CN111812452B - CT polarity self-correction method and system for low-current grounding line selection device - Google Patents
CT polarity self-correction method and system for low-current grounding line selection device Download PDFInfo
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- CN111812452B CN111812452B CN202010527515.2A CN202010527515A CN111812452B CN 111812452 B CN111812452 B CN 111812452B CN 202010527515 A CN202010527515 A CN 202010527515A CN 111812452 B CN111812452 B CN 111812452B
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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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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/175—Indicating the instants of passage of current or voltage through a given value, e.g. passage through zero
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/52—Testing for short-circuits, leakage current or ground faults
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- 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
- G01R31/72—Testing of electric windings
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
- G01R35/02—Testing or calibrating of apparatus covered by the other groups of this subclass of auxiliary devices, e.g. of instrument transformers according to prescribed transformation ratio, phase angle, or wattage rating
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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
- Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
- Y04S10/52—Outage or fault management, e.g. fault detection or location
Abstract
The invention discloses a CT polarity self-correction method and a system for a low-current grounding line selection device, which comprises the following steps: acquiring the transient and steady state information of zero sequence current of each branch circuit in a single-phase earth fault state; determining a suspected fault line according to the transient and stable state information of the zero-sequence current of each branch; performing a trip operation on the suspected faulty line; correcting the CT polarity of the suspected fault line according to the tripping operation result; acquiring zero-sequence current transient data of a suspected fault line after tripping operation; judging whether the zero-sequence current steady-state value of each branch except the suspected fault line is larger than an effective measurement threshold value or not, and if so, calculating the direction coefficient of each branch except the suspected fault line and the suspected fault line according to the zero-sequence current transient data of the suspected fault line; and correcting the CT polarity of each branch except the suspected fault line according to the direction coefficient. The invention realizes CT polarity self-correction based on a mode of adopting zero sequence CT to collect zero sequence current of each branch, and is convenient to operate.
Description
Technical Field
The invention relates to the technical field of low-current grounding systems, in particular to a CT polarity self-correction method and system for a low-current grounding line selection device.
Background
The faults of the power distribution network in the whole power system are the most, wherein the single-phase earth faults are the most, the total number of the faults is more than 80%, and the fault line can be correctly judged and isolated after the single-phase earth faults occur, so that the novel small-current earth line selection device with the tripping function is particularly important, and is gradually widely applied to the power distribution network.
At present, small current grounding line selection methods are various, but the principle mainly includes an active method and a passive method, wherein the active method needs to be additionally provided with signal injection equipment, and judgment is carried out by utilizing the variable quantity or threshold value of zero sequence current of each branch; the passive method mainly depends on voltage and current analog quantity signals acquired by the device, and utilizes the amplitude comparison of zero sequence current of each branch circuit or the relation between the zero sequence current of the bus to analyze so as to judge the fault line. However, no matter which line selection principle is adopted, whether the polarity of the zero sequence CT is correct or not directly influences the line selection accuracy of the small-current grounding line selection device.
In view of the characteristic that the zero sequence current value is very small when the system normally operates, the polarity of the CT cannot be accurately judged through actually measured information of the device, and the consistency check of the polarity of the zero sequence CT is not allowed to be carried out on the power failure of the switch cabinet under a plurality of conditions on site, so that the polarities of signals collected by the device cannot be unified directly, and the accuracy rate of line selection is influenced.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a CT polarity self-correction method and a CT polarity self-correction system for a low-current grounding line selection device, so as to solve the problem that the CT polarity is difficult to check in the prior art.
In order to achieve the technical purpose, the invention adopts the technical scheme that:
a small current grounding line selection device CT polarity self-correction method comprises the following steps:
acquiring the transient and steady state information of zero sequence current of each branch circuit in a single-phase earth fault state;
determining a suspected fault line according to the transient and stable state information of the zero sequence current of each branch;
performing a trip operation on the suspected fault line;
correcting the CT polarity of the suspected fault line according to the tripping operation result;
acquiring zero-sequence current transient data of a suspected fault line after tripping operation;
judging whether the zero-sequence current steady-state value of each branch except the suspected fault line is larger than an effective measurement threshold value or not, and if so, calculating the direction coefficient of each branch except the suspected fault line and the suspected fault line according to the zero-sequence current transient data of the suspected fault line;
and correcting the CT polarity of each branch except the suspected fault line according to the direction coefficient.
Further, the CT polarity correction method for the suspected faulty line includes:
and judging whether the ground fault of the suspected fault line disappears after the tripping operation, if so, correcting the CT polarity, and if not, modifying the CT polarity parameter of the fault line, and correcting the CT polarity.
Further, the method for acquiring the transient data of the zero sequence current of the suspected fault line includes:
and judging whether the earth fault disappears after the tripping operation, if so, acquiring zero sequence current transient data of the suspected fault line, otherwise, acquiring actual zero sequence current transient data of the suspected fault line and taking the actual zero sequence current transient data as the zero sequence current transient data required to be acquired after negation.
Further, the calculation formula of the directional coefficient is as follows:
in the formula (I), the compound is shown in the specification,DCoethe directional coefficients of branch i and branch k,
is the zero sequence current transient data of the branch circuit i,
the transient state data of the zero sequence current of the branch k is shown, and N is the length of a transient state data window.
Further, the method for correcting the CT polarity of each branch except the suspected faulty line is as follows:
for any branch outside the suspected fault line, if the direction coefficient is smaller than 0, the CT polarity of the branch is correct without correction; if the direction coefficient is larger than 0, the CT polarity of the branch is wrong, the CT polarity parameters are modified, and the CT polarity of the branch is corrected.
A low current ground selection CT polarity self-correction system, the system comprising:
a first acquisition module: the method comprises the steps of obtaining transient and steady state information of zero sequence current of each branch circuit in a single-phase earth fault state;
a confirmation module: the system is used for determining a suspected fault line according to the transient and steady state information of the zero sequence current of each branch;
an execution module: the system is used for performing a tripping operation on the suspected fault line; (ii) a
A first correction module: the CT polarity correction module is used for correcting the CT polarity of the suspected fault line according to the tripping operation result;
a second obtaining module: the method comprises the steps of obtaining zero sequence current transient data of a suspected fault line after tripping operation;
a judging module: the method is used for judging whether the zero-sequence current steady-state value of each branch except the suspected fault line is larger than an effective measurement threshold value or not, and if so, calculating the direction coefficient of each branch except the suspected fault line and the suspected fault line according to the zero-sequence current transient data of the suspected fault line;
a second correction module: and the CT polarity correction module is used for correcting the CT polarity of each branch except the suspected fault line according to the direction coefficient.
A low current grounded line selector CT polarity self-correction system, the system comprising a processor and a storage medium;
the storage medium is used for storing instructions;
the processor is configured to operate according to the instructions to perform the steps of the method described above.
A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of the method as described above.
Compared with the prior art, the invention has the following beneficial technical effects:
on the premise of executing tripping operation after single-phase earth fault, the fault line is used as CT standard polarity, the relation between the zero sequence current steady state value of each branch and an effective measurement threshold value is firstly compared, then the zero sequence current transient state quantity direction of each branch and the fault line is transversely contrasted and analyzed, whether the CT polarity of each branch is correct or not is judged, and CT polarity self-correction is realized; the invention does not need to check the polarity consistency of zero sequence CT when the switch cabinet is powered off, and is suitable for small current grounding systems, including a neutral point ungrounded system and a resonance grounding system.
Drawings
Fig. 1 is a zero sequence current transient characteristic curve of a single-phase earth fault of a small current grounding system;
fig. 2 is a logic flow diagram of a CT polarity self-correction method of a low-current grounding line selection device.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
According to theoretical analysis, when a single-phase earth fault occurs in a small-current grounding system, the transient state quantity of the zero-sequence current is not affected by the compensation of the inductance current of the arc suppression coil, and the transient direction of the zero-sequence current of a fault line is always opposite to that of a non-fault line. Taking a single-phase grounding fault of the line 1 as an example, a zero-sequence current transient characteristic curve generated in the single-phase grounding process is shown in fig. 1, and the transient characteristics of the zero-sequence current collected by the CT1# on the fault line and the CT2# and the CT3# on the non-fault line are not similar, and the directions are approximately opposite; the transient characteristics of the zero sequence currents collected by the CT2# and the CT3# on the non-fault line are similar, and the directions are the same.
As shown in fig. 2, a method for self-correcting the CT polarity of a low-current grounding line selection device includes the following steps:
the method comprises the following steps: when the system has single-phase earth fault, the transient and steady state information of the zero sequence current of each branch is obtained
；
Step two: judging a suspected fault line according to the transient and steady state information of the zero sequence current, and executing tripping operation on the suspected fault line k, and opening a switch of the line k;
step three: if the grounding fault disappears after the switch of the line k is opened, the line k is shown as an actual fault line, the CT polarity is correct, and the zero sequence current transient data of the line k is taken
(ii) a If the grounding fault does not disappear after the switch of the line k is opened, the line k is represented as a non-fault line, the CT polarity is wrong, the CT polarity parameter is modified, and the zero sequence current transient data of the line k is inverted, namely
；
Step four: judging the zero sequence current steady state value of each branch
Whether or not it is greater than the effective measurement threshold value
；
Step five: when branch i zero sequence current steady state value
Then, taking branch k as the standard polarity of CT, and carrying out transverse contrastive analysis on transient state information of branch i and branch k, wherein the formula is as follows:
in the formulaDCoeThe coefficients of the direction of the branch i and the branch k,
is the zero sequence current transient data of the branch circuit i,
the zero sequence current transient data of the branch k is obtained, and N is the length of a transient data window;
if the steady state value of the zero sequence current of the branch i is not more than the effective measurement threshold value
If so, the polarity of the CT of the branch is not judged and corrected.
Step six: according to the direction coefficients of the branch i and the branch k, the automatic correction of the polarity of the branch CT is realized:
(A1) Coefficient of current directionDCoeWhen the current is less than 0, the polarity of the CT of the i branch is correct;
(A2) Coefficient of current directionDCoeAnd when the current is more than 0, the CT polarity of the i branch is wrong, and the CT polarity parameter is modified.
A low current ground selection CT polarity self-correction system, the system comprising:
a first obtaining module: the fault line acquisition module is used for acquiring fault lines in each branch;
an execution module: for performing a trip operation on the faulty line;
a first correction module: the CT polarity correction module is used for correcting the CT polarity of the fault line according to the tripping operation result;
a second obtaining module: the fault circuit transient state quantity acquisition module is used for acquiring the transient state quantity of a fault circuit after tripping operation;
a judging module: the method is used for judging whether the zero sequence current steady state value of each branch outside the fault line is larger than an effective measurement threshold value or not, and if so, calculating the direction coefficients of each branch outside the fault line and the fault line according to the transient state quantity of the fault line;
a second correction module: and the CT polarity of each branch except the fault line is corrected according to the direction coefficient.
A low current grounded line selector CT polarity self-correction system, the system comprising a processor and a storage medium;
the storage medium is to store instructions;
the processor is configured to operate according to the instructions to perform the steps of the method described above.
A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of the method described above.
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 flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations 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.
While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (4)
1. A CT polarity self-correcting method of a small current grounding line selection device is characterized by comprising the following steps:
acquiring the transient and steady state information of zero sequence current of each branch circuit in a single-phase earth fault state;
determining a suspected fault line according to the transient and stable state information of the zero sequence current of each branch;
performing a trip operation on the suspected fault line;
correcting the CT polarity of the suspected fault line according to the tripping operation result;
acquiring zero-sequence current transient data of a suspected fault line after tripping operation;
judging whether the zero-sequence current steady-state value of each branch except the suspected fault line is larger than an effective measurement threshold value or not, and if so, calculating the direction coefficient of each branch except the suspected fault line and the suspected fault line according to the zero-sequence current transient data of the suspected fault line;
correcting the CT polarity of each branch except the suspected fault line according to the direction coefficient;
the CT polarity correction method for the suspected fault line comprises the following steps:
judging whether the ground fault of the suspected fault line disappears after the tripping operation, if so, determining that the CT polarity is correct without correction, otherwise, modifying the CT polarity parameter of the suspected fault line and correcting the CT polarity;
the method for acquiring the zero-sequence current transient data of the suspected fault line comprises the following steps:
judging whether the earth fault disappears after the tripping operation, if so, acquiring zero sequence current transient data of the suspected fault line, otherwise, acquiring actual zero sequence current transient data of the suspected fault line and taking the actual zero sequence current transient data as the zero sequence current transient data required to be acquired after negation;
the calculation formula of the direction coefficient is as follows:
in the formula, DCoe is the direction coefficient of branch I and branch k, I t_i For branch I zero-sequence current transient data, I t_k The transient data of the zero sequence current of the branch k is obtained, and N is the length of a transient data window;
the CT polarity correction method of each branch except the suspected fault line is as follows:
for any branch outside the suspected fault line, if the direction coefficient is smaller than 0, the CT polarity of the branch is correct without correction; if the direction coefficient is larger than 0, the CT polarity of the branch is wrong, the CT polarity parameter is modified, and the CT polarity of the branch is corrected.
2. A small current grounding line selection device CT polarity self-correction system is characterized by comprising:
a first acquisition module: the method comprises the steps of obtaining transient and steady state information of zero sequence current of each branch circuit in a single-phase earth fault state;
the fault line initial judgment module: the system is used for determining a suspected fault line according to the transient and steady state information of the zero sequence current of each branch;
an execution module: the system is used for performing a tripping operation on the suspected fault line;
a first correction module: the CT polarity correction module is used for correcting the CT polarity of the suspected fault line according to the tripping operation result;
a second obtaining module: the method comprises the steps of obtaining zero sequence current transient data of a suspected fault line after tripping operation;
a judging module: the system is used for judging whether the steady state value of the zero-sequence current of each branch except the suspected fault line is larger than an effective measurement threshold value or not, and if so, calculating the direction coefficient of each branch except the suspected fault line and the suspected fault line according to the transient data of the zero-sequence current of the suspected fault line;
a second correction module: the CT polarity correction module is used for correcting the CT polarity of each branch except the suspected fault line according to the direction coefficient;
the CT polarity correction method for the suspected fault line comprises the following steps:
judging whether the ground fault of the suspected fault line disappears after the tripping operation, if so, determining that the CT polarity is correct without correction, otherwise, modifying the CT polarity parameter of the suspected fault line and correcting the CT polarity;
the method for acquiring the zero-sequence current transient data of the suspected fault line comprises the following steps:
judging whether the ground fault disappears after the tripping operation, if so, obtaining zero sequence current transient data of the suspected fault line as a fault line, otherwise, obtaining actual zero sequence current transient data of the suspected fault line and taking the actual zero sequence current transient data as the zero sequence current transient data to be obtained after negation;
the calculation formula of the direction coefficient is as follows:
in the formula, DCoe is the direction coefficient of branch I and branch k, I t_i For branch I zero sequence current transient data, I t_k The transient data of the zero sequence current of the branch k is obtained, and N is the length of a transient data window;
the CT polarity correction method of each branch except the suspected fault line is as follows:
for any branch outside the suspected fault line, if the direction coefficient is smaller than 0, the CT polarity of the branch is correct without correction; if the direction coefficient is larger than 0, the CT polarity of the branch is wrong, the CT polarity parameter is modified, and the CT polarity of the branch is corrected.
3. A CT polarity self-correction system of a low-current grounding line selection device is characterized by comprising a processor and a storage medium;
the storage medium is used for storing instructions;
the processor is configured to operate in accordance with the instructions to perform the steps of the method of claim 1.
4. Computer readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of the method as claimed in claim 1.
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