CN114498575B - Flexible traction power supply system and fault direction judgment method thereof - Google Patents
Flexible traction power supply system and fault direction judgment method thereof Download PDFInfo
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- CN114498575B CN114498575B CN202111573353.7A CN202111573353A CN114498575B CN 114498575 B CN114498575 B CN 114498575B CN 202111573353 A CN202111573353 A CN 202111573353A CN 114498575 B CN114498575 B CN 114498575B
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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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60M—POWER SUPPLY LINES, AND DEVICES ALONG RAILS, FOR ELECTRICALLY- PROPELLED VEHICLES
- B60M3/00—Feeding power to supply lines in contact with collector on vehicles; Arrangements for consuming regenerative power
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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
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
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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
- H02H7/261—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 involving signal transmission between at least two stations
- H02H7/262—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 involving signal transmission between at least two stations involving transmissions of switching or blocking orders
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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Abstract
The invention discloses a flexible traction power supply system and a fault direction judgment method thereof, wherein the system comprises a first flexible traction substation and a second flexible traction substation; the first flexible traction substation comprises a first existing system traction transformer, a first flexible traction transformer, a first bus, circuit breakers QF1-QF2, a circuit breaker QF5, a circuit breaker QF7 and a circuit breaker QF9; the second flexible traction substation comprises a second existing system traction transformer, a second flexible traction transformer, a second bus, circuit breakers QF3-QF4, a circuit breaker QF6, a circuit breaker QF8 and a circuit breaker QF10. According to the flexible traction power supply system and the fault direction judging method thereof, the fault occurrence direction at the feeder line can be accurately judged, and no fault direction judging dead zone exists, so that the reliability of protection can be improved, the protection configuration is simplified, and the system can solve the quality problems of electric energy such as idle work, negative sequence, harmonic wave and the like existing in the existing traction power supply system.
Description
Technical Field
The invention belongs to the technical field of relay protection of traction power supply systems, and particularly relates to a flexible traction power supply system and a fault direction judgment method thereof.
Background
At present, existing traction power supply systems of electrified railways in various countries of the world basically adopt a three-phase-two-phase (out-of-phase) power supply mode. The transformer station obtains electricity from a three-phase power grid through a traction transformer, reduces the voltage, and outputs the electricity by two power supply arms to supply power for the traction grid. Because the voltage phase, the amplitude and the frequency of the power supply arms are difficult to be completely consistent, an electric phase splitter is required to be arranged among the power supply arms, and the existing traction power supply system has the problems of low electric energy quality and poor power supply capacity.
The flexible traction power supply system realizes through power supply between flexible traction substations by two flexible traction transformers. In the through power supply section, a power supply mode of double-end power supply is adopted, and in the power supply mode, the fault direction when the traction network fails needs to be detected so as to realize quick and reliable fault removal and isolation. However, the power direction elements which are widely used at present are due to the measurement voltage U in the event of a metallic short circuit at the protective mounting m The fault component direction element detected based on the fault component is too large in amplitude and phase change range of system impedance because the flexible traction power supply system adopts a power electronic converter, so that fault direction judgment errors can be caused, and the reliability of protection is reduced. In order to improve the safety and reliability of the flexible traction power supply system, it is very necessary to research a fault direction judgment method suitable for the flexible traction power supply system.
Disclosure of Invention
In order to solve the problems, the invention provides a flexible traction power supply system and a fault direction judgment method thereof.
The technical scheme of the invention is as follows: a flexible traction power supply system comprises a first flexible traction substation and a second flexible traction substation; the first flexible traction substation comprises a first existing system traction transformer, a first flexible traction transformer, a first bus, circuit breakers QF1-QF2, a circuit breaker QF5, a circuit breaker QF7 and a circuit breaker QF9; the second flexible traction substation comprises a second existing system traction transformer, a second flexible traction transformer, a second bus, circuit breakers QF3-QF4, a circuit breaker QF6, a circuit breaker QF8 and a circuit breaker QF10;
the first existing system traction transformer is connected with the first bus through circuit breakers QF1-QF 2; the second existing system traction transformer is connected with a second bus through circuit breakers QF3-QF4, and the first bus and the second bus are connected to a traction network through a circuit breaker QF7 and a circuit breaker QF8 respectively;
the first flexible traction transformer is connected with the first bus through a breaker QF 5; the second flexible traction transformer is connected with a second bus through a breaker QF 6; the first busbar and the second busbar are connected to the traction network by a breaker QF9 and a breaker QF10, respectively.
The first existing system traction transformer and the second existing system traction transformer are traction transformers used by the existing railway, and the first flexible traction transformer and the second flexible traction transformer adopt power electronic converters to realize three-phase-single-phase conversion to supply power for a traction network.
The invention has the beneficial effects that: according to the flexible traction power supply system, the fault occurrence direction at the feeder line can be accurately judged, and no fault direction judgment dead zone exists, so that the reliability of protection can be improved, the protection configuration is simplified, and the problems of electric energy quality such as idle work, negative sequence, harmonic wave and the like in the existing traction power supply system can be solved.
Based on the system, the invention also provides a fault direction judgment method of the flexible traction power supply system, which comprises the following steps:
s1: in a flexible traction power supply system, determining a dead zone fault section and a non-dead zone fault section when a fault occurs;
s2: and determining the fault direction of the flexible traction power supply system in the dead zone fault section and the non-dead zone fault section respectively.
Further, in step S1, the specific method for determining the dead zone fault section and the non-dead zone fault section includes: protecting installation place voltage U of feeder circuit breaker between bus and feeder line of contact network in traction network m Maximum voltage value U of voltage dead zone of power direction element S1 Comparing and testing the voltage U of the breaker protection installation position m Greater than the maximum voltage value U of the voltage dead zone of the power direction element S1 The area of the circuit breaker is used as a non-dead zone fault section, and the voltage U at the protective installation position of the circuit breaker m Less than or equal to the maximum voltage value U of the voltage dead zone of the power direction element S1 As a dead zone fault section.
Further, in step S2, a specific method for determining the fault direction of the first flexible substation is as follows: measuringCurrent I at protective installation position of circuit breaker QF9 at feeder m1 Respectively calculating the upper end G of the breaker QF9 at the feeder 1 At short-circuit fault and lower end G 2 The upper end current I of the corresponding feeder circuit breaker QF9 protection installation position when short-circuit fault occurs 1 And a lower terminal current I 2 And a current I is kept away from the upper end 1 And is not more than the lower end current I 2 Within the range of (1), simultaneously ensuring a certain sensitivity to carry out setting to obtain a current setting value I set1 Wherein the upper end current I 1 And a lower terminal current I 2 The calculation formulas of (A) and (B) are respectively as follows:
in the formula, E 2 Is the equivalent potential, Z, of the system of the second flexible traction substation S2 Is the second flexible traction substation QF6 backside system impedance, Z L1 For the second flexible traction substation QF6 to G 1 Line impedance of (E) 1 Is the equivalent potential, Z, of the first flexible traction substation system S1 Is the second flexible traction substation QF5 backside system impedance, Z L2 Is the first flexible traction substation QF5 to G 2 Line impedance of (d), G 1 ，G 2 The points are two points on the upper side and the lower side of the near end of the protection installation position of the feeder QF9, and G1 and G2 can be taken as the protection installation position of the breaker QF9 for calculation during current calculation;
if the breaker QF9 at the feeder protects the current I at the installation position m1 Less than current setting value I set1 If the current value is larger than the preset value, the fault direction is the reverse direction, and if the current value is larger than the preset value, the current value is larger than the preset value m1 Greater than or equal to current setting value I set1 The fault direction is positive direction, wherein the lower end G of the breaker QF9 at the feeder line is 2 The side fault is a positive direction fault, and the upper end G of the breaker QF9 at the feeder line 1 The side fault is a reverse fault;
determine the secondThe specific method of the fault direction of the flexible substation comprises the following steps: measuring current I at protective installation position of circuit breaker QF10 at feeder m2 Respectively calculating the upper end G of the breaker QF10 at the feeder 3 At short-circuit fault and lower end G 4 The upper end current I of the corresponding feeder circuit breaker QF10 protection installation position when short-circuit fault occurs 3 And a lower terminal current I 4 And a current I is kept away from the upper end 3 And is not more than the lower end current I 4 Within the range of (1), simultaneously ensuring a certain sensitivity to carry out setting to obtain a current setting value I set2 Wherein the upper end current I 3 And a lower terminal current I 4 The calculation formulas of (A) and (B) are respectively as follows:
in the formula, Z S2 Is the second flexible traction substation QF6 backside system impedance, Z L4 For the second flexible traction substation QF6 to G 4 Line impedance of (d), Z L3 Is the first flexible traction substation QF5 to G 3 Line impedance G of 3 ，G 4 The points are two points on the upper side and the lower side of the near end of the protective installation position of the feeder QF10, and G can be calculated during current calculation 3 、G 4 Calculating the position regarded as the QF10 protection installation position;
if the breaker QF10 at the feeder protects the current I at the installation m2 Less than current setting value I set2 If the current value is larger than the preset value, the fault direction is the reverse direction, and if the current value is larger than the preset value, the current value is larger than the preset value m2 Greater than or equal to current setting value I set2 The fault direction is positive direction, wherein the lower end G of the breaker QF10 at the feeder line is 4 The side fault is a positive direction fault, and the upper end G of the breaker QF9 at the feeder line 3 The side failure is a reverse failure.
Further, in step S2, it is determined that the failure direction determination methods of the first flexible substation and the second flexible substation are the same in the non-dead zone failure section, specifically: measuring voltage and current at protective installation positions of circuit breakers QF9 and QF10 at a feeder line, selecting a maximum sensitivity angle according to a line impedance angle, and performing phase shift on the measured voltage according to the maximum sensitivity angle, wherein if the absolute value of the phase difference between the voltage and the current after the phase shift is less than 90 degrees, the fault direction is a positive direction, and if the absolute value of the phase difference between the voltage and the current after the phase shift is greater than or equal to 90 degrees, the fault direction is a negative direction.
The invention has the beneficial effects that: the invention provides a fault direction judging method suitable for a flexible traction power supply system, which eliminates the influence of a voltage dead zone of a power direction element on fault direction judgment, can accurately judge the fault direction at a protection installation position, and improves the safety and reliability of the operation of the flexible traction power supply system.
Drawings
FIG. 1 is a block diagram of a flexible traction power supply system;
FIG. 2 is a schematic diagram of a fault direction determination process;
FIG. 3 is a schematic diagram of the relationship between the fault direction and the phase difference range of the non-dead zone fault section.
Detailed Description
The embodiments of the present invention will be further described with reference to the accompanying drawings.
As shown in fig. 1, the present invention provides a flexible traction power supply system, comprising a first flexible traction substation and a second flexible traction substation; the first flexible traction substation comprises a first existing system traction transformer, a first flexible traction transformer, a first bus, circuit breakers QF1-QF2, a circuit breaker QF5, a circuit breaker QF7 and a circuit breaker QF9; the second flexible traction substation comprises a second existing system traction transformer, a second flexible traction transformer, a second bus, circuit breakers QF3-QF4, a circuit breaker QF6, a circuit breaker QF8 and a circuit breaker QF10;
the first existing system traction transformer is connected with the first bus through circuit breakers QF1-QF 2; the second existing system traction transformer is connected with a second bus through circuit breakers QF3-QF4, and the first bus and the second bus are connected to a traction network through a circuit breaker QF7 and a circuit breaker QF8 respectively;
the first flexible traction transformer is connected with the first bus through a breaker QF 5; the second flexible traction transformer is connected with the second bus through a breaker QF 6; the first busbar and the second busbar are connected to the traction network by a circuit breaker QF9 and a circuit breaker QF10, respectively.
As shown in fig. 1, which is a schematic structural diagram of a flexible traction power supply system, the flexible traction power supply system is mainly composed of a first flexible traction substation, a second flexible traction substation, a traction network, a transformed electric phase splitting and the like, and the first flexible traction substation and the second flexible traction substation are connected to the network and run to realize through power supply within a region. When the flexible traction power supply system works normally, the existing traction transformers in the two flexible traction substations do not work, the flexible traction transformers in the substations supply power for the traction network, and the flexible traction transformers supply power for the double-end power supply mode. The power supply system can completely cancel the electric phase splitting in the first flexible traction substation and between the first flexible traction substation and the second flexible traction substation, realize the through power supply of the power supply sections on two sides of the electric phase splitting in the first flexible traction substation and the power supply section on the left side of the electric phase splitting in the second flexible traction substation, and solve the problems of electric energy quality such as idle work, negative sequence, harmonic wave and the like in the existing traction power supply system.
Based on the above system, the present invention further provides a method for determining a fault direction of a flexible traction power supply system, as shown in fig. 1, including the following steps:
s1: in a flexible traction power supply system, determining a dead zone fault section and a non-dead zone fault section when a fault occurs;
s2: and determining the fault direction of the flexible traction power supply system in the dead zone fault section and the non-dead zone fault section respectively.
In the embodiment of the present invention, in step S1, the method for determining the dead zone fault section and the non-dead zone fault section in the first flexible substation and the second flexible substation is the same, specifically: protecting installation place voltage U of feeder circuit breaker between bus and feeder line of contact network in traction network m Maximum voltage value U of voltage dead zone of power direction element S1 Comparing and testing the voltage U of the breaker protection installation position m Greater than the maximum voltage value U of the voltage dead zone of the power direction element S1 Is made as an areaFor non-dead zone fault section, the voltage U at the breaker protection installation position m Less than or equal to the maximum voltage value U of the voltage dead zone of the power direction element S1 As a dead zone fault section.
In the embodiment of the invention, because the power direction element has a voltage dead zone during direction detection, the voltage value U is measured through the protection installation position m And maximum value U of voltage dead zone S1 The comparison can determine whether the fault occurs in the dead zone fault section, and when the dead zone fault section has the fault, the fault direction needs to be judged according to the voltage and current effective value criterion because the power direction element cannot effectively judge the fault direction at the moment. According to the structure of the flexible traction power supply system, when the flexible traction power supply system works normally, the existing traction transformers of the first flexible traction substation and the second flexible traction substation do not work, and the two flexible traction transformers realize through power supply of the flexible traction power supply system. Taking the first flexible traction substation as an example, when the protection outlet near end G1 has a fault, the protection device at QF9 measures the current I 1 The current I measured at QF9 when the fault at the near end G2 of the protection outlet is provided by a flexible traction transformer of a second flexible traction substation 2 Provided by a first flexible traction transformer, when due to differences in line impedance, I 2 Will be much greater than I 1 。
In the embodiment of the present invention, in step S2, a specific method for determining the fault direction of the first flexible substation is as follows: measuring current I at protection installation position of circuit breaker QF9 at feeder m1 Respectively calculating the upper end G of the breaker QF9 at the feeder 1 At short-circuit fault and lower end G 2 The upper end current I of the corresponding feeder circuit breaker QF9 protection installation position when short-circuit fault occurs 1 And a lower terminal current I 2 And avoids the upper end current I 1 And is not more than the lower end current I 2 Within the range of (1), simultaneously ensuring a certain sensitivity to carry out setting to obtain a current setting value I set1 Wherein the upper end current I 1 And a lower terminal current I 2 The calculation formulas of (A) and (B) are respectively as follows:
in the formula, E 2 Is the equivalent potential, Z, of the system of the second flexible traction substation S2 Is the second flexible traction substation QF6 backside system impedance, Z L1 For a second flexible traction substation QF6 to G 1 Line impedance of (E) 1 Is the equivalent potential, Z, of the first flexible traction substation system S1 Is the second flexible traction substation QF5 backside system impedance, Z L2 Is the first flexible traction substation QF5 to G 2 Line impedance of (d), G 1 ，G 2 The points are two points on the upper side and the lower side of the near end of the protective installation position of the feeder QF9, and G1 and G2 can be taken as the protective QF9 installation position for calculation during current calculation;
if the breaker QF9 at the feeder protects the current I at the installation position m1 Less than current setting value I set1 If the current value is larger than the preset value, the fault direction is the reverse direction, and if the current value is larger than the preset value, the current value is larger than the preset value m1 Greater than or equal to current setting value I set1 The fault direction is positive direction, wherein the lower end G of the breaker QF9 at the feeder line is 2 The side fault is a positive direction fault, and the upper end G of the breaker QF9 at the feeder line 1 The side fault is a reverse fault;
the specific method for determining the fault direction of the second flexible substation comprises the following steps: measuring current I at protective installation position of breaker QF10 at feeder line m2 Respectively calculating the upper end G of the breaker QF10 at the feeder 3 At the time of short-circuit fault and lower end G 4 The upper end current I of the corresponding feeder circuit breaker QF10 protection installation position when short-circuit fault occurs 3 And a lower terminal current I 4 And a current I is kept away from the upper end 3 And is not more than the lower end current I 4 Within the range of (1), simultaneously ensuring a certain sensitivity to carry out setting to obtain a current setting value I set2 Wherein the upper end current I 3 And a lower terminal current I 4 The calculation formulas of (A) and (B) are respectively as follows:
in the formula, Z S2 Is the second flexible traction substation QF6 backside system impedance, Z L4 For the second flexible traction substation QF6 to G 4 Line impedance of (d), Z L3 Is the first flexible traction substation QF5 to G 3 Line impedance of (d), G 3 ，G 4 The points are two points on the upper side and the lower side of the near end of the protective installation position of the feeder QF10, and G can be calculated during current calculation 3 、G 4 Calculating the position regarded as the QF10 protection installation position;
if the breaker QF10 at the feeder protects the current I at the installation m2 Less than current setting value I set2 If the fault direction is the reverse direction, if the current value I at the breaker protection installation position is m2 Greater than or equal to current setting value I set2 The fault direction is positive direction, wherein the lower end G of the breaker QF10 at the feeder line is 4 The side fault is a positive direction fault, and the upper end G of the breaker QF9 at the feeder line 3 The side failure is a reverse failure.
In the embodiment of the present invention, in step S2, the method for determining the fault direction of the first flexible substation and the second flexible substation in the non-dead zone fault section is the same, specifically: measuring the voltage and the current of protective installation positions of the circuit breakers QF9 and QF10 at the feeder line, selecting a maximum sensitive angle according to the impedance angle of the line, and performing phase shift on the measured voltage according to the maximum sensitive angle, wherein if the absolute value of the phase difference between the voltage and the current after the phase shift is smaller than 90 degrees, the fault direction is a positive direction, and if the absolute value of the phase difference between the voltage and the current after the phase shift is larger than or equal to 90 degrees, the fault direction is a negative direction.
As shown in FIG. 3, when the non-dead zone fault section fails, the fault occurs due to U m Greater than U S1 The measuring voltage can form square wave to be compared with the phase of the current, so that the power direction can be judged by the phase difference between the voltage and the current to judge the faultThe barrier direction. When the absolute value of the phase difference of the voltage and the current is smaller than 90 degrees, namely the power is positive, the fault is judged to be a positive direction fault, and when the absolute value of the phase difference of the voltage and the current is larger than 90 degrees, namely the power is negative, the fault is judged to be a negative direction fault. Because the line has line impedance, when comparing the voltage phase and the current phase, a compensation impedance angle phi is introduced, the influence of the line impedance is reduced, and the sensitivity of direction judgment is increased.
The working principle and the process of the invention are as follows: on the basis of a power direction element principle, according to the structural characteristics of a flexible traction power supply system, a fault occurrence area is partitioned and a voltage and current effective value criterion is added, so that the fault direction can be accurately judged when a metallic short-circuit fault occurs at a protection installation position, the influence of a power direction element dead zone on the judgment of the fault direction is eliminated, and the safety and the reliability of the operation of the flexible traction power supply system are improved.
The invention has the beneficial effects that:
(1) According to the flexible traction power supply system, the fault occurrence direction at the feeder line can be accurately judged, and no fault direction judgment dead zone exists, so that the reliability of protection can be improved, the protection configuration is simplified, and the quality problems of electric energy such as idle work, negative sequence, harmonic wave and the like existing in the existing traction power supply system can be solved;
(2) The invention provides a fault direction judging method suitable for a flexible traction power supply system, which eliminates the influence of a voltage dead zone of a power direction element on fault direction judgment, can accurately judge the fault direction at a protection installation position, and improves the safety and reliability of the operation of the flexible traction power supply system.
It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.
Claims (1)
1. A fault direction judgment method of a flexible traction power supply system is characterized by comprising the following steps:
s1: in a flexible traction power supply system, determining a dead zone fault section and a non-dead zone fault section when a fault occurs;
s2: determining the fault direction of the flexible traction power supply system in the dead zone fault section and the non-dead zone fault section respectively;
the flexible traction power supply system for executing the fault direction judgment method comprises a first flexible traction substation and a second flexible traction substation; the first flexible traction substation comprises a first existing system traction transformer, a first flexible traction transformer, a first bus, circuit breakers QF1-QF2, a circuit breaker QF5, a circuit breaker QF7 and a circuit breaker QF9; the second flexible traction substation comprises a second existing system traction transformer, a second flexible traction transformer, a second bus, circuit breakers QF3-QF4, a circuit breaker QF6, a circuit breaker QF8 and a circuit breaker QF10;
the first existing system traction transformer is connected with the first bus through circuit breakers QF1-QF 2; the second existing system traction transformer is connected with a second bus through circuit breakers QF3-QF4, and the first bus and the second bus are connected to a traction network through a circuit breaker QF7 and a circuit breaker QF8 respectively;
the first flexible traction transformer is connected with the first bus through a breaker QF 5; the second flexible traction transformer is connected with a second bus through a breaker QF 6; the first busbar and the second busbar are respectively connected to a traction network through a breaker QF9 and a breaker QF10;
in step S1, the specific method for determining the dead zone fault section and the non-dead zone fault section includes: protecting installation place voltage U of feeder circuit breaker between bus and feeder line of contact network in traction network m Maximum voltage value U of voltage dead zone of power direction element S1 Comparing and testing the voltage U of the breaker protection installation position m Greater than the maximum voltage value U of the voltage dead zone of the power direction element S1 The area of the circuit breaker is used as a non-dead zone fault section, and the voltage U at the protective installation position of the circuit breaker m Less than or equal to the maximum voltage value U of the voltage dead zone of the power direction element S1 As a dead zoneA fault section;
in step S2, the specific method for determining the fault direction of the first flexible substation is as follows: measuring current I at protection installation position of circuit breaker QF9 at feeder m1 Respectively calculating the upper end G of the breaker QF9 at the feeder 1 At short-circuit fault and lower end G 2 The upper end current I of the corresponding feeder circuit breaker QF9 protection installation position when short-circuit fault occurs 1 And a lower terminal current I 2 And a current I is kept away from the upper end 1 And is not more than the lower end current I 2 Within the range of (2), setting is carried out to obtain a current setting value I set1 Wherein the upper end current I 1 And a lower terminal current I 2 The calculation formulas of (A) and (B) are respectively as follows:
in the formula, E 2 Is the equivalent potential, Z, of the system of the second flexible traction substation S2 Is the second flexible traction substation QF6 backside system impedance, Z L1 For the second flexible traction substation QF6 to G 1 Line impedance of (E) 1 Is the equivalent potential, Z, of the first flexible traction substation system S1 Is the second flexible traction substation QF5 backside system impedance, Z L2 Is the first flexible traction substation QF5 to G 2 Line impedance of (d), G 1 And G 2 The points are two points on the upper side and the lower side of the near end of the protective installation position of the feeder QF9 respectively;
if the breaker QF9 at the feeder protects the current I at the installation position m1 Less than current setting value I set1 If the current value is larger than the preset value, the fault direction is the reverse direction, and if the current value is larger than the preset value, the current value is larger than the preset value m1 Greater than or equal to current setting value I set1 The fault direction is positive direction, wherein the lower end G of the breaker QF9 at the feeder line is 2 The side fault is a positive direction fault, and the upper end G of the breaker QF9 at the feeder line 1 Side fault is inverseA directional fault;
the specific method for determining the fault direction of the second flexible substation comprises the following steps: measuring current I at protective installation position of circuit breaker QF10 at feeder m2 Respectively calculating the upper end G of the breaker QF10 at the feeder 3 At the time of short-circuit fault and lower end G 4 The upper end current I of the corresponding feeder circuit breaker QF10 protection installation position when short-circuit fault occurs 3 And a lower terminal current I 4 And a current I is kept away from the upper end 3 And is not more than the lower end current I 4 Within the range of (1), setting is carried out to obtain a current setting value I set2 Wherein the upper end current I 3 And a lower terminal current I 4 The calculation formulas of (A) and (B) are respectively as follows:
in the formula, Z S2 Is the second flexible traction substation QF6 backside system impedance, Z L4 For the second flexible traction substation QF6 to G 4 Line impedance of (d), Z L3 Is the first flexible traction substation QF5 to G 3 Line impedance of (d), G 3 And G 4 The points are two points on the upper side and the lower side of the near end of the protective installation position of the feeder QF10 respectively;
if the breaker QF10 at the feeder protects the current I at the installation m2 Less than current setting value I set2 If the current value is larger than the preset value, the fault direction is the reverse direction, and if the current value is larger than the preset value, the current value is larger than the preset value m2 Greater than or equal to current setting value I set2 The fault direction is positive direction, wherein the lower end G of the breaker QF10 at the feeder line is 4 The side fault is a positive direction fault, and the upper end G of the breaker QF9 at the feeder line 3 The side fault is a reverse fault;
in step S2, it is determined that the failure direction determination methods of the first flexible substation and the second flexible substation are the same in the non-dead zone failure section, specifically: measuring voltage and current at protective installation positions of circuit breakers QF9 and QF10 at a feeder line, selecting a maximum sensitivity angle according to a line impedance angle, and performing phase shift on the measured voltage according to the maximum sensitivity angle, wherein if the absolute value of the phase difference between the voltage and the current after the phase shift is less than 90 degrees, the fault direction is a positive direction, and if the absolute value of the phase difference between the voltage and the current after the phase shift is greater than or equal to 90 degrees, the fault direction is a negative direction.
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