CN116073341B - Method for judging positive pole ground short circuit fault interval of subway special rail reflux power supply system - Google Patents
Method for judging positive pole ground short circuit fault interval of subway special rail reflux power supply system Download PDFInfo
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- G—PHYSICS
- 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
- G01R31/50—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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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
- H02H3/087—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current for dc applications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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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
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- Y04S10/52—Outage or fault management, e.g. fault detection or location
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Abstract
The invention discloses a method for judging a positive pole ground short circuit fault interval of a subway special rail reflux power supply system, which comprises the following steps: the direct current grounding protection device collects the grounding voltage of the power substation and judges whether the grounding voltage U e of the power substation is larger than a fault judgment voltage fixed value U set or not; if the condition is met, indicating that the fault exists, and turning to the step S2; otherwise, indicating that the fault is not generated, and returning to the step S1; acquiring adjacent data and local station data, analyzing and comparing the data, and judging a fault occurrence interval; after determining a fault interval, removing faults by the action of the grounding protection devices at two sides of the fault interval; the ground protection device is individually judged for the failure of the end. The method solves the problem that the fault range is enlarged due to the fact that the short-circuit fault point interval cannot be positioned by the traditional method for judging the fault by means of the fixed value, and has the advantages of being accurate in fault range positioning and the like.
Description
Technical Field
The invention relates to the technical field of rail transit, in particular to a method for judging a positive pole ground short circuit fault interval of a special rail reflux power supply system for subways.
Background
In China, with the continuous promotion of urban process and the rapid increase of urban residents, the problem of urban road traffic congestion becomes a main obstacle for restricting the economic and social development of large and medium-sized cities. In order to turn the passive situation early, urban rail transit lines are added in first-line cities, provincial cities and coastal central cities. At present, most of domestic urban rail transit adopts a low-voltage direct current power supply mode based on running rail backflow, but the biggest disadvantage of the power supply mode is that stray current leaked from a steel rail to the ground can cause electrochemical corrosion to subway tunnels, nearby building steel bars and metal pipelines. To solve this problem, domestic scholars propose a special rail return power supply technology, i.e. the power supply return flows to the traction substation through a special rail (fourth rail) without passing through the running rail.
Although the dedicated rail return supply solves this large problem of stray currents, it has its own drawbacks. That is, when the positive electrode (line) is short-circuited to ground (the positive and negative electrodes have the same insulation level to ground), the conventional dc protection cannot cut off the fault because the short-circuit current is small. The traditional method for compensating direct current protection is to connect the negative electrode with a 5 omega resistor in series and then to connect the negative electrode with a diode to ground, as shown in fig. 1. The principle is that the earth of the positive electrode can generate leakage voltage at a 5 omega resistor, and the 64D device judges whether the positive electrode has short circuit fault or not by setting the voltage value. However, the setting value of the ground voltage is difficult to determine due to the arc resistance with an indefinite resistance value at the short-circuit point, if the minimum ground voltage is taken as the setting value, the simultaneous actions of the fault point and the protection of the nearby substation are inevitably caused, namely, a plurality of non-fault power supply sections are caused to lose power at the same time, so that the compensation method has poor selectivity.
Disclosure of Invention
The invention aims to provide a method for judging the positive pole short-circuit fault interval of a subway special rail reflux power supply system, which can solve the technical problem that the existing traction substation cannot know the short-circuit interval when the positive pole short-circuit is lost in the short-circuit to the ground.
In order to solve the technical problems, the invention adopts the following technical scheme: a method for judging a positive pole ground short circuit fault interval of a subway special rail reflux power supply system is characterized by comprising the following steps:
s1: the direct current grounding protection device collects the grounding voltage of the power substation and judges whether the grounding voltage U e of the power substation is larger than a fault judgment voltage fixed value U set or not; if the condition is met, indicating that the fault exists, and turning to the step S2; otherwise, indicating that the fault is not generated, and returning to the step S1;
s2: acquiring adjacent data and local station data, analyzing and comparing the data, and judging a fault occurrence interval;
S3: after determining a fault interval, removing faults by the action of the grounding protection devices at two sides of the fault interval;
s4: the ground protection device separately judges faults of the tail end;
S5: after the fault is removed, the tripped fault is subjected to subsequent processing, so that the fault can be truly removed, and the reliable tripping after the secondary short-circuit fault occurs is ensured.
The further technical proposal is that: when the positive electrode is shorted to the ground, the diode is conducted due to the rise of the ground potential, and the short-circuit current flows through the ground resistor to form a detectable voltage to the ground U e. The circuit principle shows that the ground potential at the short-circuit point is highest, and the potential gradually decreases along the two sides of the line. U set is the fault determination ground voltage setpoint, i.e., the minimum detectable ground potential at the time of the fault. If U e>Uset, the substation protection device acquires the 64D grounding voltage U el1、Uer1 of the two adjacent left and right stations through the GOOSE network. If U e>Uel1 and U e>Uer1, i.e. the local voltages to ground are higher than the voltages to ground of two adjacent points, the fault interval is considered to be one of the left and right interval sections.
The further technical proposal is that: for the terminal station, namely, the condition that a certain side of two ends of a line does not have a neighbor, the left and right terminal station marker bits are set, and the fault detection is different. When the marker position at the left end is set, if U e>Uset and U e>Uer1 are detected, namely the local ground voltage is higher than the fault minimum voltage fixed value and higher than the right adjacent voltage, the fault interval is considered to be positioned between the local ground voltage and the right adjacent ground voltage; if the condition is still met within the delay time T set, the fault side breaker is tripped, and a GOOSE command is issued to jointly trip the right adjacent breaker. When the marker position at the tail end of the right side is set, if the detection result shows that if U e>Uset and U e>Uel1 are detected, namely the local ground voltage is higher than the fault minimum voltage fixed value and higher than the left adjacent voltage, the fault interval is considered to be between the local ground voltage and the left adjacent ground voltage; if the condition is still met within the delay time T set, the fault side breaker is tripped, and the GOOSE command is issued to jointly trip the left adjacent breaker.
The further technical proposal is that: for the power substation in the middle of the line, three cases are treated:
case1: there are more than 3 adjacent places on the left and right sides of the place
The protection device reads the ground voltage of the left and right 3 neighbors and the distance between the protection device and the 3 neighbors through the GOOSE network. Taking the position of the point as the origin of coordinates and the distance between adjacent points as the x axis, and considering the right side of the point as the x positive direction; taking the ground voltage as the y axis, quadratic interpolation can be used to fit voltage drop gradient curves on the left side and the right side. Taking the right side as an example, the protection device reads the ground voltages U er1、Uer2、Uer3 of the three places on the right side through the GOOSE network, reads the distances L r1、Lr2、Lr3 between the three places on the right side, and the quadratic interpolation polynomial f r (x) based on Lagrange on the right side can be described as
Similarly, the left Lagrangian-based quadratic interpolation polynomial f l (x) can be written as
Where U el1、Uel2、Uel3 is the ground voltage of the three points on the left side of the point, and L l1、Ll2、Ll3 is the distance between the three points on the left side of the point.
Let f l(x)＝fr (x), the fitting fault point x value can be solved. If the solution x is larger than 0, the fault point is determined to be on the right side of the origin; if the solution x is smaller than 0, the fault point is determined to be on the left side of the place.
Case2: only 2 adjacent places exist on one side of the place
Taking the example that there are only 2 neighbors on the left: the protection device reads the ground voltage of the left 2 neighbors and the distance between the protection device and the left 2 neighbors through the GOOSE network. And reading the ground voltage of the 3 neighbors on the right side and the distances between the ground voltage and the 3 neighbors on the right side through a GOOSE network. Taking the origin of coordinates as an x-axis, and taking the distance between adjacent points as an x-axis, wherein the right side of the point is x-positive; taking the ground voltage as the y-axis, one interpolation can be used to fit the left-side voltage drop gradient line, and a quadratic interpolation can be used to fit the right-side voltage drop gradient line.
The specific principle is as follows: the protection device uses GOOSE to read the right 3 ground voltages U er1、Uer2、Uer3 and the right 2 distance L r1、Lr2、Lr3, then the right Lagrangian-based quadratic interpolation polynomial f r (x) can be described as
Similarly, the protection device reads the left 2 ground voltages U el1、Uel2 through the GOOSE network and reads the right 2 distances L l1、Ll2, and the first-order interpolation polynomial f l (x) based on lagrangian can be written as:
Let f l(x)＝fr (x), the fitting fault point x value can be solved. If the solution x is larger than 0, the fault point is determined to be on the right side of the origin; if the solution x is smaller than 0, the fault point is determined to be on the left side of the place.
Case3: only 1 adjacent place exists on one side of the place
If there are only 1 neighbors on the left side, then the fault is directly determined to occur on the right side of the subject. Similarly, if there are only 1 neighbors on the right side, the fault is directly determined to occur on the left side of the house. Taking the example that only 1 substation exists on the left side, because a plurality of substations on the right side are arranged on the left side, all the 64D devices among the substations can be seen as parallel connection, the total resistance is much smaller than that on the left side, the voltage drop gradient on the left side is much smaller than that on the right side, and the probability of short circuit fault on the right side is much larger than that on the left side under the condition that the voltage of the power substation is highest. Even if an error occurs, the subsequent compensation operation of the method can still ensure that the fault can be reliably removed.
The further technical proposal is that: the conditions of tripping and simultaneous setting of the tail end marker bit by the joint tripping are constructed, so that the problem of fitting distortion caused by uneven line resistance and overlarge spacing is prevented, namely, the special condition that the voltage to the ground still exists due to incapability of cutting off faults is prevented. Because even though the ground voltage still exists due to the judgment error, the protection device can immediately judge that the fault exists between the local place and the adjacent place after detecting that the ground voltage is higher than the adjacent place due to the fact that the tail end mark bit is set, and the fault can be reliably cut off.
The beneficial effects of adopting above-mentioned technical scheme to produce lie in: the method solves the problem that the fault range is enlarged due to the fact that the short-circuit fault point interval cannot be positioned by the traditional method for judging the fault by means of the fixed value, and has the advantages of being accurate in fault range positioning and the like.
Drawings
The invention will be described in further detail with reference to the drawings and the detailed description.
FIG. 1 is a schematic diagram of the ground resistance of a 64D device in a method according to an embodiment of the invention;
FIG. 2 is a schematic diagram of a transformer substation circuit in a method according to an embodiment of the invention;
FIG. 3 is a schematic representation of the value of case 1 in the method according to the embodiment of the present invention;
FIG. 4 is a schematic diagram of the value of case 2 in the method according to the embodiment of the present invention;
FIG. 5 is a schematic representation of the value of case 3 in the method according to the embodiment of the present invention;
FIG. 6 is a schematic diagram of the method according to the embodiment of the present invention in case 3;
FIG. 7 is a schematic block diagram of fault determination in cases 1 and 2 (for example, left side fault in this example) in the method according to the embodiment of the present invention;
FIG. 8 is a schematic block diagram of fault determination in case 3 (taking the example that only 1 transformer remains on the right side) in the method according to the embodiment of the present invention;
FIG. 9 is a schematic diagram of determining end failure in a method according to an embodiment of the present invention (taking the left end as an example);
Fig. 10 is a flowchart of a method according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways other than those described herein, and persons skilled in the art will readily appreciate that the present invention is not limited to the specific embodiments disclosed below.
As shown in fig. 10, the invention provides a method for judging a positive pole to ground short circuit fault interval of a subway special rail reflux power supply system, which comprises the following steps:
The 64D ground protection device mainly comprises a ground resistor and a diode, and as shown in fig. 1, the 64D ground protection device judges whether a fault occurs by detecting the voltage to ground. The 64D ground protection device of each traction substation needs to support a GOOSE communication protocol and access the GOOSE switch of the traction substation, and the GOOSE switches of adjacent stations are cascaded together.
The marker bits at the left end and the right end are respectively set for the left end and the right end, and the length of the line between the left adjacent place and the right adjacent place of the current station is input in the fixed value of each protection device of the power substation.
When the positive pole is short-circuited to the ground, the grounding diode is conducted, the short-circuit current flows through the grounding resistor to form detectable grounding voltage U e, when U e exceeds a fault judging grounding voltage fixed value U set, whether the left/right tail end zone bit of the circuit breaker is set or not is judged first, if so, whether the current grounding voltage U e is higher than the right/left adjacent grounding voltage U er1、Uel1 or not is judged through a GOOSE network, if so, a fault interval is considered to be between the current ground and the right/left adjacent ground, and if the condition is still met within a delay time T set, the circuit breaker on the fault side of the circuit breaker is jumped up in parallel.
If the flag bit is not set, judging whether the local ground voltage U e is higher than the left and right adjacent ground voltages U er1、Uel1 through the GOOSE network, and if the local ground voltages are higher than the ground voltages of the two adjacent grounds, considering that the fault interval is one of the left and right interval sections.
The circuit schematic diagram of the substation is shown in fig. 2, and three cases are treated for the substation in the middle of the line:
case1: there are more than 3 adjacent places on the left and right sides of the place
As shown in fig. 3, the traction station 4 detects that the ground voltage is highest, and 3 or more traction stations are arranged on the left side and the right side, and the protection device reads the ground voltage of the left and the right 3 adjacent stations and the distances between the left and the right 3 adjacent stations through the GOOSE network. Taking the coordinate origin as the coordinate origin, taking the distance between adjacent points as the x axis, and considering the right side of the point as the x positive direction; taking the ground voltage as the y axis, quadratic interpolation can be used to fit the left and right side ground voltage drop gradient curves. Taking the right side as an example, the protection device reads the ground voltages U er1、Uer2、Uer3 of the three places on the right side through the GOOSE network, and reads the distances L r1、Lr2、Lr3 between the three places on the right side, and the quadratic interpolation polynomial f r (x) on the right side based on lagrangian can be described as:
Similarly, the Lagrangian-based quadratic interpolation polynomial f l (x) on the left side can be written as
Where U el1、Uel2、Uel3 is the ground voltage of the three points on the left side of the point, and L l1、Ll2、Ll3 is the distance between the three points on the left side of the point.
Let f 1(x)＝fr (x), can solve out the value of fitting fault point x, because this is the origin, if solve x and be greater than 0, then confirm the fault point on this right side, if still satisfy the condition in time delay T set, jump this fault side circuit breaker and connect in parallel and jump the fault side circuit breaker of the right neighborhood.
If the solution x is smaller than 0, the fault point is determined to be on the left side of the place. If the condition is still met within the delay time T set, the fault side circuit breaker of the trip station is connected in parallel with the fault side circuit breaker of the trip station.
Taking data samples of the ground voltage (including the ground voltage of each station and the distance data between each station) when 4 typical stations fail, fitting a curve by the fitting method, and calculating a fitting judgment result, as shown in the following table 1:
TABLE 1 case 1 Curve fitting results
| Left fitting results | Right fitting results | Fitting fault location | Whether or not to be correct | |
| Sample 1 | 6.2x2+40x+152 | 4.5x2-38.7x+129 | -0.32 | Is that |
| Sample 2 | 7.1x2+57x+206 | 9.5x2-88.5x+287 | -0.55 | Is that |
| Sample 3 | 7.5x2+61.4x+223 | 7.7x2-76.6x+260 | 0.26 | Is that |
| Sample 4 | 8.7x2+75.3x+260 | 7.3x2-68.5x+222 | -0.25 | Is that |
Case2: only 2 adjacent places exist on one side of the place
As shown in fig. 4, the traction station 3 detects the highest ground voltage, but the traction station 3 has only 2 adjacent stations on the left side, the data amount is insufficient, the lagrangian quadratic interpolation fitting cannot be used, and only one interpolation fitting can be used, namely, the protection device uses GOOSE to read the ground voltages U el1、Uel2 of the left 2 stations, reads the distances L l1、Ll2 of the right 2 stations, and the lagrangian-based one-time interpolation polynomial f 1 (x) on the left side can be written as
As shown in fig. 4, more than 3 traction stations exist on the right side, quadratic interpolation fitting can still be adopted, that is, the protection device uses GOOSE to read the voltages to ground U er1、Uer2、Uer3 of the 3 stations on the right side, and reads the distances L r1、Lr2、Lr3 of the 3 stations on the right side, then the quadratic interpolation polynomial f r (x) on the right side based on lagrangian can be described as:
Let f l(x)＝fr (x), can solve out the value of fitting fault point x, because this is the origin, if solve x >0, then confirm the fault point on this right side, if still satisfy the condition in time delay T set, jump this fault side circuit breaker and connect in parallel and jump the fault side circuit breaker of the right neighborhood.
If x <0 is solved, the fault point is considered to be on the left side of the place. If the condition is still met within the delay time T set, the fault side circuit breaker of the trip station is connected in parallel with the fault side circuit breaker of the trip station.
Taking data samples of the ground voltage (including the ground voltage of each station and the distance data between each station) when 4 typical stations fail, fitting a curve by the fitting method, and calculating a fitting judgment result, as shown in the following table 2:
TABLE 2 case 2 Curve fitting results
| Left fitting results | Right fitting results | Fitting fault location | Whether or not to be correct | |
| Sample 1 | 14.1x+148 | 4.6x2-41.5x+129 | -0.33 | Is that |
| Sample 2 | 13.2x+143 | 4.4x2-42.5x+144 | -0.35 | Is that |
| Sample 3 | 11.8x+131 | 5.1x2-43x+162 | 0.59 | Is that |
| Sample 4 | 12.1x+134 | 5.4x2-45.6x+168 | 0.62 | Is that |
Case3: only 1 adjacent place exists on one side of the place
As shown in fig. 5, the traction station 2 detects the highest voltage to ground, but there is only one adjacent station on the left side, in this case, no fitting operation can be performed, and it can be directly determined that the fault occurs on the right side of the station, if the condition is still satisfied within the delay time T set, the fault side circuit breaker is tripped out and the fault side circuit breaker is tripped out in parallel.
The judgment principle is shown in fig. 6, because the right power substations are many, the devices among the power substations 64D can be seen as parallel connection, the total resistance is much smaller than that of the left power substations, the left voltage drop gradient is much smaller than that of the right voltage drop gradient, as shown in fig. 6, if the traction station 2 is positioned at the left side of the L e, the direct judgment that the fault appears at the right side of the power substation is not wrong, if the traction station 2 is positioned at the right side of the L e, the fault appears between the left end station and the traction station 2 because the ground voltage at the left end is higher than that of the traction station 2, the fault cannot be judged directly due to the existence of the mark bit at the end, and the only fault point is that the traction station 2 is positioned in the L e, so that the judgment fault appears. However, since the overall drop gradient of the right-side ground voltage is large, and the drop gradient of the left-side ground voltage is small, the length of L e is short in practice. The probability of error is low and even if error occurs, the subsequent compensation operation of the method can still ensure that the fault can be reliably removed.
The conditions of tripping and simultaneous setting of the tail end marker bit by the joint tripping are constructed, so that the problem of fitting distortion caused by uneven line resistance and overlarge spacing is prevented, namely, the special condition that the voltage to the ground still exists due to incapability of cutting off faults is prevented. For example, if the right neighbor is tripped, the right end of the right neighbor is set to the zone bit, and the right neighbor is set to the left end of the left neighbor to the zone bit. Taking the left end marker bit as an example, once the left end marker bit is set, the fault existing between the ground voltage and the right adjacent place can be judged only by detecting that the ground voltage is higher than the fault judging voltage fixed value U set and higher than the right adjacent place ground voltage U er1, and if the condition is still met within the delay time T set, the fault side circuit breaker of the trip-out switch is connected in parallel to the fault side circuit breaker of the trip-out switch.
Therefore, even if the short-circuit voltage to the ground still exists due to the judgment error, the protection device can immediately judge that the fault exists between the local place and the adjacent place after detecting that the local voltage to the ground is higher than the adjacent place due to the fact that the tail end marker bit is set, and the fault can be reliably cut off.
After the earth leakage relay protection device in the intelligent substation adopts the processing method, the positioning and automatic removal of the positive pole earth short circuit fault interval under the special rail reflux power supply mode can be realized.
Claims (3)
1. A method for judging a positive pole ground short circuit fault interval of a subway special rail reflux power supply system is characterized by comprising the following steps:
s1: the direct current grounding protection device collects the grounding voltage of the power substation and judges whether the grounding voltage U e of the power substation is larger than a fault judgment voltage fixed value U set or not; if the condition is met, indicating that the fault exists, and turning to the step S2; otherwise, indicating that the fault is not generated, and returning to the step S1;
S2: acquiring data of adjacent substations and data of the current substation, analyzing and comparing the data, and judging a fault occurrence interval;
S3: after determining a fault interval, removing faults by the action of the grounding protection devices at two sides of the fault interval;
s4: the ground protection device separately judges faults of the tail end;
s5: after the fault is removed, the tripped substation is subjected to subsequent processing, so that the fault is truly removed, and reliable tripping after the secondary short-circuit fault occurs is ensured;
In the step S2:
if U e>Uset is detected, the transformer substation protection device acquires the voltage to ground U el1、Uer1 of the transformer substation protection devices of the two adjacent transformer stations through a GOOSE network; if U e>Uel1 and U e>Uer1, considering the fault section to be one of the left section and the right section of the power substation;
For the power substation in the middle of the line, three cases are treated:
First case: 3 or more adjacent stations exist at the left side and the right side of the transformer station;
The direct current grounding protection device reads the grounding voltage of the left and right 3 neighbors and the distance between the direct current grounding protection device and the 3 neighbors of the local substation through a GOOSE network; taking the position of the substation as the origin of coordinates and the distance between adjacent substations as the x axis, and considering the right side of the substation as the x positive direction; taking the ground voltage as a y axis, and fitting voltage drop gradient curves at the left side and the right side by using quadratic interpolation; the protection device of the substation reads the ground voltage U er1、Uer2、Uer3 of the three places on the right side through the GOOSE network and reads the distance L r1、Lr2、Lr3 of the three places on the right side from the substation, and the quadratic interpolation polynomial f r (x) on the right side based on Lagrangian can be described as follows:
similarly, the Lagrangian-based quadratic interpolation polynomial f l (x) on the left side can be written as:
wherein U el1、Uel2、Uel3 is the ground voltage of the three places on the left side of the power substation, and L l1、Ll2、Ll3 is the distance between the three places on the left side of the power substation and the power substation;
Let f l(x)＝fr (x), can solve the fitting fault point x value; since the power substation is the origin, if x is greater than 0, the fault point is determined to be on the right side of the power substation; if the solution x is smaller than 0, the fault point is determined to be at the left side of the substation;
second case: only 2 adjacent substations exist on the left side and the right side of the substation;
The protection device reads the ground voltage of the left 2 adjacent places and the distance between the protection device and the left 2 adjacent places of the local substation through a GOOSE network; the ground voltage of the 3 adjacent places on the right side and the distance between the power substation and the 3 adjacent places on the right side are read through a GOOSE network; taking the power substation as a coordinate origin, taking the distance between adjacent power substations as an x axis, and taking the right side of the power substation as an x forward direction; taking the ground voltage as a y axis, fitting a left voltage drop gradient line by using primary interpolation and fitting a right voltage drop gradient line by using secondary interpolation;
The protection device of the substation uses GOOSE to read the voltages to ground U er1、Uer2、Uer3 of the 3 places on the right side and read the distances L r1、Lr2、Lr3 of the 2 places on the right side from the substation, and then the quadratic interpolation polynomial f r (x) on the right side based on lagrangian can be described as:
The protection device of the substation reads the ground voltage U el1、Uel2 of the left 2 places through the GOOSE network and reads the distance L l1、Ll2 of the right 2 places from the substation, and then the primary interpolation polynomial f l (x) based on Lagrange can be written as:
Let f l(x)＝fr (x), can solve the fitting fault point x value; since the power substation is the origin, if x is greater than 0, the fault point is determined to be on the right side of the power substation; if the solution x is smaller than 0, the fault point is determined to be at the left side of the substation;
Third case: only 1 adjacent place exists on the left side and the right side of the transformer station;
If only 1 adjacent place exists on the left side, directly identifying that the fault occurs on the right side of the power substation; if only 1 adjacent place exists on the right side, directly identifying that the fault occurs on the left side of the power substation;
The step S4 specifically includes the following steps:
judging the faults of the tail ends independently by setting left/right tail end marker bits on the tail ends; if the marker position at the left end is set, the short-circuit point between the current transformer substation and the right neighbor can be judged only by judging that the ground voltage U e of the current transformer substation is higher than the ground voltage U er1 of the right neighbor; if the marker position at the right end is set, the short-circuit point between the current transformer substation and the left neighbor substation can be judged only by judging that the ground voltage U e of the current transformer substation is higher than the ground voltage U el1 of the left neighbor substation.
2. The method for judging the positive pole-to-ground short circuit fault interval of the subway special rail reflux power supply system according to claim 1, wherein the method comprises the following steps:
Setting left and right tail end marker bits for the tail end station, and when the left tail end marker bit is set, if U e>Uset and U e>Uer1 are detected, considering that a fault interval is positioned between the local substation and the right adjacent substation; if the condition is still met within the delay time T set, tripping the circuit breaker at the fault side of the substation, and concurrently commanding the joint tripping of the right adjacent circuit breaker by the GOOSE; when the marker position at the tail end of the right side is set, if U e>Uset and U e>Uel1 are detected, the fault interval is considered to be between the local substation and the left neighboring substation; if the condition is still met within the delay time T set, the fault side breaker of the substation is tripped, and the fault side breaker is commanded to trip the left adjacent breaker by the GOOSE.
3. The method for judging the positive pole-to-ground short circuit fault interval of the subway special rail reflux power supply system according to claim 1, wherein the method comprises the following steps: the step S5 specifically includes the following steps:
The conditions of tripping and simultaneous setting of the tail end marker bit by the joint tripping are constructed, so that the problem of fitting distortion caused by uneven line resistance and overlarge spacing is prevented, namely, the special condition that the voltage to the ground still exists due to incapability of cutting off faults is prevented.
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