CN116466266A - Novel short-circuit fault identification method based on sequence impedance difference angle - Google Patents
Novel short-circuit fault identification method based on sequence impedance difference angle Download PDFInfo
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- CN116466266A CN116466266A CN202310489594.6A CN202310489594A CN116466266A CN 116466266 A CN116466266 A CN 116466266A CN 202310489594 A CN202310489594 A CN 202310489594A CN 116466266 A CN116466266 A CN 116466266A
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/52—Testing for short-circuits, leakage current or ground faults
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- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
- Y04S10/52—Outage or fault management, e.g. fault detection or location
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Abstract
The invention discloses a novel short-circuit fault identification method based on a sequence impedance difference angle, which uses the sequence impedance difference angle as a short-circuit fault identification criterion and judges the fault type and position according to the magnitude of a positive sequence impedance difference angle and a negative sequence impedance difference angle calculated value. Comparing the calculated negative sequence impedance difference angle with a negative sequence set value, and if the negative sequence impedance difference angle is reduced to the negative sequence set value, judging that the internal short circuit fault exists, and sending out a tripping signal. If the negative sequence impedance difference angle does not drop to the negative sequence set value, the corresponding positive sequence impedance difference angle is compared with the positive sequence set value, if the positive sequence impedance difference angle rises to the positive sequence set value, the internal three-phase short circuit fault is judged, a tripping signal is sent out, otherwise, the external short circuit fault or the normal condition is judged, and the tripping signal is not sent out. The method can identify all types of short-circuit faults and distinguish different short-circuit fault positions from different short-circuit fault types.
Description
Technical Field
The invention relates to the technical field of relay protection of power grids after photovoltaic power supply access, in particular to a novel short circuit fault identification method based on a sequence impedance difference angle.
Background
As the duty cycle of photovoltaic power sources in power distribution networks continues to increase, the problems and challenges faced by conventional protection schemes continue to rise. Because the power flow direction of the photovoltaic power supply in the system is bidirectional, the traditional protective relay can be influenced, and the internal short circuit fault can not be accurately judged, so that the traditional protective scheme is greatly influenced, and a novel relay protection method capable of reliably judging the internal short circuit fault is needed.
Today, many transmission grids, mesh distribution grids, and modern smart grids are powered by photovoltaic power, and conventional protection schemes have failed to meet the needs. At present, a power distribution system connected with a photovoltaic power supply is applied to a relay based on distance protection, but the protection method is influenced by a control strategy and the change of the current of a power grid at a short-circuit fault point. Therefore, the conventional distance protection relay has a limitation in the protection of the power distribution system connected to the photovoltaic power supply.
Disclosure of Invention
In order to solve the problems, a novel short circuit fault identification method based on a sequence impedance difference angle is provided.
The object of the invention is achieved in the following way:
a novel short-circuit fault identification method based on sequence impedance difference angle uses the sequence impedance difference angle as a short-circuit fault identification criterion and judges the fault type and position according to the magnitude of positive sequence impedance difference angle and negative sequence impedance difference angle calculated values.
The method comprises the following steps:
step 1: firstly, according to the acquired instantaneous values of three-phase voltages and currents at buses at two sides of a line, positive sequence components and negative sequence components of the voltages and the currents are calculated in real time, and then positive sequence impedance and negative sequence impedance at the buses at two sides are calculated;
first, sampling point t 0 The difference between positive sequence impedance and negative sequence impedance is obtained by making the difference between positive sequence impedance and negative sequence impedance at the buses at two sides of the moment,
and then the next sampling point t 1 The positive sequence impedance difference at the bus bars at the two sides at the moment is obtained, and the negative sequence impedance difference is obtained;
then the sampling point t 0 Time and next sampling point t 1 Subtracting the differences of the positive sequence impedance at the moment to obtain a positive sequence impedance difference angle; sampling point t 0 Time and next sampling point t 1 Subtracting the differences of the negative sequence impedance at the moment to obtain a negative sequence impedance difference angle;
step 2: finally, comparing the negative sequence impedance difference angle calculated in the last step with a set value of the negative sequence impedance difference angle, judging that the internal short circuit is fault if the negative sequence impedance difference angle is reduced to the set value of the negative sequence impedance difference angle, and sending out a tripping signal; if the negative sequence impedance difference angle does not drop to the set value of the negative sequence impedance difference angle, the corresponding positive sequence impedance difference angle is compared with the set value of the positive sequence impedance difference angle, if the positive sequence impedance difference angle rises to the set value of the positive sequence impedance difference angle, the internal three-phase short circuit fault is judged, a tripping signal is sent out, otherwise, the external short circuit fault or the normal condition is judged, and the tripping signal is not sent out.
The positive sequence and negative sequence components of the voltage and the current are calculated in the step 1, and the specific calculation method is as follows:
wherein the subscript x=p of voltage U and current I, Q represents bus P and Q, respectively; subscripts 0,1,2 represent zero sequence, positive sequence, and negative sequence, respectively; subscripts a, b, c for voltage U and current I represent a phase, b phase, and c phase, respectively; alpha=1 < 120 °;
further calculating positive sequence impedance and negative sequence impedance at the buses at two sides;
wherein Z is 1，x And Z 2，x Respectively representing positive sequence impedance and negative sequence impedance, wherein subscript x=p, and Q respectively represents bus P and Q;
and will sample point t 0 The positive sequence impedance difference at the bus bars at the two sides at the moment is obtained, and the negative sequence impedance difference is obtained; the next sampling point t is obtained by the same method 1 A difference in positive sequence impedance and a difference in negative sequence impedance at the time;
t 0 time and t 1 The method for calculating the difference between the positive sequence impedance and the negative sequence impedance at the buses at two sides of the moment is as follows:
ΔZ 1t ＝Z 1，Pt -Z 1，Qt (4)
ΔZ 2t ＝Z 2，Pt -Z 2，Qt (5)
wherein DeltaZ 1t And DeltaZ 2t Respectively representing the difference between the positive sequence impedance and the negative sequence impedance, subscript t=t 0 ，t 1 Respectively represent t 0 Time sum t 1 Time;
further let t 0 Time and t 1 Subtracting the differences of the positive sequence impedance at the moment to obtain a positive sequence impedance difference angle; let t 0 Time and t 1 Subtracting the differences of the negative sequence impedance at the moment to obtain a negative sequence impedance difference angle;
wherein the method comprises the steps ofAt t 0 Difference of positive sequence impedance of time, +.>At t 1 Difference of positive sequence impedance of time, +.>Is the positive sequence impedance difference angle->At t 0 Difference of negative sequence impedance of time +.>At t 1 Difference of negative sequence impedance of time +.>Is the negative sequence impedance difference angle.
The set value of the negative sequence impedance difference angle is set to be-50 degrees; the set value of the positive sequence impedance difference angle is set to 40 degrees.
The invention has the beneficial effects that: compared with the prior art, the invention uses the sequence impedance difference angle as a short circuit fault identification criterion, uses the calculated values of the positive sequence impedance difference angle and the negative sequence impedance difference angle as short circuit fault identification parameters, can identify all types of short circuit faults, and can distinguish different short circuit fault positions and different short circuit fault types.
Drawings
Fig. 1 is a flowchart of a novel short-circuit fault identification method based on a sequence impedance difference angle according to an embodiment of the present invention.
FIG. 2 is a schematic circuit diagram of a method for verifying the effectiveness of the proposed novel short-circuit fault recognition method based on the sequence impedance difference angle in the example of the embodiment of the present invention.
Fig. 3 is a diagram of simulation results of a negative sequence impedance difference angle in a short-circuit fault recognition method provided when a three-phase short-circuit occurs in a simulation circuit according to an example of the embodiment of the present invention.
Fig. 4 is a diagram of simulation results of a positive sequence impedance difference angle in a short-circuit fault recognition method provided when a three-phase short-circuit occurs in a simulation circuit according to an example of the embodiment of the present invention.
Detailed Description
The invention will be described in further detail with reference to the drawings and the detailed description.
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
A novel short-circuit fault identification method based on sequence impedance difference angle uses the sequence impedance difference angle as a short-circuit fault identification criterion and judges the fault type and position according to the magnitude of positive sequence impedance difference angle and negative sequence impedance difference angle calculated values.
Step 1: firstly, according to the collected instantaneous values of three-phase voltages and currents at buses at two sides of a line, positive sequence components and negative sequence components of the voltages and the currents are calculated in real time, and then positive sequence impedance and negative sequence impedance at the buses at two sides are calculated. Sampling at a sampling frequency of 1kHz and sampling point t 0 The positive sequence impedance difference at the bus bars at the two sides at the moment is obtained, and the negative sequence impedance difference is obtained. The next sampling point t is obtained by the same method 1 The difference in positive sequence impedance and the difference in negative sequence impedance at the time instant. Further let t 0 Time and t 1 Subtracting the differences of the positive sequence impedance at the moment to obtain a positive sequence impedance difference angle; let t 0 Time and t 1 The difference of the negative sequence impedance at the moment is subtracted to obtain a negative sequence impedance difference angle.
The positive sequence and negative sequence components of the voltage and current are calculated by the following specific calculation method:
wherein the subscript x=p of voltage U and current I, Q represents bus P and Q, respectively; subscripts 0,1,2 represent zero sequence, positive sequence, and negative sequence, respectively; subscripts a, b, c represent phase a, phase b, and phase c, respectively; α=1° 120 °.
Further calculating positive sequence impedance and negative sequence impedance at the buses at two sides;
wherein Z is 1,x And Z 2,x Positive and negative sequence impedances are represented respectively, the subscript x=p, Q represents bus bars P and Q, respectively.
And will sample point t 0 The positive sequence impedance difference at the bus bars at the two sides at the moment is obtained, and the negative sequence impedance difference is obtained. The next sampling point t is obtained by the same method 1 The difference in positive sequence impedance and the difference in negative sequence impedance at the time instant.
t 0 Time and t 1 The method for calculating the difference between the positive sequence impedance and the negative sequence impedance at the buses at two sides of the moment is as follows:
ΔZ 1t ＝Z 1,Pt -Z 1,Qt (4)
ΔZ 2t ＝Z 2,Pt -Z 2,Qt (5)
wherein DeltaZ 1t And DeltaZ 2t Respectively representing the difference between the positive sequence impedance and the negative sequence impedance, subscript t=t 0 ，t 1 Respectively represent t 0 Time sum t 1 Time of day.
Further let t 0 Time and t 1 Subtracting the differences of the positive sequence impedance at the moment to obtain a positive sequence impedance difference angle; let t 0 Time and t 1 The difference of the negative sequence impedance at the moment is subtracted to obtain a negative sequence impedance difference angle.
Wherein the method comprises the steps ofAt t 0 Difference of positive sequence impedance of time, +.>At t 1 Difference of positive sequence impedance of time, +.>Is the positive sequence impedance difference angle->At t 0 Difference of negative sequence impedance of time +.>At t 1 Difference of negative sequence impedance of time +.>Is the negative sequence impedance difference angle.
Step 2: and finally, comparing the negative sequence impedance difference angle calculated in the last step with a negative sequence set value, and if the negative sequence impedance difference angle is reduced to the negative sequence set value, judging that the internal short circuit fault exists, and sending a tripping signal. If the negative sequence impedance difference angle does not drop to the negative sequence set value, the corresponding positive sequence impedance difference angle is compared with the positive sequence set value, if the positive sequence impedance difference angle rises to the positive sequence set value, the internal three-phase short circuit fault is judged, a tripping signal is sent out, otherwise, the external short circuit fault or the normal condition is judged, and the tripping signal is not sent out. As shown in fig. 1.
According to the operation experience of the power system, the set values of the negative sequence impedance difference angle and the positive sequence impedance difference angle are specifically as follows: the negative sequence impedance difference angle is larger than-30 degrees in normal operation, is-130 degrees when single-phase short-circuit faults occur, and is-70 degrees when two-phase and two-phase grounding short-circuit faults occur, so that the set value of the negative sequence impedance difference angle is set to be-50 degrees; and the positive-sequence impedance difference angle is 80 ° at the time of a three-phase short-circuit fault, so the set value of the positive-sequence impedance difference angle is set to 40 ° in the present invention.
The novel short-circuit fault recognition method using the sequence impedance difference angle mentioned above is verified as a specific example.
And (3) constructing a novel short-circuit fault identification method for verifying the proposed use sequence impedance difference angle by using a simulation software MATLAB (matrix laboratory) through a double-bus distribution network simulation system shown in figure 2. Wherein the system voltage is 120kV, the system frequency is 50Hz, and the line length is 75km.
0.4 assuming normal operation of the system before short-circuit failure s When a three-phase short-to-ground short fault occurs between the two buses P, Q shown in fig. 2, the duration of the short fault is 0.2 seconds. FIG. 3 shows the variation of the negative sequence impedance difference angle before and after the occurrence of a short circuit fault, FIG. 3 shows the negative sequence impedance difference angle being shortThe path fault period fluctuates between-200 ° to 200 °, so the negative sequence impedance difference angle cannot be correctly determined in the event of the short-circuit fault. Fig. 4 shows a change of the positive-sequence impedance difference angle before and after the occurrence of the short-circuit fault, and fig. 4 shows that the positive-sequence impedance difference angle rises to 80 ° immediately after the occurrence of the short-circuit fault, exceeds a set value of 40 ° and is continuously greater than the set value during the short-circuit fault, so that the internal short-circuit fault can be correctly judged according to the positive-sequence impedance difference angle, and the short-circuit fault is of the three-phase short-circuit ground fault type, and a trip signal is sent.
Simulation results prove the accuracy and the effectiveness of the proposed novel short-circuit fault identification method using the sequence impedance difference angle on the judgment of different types of short-circuit faults under various conditions. Compared with the traditional mode, the method and the device for judging the short-circuit fault according to the sequence impedance difference angle can not be influenced by a control strategy and the current change of the power grid at the short-circuit fault point, can identify all types of short-circuit faults, and can distinguish different short-circuit fault positions and different short-circuit fault types.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that it will be apparent to those skilled in the art that several changes and modifications can be made without departing from the general inventive concept, and these should also be regarded as the scope of the invention.
Claims (4)
1. A novel short circuit fault identification method based on a sequence impedance difference angle is characterized by comprising the following steps of: the method uses the sequence impedance difference angle as a short circuit fault identification criterion, and judges the fault type and the fault position according to the magnitude of the positive sequence impedance difference angle and the negative sequence impedance difference angle calculated value.
2. The novel short-circuit fault identification method based on the order impedance difference angle according to claim 1, wherein the method comprises the following steps: the method comprises the following steps:
step 1: firstly, according to the acquired instantaneous values of three-phase voltages and currents at buses at two sides of a line, positive sequence components and negative sequence components of the voltages and the currents are calculated in real time, and then positive sequence impedance and negative sequence impedance at the buses at two sides are calculated;
first, sampling point t 0 The difference between positive sequence impedance and negative sequence impedance is obtained by making the difference between positive sequence impedance and negative sequence impedance at the buses at two sides of the moment,
and then the next sampling point t 1 The positive sequence impedance difference at the bus bars at the two sides at the moment is obtained, and the negative sequence impedance difference is obtained;
then the sampling point t 0 Time and next sampling point t 1 Subtracting the differences of the positive sequence impedance at the moment to obtain a positive sequence impedance difference angle; sampling point t 0 Time and next sampling point t 1 Subtracting the differences of the negative sequence impedance at the moment to obtain a negative sequence impedance difference angle;
step 2: finally, comparing the negative sequence impedance difference angle calculated in the last step with a set value of the negative sequence impedance difference angle, judging that the internal short circuit is fault if the negative sequence impedance difference angle is reduced to the set value of the negative sequence impedance difference angle, and sending out a tripping signal; if the negative sequence impedance difference angle does not drop to the set value of the negative sequence impedance difference angle, the corresponding positive sequence impedance difference angle is compared with the set value of the positive sequence impedance difference angle, if the positive sequence impedance difference angle rises to the set value of the positive sequence impedance difference angle, the internal three-phase short circuit fault is judged, a tripping signal is sent out, otherwise, the external short circuit fault or the normal condition is judged, and the tripping signal is not sent out.
3. The novel short-circuit fault identification method based on the order impedance difference angle according to claim 1, wherein the method comprises the following steps: the positive sequence and negative sequence components of the voltage and the current are calculated in the step 1, and the specific calculation method is as follows:
wherein the subscript x=p of voltage U and current I, Q represents bus P and Q, respectively; subscripts 0,1,2 represent zero sequence, positive sequence, and negative sequence, respectively; subscripts a, b, c for voltage U and current I represent a phase, b phase, and c phase, respectively; alpha=1 < 120 °;
further calculating positive sequence impedance and negative sequence impedance at the buses at two sides;
wherein Z is 1,x And Z 2,x Respectively representing positive sequence impedance and negative sequence impedance, wherein subscript x=p, and Q respectively represents bus P and Q;
and will sample point t 0 The positive sequence impedance difference at the bus bars at the two sides at the moment is obtained, and the negative sequence impedance difference is obtained; the next sampling point t is obtained by the same method 1 A difference in positive sequence impedance and a difference in negative sequence impedance at the time;
t 0 time and t 1 The method for calculating the difference between the positive sequence impedance and the negative sequence impedance at the buses at two sides of the moment is as follows:
ΔZ 1t ＝Z 1,Pt -Z 1,Qt (4)
ΔZ 2t ＝Z 2,Pt -Z 2,Qt (5)
wherein DeltaZ 1t And DeltaZ 2t Respectively representing the difference between the positive sequence impedance and the negative sequence impedance, subscript t=t 0 ,t 1 Respectively represent t 0 Time sum t 1 Time;
further let t 0 Time and t 1 Subtracting the differences of the positive sequence impedance at the moment to obtain a positive sequence impedance difference angle; let t 0 Time and t 1 Subtracting the differences of the negative sequence impedance at the moment to obtain a negative sequence impedance difference angle;
wherein the method comprises the steps ofAt t 0 Difference of positive sequence impedance of time, +.>At t 1 Difference of positive sequence impedance of time, +.>Is the positive sequence impedance difference angle->At t 0 Difference of negative sequence impedance of time +.>At t 1 Difference of negative sequence impedance of time +.>Is the negative sequence impedance difference angle.
4. The novel short-circuit fault identification method based on the order impedance difference angle according to claim 1, wherein the method comprises the following steps: the set value of the negative sequence impedance difference angle is set to be-50 degrees; the set value of the positive sequence impedance difference angle is set to 40 degrees.
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