claim 10 based on transient state component spectrum signature, it is characterised in that institute Calculating sub module is stated, including：Fourier algorithm model；

    By the fourier algorithm model, the frequency spectrum of the β moulds electric current is calculated as follows

    <mrow> <mi>I</mi> <mrow> <mo>(</mo> <msub> <mi>f</mi> <mi>N</mi> </msub> <mo>)</mo> </mrow> <mo>=</mo> <munderover> <mo>&amp;Sigma;</mo> <mrow> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow> <mi>N</mi> <mo>-</mo> <mn>1</mn> </mrow> </munderover> <msub> <mi>i</mi> <mi>&amp;beta;</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&amp;pi;</mi> </mrow> <mi>N</mi> </mfrac> </mrow> </msup> <mo>,</mo> <mi>N</mi> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mn>1</mn> <mo>,</mo> <mn>...</mn> <mo>,</mo> <mi>N</mi> <mo>-</mo> <mn>1</mn> </mrow>

    In formula, I (f_N) represent：Current amplitude；N is represented:Frequency spectrum number；i_βRepresent：Current beta modulus value；N is represented：Sampled value.
12. 12. the transmission line protection system as claimed in claim 9 based on transient state component spectrum signature, it is characterised in that institute State fault processing module, the first processing submodule and second processing submodule；

    The first processing submodule, for judging the difference on the frequency of line both sides β mould current spectrums and the size of definite value Ifset；

    When the absolute value of the difference on the frequency of the both sides β mould current spectrums is less than definite value Ifset, it is determined as external area error；

    Otherwise, it is determined that it is troubles inside the sample space；

    The second processing submodule, for the amplitude and the size of threshold value Iset of the β mould current spectrums for judging circuit both sides；

    As the frequency values for being more than the threshold value Iset in β mould current spectrums in side in circuit both sides without amplitude, opposite side frequency spectrum β The frequency values for having amplitude to be more than the threshold value Iset in mould current spectrum, are judged as troubles inside the sample space；

    When the frequency values for being more than the threshold value Iset in β moulds current spectrum in circuit both sides without amplitude, Protection criteria exits.