CN114019417B - Line protection current loop neutral line open circuit detection method - Google Patents
Line protection current loop neutral line open circuit detection method Download PDFInfo
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- CN114019417B CN114019417B CN202111317427.0A CN202111317427A CN114019417B CN 114019417 B CN114019417 B CN 114019417B CN 202111317427 A CN202111317427 A CN 202111317427A CN 114019417 B CN114019417 B CN 114019417B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/54—Testing for continuity
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/20—Systems supporting electrical power generation, transmission or distribution using protection elements, arrangements or systems
Abstract
The invention provides a method for detecting open circuit of a neutral line of a circuit protection current loop, which comprises the following steps: the circuit breaker is characterized in that each group of side circuit breakers and middle circuit breakers in the extra-high voltage circuit are provided with a group of circuit protection devices, a current transformer is arranged in each circuit protection device, sampling circuits are respectively taken from different secondary windings of the current transformer to form sampling signals, the signals are stored in storage blocks of corresponding storage units according to different attributes of the sampling signals and are sent to a processing module in real time, the processing module is provided with a plurality of processing units, each processing unit respectively processes the sampling signals to determine triggering conditions of abnormal circuit states, the triggering conditions have at least one state causing circuit abnormality, and finally a judging module judges whether open circuit faults of the neutral line occur or not, and determines the reasons of the open circuit faults of the neutral line based on at least one state causing circuit abnormality.
Description
Technical Field
The invention relates to the technical field of open circuit detection of a neutral line of a line protection current loop, in particular to a method for detecting the open circuit of the neutral line of the line protection current loop.
Background
With the rapid development of high-voltage direct-current transmission and the continuous increase of the grid-connected scale of new energy such as wind power, photovoltaic and the like, the electronization characteristics of the power grid are increasingly obvious, the operating characteristics of the power grid are obviously changed, and higher requirements are put forward on the reliable operation of relay protection. The current differential protection is the preferred main protection of the extra-high voltage line with the advantages of good selectivity, high sensitivity, no influence of system oscillation and the like. The operation practice shows that the performance of the current differential protection action is closely related to the reliability of a current loop.
The judgment of the open circuit of the current loop is an important measure for improving the reliability of differential protection. The differential protection at two sides is required to be started at the same time to allow the outlet to trip, so that the problem of false operation of the differential protection when a certain phase of a current loop is disconnected is well solved, but the problem of judging open circuit of a neutral line cannot be effectively solved all the time. Because the open circuit of the neutral line has strong concealment and high safety risk, the incorrect action of the relay protection caused by the open circuit of the neutral line occurs on site for many times, and becomes a key factor influencing the reliability of the relay protection.
After the development of more than ten years, the relay protection fault information system has been generally applied to the ultrahigh-voltage station, and the online monitoring and wave recording online analysis of the relay protection equipment are realized. The system connects various secondary devices such as relay protection devices, fault oscillographs and the like into an industrial Internet of things, lays a solid foundation for sharing and application of power grid fault information, and is used for relay protection state maintenance in the industry. The deepened application of the system creates favorable conditions for improving relay protection management, technology and operation level.
Currently, there are two wiring methods for the line protection current loop, as shown in fig. 1 and 2. The other is that A, B, C, N four wires from the secondary side terminal of the current transformer of the side and breaker are respectively connected in parallel to form current at the terminal row of the local control cubicle, and then are sequentially connected to the line protection and fault recording device. For analytical convenience, this is referred to herein as the first type of wiring. In recent engineering, secondary currents of edge and interrupt devices are respectively introduced into a line for protection, and are connected in parallel at a terminal block of a protection screen and then connected into a fault recording device, which is called as a second type of wiring. The second type of wiring line protection can collect each set of breaker current and thus can be used for protection performance improvement, while the first type of wiring cannot.
The zero sequence current passes through the neutral line loop to form a path. The neutral line loop is a whole, and any link is abnormal, so that the open circuit or poor contact of the loop is caused, the transmission and the transformation of the zero-sequence current are influenced, and the accuracy of the secondary current is further influenced. The zero sequence current comprises an external connection mode and a self-generating mode, the external connection mode and the self-generating mode are adopted, the external connection mode is obtained by sampling the neutral line current of the current loop, the sampling three-phase current is obtained by adding software, and the external connection mode and the self-generating mode are both used in line protection.
Open circuit of the neutral line of the current loop can cause that the three-phase and zero-sequence currents measured by the protection device during the earth fault do not accord with the actual conditions, thereby causing incorrect action of line protection. The current line protection mainly comprises the functions of differential protection, distance protection, zero-sequence current protection and the like.
When the area is out of the ground, no matter a branch circuit or a neutral line of the branch circuit or the neutral line of the loop is open, the current measured by the protection device on the side can not truly reflect primary current, so that differential current occurs, and the differential protection malfunction can be caused after the differential current reaches a fixed value. When a single-phase fault occurs in a zone, the open circuit of a neutral line of a branch circuit or a sum circuit can cause the non-fault phase current of the current side to be inconsistent with the actual value, so that the differential protection mistakenly jumps three phases due to the phase selection error.
In order to prevent misoperation in case of external fault, the grounding distance protection is locked by zero sequence current. When the ground fault occurs in the area, the zero sequence current measured by the protection device is zero due to the open circuit with the neutral line of the loop, and the protection action condition is not met, so that the ground distance protection is refused to operate. The open circuit of the neutral line of the branch circuit can affect the accuracy of the zero sequence current measured by the protection device, and may cause the distance protection to malfunction when the distance protection is out of the zone and the earth fault or to fail when the distance protection is in the zone and the earth fault.
And the neutral line of the loop is opened, so that the zero sequence current measured by the protection device is zero, and the zero sequence current protection is refused to operate when the grounding fault occurs in the zone. The open circuit of the neutral line of the branch circuit can lead the zero sequence current of the line not to be transmitted and changed accurately, and can cause the failure of the zero sequence current protection when the earth fault exists in the region or the misoperation when the earth fault exists outside the region.
Disclosure of Invention
In view of the above, the main objective of the present invention is to provide a method for detecting open circuit of a neutral line in a line protection current loop.
The technical scheme adopted by the invention is as follows:
the method for detecting the open circuit of the neutral line of the line protection current loop judges the loop integrity by comparing the currents of double protection devices which are arranged in a dual mode.
The method comprises the following steps: each group of side circuit breakers and middle circuit breakers in the extra-high voltage line are provided with a group of line protection devices, current transformers are arranged in the line protection devices, sampling circuits are respectively taken from different secondary windings of the current transformers to form sampling signals,
establishing a classification label by utilizing the geographical position of each group of side circuit breakers and middle circuit breakers in the ultrahigh voltage line, the sampling relation and the sampling mode of a group of current transformers correspondingly arranged at each group of side circuit breakers and middle circuit breakers, and the attribute of each group of current transformers, and correspondingly writing the classification label into the attribute of the formed sampling signal;
and then the sampling signals are correspondingly stored in a storage block of the storage unit according to the attributes of the sampling signals and are sent to a processing module in real time, the processing module is provided with a plurality of processing units and a judging module, each processing unit processes the sampling signals to determine a triggering condition of a line abnormal state, the triggering condition comprises at least one state causing the line abnormal, and the judging module determines the reason of the fault of the open circuit of the neutral line according to the at least one state causing the line abnormal.
Furthermore, each group of side circuit breakers and middle circuit breaker are provided with a positioning device, when the sampling circuit is respectively taken from different secondary windings of the current transformer to form a sampling signal, the sampling circuit simultaneously sends a linkage signal to the positioning device, and corresponding positioning information is also obtained while the sampling signal is obtained.
Further, the state causing the line abnormality is configured to determine a trigger condition of the line abnormality state in accordance with a set first calculation section or in accordance with a set second calculation section.
Furthermore, the first calculating part obtains the sampling signal through the current loop, and the first calculating part determines the triggering condition of the abnormal state of the line according to the sampling signal obtained by the current loop.
Furthermore, the second calculating part obtains the sampling signal through the sampling circuit, and the second calculating part determines the triggering condition of the abnormal state of the line according to the sampling signal obtained by the sampling circuit.
Further, the sampling circuit has one or more identification features, and one or more sampling units are executed by using the one or more identification features to sample different secondary windings of the corresponding current transformer in real time.
Further, the identification feature has:
a plurality of tags having different attributes;
having an associated information list containing and storing tags;
the linkage unit is provided, and loads one or more labels with different attributes when one or more sampling units are executed, and samples different secondary windings of corresponding current transformers in real time; the linkage unit simultaneously sends linkage signals to the positioning device, and acquires corresponding positioning information while acquiring the sampling signals.
And calling current data sampled by the double-set protection devices of all lines of the total station after the power grid fails. And then, the collected zero sequence current is judged line by line. When the inconsistency of the zero sequence currents of the double protection devices of a certain line is detected, alarm information is sent immediately to prompt operating personnel that the open circuit risk exists in the neutral line of the line protection current loop, and the maintenance personnel should be informed as soon as possible to arrange to eliminate the fault, so that the potential safety hazard is eliminated in time.
Drawings
The invention is illustrated and described only by way of example and not by way of limitation in the scope of the invention as set forth in the following drawings, in which:
FIG. 1 is a schematic diagram of a protection current loop for a first type of wiring line;
FIG. 2 is a schematic diagram of a protection current loop of a second type of wiring line;
FIG. 3 is a comparison of two sets of line protection measurement currents of the present invention;
FIG. 4 is a comparison of two sets of line protection measurement currents in accordance with the present invention;
FIG. 5 is a flow chart of the method of the present invention.
Detailed Description
In order to make the objects, technical solutions, design methods, and advantages of the present invention more apparent, the present invention will be further described in detail by specific embodiments with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
After the power system breaks down, the adjacent line protection is started and fault recording is carried out. The recording data includes information such as alternating current, alternating voltage and switching value input, which are obtained through a relevant secondary circuit. The data can be used for judging the operation condition and the fault property of the power grid, and can also be used for relay protection and online monitoring of related secondary circuits. The fault recording data is deeply excavated and fully utilized, and a new method is provided for timely discovering the defects of relay protection and related secondary circuits.
To prevent false activation in case of an out-of-range fault, conventional differential protection employs a rate braking characteristic and has an activation threshold. When the neutral line is open and a ground fault occurs outside the area, the differential protection detects unbalanced current, and the differential protection malfunctions only when the unbalanced current exceeds a certain range. This creates conditions for checking the correctness of the current loop by using the line protection recording data in case of external fault.
The protection of the extra-high voltage line is configured according to a dual principle, each set of protection current is taken from different secondary windings of the current transformer, and current loops are completely independent. When the power grid fails, the integrity of A, B, C and the N loop can be judged by calling two sets of current sampling values of the protection device of the same line and comparing the three-phase current and the zero-sequence current respectively. The present document focuses on neutral circuits, and therefore, zero sequence currents are mainly used for discrimination. Under the condition that the neutral line of the current loop is correctly wired, two sets of protection zero sequence current sampling values of the same line are identical, and the difference between the two zero sequence current sampling values does not exceed 10% in consideration of measurement errors. When the difference of the two sets of protection zero sequence currents exceeds a certain value, the open circuit of one set of protection neutral line can be judged by combining other information.
Referring to fig. 5, the technical scheme adopted by the invention is as follows:
a method for detecting open circuit of neutral line in circuit protection current loop,
the method comprises the following steps: each group of side circuit breakers and middle circuit breakers in the extra-high voltage line are provided with a group of line protection devices, current transformers are arranged in the line protection devices, sampling circuits are respectively taken from different secondary windings of the current transformers to form sampling signals,
establishing a classification label by utilizing the geographical position of each group of side circuit breakers and middle circuit breakers in the ultrahigh voltage line, the sampling relation and the sampling mode of a group of current transformers correspondingly arranged at each group of side circuit breakers and middle circuit breakers, and the attribute of each group of current transformers, and correspondingly writing the classification label into the attribute of the formed sampling signal;
and then the sampling signals are correspondingly stored in a storage block of the storage unit according to the attributes of the sampling signals and are sent to a processing module in real time, the processing module is provided with a plurality of processing units and a judging module, each processing unit processes the sampling signals to determine a triggering condition of a line abnormal state, the triggering condition comprises at least one state causing the line abnormal, and the judging module determines the reason of the fault of the open circuit of the neutral line according to the at least one state causing the line abnormal.
Furthermore, each group of side circuit breakers and middle circuit breakers are provided with positioning devices, when sampling circuits are respectively taken from different secondary windings of the current transformer to form sampling signals, the sampling circuits simultaneously send linkage signals to the positioning devices, and corresponding positioning information is also acquired while the sampling signals are acquired.
Further, the state causing the line abnormality is configured to determine a trigger condition of the line abnormality state in accordance with a set first calculation section or in accordance with a set second calculation section.
Further, the first calculating part obtains the sampling signal through the current loop, and the first calculating part determines the trigger condition of the abnormal state of the line according to the sampling signal obtained by the current loop.
Furthermore, the second calculating part obtains the sampling signal through the sampling circuit, and the second calculating part determines the triggering condition of the abnormal state of the line according to the sampling signal obtained by the sampling circuit.
Further, the sampling circuit has one or more identification features, and one or more sampling units are executed by using the one or more identification features to sample different secondary windings of the corresponding current transformer in real time.
Further, the identification feature has:
a plurality of tags having different attributes;
having an associated information list containing and storing tags;
the linkage unit is provided, and loads one or more labels with different attributes when one or more sampling units are executed, and samples different secondary windings of corresponding current transformers in real time; the linkage unit simultaneously sends linkage signals to the positioning device, and acquires corresponding positioning information while acquiring the sampling signals.
Based on the above scheme, in practical application, the method for identifying the open circuit of the neutral line of the current loop comprises the following steps:
|Ih1-Ih2|≥ε(1)
in the formula Ih1、Ih2Zero sequence currents of 2 groups of line protection devices 1 and 2 arranged at each group of side circuit breakers and middle circuit breakers in the extra-high voltage line are respectively provided. For the first calculation section, the current is obtained through a sum current loop; for the second calculation part, the current is calculated through two groups of breaker zero-sequence currentsAnd obtaining the compound. ε is the threshold value, and 0.15A is taken to account for sampling errors.
When the formula (1) is satisfied, the open circuit defect of the neutral line of the current loop exists in a certain set of protection of the circuit.
The first calculation unit cannot obtain two sets of breaker currents in line protection, and cannot distinguish a branch circuit or an open circuit with a neutral line of the circuit due to the limitation of current information.
For the second calculation part, the line protection can collect two groups of breaker currents, and the following criterion can be further constructed
|Is1-Is2|≥ε (2)
|Im1-Im2|≥ε (3)
In the formula Is1、Is2，Im1、Im2Zero sequence currents input to the line protection 1 and 2 are respectively input to the edge breaker and the interrupt breaker CT.
And when the formula (2) or (3) is met, judging the circuit breaker to be an edge circuit breaker or a middle circuit breaker branch circuit neutral line open circuit respectively.
Fig. 2 and fig. 3 show zero sequence current comparisons of two protection devices in a line in the case of two-start neutral open circuits. Obviously, the method can accurately judge the open circuit of the neutral line of the current loop.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen in order to best explain the principles of the embodiments, the practical application, or improvements made to the technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.
Claims (7)
1. The method for detecting the open circuit of the neutral line of the line protection current loop is characterized by comprising the following steps: each group of side circuit breakers and middle circuit breakers in the ultrahigh voltage line are provided with a group of line protection devices, current transformers are arranged in the line protection devices, sampling circuits are respectively taken from different secondary windings of the current transformers to form sampling signals,
establishing a classification label by utilizing the geographical position of each group of side circuit breakers and middle circuit breakers in the ultrahigh voltage line, the sampling relation and the sampling mode of a group of current transformers correspondingly arranged at each group of side circuit breakers and middle circuit breakers, and the attribute of each group of current transformers, and correspondingly writing the classification label into the attribute of the formed sampling signal;
and then the sampling signals are correspondingly stored in a storage block of the storage unit according to the attributes of the sampling signals and are sent to a processing module in real time, the processing module is provided with a plurality of processing units and a judging module, each processing unit processes the sampling signals to determine a triggering condition of a line abnormal state, the triggering condition comprises at least one state causing the line abnormal, and the judging module determines the reason of the fault of the open circuit of the neutral line according to the at least one state causing the line abnormal.
2. The method according to claim 1, wherein each group of side breakers and middle breakers is provided with a positioning device, and when the sampling circuits are respectively obtained from different secondary windings of the current transformer to form sampling signals, the sampling circuits simultaneously transmit linkage signals to the positioning devices, and obtain the sampling signals and corresponding positioning information.
3. The line protection current circuit neutral open circuit detection method according to claim 1, wherein the state causing the line abnormality is configured to determine a trigger condition of the line abnormality state in accordance with a set first calculation section or in accordance with a set second calculation section.
4. The method as claimed in claim 3, wherein the first calculating portion obtains the sampling signal through the current loop, and the first calculating portion determines the triggering condition of the abnormal line state according to the sampling signal obtained by the current loop.
5. The method as claimed in claim 3, wherein the second calculating portion obtains the sampling signal through a sampling circuit, and the second calculating portion determines the trigger condition of the abnormal line state according to the sampling signal obtained by the sampling circuit.
6. The method of claim 1, wherein the sampling circuit has one or more identification features, and wherein the one or more sampling units are implemented using the one or more identification features to sample different secondary windings of the corresponding current transformers in real time.
7. The line protection current loop neutral open circuit detection method of claim 6, wherein said identification feature comprises:
a plurality of tags having different attributes;
having an associated information list containing and storing tags;
the linkage unit is provided, and loads one or more labels with different attributes when one or more sampling units are executed, and samples different secondary windings of corresponding current transformers in real time; the linkage unit simultaneously sends linkage signals to the positioning device, and acquires corresponding positioning information while acquiring the sampling signals.
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