CN114512968A - Method and system for limiting short-circuit current of power system - Google Patents
Method and system for limiting short-circuit current of power system Download PDFInfo
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- CN114512968A CN114512968A CN202210102479.4A CN202210102479A CN114512968A CN 114512968 A CN114512968 A CN 114512968A CN 202210102479 A CN202210102479 A CN 202210102479A CN 114512968 A CN114512968 A CN 114512968A
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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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- 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
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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
- H02H7/22—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 for distribution gear, e.g. bus-bar systems; for switching devices
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Abstract
The invention discloses a method and a system for limiting short-circuit current of a power system, wherein the method comprises the following steps: acquiring switch current and bus voltage of each switch in a transformer substation, judging whether a power system has a ground fault according to the switch current and the bus voltage, and determining a fault type and a fault position when the power system has the ground fault; comparing the fault type and the fault position with a preset target fault type and a target fault position of which the short-circuit current exceeds the standard when the switch is switched on and switched off, and determining whether the switch on-off short-circuit current exceeds the standard or not; when the fact that the on-off short-circuit current of the switch exceeds the standard is determined, matching is conducted according to the fault type, the fault position and the preset on-off branch corresponding to the situation that different types of faults occur at different positions, and a target on-off branch is determined; before the conventional circuit breaker completes opening, the target opening branch is opened to limit the short-circuit current of the power system.
Description
Technical Field
The present invention relates to the field of power system control technology, and more particularly, to a method and system for limiting short-circuit current of a power system.
Background
With the rapid development of power grids, the scale of the power grids is increasing day by day, and the short-circuit current level in the power system in China is increasing year by year. Excessive short-circuit current can be detrimental to the safe and stable operation of the power system and the electrical equipment itself. In order to ensure the safe operation of the power system, the electrical equipment in the power grid must be strengthened or replaced to solve the problem caused by the exceeding of the short-circuit current, so that on one hand, the investment and technical requirements of the system on the electrical equipment are greatly improved, and in addition, the situation that no suitable breaker is selected can occur due to the limitation of the breaking capacity of the breaker. Therefore, in order to avoid a series of hazards caused by the exceeding of the short-circuit current, how to limit the level of the short-circuit current within the safety margin becomes a problem which needs to be solved in the development process of the modern power grid.
The conventional control means of the short-circuit current adopted in the actual power system mainly comprises the steps of circuit shutdown, installation of a current-limiting reactance and the like, and the problems of power supply reliability reduction, system loss increase and the like are caused after the measures are adopted. The conventional fault current limiter is relatively less applied in the 500kV level, and is often high in manufacturing cost, large in station area and difficult to popularize and apply.
When a short-circuit grounding fault occurs in an electric power system, a short-circuit current can pass through a fault point, and when the level of the short-circuit current exceeds the breaking capacity of a breaker, a short circuit can not be cut off. The current open short circuit current level of the conventional circuit breaker does not exceed 63 kA. When the short-circuit current level exceeds 63kA, relevant current limiting measures need to be taken.
Disclosure of Invention
The invention provides a method and a system for limiting short-circuit current of an electric power system, which are used for solving the problem of how to limit the short-circuit current of the electric power system.
In order to solve the above problem, according to an aspect of the present invention, there is provided a method of limiting a short-circuit current of a power system, the method including:
acquiring switch current and bus voltage of each switch in a transformer substation, judging whether a power system has a ground fault according to the switch current and the bus voltage, and determining a fault type and a fault position when the power system has the ground fault;
comparing the fault type and the fault position with a preset target fault type and a target fault position of which the short-circuit current exceeds the standard when the switch is switched on and switched off, and determining whether the switch on-off short-circuit current exceeds the standard or not;
when the fact that the on-off short-circuit current of the switch exceeds the standard is determined, matching is conducted according to the fault type, the fault position and the preset on-off branch corresponding to the situation that different types of faults occur at different positions, and a target on-off branch is determined;
before the conventional circuit breaker completes opening, the target opening branch is opened to limit the short-circuit current of the power system.
Preferably, the determining whether the power system has a ground fault according to the switching current and the bus voltage, and determining a fault type and a fault location when the fault occurs, includes: :
when the instantaneous value of the single-phase switching current is larger than or equal to a preset current instantaneous threshold, or the current rising rate exceeds a preset rising rate threshold, or the bus voltage is smaller than or equal to a preset bus voltage threshold, determining that a fault occurs, wherein the fault type is a single-phase fault;
when the three-phase switching current instantaneous value is greater than or equal to a preset current instantaneous threshold, or the current rise rate exceeds a preset rise rate threshold, or the bus voltage is less than or equal to a preset bus voltage threshold, determining that a fault occurs, wherein the fault type is a three-phase fault;
and determining the branch current of each branch according to the switching current, and comparing the direct current circuit with the preset first short-circuit current of each branch when different types of faults occur at different positions to determine the fault position.
Preferably, wherein the method further comprises:
establishing a simulation model according to the operation data of the power system, and carrying out simulation calculation based on the simulation model to obtain a second short-circuit current of each switch when different types of faults occur at different positions;
and selecting the fault type and the fault position corresponding to the second short-circuit current which is greater than or equal to the preset second short-circuit current threshold as the target fault type and the target fault position of the switch with the switching-on short-circuit current exceeding the standard.
Preferably, wherein the method further comprises:
sorting the first short-circuit current of each branch in a descending order according to any type of fault at any position, determining a branch sequence, and initializing i to be 1;
selecting the ith branch in the branch sequence as a current key branch;
disconnecting the current key branch, and acquiring a third short-circuit current and a system stability level of the switch when different types of faults occur at different positions;
when the third short-circuit current is smaller than a third short-circuit current threshold value and the system stability is stable, determining the current key branch as the target cut-off branch; otherwise, updating i +1, and re-determining the current critical branch until the third short-circuit current is smaller than the third short-circuit current threshold and the system stability is stable, and determining that the current critical branch is the corresponding cut-off branch when any type of fault occurs at any position.
Preferably, wherein the method further comprises:
and establishing a simulation model according to the operation data of the power system, and carrying out simulation calculation based on the simulation model to obtain the first short-circuit current of each branch circuit when different types of faults occur at different positions.
Preferably, wherein the method further comprises:
and when the fault is removed, judging the coincidence condition, and when the bus voltage is recovered to be normal, recovering the conduction of the target cut-off branch.
Preferably, wherein the method further comprises:
if the fault type is a single-phase fault and the fault position is a power transmission line, judging a coincidence condition after the disconnection time of the target disconnection branch reaches a first preset time threshold; otherwise, judging the coincidence condition after the breaking time of the target breaking branch reaches a second preset time threshold.
According to another aspect of the present invention, there is provided a system for limiting short circuit current in an electrical power system, the system comprising:
the fault determining unit is used for acquiring the switch current and the bus voltage of each switch in the transformer substation, judging whether the power system has a ground fault according to the switch current and the bus voltage, and determining the fault type and the fault position when the power system has the ground fault;
the short-circuit current exceeding judging unit is used for comparing the fault type and the fault position with a preset target fault type and a target fault position where the short-circuit current exceeds the standard when the switch is switched on and switched off, and determining whether the switch on-off short-circuit current exceeds the standard or not;
the target cut-off branch determining unit is used for matching the corresponding cut-off branches when the fact that the on-off short-circuit current exceeds the standard is determined, and determining the target cut-off branch according to the fault type, the fault position and the preset different types of faults occurring at different positions;
and the action unit is used for disconnecting the target cut-off branch circuit before the conventional circuit breaker completes the opening so as to limit the short-circuit current of the power system.
Preferably, the fault determining unit, which determines whether a ground fault occurs in the power system according to the switching current and the bus voltage, and determines a fault type and a fault location when a fault occurs, includes: :
when the instantaneous value of the single-phase switching current is larger than or equal to a preset current instantaneous threshold, or the current rising rate exceeds a preset rising rate threshold, or the bus voltage is smaller than or equal to a preset bus voltage threshold, determining that a fault occurs, wherein the fault type is a single-phase fault;
when the three-phase switching current instantaneous value is greater than or equal to a preset current instantaneous threshold, or the current rise rate exceeds a preset rise rate threshold, or the bus voltage is less than or equal to a preset bus voltage threshold, determining that a fault occurs, wherein the fault type is a three-phase fault;
and determining the branch current of each branch according to the switching current, and comparing the direct current circuit with the preset first short-circuit current of each branch when different types of faults occur at different positions to determine the fault position.
Preferably, wherein the system further comprises:
the second short-circuit current determining unit is used for establishing a simulation model according to the operation data of the power system, carrying out simulation calculation based on the simulation model and obtaining second short-circuit current of each switch when different types of faults occur at different positions;
and the target fault type and position determining unit is used for selecting the fault type and the fault position corresponding to the second short-circuit current which is greater than or equal to the preset second short-circuit current threshold as the target fault type and the target fault position with the switch-on short-circuit current exceeding the standard.
Preferably, wherein the system further comprises: a broken branch determining unit for:
sorting the first short-circuit current of each branch in a descending order according to any type of fault at any position, determining a branch sequence, and initializing i to be 1;
selecting the ith branch in the branch sequence as a current key branch;
disconnecting the current key branch, and acquiring a third short-circuit current and a system stability level of the switch when different types of faults occur at different positions;
when the third short-circuit current is smaller than a third short-circuit current threshold value and the system stability is stable, determining the current key branch as the target cut-off branch; otherwise, updating i +1, and re-determining the current critical branch until the third short-circuit current is smaller than the third short-circuit current threshold and the system stability is stable, and determining that the current critical branch is the corresponding cut-off branch when any type of fault occurs at any position.
Preferably, wherein the system further comprises:
and the first short-circuit current determining unit is used for establishing a simulation model according to the operation data of the power system, carrying out simulation calculation based on the simulation model and obtaining the first short-circuit current of each branch circuit when different types of faults occur at different positions.
Preferably, wherein the system further comprises:
and the recovery unit is used for judging a coincidence condition after the fault is removed, and recovering the conduction of the target cut-off branch when the bus voltage is recovered to be normal.
Preferably, the recovery unit further comprises:
if the fault type is a single-phase fault and the fault position is a power transmission line, judging a coincidence condition after the disconnection time of the target disconnection branch reaches a first preset time threshold; otherwise, judging the coincidence condition after the breaking time of the target breaking branch reaches a second preset time threshold.
The invention provides a method and a system for limiting short-circuit current of a power system, comprising the following steps: acquiring switch current and bus voltage of each switch in a transformer substation, judging whether a power system has a ground fault according to the switch current and the bus voltage, and determining a fault type and a fault position when the power system has the ground fault; determining whether the switching-on/off short-circuit current exceeds the standard or not according to the fault type and the fault position; when the fact that the on-off short-circuit current of the switch exceeds the standard is determined, matching is conducted according to the fault type, the fault position and the preset on-off branch corresponding to the situation that different types of faults occur at different positions, and a target on-off branch is determined; before the conventional circuit breaker completes opening, the target opening branch is opened to limit the short-circuit current of the power system. The method can quickly detect the fault, determine the position and the type of the fault and quickly cut off the target cut-off branch, thereby limiting the short-circuit current, reducing the cut-off short-circuit current level of the system breaker and ensuring the safety of the system and equipment.
Drawings
A more complete understanding of exemplary embodiments of the present invention may be had by reference to the following drawings in which:
FIG. 1 is a flow chart of a method 100 of limiting short circuit current in a power system according to an embodiment of the present invention;
FIG. 2 is a schematic wiring diagram of a typical 500kV system according to an embodiment of the invention;
FIG. 3 is a control schematic of an apparatus for limiting short circuit current according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of 500kV system short circuit current suppression according to an embodiment of the invention;
fig. 5 is a schematic structural diagram of a system 500 for limiting short-circuit current of a power system according to an embodiment of the present invention.
Detailed Description
The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for complete and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, the same units/elements are denoted by the same reference numerals.
Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
Fig. 1 is a flow chart of a method 100 for limiting short circuit current of a power system according to an embodiment of the invention. As shown in fig. 1, a method 100 for limiting short-circuit current of an electrical power system according to an embodiment of the present invention starts with step 101, obtains switch current and bus voltage of each switch in a substation in step 101, determines whether a ground fault occurs in the electrical power system according to the switch current and the bus voltage, and determines a fault type and a fault location when a fault occurs.
Preferably, the determining whether the power system has a ground fault according to the switching current and the bus voltage, and determining a fault type and a fault location when the fault occurs, includes: :
when the instantaneous value of the single-phase switching current is larger than or equal to a preset current instantaneous threshold, or the current rising rate exceeds a preset rising rate threshold, or the bus voltage is smaller than or equal to a preset bus voltage threshold, determining that a fault occurs, wherein the fault type is a single-phase fault;
when the three-phase switching current instantaneous value is greater than or equal to a preset current instantaneous threshold, or the current rise rate exceeds a preset rise rate threshold, or the bus voltage is less than or equal to a preset bus voltage threshold, determining that a fault occurs, wherein the fault type is a three-phase fault;
and determining the branch current of each branch according to the switching current, and comparing the direct current circuit with the preset first short-circuit current of each branch when different types of faults occur at different positions to determine the fault position.
Preferably, wherein the method further comprises:
and establishing a simulation model according to the operation data of the power system, and carrying out simulation calculation based on the simulation model to obtain the first short-circuit current of each branch circuit when different types of faults occur at different positions.
The existing typical 500kV system wiring diagram is shown in fig. 2, and in the region of the power system with high short-circuit current, the short-circuit current is generally formed by collecting a plurality of branch fault currents. As shown in fig. 2. When a fault occurs, the fault current of the circuit breaker directly connected with the fault point is the sum of the fault currents of the branches, and at the moment, the fault current is large and may exceed the breaking capacity of the circuit breaker. Therefore, in the embodiment of the invention, the fault is quickly detected, the fault position and type are determined, and the target cut-off branch is quickly cut off, so that the short-circuit current is limited, the cut-off short-circuit current level of the system breaker is reduced, and the safety of the system and equipment is ensured.
In the embodiment of the present invention, rapid detection of a failure and determination of a location and a type are first performed. Specifically, the switching current and the substation bus voltage of each switch in the substation are detected. And when the instantaneous value of the switching current is greater than or equal to a preset current instantaneous threshold, or the current rise rate exceeds a preset rise rate threshold, or the bus voltage is less than or equal to a preset bus voltage threshold, determining that the system has a fault. And if the faulted phases comprise three phases, determining that the fault occurs and the fault type is a single-phase fault. When the fault position is determined, judgment is carried out according to the collected switching current, specifically, the branch current of each branch is determined according to the switching current, and the fault position is determined according to comparison between the direct current circuit and a preset first short-circuit current of each branch when different types of faults occur at different positions.
According to the method and the device, a detailed simulation model considering the wiring topology of the transformer substation is established according to system operation data, and simulation calculation is performed by using the detailed simulation model, so that the first short-circuit current of each branch circuit when different types of faults occur at different positions is calculated and obtained.
In step 102, the fault type and the fault position are compared with a preset target fault type and a target fault position of which the short-circuit current exceeds the standard when the switch is switched on and switched off, and whether the switch on-off short-circuit current exceeds the standard is determined.
Preferably, wherein the method further comprises:
establishing a simulation model according to the operation data of the power system, and carrying out simulation calculation based on the simulation model to obtain a second short-circuit current of each switch when different types of faults occur at different positions;
and selecting the fault type and the fault position corresponding to the second short-circuit current which is greater than or equal to the preset second short-circuit current threshold as the target fault type and the target fault position of the switch with the switching-on short-circuit current exceeding the standard.
In the embodiment of the present invention, it is further required to perform simulation calculation according to the detailed simulation model, determine a second short-circuit current actually cut off by the switch when different types of faults and different fault types occur at different fault positions, and determine a fault position and a fault type where the level of the cut-off short-circuit current exceeds the standard according to the second short-circuit current, which are used as a target fault position and a target fault type, so that the control device can be used for determining whether the switch cut-off short-circuit current exceeds the standard.
In the embodiment of the invention, the fault position and type obtained in step 101 are compared with the target fault position and the target fault type, and when the obtained fault position and fault type are the target fault position and the target fault type with the switching-on/switching-off current exceeding the standard, it is determined that the switching-on/switching-off short-circuit current exceeding the standard exists.
In step 103, when it is determined that the on-off short-circuit current exceeds the standard, matching is performed according to the fault type, the fault position and the preset on-off branch corresponding to the different types of faults occurring at different positions, and a target on-off branch is determined.
Preferably, wherein the method further comprises:
sorting the first short-circuit current of each branch in a descending order according to any type of fault at any position, determining a branch sequence, and initializing i to be 1;
selecting the ith branch in the branch sequence as a current key branch;
disconnecting the current key branch, and acquiring a third short-circuit current and a system stability level of the switch when different types of faults occur at different positions;
when the third short-circuit current is smaller than a third short-circuit current threshold value and the system stability is stable, determining the current key branch as the target cut-off branch; otherwise, updating i +1, and re-determining the current critical branch until the third short-circuit current is smaller than the third short-circuit current threshold and the system stability is stable, and determining that the current critical branch is the corresponding cut-off branch when any type of fault occurs at any position.
In step 104, before the conventional circuit breaker completes opening, the target open branch is opened to limit the short-circuit current of the power system.
In the embodiment of the invention, when it is determined that the on-off short-circuit current of the switch exceeds the standard, the target on-off branch is determined according to the matching of the fault type and the fault position obtained in the step 101 and the preset on-off branch corresponding to the different types of faults occurring at different positions. The quick switch is used as a branch circuit breaking device, redundant configuration is achieved through series connection of the double switches, and serious consequences caused by movement of the switch are avoided. When a fault is detected and the fault type and the fault position belong to the working condition that the cut-off current of the circuit breaker exceeds the standard, a fast switch is commanded to act to cut off the fault branch, so that the fault current is limited.
The method for determining the open branch circuit of any type at any position by using the following modes comprises the following steps:
a) according to the system operation data, establishing a detailed simulation model considering the wiring topology of the transformer substation, and calculating a first short-circuit current level provided by each branch circuit when the transformer substation is in fault; and sorting the first short-circuit current in a descending order, determining a branch sequence, and selecting a first branch in the branch sequence as a key branch, namely selecting the branch providing the maximum short-circuit current as the key branch.
b) And calculating a third short-circuit current which is actually switched on and off when different types of faults occur at different fault positions of the transformer substation after the key branch is switched off, if the third short-circuit current meets the requirement (namely is smaller than a preset third short-circuit threshold), further calculating the system stability level under the fault condition, and if the system stability meets the requirement, selecting the branch as the branch switched on and off during the fault.
c) And if the system stability does not meet the requirement at the moment, selecting the next branch in the branch sequence, and repeating the steps.
Preferably, wherein the method further comprises:
and when the fault is removed, judging the coincidence condition, and when the bus voltage is recovered to be normal, recovering the conduction of the target cut-off branch.
Preferably, wherein the method further comprises:
if the fault type is a single-phase fault and the fault position is a power transmission line, judging a coincidence condition after the disconnection time of the target disconnection branch reaches a first preset time threshold; otherwise, judging the coincidence condition after the breaking time of the target breaking branch reaches a second preset time threshold.
In the embodiment of the invention, after the fault occurs, the branch is disconnected, and after the fault is removed, the disconnected branch needs to be quickly recovered, so that the influence on the system is reduced. In order to realize quick recovery after a fault, the bus voltage of the transformer substation is detected in real time after the branch is disconnected, and when the bus voltage is recovered to be normal and the voltage difference and the phase angle difference between the bus voltage and the branch are within the allowable range, the conduction of the target disconnected branch is recovered.
Wherein, different recovery strategies are set according to different fault positions and types. If the fault is a single-phase fault and the fault position is on the power transmission line, judging the reclosing condition 1s after the branch is opened, and if the condition is met, reclosing the opened branch; in other cases (for example, the fault position is a transformer), the condition judgment is carried out after 0.2s after the branch is disconnected, and the disconnected branch is coincided when the condition is met, so that the disconnection time and the probability of the branch are reduced.
Fig. 3 is a control schematic diagram of an apparatus for limiting a short-circuit current according to an embodiment of the present invention. As shown in fig. 3, the apparatus specifically includes the following:
a control device: comprises a measuring module and a control module. And the measuring module acquires the bus voltage of the transformer substation, the current electrical quantity of the switch and the state of the switch equipment in real time. The control module is used for switching on and off the action of the device.
Quick cut-off device: and installing the transformer substation key branch according to the selection method. The cut-off device comprises two quick switches connected in series to ensure that reliable current limiting can still be achieved when a single switch is actuated.
The specific control strategy is as follows:
1) and in the normal running state of the system, the cut-off device is in the normal closed running state.
2) The control device monitors the current and the current of the transformer substation in real time, quickly judges faults, and sends a command to the on-off device to be switched off when the faults are judged and the on-off current of the breaker exceeds the standard due to the fault position and the type.
3) The relay protection of the system normally acts, and the conventional circuit breaker is switched on and off to remove the fault.
4) After the fault is removed, the control device judges whether a coincidence condition is met, and after the coincidence condition is met, the broken branch is coincided.
The effectiveness of the above-described device in breaking large short circuit currents was simulated using a typical system architecture. A typical system wiring principle is shown in fig. 4, in which the branch of line 1 is provided with a quick-disconnect device. When the system is in failure, the short-circuit current reaches 64kA at maximum. Exceeding the breaking capacity of 63kA of the prior circuit breaker. At this time, the conventional limiting measures include a shutdown of a part of the line, which has a great influence on the normal operation of the system.
By adopting the method, the short-circuit current levels of different branches are calculated when the transformer substation is in fault, the system stability is analyzed and calculated, and the switching-off device is installed on the branch of the line 1. When the system normally runs, the on-off device is in a closed state, and the normal running mode of the system is not influenced at the moment. When a transformer substation breaks down, after the control device detects the fault, the on-off device is firstly enabled to be rapidly switched off, the short-circuit current is limited, and the limited short-circuit current level is 58kA and is lower than the on-off short-circuit current level of the breaker by 63 kA.
The method can quickly cut off the key branch circuit which is connected with the fault point and provides the short-circuit current by quickly detecting the fault and judging the fault position after the short-circuit fault occurs in the system, thereby limiting the short-circuit current, reducing the level of the cut-off short-circuit current of the breaker of the system and ensuring the safety of the system and equipment.
Fig. 5 is a schematic structural diagram of a system 500 for limiting short-circuit current of a power system according to an embodiment of the present invention. As shown in fig. 5, a system 500 for limiting short-circuit current of an electrical power system according to an embodiment of the present invention includes: a fault determination unit 501, a short-circuit current exceeding judgment unit 502, a target open branch determination unit 503 and an action unit 504.
Preferably, the fault determining unit 501 is configured to obtain a switch current and a bus voltage of each switch in the substation, determine whether a ground fault occurs in the power system according to the switch current and the bus voltage, and determine a fault type and a fault location when a fault occurs.
Preferably, the fault determining unit 501, which determines whether a ground fault occurs in the power system according to the switching current and the bus voltage, and determines a fault type and a fault location when a fault occurs, includes: :
when the instantaneous value of the single-phase switching current is larger than or equal to a preset current instantaneous threshold, or the current rising rate exceeds a preset rising rate threshold, or the bus voltage is smaller than or equal to a preset bus voltage threshold, determining that a fault occurs, wherein the fault type is a single-phase fault;
when the three-phase switching current instantaneous value is greater than or equal to a preset current instantaneous threshold, or the current rise rate exceeds a preset rise rate threshold, or the bus voltage is less than or equal to a preset bus voltage threshold, determining that a fault occurs, wherein the fault type is a three-phase fault;
and determining the branch current of each branch according to the switching current, and comparing the direct current circuit with the preset first short-circuit current of each branch when different types of faults occur at different positions to determine the fault position.
Preferably, the short-circuit current exceeding judgment unit 502 is configured to compare the fault type and the fault position with a preset target fault type and a target fault position where a short-circuit current exceeds the standard when the switch is turned on or off, and determine whether a switch on-off short-circuit current exceeds the standard.
Preferably, wherein the system further comprises:
the second short-circuit current determining unit is used for establishing a simulation model according to the operation data of the power system, carrying out simulation calculation based on the simulation model and obtaining second short-circuit current of each switch when different types of faults occur at different positions;
and the target fault type and position determining unit is used for selecting the fault type and the fault position corresponding to the second short-circuit current which is greater than or equal to the preset second short-circuit current threshold as the target fault type and the target fault position with the switch-on short-circuit current exceeding the standard.
Preferably, the target open-close branch determining unit 503 is configured to, when it is determined that the switch open-close short-circuit current exceeds the standard, determine a target open-close branch according to the fault type, the fault location, and a preset open-close branch corresponding to the fault occurring at different locations.
Preferably, wherein the system further comprises: a broken branch determining unit for:
sorting the first short-circuit current of each branch in a descending order according to any type of fault at any position, determining a branch sequence, and initializing i to be 1;
selecting the ith branch in the branch sequence as a current key branch;
disconnecting the current key branch, and acquiring a third short-circuit current and a system stability level of the switch when different types of faults occur at different positions;
when the third short-circuit current is smaller than a third short-circuit current threshold value and the system stability is stable, determining the current key branch as the target cut-off branch; otherwise, updating i +1, and re-determining the current critical branch until the third short-circuit current is smaller than the third short-circuit current threshold and the system stability is stable, and determining that the current critical branch is the corresponding cut-off branch when any type of fault occurs at any position.
Preferably, wherein the system further comprises:
and the first short-circuit current determining unit is used for establishing a simulation model according to the operation data of the power system, carrying out simulation calculation based on the simulation model and obtaining the first short-circuit current of each branch circuit when different types of faults occur at different positions.
Preferably, the action unit 504 is configured to open the target open branch to limit the short-circuit current of the power system before the conventional circuit breaker completes the opening.
Preferably, wherein the system further comprises:
and the recovery unit is used for judging a coincidence condition after the fault is removed, and recovering the conduction of the target cut-off branch when the bus voltage is recovered to be normal.
Preferably, the recovery unit further comprises:
if the fault type is a single-phase fault and the fault position is a power transmission line, judging a coincidence condition after the disconnection time of the target disconnection branch reaches a first preset time threshold; otherwise, judging the coincidence condition after the breaking time of the target breaking branch reaches a second preset time threshold.
The system 500 for limiting short-circuit current of an electrical power system according to an embodiment of the present invention corresponds to the method 100 for limiting short-circuit current of an electrical power system according to another embodiment of the present invention, and is not described herein again.
The invention has been described with reference to a few embodiments. However, other embodiments of the invention than the one disclosed above are equally possible within the scope of the invention, as would be apparent to a person skilled in the art from the appended patent claims.
Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the [ device, component, etc ]" are to be interpreted openly as referring to at least one instance of said device, component, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.
Claims (14)
1. A method of limiting short circuit current in an electrical power system, the method comprising:
acquiring switch current and bus voltage of each switch in a transformer substation, judging whether a power system has a ground fault according to the switch current and the bus voltage, and determining a fault type and a fault position when the power system has the ground fault;
comparing the fault type and the fault position with a preset target fault type and a target fault position of which the short-circuit current exceeds the standard when the switch is switched on and switched off, and determining whether the switch on-off short-circuit current exceeds the standard or not;
when the fact that the on-off short-circuit current of the switch exceeds the standard is determined, matching is conducted according to the fault type, the fault position and the preset on-off branch corresponding to the situation that different types of faults occur at different positions, and a target on-off branch is determined;
before the conventional circuit breaker completes opening, the target opening branch is opened to limit the short-circuit current of the power system.
2. The method of claim 1, wherein the determining whether the power system has a ground fault according to the switch current and the bus voltage, and determining a fault type and a fault location when the fault occurs comprises: :
when the instantaneous value of the single-phase switching current is larger than or equal to a preset current instantaneous threshold, or the current rising rate exceeds a preset rising rate threshold, or the bus voltage is smaller than or equal to a preset bus voltage threshold, determining that a fault occurs, wherein the fault type is a single-phase fault;
when the three-phase switching current instantaneous value is greater than or equal to a preset current instantaneous threshold, or the current rise rate exceeds a preset rise rate threshold, or the bus voltage is less than or equal to a preset bus voltage threshold, determining that a fault occurs, wherein the fault type is a three-phase fault;
and determining the branch current of each branch according to the switching current, and comparing the direct current circuit with the preset first short-circuit current of each branch when different types of faults occur at different positions to determine the fault position.
3. The method of claim 1, further comprising:
establishing a simulation model according to the operation data of the power system, and carrying out simulation calculation based on the simulation model to obtain a second short-circuit current of each switch when different types of faults occur at different positions;
and selecting the fault type and the fault position corresponding to the second short-circuit current which is greater than or equal to the preset second short-circuit current threshold as the target fault type and the target fault position of the switch with the switching-on short-circuit current exceeding the standard.
4. The method of claim 1, further comprising:
sorting the first short-circuit current of each branch in a descending order according to any type of fault at any position, determining a branch sequence, and initializing i to be 1;
selecting the ith branch in the branch sequence as a current key branch;
disconnecting the current key branch, and acquiring a third short-circuit current and a system stability level of the switch when different types of faults occur at different positions;
when the third short-circuit current is smaller than a third short-circuit current threshold value and the system stability is stable, determining the current key branch as the target cut-off branch; otherwise, updating i +1, and re-determining the current critical branch until the third short-circuit current is smaller than the third short-circuit current threshold and the system stability is stable, and determining that the current critical branch is the corresponding cut-off branch when any type of fault occurs at any position.
5. The method according to claim 2 or 4, characterized in that the method further comprises:
and establishing a simulation model according to the operation data of the power system, and carrying out simulation calculation based on the simulation model to obtain the first short-circuit current of each branch circuit when different types of faults occur at different positions.
6. The method of claim 1, further comprising:
and when the fault is removed, judging the coincidence condition, and when the bus voltage is recovered to be normal, recovering the conduction of the target cut-off branch.
7. The method of claim 6, further comprising:
if the fault type is a single-phase fault and the fault position is a power transmission line, judging a coincidence condition after the disconnection time of the target disconnection branch reaches a first preset time threshold; otherwise, judging the coincidence condition after the breaking time of the target breaking branch reaches a second preset time threshold.
8. A system for limiting short circuit current in an electrical power system, the system comprising:
the fault determining unit is used for acquiring the switch current and the bus voltage of each switch in the transformer substation, judging whether the power system has a ground fault according to the switch current and the bus voltage, and determining the fault type and the fault position when the power system has the ground fault;
the short-circuit current exceeding judging unit is used for comparing the fault type and the fault position with a preset target fault type and a target fault position where the short-circuit current exceeds the standard when the switch is switched on and switched off, and determining whether the switch on-off short-circuit current exceeds the standard or not;
the target cut-off branch determining unit is used for matching the corresponding cut-off branches when the fact that the on-off short-circuit current exceeds the standard is determined, and determining the target cut-off branch according to the fault type, the fault position and the preset cut-off branches when different types of faults occur at different positions;
and the action unit is used for disconnecting the target cut-off branch circuit before the conventional circuit breaker completes the opening so as to limit the short-circuit current of the power system.
9. The system of claim 8, wherein the fault determination unit determines whether a ground fault occurs in the power system according to the switching current and the bus voltage, and determines a fault type and a fault location when a fault occurs, including: :
when the instantaneous value of the single-phase switching current is larger than or equal to a preset current instantaneous threshold, or the current rising rate exceeds a preset rising rate threshold, or the bus voltage is smaller than or equal to a preset bus voltage threshold, determining that a fault occurs, wherein the fault type is a single-phase fault;
when the three-phase switching current instantaneous value is greater than or equal to a preset current instantaneous threshold, or the current rise rate exceeds a preset rise rate threshold, or the bus voltage is less than or equal to a preset bus voltage threshold, determining that a fault occurs, wherein the fault type is a three-phase fault;
and determining the branch current of each branch according to the switching current, and comparing the direct current circuit with the preset first short-circuit current of each branch when different types of faults occur at different positions to determine the fault position.
10. The system of claim 8, further comprising:
the second short-circuit current determining unit is used for establishing a simulation model according to the operation data of the power system, carrying out simulation calculation based on the simulation model and obtaining second short-circuit current of each switch when different types of faults occur at different positions;
and the target fault type and position determining unit is used for selecting the fault type and the fault position corresponding to the second short-circuit current which is greater than or equal to the preset second short-circuit current threshold as the target fault type and the target fault position with the switch-on short-circuit current exceeding the standard.
11. The system of claim 8, further comprising: a broken branch determining unit for:
sorting the first short-circuit current of each branch in a descending order according to any type of fault at any position, determining a branch sequence, and initializing i to be 1;
selecting the ith branch in the branch sequence as a current key branch;
disconnecting the current key branch, and acquiring a third short-circuit current and a system stability level of the switch when different types of faults occur at different positions;
when the third short-circuit current is smaller than a third short-circuit current threshold value and the system stability is stable, determining the current key branch as the target cut-off branch; otherwise, updating i +1, and re-determining the current critical branch until the third short-circuit current is smaller than the third short-circuit current threshold and the system stability is stable, and determining that the current critical branch is the corresponding cut-off branch when any type of fault occurs at any position.
12. The system according to claim 9 or 11, characterized in that the system further comprises:
and the first short-circuit current determining unit is used for establishing a simulation model according to the operation data of the power system, carrying out simulation calculation based on the simulation model and obtaining the first short-circuit current of each branch circuit when different types of faults occur at different positions.
13. The system of claim 8, further comprising:
and the recovery unit is used for judging a coincidence condition after the fault is removed, and recovering the conduction of the target cut-off branch when the bus voltage is recovered to be normal.
14. The system of claim 13, wherein the recovery unit further comprises:
if the fault type is a single-phase fault and the fault position is a power transmission line, judging a coincidence condition after the disconnection time of the target disconnection branch reaches a first preset time threshold; otherwise, judging the coincidence condition after the breaking time of the target breaking branch reaches a second preset time threshold.
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| CN202210102479.4A CN114512968A (en) | 2022-01-27 | 2022-01-27 | Method and system for limiting short-circuit current of power system |
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| CN202210102479.4A CN114512968A (en) | 2022-01-27 | 2022-01-27 | Method and system for limiting short-circuit current of power system |
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