CN104198884A - Differential principle based large-scale power grid intelligent trouble diagnosis method - Google Patents
Differential principle based large-scale power grid intelligent trouble diagnosis method Download PDFInfo
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Abstract
The invention discloses a differential principle based large-scale power grid intelligent trouble diagnosis method. The differential principle based large-scale power grid intelligent trouble diagnosis method comprises fault recording sampling, calculation of a phase current differential value with electric transmission and transformation equipment serving as a unit when the power grid normally operates, differential current calculation of primary current of the power grid equipment with power grid independent equipment serving as a calculation unit according to the fault data transmitted by a fault recorder and comparison of the differential current value and a differential current setting value to judge whether out-of-limit or not. The differential principle based large-scale power grid intelligent trouble diagnosis method has the advantages of being wide in applicable range and accurate in judgment, allowing automatic medical result push, not being influenced by factors such as a system operation mode and system oscillation and the like due to the fact that a fault position is accurately and quickly positioned according to the differential principle and a medical result is automatically pushed in a main wiring diagram.
Description
Technical Field
The invention relates to the field of intelligent fault diagnosis methods for power grids, in particular to a large-scale intelligent fault diagnosis method for power grids based on a differential principle.
Background
With the continuous strengthening of the power grid connection, the power transmission capacity of the power grid is effectively improved, but the possibility of the expansion of the accident spread range caused by the local faults of the power grid is continuously improved, and the difficulty in accurately identifying the faults is greatly increased. Therefore, in recent years, each company has increased the construction strength of technical support systems such as fault recording networking systems and relay protection information systems, when a power grid fails, various fault information such as breaker action information, fault recording information and protection action timing sequence information can be timely transmitted to a dispatching end, but an operator cannot quickly, accurately and visually judge the fault property simply based on numerous discrete fault information such as breaker deflection, fault recorder analog quantity and protection device action items, and the recovery power supply speed and the safe operation of the power grid are greatly influenced.
Aiming at the difficult problem, many scholars at home and abroad propose power grid fault diagnosis by methods such as a Petri network, a rough set, a multi-source information fusion technology, an expert diagnosis system and the like, and the researches have certain effects, but more fault information is needed, the criteria are more complex, and the practical engineering application has greater limitations.
When a large-scale power grid is abnormal or has faults, various fault information can be timely transmitted to a dispatching end, but an operator cannot quickly, accurately and visually judge the fault property simply based on numerous discrete fault information such as circuit breaker deflection, fault recorder analog quantity, protection device action items and the like, and the restoration power supply speed and the safe operation of the power grid are greatly influenced.
Disclosure of Invention
The invention aims to solve the problems, provides a large-scale power grid intelligent fault diagnosis method based on a differential principle, can accurately and quickly locate a fault position, automatically pushes a diagnosis result on a main wiring diagram, has the advantages of wide application range, accurate judgment, automatic pushing of the diagnosis result, no influence of factors such as a system operation mode, system oscillation and the like, provides a power transmission line fault diagnosis method, and specifically explains the power transmission line fault diagnosis method by taking double-bus wiring as an example.
In order to achieve the purpose, the invention adopts the following technical scheme:
a large-scale power grid intelligent fault diagnosis method based on a differential principle comprises the following steps:
step 1, automatically calling fault recording sampling at set time intervals;
step 2, when the power grid normally runs, phase current differential value calculation is carried out by taking the power transmission and transformation equipment as a unit; if the difference current calculated value is lower than the differential current starting fixed value, returning to the step 1; if the differential current calculated value is larger than the differential current starting fixed value of the corresponding equipment, turning to the step 3;
step 3, remotely adjusting parameters of the fault recorder or checking whether the fault recorder is completely connected to equipment participating in differential current calculation and whether a current loop has a multipoint grounding problem on site and eliminating defects in time until a differential current calculation value is lower than a differential current starting fixed value;
step 4, when the power grid fails, calculating the difference current of the phase current of the power grid equipment by respectively taking the power grid independent equipment as a calculation unit according to the fault data transmitted by the fault recorder; the grid-independent device comprises: bus equipment, transformer equipment and a power transmission line;
for the transmission line fault, firstly, carrying out fault primary selection on the transmission line, screening out suspected fault lines, and then calculating a differential current value of the suspected fault lines;
step 5, comparing the differential flow value with the differential flow setting value, judging that a fault occurs if the differential flow value exceeds the limit, and simultaneously positioning the fault position and determining a protection action; if the differential flow value is not out of limit, judging that no fault or an out-of-area fault exists; in both cases, the fault diagnosis report is automatically pushed.
In step 4, the method for performing fault initial selection on the power transmission line includes: a branch current phase comparison method and a comprehensive direction element identification method;
the branch current phase comparison method comprises the following steps:
firstly, judging whether the bus fault is a suspected bus fault, if not, judging the phase of each branch current, and judging the branch with the suspected fault by phase comparison;
the comprehensive direction element identification method comprises the following steps:
for asymmetric faults, judging whether the line is a suspected fault line or not by judging the directions of the zero-sequence directional element and the negative-sequence directional element according to different fault types;
and for symmetric faults, adopting an impedance direction element to identify suspected fault lines.
In the step 4, the method for the power transmission line to perform the fault initial selection is a branch current phase comparison method:
for the condition that the number of the line branches is more than or equal to 3 and the two buses run in parallel:
(1) if the bus differential current value is greater than A and the differential current value/braking current value is greater than B, the bus fault is detected; wherein A and B are both action setting values which are set values;
(2) if the fault condition does not meet the condition (1), the fault condition is a line branch fault or a main transformer branch fault, and the suspected fault branch is judged as follows:
the first step is as follows: selecting the branch with the largest fault current as a reference branch, and taking the fault current as the reference branch current;
the second step is that: and respectively carrying out phase comparison on the fault current of other current branches and the reference branch current:
if the phase difference between the current of all the branches and the current of the reference branch meets 120-240 degrees, the reference branch is a suspected fault branch;
if only 1 branch circuit and the reference branch circuit meet the phase difference of 120-240 degrees, the phase difference of all the rest branch circuits and the reference branch circuit meet about-60 degrees; the branch with the phase difference of 120-240 degrees with the reference branch is a suspected fault branch.
In the step 4, the method for the power transmission line to perform the fault initial selection is a branch current phase comparison method:
for the case that the number of the line branches is 2, two buses run in parallel:
(1) if the bus differential current value is greater than A and the differential current value/braking current value is greater than B, the bus fault is detected; wherein A and B are both action setting values which are set values;
(2) if the fault condition does not meet the condition (1), the fault condition is a line branch fault or a main transformer branch fault, and the suspected fault branch is judged as follows:
and the line with positive measured impedance is a suspected fault branch, and the line with negative measured impedance is a non-fault line.
In the step 4, the method for the power transmission line to perform the fault initial selection is a branch current phase comparison method:
for the case that the number of the line branches is 1, two buses run in parallel:
(1) if the bus differential current value is greater than A and the differential current value/braking current value is greater than B, the bus fault is detected; wherein A and B are both action setting values which are set values;
(2) if the fault does not meet the condition (1), the fault is a line branch fault or a main transformer branch fault, and if the secondary current of the current of a certain line branch is less than C, and C is a set value, the line branch is a suspected fault branch.
In the step 4, the method for the power transmission line to perform the fault initial selection is a comprehensive direction element identification method:
for asymmetric faults, the specific judgment method is as follows:
(1) single-phase fault: the zero sequence direction element and the negative sequence direction element are positive directions;
(2) two-phase ground fault: the zero sequence direction element and the negative sequence direction element are positive directions;
(3) two-phase short-circuit ungrounded fault: no zero sequence, the negative sequence direction element is positive;
if the direction elements on both sides of a certain line are displayed as positive directions, the line is a suspected fault line.
The zero sequence direction element satisfies the following conditions for the positive direction:
the zero sequence direction element satisfies the following conditions for the positive direction:
the negative sequence direction element satisfies the following conditions for the positive direction:
wherein,is a zero-sequence current, and is a zero-sequence current,is a zero-sequence voltage, and is,is a negative-sequence current, and is,is a negative sequence voltage.
In the step 4, the method for the power transmission line to perform the fault initial selection is a comprehensive direction element identification method:
for the symmetry fault, the specific judgment method is as follows:
when a power grid system has a symmetric fault, the power transmission line has no zero sequence and negative sequence components, a phase-to-phase impedance direction element is adopted for identifying a fault line, a phase-to-phase distance relay is used for judging the direction of the phase-to-phase impedance direction element, and if the polarization voltage and the working voltage of the phase-to-phase distance relay meet the following action criterion equation, the phase-to-phase impedance direction element is proved to be in a positive direction; the criterion equation is as follows:
wherein,in order to be the polarization voltage, <math>
<mrow>
<msub>
<mover>
<mi>U</mi>
<mo>·</mo>
</mover>
<mi>ΦΦ</mi>
</msub>
<mo>-</mo>
<msub>
<mi>Z</mi>
<mi>set</mi>
</msub>
<msub>
<mover>
<mi>I</mi>
<mo>·</mo>
</mover>
<mi>ΦΦ</mi>
</msub>
</mrow>
</math> in order to be at the operating voltage,in order to obtain the voltage between the phases of the fault,for fault phase current, ZsetFixed line positive sequence impedance fixed value ZL11.2-1.5 times of the total weight of the composition;
and if the interphase impedance direction elements on the two sides of a certain line meet the corresponding action criterion, the line is a suspected fault line.
The invention has the beneficial effects that:
the invention utilizes the differential principle to accurately and quickly locate the fault position, automatically pushes the diagnosis result on the main wiring diagram, has the advantages of wide application range, accurate judgment, automatic pushing of the diagnosis result, no influence of factors such as system operation mode, system oscillation and the like, automatically pushes the fault current, the fault position and the diagnosis result of each interval, and uniformly and visually displays on the main wiring diagram, thereby providing urgent decision support for accident handling, fundamentally changing the traditional mode of manual fault diagnosis, providing urgent decision support for accident handling, and effectively improving the large-scale grid handling capability.
The line fault identification method provided by the invention has the advantages of simple principle, accurate judgment, no influence of a net rack topological structure, no voltage quantity, accurate positioning of a fault line, no influence of load, oscillation, power inversion and the like. Firstly, suspected line faults are judged, then, the fault lines are further identified by utilizing a differential principle, the judgment result is accurate and reliable, and the workload is greatly reduced.
Drawings
FIG. 1 is a schematic diagram of a differential flow calculation partition chart fault diagnosis of wide-area fault recording information;
FIG. 2 is a flow chart of the grid fault diagnosis system of the present invention;
FIG. 3 is a schematic diagram of differential wiring of a three-winding transformer;
fig. 4 is a bus fault diagnosis case of case 1 of the present invention;
fig. 5 is a schematic diagram of the operation mode of the power grid before the fault in case 2 of the present invention.
The specific implementation mode is as follows:
the invention is further illustrated by the following examples in conjunction with the accompanying drawings:
fig. 1 is a differential flow calculation partition diagram fault diagnosis schematic diagram of wide-area fault recording information, and it can be seen from the diagram that the differential flow calculation region division is respectively identical to each interval differential main protection range, and the differential principle is used for judging accurately, accurately positioning fault position and evaluating protection action behavior without special advantages of system operation mode, transition resistance, load current, power reversal, system diagnosis and the like.
When the power grid normally operates, fault recording sampling is automatically called at fixed time intervals, phase current differential values are calculated by taking power transmission and transformation equipment as units, and the differential value is almost zero. If the difference current calculated value is larger than the difference current threshold value of the corresponding equipment (the maximum difference current value possibly caused by factors such as unbalanced load, CT errors and the like when the difference current threshold value of each equipment is set as the maximum operation mode of the power grid), the access interval channel name, the CT polarity and the transformation ratio coefficient of the fault recorder are remotely adjusted through the scheduling master station, or whether the fault recorder is completely accessed to the equipment participating in the difference current calculation and whether the current loop has the multipoint grounding problem or not are checked on site and eliminated in time, so that the difference current calculated values of all power transmission and transformation equipment are close to zero when the power grid normally operates.
When the power grid has a fault, the differential current of the primary current of the power grid is calculated by respectively taking the power grid independent equipment as a calculation unit according to fault data sent by a fault recorder; and comparing the differential flow value with the differential flow setting value to realize accurate fault position positioning and protection action behavior evaluation. The specific flow is shown in figure 2 below:
the fault diagnosis method only needs fault recorder data, and during fault diagnosis, the fault recorder data are equivalent to data acquisition parts of bus protection, transformer protection and line protection devices, so that the branch circuits, the types and the polarities of CT secondary windings accessed to the fault recorder meet the following requirements, are limited to space, and take a 220kV transformer substation bus equipment fault identification method in a double-bus connection form as an example:
(1) the transformer substation is provided with the main transformer fault oscillograph independently, all main transformer 220kV high-voltage side current analog quantities of the transformer substation are connected to the line fault oscillograph of the transformer substation in series, and all branch circuits of a bus in a conventional station are connected into the same fault oscillograph to achieve sampling synchronization. All fault oscillographs in the intelligent station adopt unified synchronous clocks, and all branches of a bus do not need to be connected to the same fault oscillograph.
(2) The CT winding connected to the fault recorder should be a line side CT winding (protection level).
(3) The primary homonymous terminal of the CT of the line and the transformer branch accessed to the fault oscillograph is arranged on the bus side, the primary homonymous terminal of the bus CT is arranged on the I bus side, and the corresponding secondary winding of the CT is outgoing lines at the homonymous terminal. If the orientation of the primary homonymous terminal of the CT connected into the fault recorder is opposite to that of the primary homonymous terminal, the corresponding secondary winding of the CT is changed into a non-homonymous terminal to be outgoing so as to meet the requirement of polarity setting.
1. Bus equipment
The calculation formula of the bus large difference and the bus small difference is as follows:
large differential current: i iscd＝I1+I2+…+In
II, mother small difference current: i iscd1＝I1×S11+I2×S12+…+In×S1n+IML×SML
II bus small difference current: i iscd2＝I1×S21+I2×S22+…+In×S2n-IML×SML
In the formula I1,I2,…,InRepresenting each branch current vector; i isMLRepresenting a digital value of the bus tie current; s11,S12,…,S1nThe position of a mother knife switch of each branch I is shown (0 represents the knife switch is switched off, and 1 represents the knife switch is switched on); s21,S22,…,S2nRepresenting the position of the main knife switch of each branch II; sMLThe bus parallel operation state is shown (0 indicates the split operation, and 1 indicates the parallel operation).
The large difference loop is a differential loop formed by all the other branch currents on the bus except the bus-coupled switch; the bus differential circuit is a differential circuit formed by branch currents connected with the bus, and comprises a bus-coupled switch associated with the bus.
2. Transformer device
Differential current of the transformer:respectively the regulated current vectors of each side of the transformer. Referring to FIG. 3 below, taking Y/Y/Δ -11 as an example, the differential current is calculated as follows:
phase A differential flow:
b phase difference stream:
c phase difference stream:
in the above formula, the first and second equations,a, b and c phases at high, medium and low voltage sides respectivelyCurrent phasor secondary values; k is a radical ofH,kM,kLCT transformation ratios of a high-voltage side, a medium-voltage side and a low-voltage side are respectively set; vH,VM,VLRated voltages of a high voltage side, a medium voltage side and a low voltage side are respectively provided.
All fault recording data of equipment in the station such as a bus, a transformer and the like are in the same transformer station, so that the fault can be accurately identified by using a differential principle conveniently.
3. Power transmission line
The transmission line is different from bus and transformer equipment, fault data of the transmission line is stored in fault oscillographs in two different transformer substations, and if the fault line identification is directly carried out by adopting a line differential principle, the method has the advantages of simple principle, accurate judgment, no influence of a net rack topological structure, no voltage quantity, accurate positioning of the fault line, no influence of load, oscillation, power reversal and the like. However, because the opposite-side fault recording information of the line is needed, and the unified clock of the data of the whole network is difficult to realize at present, operations such as data mapping at two sides, fault data sampling synchronization and the like need to be manually carried out, so that the system preferentially adopts the following two methods to carry out fault line primary selection so as to reduce workload, and carries out rechecking and confirmation on suspected fault lines by utilizing a differential principle.
3.1 phase comparison of currents in branches
The method has the advantages that the method does not need the recording information of the fault on the opposite side of the line, does not need the voltage quantity, has high calculation speed and can carry out identification only by the current quantity.
(1) The transformer substation of "access main branch (circuit branch quantity is more than or equal to 3, mother unites the position):
1) if the differential current value of the bus is greater than 400A and the differential current value/braking current value is greater than 0.4, the bus is in fault;
2) if the fault does not meet 1), the fault is determined to be a line/main transformer interval fault, and the judgment is as follows:
the first step is as follows: and selecting the branch with the largest (or larger) fault current, and taking the fault current as a reference vector.
The second step is that: and the fault currents of other current branches (the secondary current is more than 0.4A) are respectively compared with the reference branch current in phase.
Thirdly, phase difference between all branch circuit currents and the reference branch circuit current is about 180 degrees, and the reference branch circuit is a fault branch circuit; if only 1 branch and the reference branch have phase difference of about 180 degrees (120-240 degrees), and the phase difference of all other branches and the reference branch is about 0 degree (-60 degrees); the branch whose phase difference with the reference branch is about 180 degrees is a fault branch. (the branch with the largest fault current is the general one)
(2) "insert the transformer substation that becomes the main branch road" (circuit branch road quantity 2, mother allies oneself with the position):
1) if the differential current value of the bus is greater than 400A and the differential current value/braking current value is greater than 0.4, the bus is in fault;
2) if the fault does not meet 1), the fault is determined to be a line/main transformer interval fault, and an impedance direction element is sampled for judgment, and the judgment is as follows:
the line with positive measurement impedance (comprising three grounding impedance elements and three interphase impedance elements) is a fault branch line, and the line with negative measurement impedance is a non-fault line.
(3) "insert the transformer substation that becomes the main branch road" (circuit branch road quantity 1, mother allies oneself with the position):
1) if the differential current value of the bus is greater than 400A and the differential current value/braking current value is greater than 0.4, the bus is in fault;
2) if the current does not meet 1), the fault is determined to be a line/main transformer interval fault, and the secondary current of the line branch current is less than 0.4A, the fault branch is the line branch.
3.2 Integrated Direction element identification
The method has the advantages that the method is not influenced by the topological structure of the net rack, the recording information of the fault on the side is not needed, and the identification can be carried out only by the voltage and the current of the side.
(1) Asymmetric fault
1) Single-phase fault: the zero sequence direction and the negative sequence direction elements are positive direction
2) Two-phase ground fault: the zero sequence direction and the negative sequence direction elements are positive direction
3) Two-phase short circuit ungrounded fault, no zero sequence, and positive sequence direction
Empirical data shows that when the zero sequence and negative sequence primary current of a system of 220kV or above is larger than 300A, an asymmetric fault occurs in a power grid, and then fault line identification is carried out by using a zero negative sequence directional element.
Zero sequence positive direction element:
the zero sequence current and the zero sequence voltage in the formula are both produced by self, namely, the zero sequence current and the zero sequence voltage are obtained through automatic calculation of the collected A, B, C three-phase current and voltage, but are not directly collected after external input.
Negative sequence positive direction element:
in which the negative sequence current and the negative sequence voltage are both self-generated.
(2) Symmetry fault (three-phase short circuit)
When the power grid system has symmetrical faults, zero negative sequence components do not exist, so that fault line identification can be carried out only by adopting impedance direction elements, ZAB、ZAC、ZBCThe positive direction is the direction which satisfies the following criteria.
The interphase distance relay adopts an ohmic relay with offset characteristics. The action criterion is
The voltage is memorized before failure.
ZsetCan be fixed to obtain 'line positive sequence impedance constant value' zL11.2 to 1.5 times of the total weight of the composition.
After the calculation of the direction element is completed, all positive direction lines are marked on the main wiring diagram. If both sides of the line are displayed in the positive direction, the line is a suspected fault line, then the differential current value of fault currents on both sides of the line is calculated manually, if the differential current value is greater than the differential current setting value, the line is a fault line, and fault point positioning of the line can be carried out by adopting a single-end distance measurement method, a double-end impedance distance measurement method, a traveling wave distance measurement method and other comprehensive distance measurement methods to accurately position fault points.
The concrete calculation example is as follows:
case 1, thunderstorm weather in a certain area, station A: 220kV busbar differential protection action, 220kV busbar 200A switch, the II line 213 switch of this side break off the floodgate, contralateral B station: line II 213 switches off.
During fault analysis, a related region of differential flow calculation, a differential algorithm starting value and a ratio differential element action characteristic curve can be selected autonomously. As is apparent from fig. 4, when the fault occurs, the calculated value of the bus differential flow falls into the action region, which can accurately determine that the bus is switched to A, C two-phase ground fault by phase a connection; the circuit has no fault, and the main differential sends a long jump command to trip off the switch at the opposite side of the circuit after the main differential is operated.
Case 2, in thunderstorm weather in a certain area, the operation mode before the fault is shown in fig. 5, wherein the circuit breaker on the D side of the substation of a line L8 is in a separated position. When a power grid fails, three-phase tripping of circuit breakers on two sides of the line L4 is not overlapped, and three-phase tripping of a #1 main transformer high-voltage side of the transformer substation C and a bus tie circuit breaker is performed.
By utilizing the diagnosis method, calculation and analysis are carried out according to fault recording data which are transmitted to a dispatching end after faults, firstly, the differential current value of bus equipment and the fault directions of two sides of a tripping line are respectively calculated, the fault direction can be obtained through calculation, three buses and transformer equipment of a transformer substation A, B, C have no fault, lines L4, L7 and L8 are suspected fault lines, then the differential current value of the suspected fault lines is calculated one by one (see table 1 in detail), and the power grid fault can be accurately judged to be an A-phase grounding fault in a line L8 generation area through the table 1.
TABLE 1 suspected fault line differential flow calculation
Through field inspection, the fault is that the tail end of the line L8 has an A-phase grounding fault, the circuit breaker on the C side of the line transformer substation cannot timely isolate a fault point due to the fault of the operating mechanism, the circuit breaker failure protection trips the high-voltage side of the #1 main transformer and the bus-tie switch through set time-delay action, and the L4 line trips the circuit breaker on the opposite side due to the fact that charging overcurrent protection is switched by mistake during normal operation, and the circuit breaker on the other side trips.
When a power grid fails, an operator cannot quickly, accurately and visually judge the failure property based on a plurality of discrete failure information such as circuit breaker deflection, failure recorder analog quantity, protection device action items and the like. Aiming at the key problem of rapid and accurate identification of faults, the invention innovatively provides a large-scale power grid intelligent fault diagnosis method based on a differential principle, the differential principle is utilized to judge accurately, fault positions are accurately positioned and protective action behaviors are evaluated without special advantages of a system operation mode, transition resistance, load current, power reversal, system diagnosis and the like, the fault current, the fault positions and diagnosis results at intervals are uniformly and visually displayed on a main wiring diagram, and urgent decision support is provided for accident handling. The system can accurately judge the fault position in the fault processing of multiple power grids, provides urgent decision support for quickly recovering power supply, and has strong engineering application value.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.
Claims (8)
1. A large-scale power grid intelligent fault diagnosis method based on a differential principle is characterized by comprising the following steps:
step 1, automatically calling fault recording sampling at set time intervals;
step 2, when the power grid normally runs, phase current differential value calculation is carried out by taking the power transmission and transformation equipment as a unit; if the difference current calculated value is lower than the differential current starting fixed value, returning to the step 1; if the differential current calculated value is larger than the differential current starting fixed value of the corresponding equipment, turning to the step 3;
step 3, remotely adjusting parameters of the fault recorder or checking whether the fault recorder is completely connected to equipment participating in differential current calculation and whether a current loop has a multipoint grounding problem on site and eliminating defects in time until a differential current calculation value is lower than a differential current starting fixed value;
step 4, when the power grid fails, calculating the difference current of the phase current of the power grid equipment by respectively taking the power grid independent equipment as a calculation unit according to the fault data transmitted by the fault recorder; the grid-independent device comprises: bus equipment, transformer equipment and a power transmission line;
for the transmission line fault, firstly, carrying out fault primary selection on the transmission line, screening out suspected fault lines, and then calculating a differential current value of the suspected fault lines;
step 5, comparing the differential flow value with the differential flow setting value, judging that a fault occurs if the differential flow value exceeds the limit, and simultaneously positioning the fault position and determining a protection action; if the differential flow value is not out of limit, judging that no fault or an out-of-area fault exists; in both cases, the fault diagnosis report is automatically pushed.
2. The differential principle-based intelligent fault diagnosis method for the large-scale power grid according to claim 1, wherein in the step 4, the method for performing fault initial selection on the power transmission line comprises the following steps: a branch current phase comparison method and a comprehensive direction element identification method;
the branch current phase comparison method comprises the following steps:
firstly, judging whether the bus fault is a suspected bus fault, if not, judging the phase of each branch current, and judging the branch with the suspected fault by phase comparison;
the comprehensive direction element identification method comprises the following steps:
for asymmetric faults, judging whether the line is a suspected fault line or not by judging the directions of the zero-sequence directional element and the negative-sequence directional element according to different fault types;
and for symmetric faults, adopting an impedance direction element to identify suspected fault lines.
3. The differential principle-based intelligent fault diagnosis method for the large-scale power grid according to claim 1 or 2, wherein in the step 4, the method for performing fault initial selection on the power transmission line is a branch current phase comparison method:
for the condition that the number of the line branches is more than or equal to 3 and the two buses run in parallel:
(1) if the bus differential current value is greater than A and the differential current value/braking current value is greater than B, the bus fault is detected; wherein A and B are both action setting values which are set values;
(2) if the fault condition does not meet the condition (1), the fault condition is a line branch fault or a main transformer branch fault, and the suspected fault branch is judged as follows:
the first step is as follows: selecting the branch with the largest fault current as a reference branch, and taking the fault current as the reference branch current;
the second step is that: and respectively carrying out phase comparison on the fault current of other current branches and the reference branch current:
if the phase difference between the current of all the branches and the current of the reference branch meets 120-240 degrees, the reference branch is a suspected fault branch;
if only 1 branch circuit and the reference branch circuit meet the phase difference of 120-240 degrees, the phase difference of all the rest branch circuits and the reference branch circuit meet about-60 degrees; the branch with the phase difference of 120-240 degrees with the reference branch is a suspected fault branch.
4. The differential principle-based intelligent fault diagnosis method for the large-scale power grid according to claim 1 or 2, wherein in the step 4, the method for performing fault initial selection on the power transmission line is a branch current phase comparison method:
for the case that the number of the line branches is 2, two buses run in parallel:
(1) if the bus differential current value is greater than A and the differential current value/braking current value is greater than B, the bus fault is detected; wherein A and B are both action setting values which are set values;
(2) if the fault condition does not meet the condition (1), the fault condition is a line branch fault or a main transformer branch fault, and the suspected fault branch is judged as follows:
and the line with positive measured impedance is a suspected fault branch, and the line with negative measured impedance is a non-fault line.
5. The differential principle-based intelligent fault diagnosis method for the large-scale power grid according to claim 1 or 2, wherein in the step 4, the method for performing fault initial selection on the power transmission line is a branch current phase comparison method:
for the case that the number of the line branches is 1, two buses run in parallel:
(1) if the bus differential current value is greater than A and the differential current value/braking current value is greater than B, the bus fault is detected; wherein A and B are both action setting values which are set values;
(2) if the fault does not meet the condition (1), the fault is a line branch fault or a main transformer branch fault, and if the secondary current of the current of a certain line branch is less than C, and C is a set value, the line branch is a suspected fault branch.
6. The differential principle-based intelligent fault diagnosis method for the large-scale power grid according to claim 1 or 2, wherein in the step 4, the method for performing fault initial selection on the power transmission line is a comprehensive directional element identification method:
for asymmetric faults, the specific judgment method is as follows:
(1) single-phase fault: the zero sequence direction element and the negative sequence direction element are positive directions;
(2) two-phase ground fault: the zero sequence direction element and the negative sequence direction element are positive directions;
(3) two-phase short-circuit ungrounded fault: no zero sequence, the negative sequence direction element is positive;
if the direction elements on both sides of a certain line are displayed as positive directions, the line is a suspected fault line.
7. The method according to claim 6, wherein the zero sequence direction element satisfies, for a positive direction:
the zero sequence direction element satisfies the following conditions for the positive direction:
the negative sequence direction element satisfies the following conditions for the positive direction:
wherein,is a zero-sequence current, and is a zero-sequence current,is a zero-sequence voltage, and is,is a negative-sequence current, and is,is a negative sequence voltage.
8. The differential principle-based intelligent fault diagnosis method for the large-scale power grid according to claim 1 or 2, wherein in the step 4, the method for performing fault initial selection on the power transmission line is a comprehensive directional element identification method:
when a power grid system has a symmetric fault, the power transmission line has no zero sequence and negative sequence components, a phase-to-phase impedance direction element is adopted for identifying a fault line, a phase-to-phase distance relay is used for judging the direction of the phase-to-phase impedance direction element, and if the polarization voltage and the working voltage of the phase-to-phase distance relay meet the following action criterion equation, the phase-to-phase impedance direction element is proved to be in a positive direction; the criterion equation is as follows:
wherein,in order to be the polarization voltage, <math>
<mrow>
<msub>
<mover>
<mi>U</mi>
<mo>·</mo>
</mover>
<mi>ΦΦ</mi>
</msub>
<mo>-</mo>
<msub>
<mi>Z</mi>
<mi>set</mi>
</msub>
<msub>
<mover>
<mi>I</mi>
<mo>·</mo>
</mover>
<mi>ΦΦ</mi>
</msub>
</mrow>
</math> in order to be at the operating voltage,in order to obtain the voltage between the phases of the fault,for fault phase current, ZsetFixed line positive sequence impedance fixed value ZL11.2-1.5 times of the total weight of the composition;
and if the interphase impedance direction elements on the two sides of a certain line meet the corresponding action criterion, the line is a suspected fault line.
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Address after: 250001, No. two, No. 150, Ji'nan, Shandong Co-patentee after: Shandong Mountain Power Technology Limited by Share Ltd Patentee after: State Grid Shandong Electric Power Company Co-patentee after: State Grid Corporation of China Address before: 250001, No. two, No. 150, Ji'nan, Shandong Co-patentee before: Shandong Shandong University Electric Power Technology Co., Ltd. Patentee before: State Grid Shandong Electric Power Company Co-patentee before: State Grid Corporation of China |