CN111880048B - Low-current grounding line selection method and equipment applied to resonant grounding system - Google Patents
Low-current grounding line selection method and equipment applied to resonant grounding system Download PDFInfo
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- CN111880048B CN111880048B CN202010850132.9A CN202010850132A CN111880048B CN 111880048 B CN111880048 B CN 111880048B CN 202010850132 A CN202010850132 A CN 202010850132A CN 111880048 B CN111880048 B CN 111880048B
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- G01—MEASURING; TESTING
- 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
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
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- G—PHYSICS
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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
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/088—Aspects of digital computing
Abstract
The invention discloses a small current grounding line selection method and equipment applied to a resonant grounding system, wherein the method comprises the following steps: step 1: the dispatching system acquires the reactive power value and the zero sequence current value steady state quantity of each line before and after grounding in real time, and respectively calculates the variable quantity before and after grounding; and 2, step: according to the step 1, calculating the maximum grounded line of the capacitance current by adopting a line selection criterion based on triangular mode fusion, and performing trial pulling on the line; and 3, step 3: after the circuit with the maximum capacitance current is pulled to be grounded, zero sequence current values and reactive power value variable quantities of other circuits on the bus before and after the switch is separated are calculated again; and 4, step 4: and (3) according to the zero sequence current value and the reactive power value variable quantity of other circuits on the bus before and after the switch is separated, calculating the circuit which has the largest capacitance current change before and after the switch is pulled and is closest to the capacitance current of the tested circuit in the step (2) in the same way, wherein the circuit is a real ground fault circuit.
Description
Technical Field
The invention relates to the technical field of low-current grounding line selection, in particular to a low-current grounding line selection method and equipment applied to a resonant grounding system.
Background
In China, a 6-35 kV medium-voltage distribution network widely adopts a neutral point non-effective grounding mode, namely a small-current grounding system which is not grounded and is grounded (resonant grounding) through an arc suppression coil. When the system has single-phase earth fault, the earth current is very small because a short circuit loop with low impedance can not be formed, and the system and the equipment can not be influenced. Along with the rapid development of urban power grids, the proportion of cable lines is higher and higher, the current of a fault point is increased and the arc is not easy to extinguish when the cable lines are grounded, and the situation that the single-phase grounding fault of the same-channel cable is not processed in time can be possibly developed into a large-area power failure accident, the power supply service quality is seriously influenced, and the damage is extremely large, so that most of the existing large-city power distribution networks adopt a resonance grounding mode of grounding through arc suppression coils. Although resonance grounding can effectively reduce current flowing through a fault point, so that electric arcs are easier to extinguish, an arc suppression coil covers a real grounding phenomenon, the fault amount is not prominent and is not easy to identify, a large amount of researches prove that a resonance grounding system can not select lines through steady-state amount, and compared with a traditional neutral point direct grounding system, the line selection difficulty is higher, the line selection time is longer, the existing risk is higher, and a large amount of power supply service problems are easily caused.
At present, the theoretical research on low-current grounding line selection at home and abroad mainly focuses on line selection at a station end. Although most of small-current grounding line selection devices based on transient zero sequence quantity, wavelet analysis and injection method judgment methods are rapid and accurate in judgment, the small-current grounding line selection devices are subjected to more electromagnetic interference on site, high in installation cost and inaccurate in line selection of grounding lines containing arc suppression coils, the practical application effect of the small-current grounding line selection devices in a transformer substation is not ideal, the number of single-phase grounding faults is few in practical use, and line selection is achieved by means of manual route pulling of a dispatcher.
Disclosure of Invention
Aiming at the defects of a small-current grounding line selection method in the background technology, the invention provides a small-current grounding line selection method and equipment applied to a resonant grounding system for solving the problems, and realizes the small-current grounding line selection method based on a dispatching master station end, the line selection speed is high, the average fault processing time is shortened to 10min from past 40min, the line selection success rate is increased to more than 85% from 50%, the small-current grounding fault processing time of the resonant grounding system is greatly shortened, the single-phase fault line selection success rate and efficiency of a neutral point grounded through an arc suppression coil are greatly improved, the equipment damage and the potential safety hazard caused by long-time single-phase grounding are reduced, the group injury and the personal electric shock safety risk of same-channel cable equipment caused by single-phase grounding faults of a large-city power distribution network are effectively solved, the forest fire risk caused by the grounding faults is reduced to a certain extent, and the safe and stable operation of the power network is better ensured.
At present, the power grid dispatching department in China basically adopts a smart power grid dispatching system (D5000) to regulate and control operation, the small-current grounding line selection function developed on a dispatching master station end system has greater practical applicability, a dispatcher can be assisted to judge a single-phase grounding line in the shortest time, the safe and stable operation of the power grid is better ensured, and the research on the small-current grounding line selection function based on a dispatching master station end is urgent.
The invention is realized by the following technical scheme:
in a first aspect, the present invention provides a small current grounding line selection method applied to a resonant grounding system, the method comprising the following steps:
step 1: the dispatching system obtains the reactive power value and the zero sequence current value steady state quantity of each line before and after grounding in real time, and respectively calculates the variable quantity delta Q before and after grounding i And Δ I i0 ；
Step 2: calculating the variable quantity of the reactive power value and the zero sequence current value before and after grounding according to the step 1, calculating the maximum capacitance current circuit after grounding by adopting a line selection criterion based on triangular mode fusion, and performing trial pulling on the circuit;
description of the drawings: the variable quantity of the reactive power value and the zero sequence current value before and after grounding is generated by the capacitance current of each line after grounding, and the arc suppression coil generates inductance current to compensate the capacitance current, so that the real grounding phenomenon is covered, the fault quantity is not outstanding and is difficult to identify, and the state of arc suppression coil compensation can be broken by selecting the line of the line with the maximum capacitance current after grounding for trial pulling, so that the next fault line selection can be carried out;
and step 3: after the circuit with the maximum capacitance current is pulled to be grounded, zero sequence current values and reactive power value variable quantities of other circuits on the bus before and after the switch is separated are calculated again;
and 4, step 4: and (4) calculating the maximum change of the capacitance current before and after the switch is pulled by a test and the circuit closest to the capacitance current of the tested circuit in the step (2) by using a line selection method based on triangular mode fusion according to the zero sequence current value and the reactive power value change of other circuits on the bus before and after the switch is separated from the switch calculated in the step (3), wherein the circuit is a real ground fault circuit.
Description of the invention: because the arc coil gear is not changed in the grounding process, the compensated inductive current is not changed, so that the total capacitance current on the whole section of bus after a certain line is pulled open in a test is reduced, the capacitance current of the grounding line is increased, and the current increase is just the ground capacitance current of the pull-out test line.
The working principle is as follows:
taking zero sequence current as an example, a schematic diagram of a single-phase fault of a neutral point ungrounded system is shown in fig. 2, three phases are symmetrical under normal conditions, and the sum of capacitance current to ground is zero. When a ground fault occurs in phase a of line 1:
for the non-grounded line, the three relative ground capacitance currents are respectively:
the zero sequence current felt by the non-grounded circuit is as follows:
wherein
The zero sequence current of the ungrounded circuit is the earth capacitance current of the circuit per se.
For the grounded line, the ungrounded phase has its own capacitive current flowing through it, and the current flowing through the fault point of the grounded phase is the sum of all ungrounded phase to ground capacitive currents in the power grid, that is:
in the formula:
is the sum of the single-phase capacitance to ground of the system.
The zero sequence current felt by the grounding circuit is as follows:
when the neutral point is grounded through the arc suppression coil, the neutral point generates an inductive current under the action of the neutral point voltage
It will return along the ground phase through the ground point, so the zero sequence current that the ground line felt at this time is:
the analysis shows that for a neutral point ungrounded system, the zero sequence current value of a grounded line is far larger than that of other lines, and a scheduling main station end can select lines according to the magnitude of the zero sequence current; however, for the resonant grounding system, due to the effect of the inductance current of the arc suppression coil, the zero sequence current of the grounding circuit becomes smaller after compensation, even smaller than the zero sequence current of most ungrounded circuits, which causes considerable trouble to the line selection of a dispatcher.
For a resonant grounding system, when grounding occurs, the compensation current of the arc suppression coil after grounding is kept unchanged until grounding is restored. The existence of the inductive compensation current can cover the real grounding information, so that the zero sequence current value of the fault line is reduced greatly. Therefore, it is proposed to use the pilot pulling method
When arbitrarily trying to pull out a line I, if the line is a non-grounded line (the zero sequence current amplitude of the line is 3I) 0i ＝3ωC 0i U 0 ) The grounding point will not flow through the grounding capacitance current of the pulled line any more, and the zero sequence current of the grounding line inductance will change to:
its effective value will become:
therefore, line selection can be performed according to the variation of the zero sequence current of all the lines before and after the trial pull, and the line with the zero sequence current value which is changed from small to large and is the maximum zero sequence current value of the line to be subjected to trial pull adjustment is the real fault grounding line. The criterion for judging the fault line through the zero sequence current is as follows:
ΔI f0 ＝min{|Δ3I 01 ″-max(3I 0i )|} (8)
the analysis and method for determination by reactive power is similar to that based on power = voltage × current, and the voltage is generally stable and constant, and the change of the zero sequence current is proportional to the reactive power in the forward direction, and the change of the reactive power is actually caused by the zero sequence current, so the analysis and method for determination by reactive power is similar to that of the zero sequence current.
Further, the variation of the reactive power value and the zero sequence current value before and after grounding is calculated in step 1, wherein the variation calculation method adopts a mode of selecting multiple values and averaging to calculate the variation.
Specifically, the multiple values are selected and averaged to calculate, and the time when the small-current ground fault occurs is recorded as t f In order to ensure that zero sequence current and reactive power values before and after grounding can be accurately obtained, multiple values are selected and averaged to calculate, and values at 2 moments before grounding are selected and averaged to serve as a calculated value I before grounding i0b And Q ib After grounding, the values of 4 moments are selected and averaged to be used as a calculated value I after grounding i0a And Q ia The amount of change is Δ I i0 ＝I i0b -I i0a 、ΔQ i ＝Q ia -Q ib ，ΔQ i For the change of the value of the reactive power before and after earthing, Δ I i0 The variable quantity of the zero sequence current value before and after grounding is obtained.
Further, step 2: calculating the variable quantity of the reactive power value and the zero sequence current value before and after grounding according to the step 1, calculating the maximum circuit of the capacitance current after grounding by adopting a line selection criterion based on triangular mode fusion, and performing trial pulling on the circuit;
the variable quantity of the reactive power value and the zero sequence current value before and after grounding is generated by the capacitance current of each line after grounding, and the arc suppression coil generates inductance current to compensate the capacitance current, so that the real grounding phenomenon is covered, the fault quantity is not outstanding and is difficult to identify, and the state of arc suppression coil compensation can be broken by selecting the line of the line with the maximum capacitance current after grounding for trial pulling, so that the next fault line selection can be carried out;
in order to select the maximum grounded line of the capacitive current and comprehensively evaluate the influence of the variable quantity of the reactive power value and the zero sequence current value of each line, a line selection criterion based on triangular mode fusion is provided, and the method comprises the following steps:
s21: calculating the variable quantity delta Q of the reactive power value and the zero sequence current value before and after grounding for the step 1 i And Δ I i0 Normalization processing is carried out, zero sequence current variable index and reactive power variable index are calculated, the fusibility of the two indexes is ensured, and the defects of high efficiency, low power consumption and the like of the power converter are overcomeThe amplitude of the reactive change is limited;
in the formula, λ i Is an index of zero sequence current variation, mu i Is an index of the reactive power variation, | Δ I i0 L is the zero sequence current variation of the ith line, | Δ Q i I is the reactive power variation of the ith line, sigma delta I 0 I is the sum of the zero sequence current variable quantities of all outgoing lines, and Sigma delta Q is the sum of the reactive power variable quantities of all outgoing lines;
s22: fusing the two sub-indexes calculated in the step S21 based on a triangular mode fusion operator, and realizing comprehensive evaluation calculation of the maximum probability of the capacitance current of each line by utilizing the homodromous additivity and the inverse harmony of the triangular mode operator; the specific calculation is as follows:
wherein F (lambda) i ,μ i ) A fusion criterion for the ith line;
the maximum probability of the capacitance current of each line is:
in the formula, P i And (6) as the maximum probability of the capacitance current of the ith line, and sigma F (lambda, mu) is the fusion criterion sum of all the lines.
Further, the line selection method using trigonometric fusion in step 4 is the same as that in step 2.
In a second aspect, the present invention also provides an apparatus, comprising:
one or more processors;
a memory for storing one or more programs,
the one or more programs, when executed by the one or more processors, cause the one or more processors to perform the method for low current ground selection for a resonant grounding system.
Compared with the prior art, the cost for deploying the line selection device at the end part of the station is high, 1 set of line selection device is required to be deployed independently for 1 station, and the power failure operation is required to be carried out on the site, so that the normal operation of a power grid and the normal power utilization of users are influenced. The method can be applied to all plant stations only by deploying 1 set of programs on the dispatching master station end, and the normal operation of a power grid and the normal power utilization of users cannot be influenced.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. the method has intuitive line selection result and high line selection speed, shortens the average fault processing time from 40min to 10min after implementation, increases the line selection success rate from 50% to more than 85%, greatly shortens the small-current ground fault processing time of the resonance grounding system, greatly improves the line selection success rate and efficiency of the single-phase fault of which the neutral point is grounded through the arc suppression coil, reduces equipment damage and potential safety hazard caused by long-time single-phase grounding, effectively solves the group injury of cable equipment in the same ditch and the personal electric shock safety risk caused by the single-phase grounding fault of the cable of the power distribution network in a large city, and reduces the safety and stable operation of the power grid better in the forest grassland fire risk caused by the grounding fault to a certain extent.
2. The method has wide application range, is suitable for the small current grounding fault of the resonance grounding system in the 10-35kV power distribution network system in China, is suitable for various levels of dispatching control systems in provinces, regions, cities and counties in China, and has strong practicability and strong popularization.
3. The invention breaks through the wide understanding that the small current grounding fault of the resonance grounding system can only select the line by using the transient quantity but not select the line by using the steady-state quantity, and breaks through the current situation that the line selection is carried out at the power grid dispatching master station end instead of the line selection at the current large number of power grid plant stations.
4. The invention has obvious economic benefit, the whole line selection invention only has low cost of algorithm and software, is not influenced by field factors and electromagnetic interference, can be suitable for all stations by only deploying 1 set at the dispatching main station end, and can not influence the normal operation of a power grid and the normal power consumption of users. The cost for deploying the line selection device at the end part of the plant station is high, 1 set of line selection device needs to be deployed independently for each 1 plant station, and the power failure operation needs to be carried out on the site, so that the normal operation of a power grid and the normal power utilization of users are influenced.
5. The invention adopts the analysis and the method for breaking the compensation state of the arc cancellation coil by trial pulling the maximum capacitance current line after grounding, belongs to originality, and has high success rate, high speed and good efficiency aiming at small current grounding line selection.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:
fig. 1 is a flow chart of a low current grounding line selection method applied to a resonant grounding system according to the present invention.
Fig. 2 is a schematic diagram of a single-phase earth fault of a system with a neutral point not grounded.
FIG. 3 is a schematic diagram of a first route selection strategy for a Hopu station to ground according to an embodiment of the present invention.
FIG. 4 is a schematic diagram of a second routing strategy for ground connection of a Mipu station according to an embodiment of the present invention.
FIG. 5 is a diagram of the ground alarm query result of Xipu station according to one embodiment of the present invention.
Fig. 6 is a schematic diagram of a first grounding route selection of a star station according to an embodiment of the present invention.
Fig. 7 is a schematic diagram of a second grounding route selection strategy of a star station according to an embodiment of the present invention.
Fig. 8 is a diagram of the result of the earth alarm inquiry of the star station according to the embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that: it is not necessary to employ these specific details to practice the present invention. In other instances, well-known structures, circuits, materials, or methods have not been described in detail so as not to obscure the present invention.
Throughout the specification, reference to "one embodiment," "an embodiment," "one example" or "an example" means: the particular features, structures, or characteristics described in connection with the embodiment or example are included in at least one embodiment of the invention. Thus, the appearances of the phrase "one embodiment," "an embodiment," "one example" or "an example" in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combination and/or sub-combination in one or more embodiments or examples. Further, those of ordinary skill in the art will appreciate that the illustrations provided herein are for illustrative purposes and are not necessarily drawn to scale. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
In the description of the present invention, it is to be understood that the terms "front", "rear", "left", "right", "upper", "lower", "vertical", "horizontal", "high", "low", "inner", "outer", etc. indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and therefore, should not be taken as limiting the scope of the invention.
Examples
As shown in fig. 1 to 8, the present invention relates to a low current grounding line selection method applied to a resonant grounding system, which comprises the following steps:
step 1: the dispatching system acquires the reactive power value and the zero sequence current value steady state quantity of each line before and after grounding in real time, and respectively calculates the reactive power value and the zero sequence current value steady state quantity before and after groundingAmount of change Δ Q of i And Δ I i0 ；
Step 2: calculating the variable quantity of the reactive power value and the zero sequence current value before and after grounding according to the step 1, calculating the maximum capacitance current circuit after grounding by adopting a line selection criterion based on triangular mode fusion, and performing trial pulling on the circuit;
description of the invention: the variable quantity of the reactive power value and the zero sequence current value before and after grounding is generated by the capacitance current of each line after grounding, and the arc suppression coil generates inductance current to compensate the capacitance current, so that the real grounding phenomenon is covered, the fault quantity is not outstanding and is difficult to identify, and the state of arc suppression coil compensation can be broken by selecting the line of the line with the maximum capacitance current after grounding for trial pulling, so that the next fault line selection can be carried out;
and step 3: after the circuit with the maximum capacitance current is pulled to be grounded, zero sequence current values and reactive power value variable quantities of other circuits on the bus before and after the switch is separated are calculated again;
and 4, step 4: and (3) calculating the line which has the maximum change of the capacitance current before and after the switch is pulled and is closest to the capacitance current of the tested line in the step (2) by using a line selection method based on triangular mode fusion according to the zero sequence current value and the reactive power value variable quantity of other lines on the bus before and after the switch is separated, wherein the line is the real ground fault line.
Description of the invention: because the arc coil gear is not changed in the grounding process, the compensated inductive current is not changed, so that the total capacitive current on the whole bus after a certain line is pulled open in a test is reduced, the capacitive current of the grounding line is increased, and the current increase is just the ground capacitive current of the pull-test line.
Fig. 1 is a flow chart of a low-current grounding line selection method applied to a resonant grounding system according to the present invention, and the method is implemented as follows according to the above specific flow:
example one, 1, 5 months and 30 days worth of effort the rhinopu purco road was grounded. The method comprises the following specific steps:
after a new main station end grounding line selection program of the Chengdu company is started (the line selection program uses the small-current grounding line selection method applied to the resonant grounding system provided by the invention), the station is judged to be arc suppression coil overcompensation grounding, a first strategy is given after grounding, and as shown in fig. 3, a dispatcher tries to pull open and sequence a first line (namely data with the ID of the 13 th line in fig. 3), namely a line pump open circuit with the maximum reactive change (the station does not sample zero sequence current) according to the strategy, wherein the first line is a line pump open circuit with the maximum reactive change, and the line selection program is divided into three lines, namely, the line pump open circuit and the zero sequence current. After the trial pull, the method of the present invention then gives a second route selection strategy, as shown in fig. 4. The dispatcher pulls and sequences the first line (namely the data with the ID of the 14 th line in the figure 4), namely the line Pukou with the maximum reactive power change according to the strategy, and the line is the real ground fault line and the ground return; wherein the 9 th data in fig. 4 is obtained from the first line selection strategy.
The whole grounding process and the dispatcher operation process are shown as alarm query in fig. 5.
Example two, 2, 6 months, 2 days, five earthed paths for stars and hours. The method comprises the following specific steps:
after a bus of 10kVII and III of a star-based station is grounded and a novel main station end grounding line selection program of the Chengdu company is started (the line selection program uses a low-current grounding line selection method applied to a resonant grounding system provided by the invention), the station is judged to be over-compensated grounding of an arc suppression coil, and a first strategy is given after grounding, as shown in fig. 6, a dispatcher tries to pull open the 1 st line (namely the line is ranked as 1 by a comprehensive line selection method, namely the data ID of the 12 th line in fig. 6) of the ranking according to the strategy, namely the line with the largest change of zero-sequence current. After the trial pull, the method of the present invention then gives a second route selection strategy, as shown in fig. 7. The dispatcher pulls up the 1 st line (i.e. the line is ranked as 1 by the comprehensive line selection method, i.e. the data with the ID of the 11 th line in FIG. 7) according to the strategy, i.e. five lines of the line with the largest change of zero sequence current, and the line is the true earth fault line and the earth returns.
The whole grounding process and the dispatcher operation process are shown as alarm query in fig. 8.
According to the implementation result, the method has the advantages that (1) the line selection result is visual, the line selection speed is high, after the method is implemented, the average fault processing time is shortened to 10min from 40min in the past, the line selection success rate is increased to more than 85% from 50%, the small-current ground fault processing time of the resonant grounding system is greatly shortened, the line selection success rate and efficiency of the single-phase fault with the neutral point grounded through the arc suppression coil are greatly improved, the equipment damage and the potential safety hazard caused by long-time single-phase grounding are reduced, the group injury of the cable equipment in the same channel and the personal electric shock safety risk caused by the single-phase grounding fault of the cable of the power distribution network in a large city are effectively solved, the forest and grassland fire risk caused by the grounding fault is reduced to a certain extent, and the safe and stable operation of the power grid is better ensured.
(2) The method has wide application range, is suitable for the small current grounding fault of the resonance grounding system in the 10-35kV power distribution network system in China, is suitable for all levels of dispatching control systems in provinces, regions, cities and counties in China, and has strong practicability and strong popularization.
(3) The invention breaks through the wide understanding that the small current grounding fault of the resonance grounding system can only select the line by using the transient quantity but not select the line by using the steady-state quantity, and breaks through the current situation that the line selection is carried out at the power grid dispatching master station end instead of the line selection at the current large number of power grid plant stations.
(4) The invention has obvious economic benefit, only has low cost of algorithm and software in the whole line selection method, is not influenced by field factors and electromagnetic interference, can be suitable for all stations by only deploying 1 set at the dispatching main station end, and can not influence the normal operation of a power grid and the normal power utilization of users. The cost for deploying the line selection device at the end of the plant station is high, 1 set of line selection device needs to be deployed independently for each 1 plant station, and power failure operation needs to be carried out on the site, so that normal operation of a power grid and normal power utilization of users are influenced.
(5) The invention adopts the analysis and the method for breaking the compensation state of the cancellation arc coil by trial pulling the maximum capacitance current circuit after grounding, belongs to originality, and has good effect on small current grounding and line selection.
In a third embodiment, the present invention further provides an apparatus, including:
one or more processors;
a memory for storing one or more programs,
when the one or more programs are executed by the one or more processors, the one or more processors are caused to perform the low current ground routing method applied to the resonant grounding system.
Compared with the prior art, the cost for deploying the line selection device at the end part of the station is high, 1 set of line selection device is required to be deployed independently for 1 station, and the power failure operation is required to be carried out on the site, so that the normal operation of a power grid and the normal power utilization of users are influenced. The invention can be applied to all stations by only deploying 1 sleeve of the equipment at the dispatching master station end, and the normal operation of a power grid and the normal power utilization of users can not be influenced.
In a fourth embodiment, the present invention further provides a computer readable storage medium storing a computer program, where the computer program is executed by a processor to implement the method for selecting a low current ground line applied to a resonant grounding system.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (4)
1. A low current grounding line selection method applied to a resonant grounding system is characterized by comprising the following steps:
step 1: the dispatching system acquires the reactive power value and the zero sequence current value steady state quantity of each line before and after grounding in real time, and respectively calculates the variable quantity delta Q before and after grounding i And Δ I i0 ；
And 2, step: calculating the variable quantity of the reactive power value and the zero sequence current value before and after grounding according to the step 1, calculating the maximum circuit of the capacitance current after grounding by adopting a line selection criterion based on triangular mode fusion, and performing trial pulling on the circuit;
and 3, step 3: after the grounding is tried, the circuit with the maximum capacitance current is pulled, and zero sequence current values and reactive power value variable quantities of other circuits on the buses before and after the switch is separated are calculated again;
and 4, step 4: according to the zero sequence current value and the reactive power value variable quantity of other circuits on the bus before and after the switch is separated, which are calculated in the step 3, the circuit which has the largest capacitance current change before and after the switch is tried to be pulled and is closest to the capacitance current of the circuit to be pulled in the step 2 is calculated by using a line selection criterion based on the triangular mold fusion, and the circuit is a real ground fault circuit;
in the step 2, the maximum capacitance current line after grounding is calculated by adopting a line selection criterion based on triangular mode fusion, and the specific steps are as follows:
s21: calculating the variable quantity delta Q of the reactive power value and the zero sequence current value before and after grounding for the step 1 i And Δ I i0 Carrying out normalization processing to calculate a zero sequence current variable index and a reactive power variable index;
in the formula of lambda i Is an index of zero sequence current variation, mu i Is the index of the reactive power variation, | Delta I i0 L is the zero sequence current variation of the ith line, | Δ Q i I is the reactive power variation of the ith line, sigma delta I 0 I is the sum of the zero sequence current variable quantities of all outgoing lines, and Sigma delta Q is the sum of the reactive power variable quantities of all outgoing lines;
s22: fusing the two sub-indexes calculated in the step S21 based on a triangular mode fusion operator, and realizing comprehensive evaluation calculation of the maximum probability of the capacitance current of each line by utilizing the homodromous additivity and the reverse harmony of the triangular mode operator; the specific calculation is as follows:
wherein F (lambda) i ,μ i ) The fusion criterion is the ith line;
the maximum probability of the capacitance current of each line is:
in the formula, P i And (6) as the maximum probability of the capacitance current of the ith line, and sigma F (lambda, mu) is the fusion criterion sum of all the lines.
2. The method of claim 1, wherein the variation of the reactive power value and the zero sequence current value before and after grounding is calculated in step 1, wherein the variation is calculated by selecting multiple values and averaging.
3. The method as claimed in claim 2, wherein the multiple values are calculated by averaging, and the time when the low-current ground fault occurs is recorded as t f Before grounding, the values of 2 moments are selected and averaged to be used as a calculated value I before grounding i0b And Q ib After grounding, the values of 4 moments are selected and averaged to be used as a calculated value I after grounding i0a And Q ia The amount of change is DeltaI i0 ＝I i0b -I i0a 、ΔQ i ＝Q ia -Q ib ，ΔQ i For the change of the value of the reactive power before and after earthing, Δ I i0 The variable quantity of the zero sequence current value before and after grounding is obtained.
4. A low current ground selection device for use in a resonant grounding system, said device comprising:
one or more processors;
a memory for storing one or more programs,
the one or more programs, when executed by the one or more processors, cause the one or more processors to perform a low current ground routing method as recited in any of claims 1-3 applied to a resonant grounding system.
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