CN114675212A - Method for studying and judging abnormal connection of neutral point of distribution transformer - Google Patents
Method for studying and judging abnormal connection of neutral point of distribution transformer Download PDFInfo
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- CN114675212A CN114675212A CN202210299999.9A CN202210299999A CN114675212A CN 114675212 A CN114675212 A CN 114675212A CN 202210299999 A CN202210299999 A CN 202210299999A CN 114675212 A CN114675212 A CN 114675212A
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- 230000005856 abnormality Effects 0.000 claims description 4
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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
- G01R31/62—Testing of transformers
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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
- G01R31/08—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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- 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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks
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- Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)
Abstract
The invention discloses a method for studying and judging the connection abnormity of a neutral point of a distribution transformer, which comprises the following steps: acquiring a three-phase voltage curve and a zero-sequence current curve of the same day at the low-voltage side of the distribution transformer; forming a data set by each phase voltage value and each zero sequence current value at the same moment to obtain a plurality of data sets; respectively calculating zero sequence voltage amplitude values corresponding to the data sets; respectively calculating the three-phase voltage unbalance of each data set; calculating the correlation between the zero sequence voltage and the zero sequence current; if the three-phase voltage of the distribution transformer is unbalanced and the zero-sequence voltage and the zero-sequence current have strong correlation, the distribution transformer has abnormal connection of the neutral point of the electric line. The method is simple and practical, effectively improves the working efficiency and reduces the missing rate.
Description
Technical Field
The invention belongs to the field of power distribution network monitoring, and particularly relates to a method for studying and judging abnormal connection of a neutral point of a distribution transformer.
Background
The maintenance of the healthy operation of the distribution transformer is one of the key links for guaranteeing the social electricity utilization. The problem of unbalanced three-phase voltage is caused by abnormal connection of the neutral point of the distribution transformer, so that the quality of electric energy supplied by a low-voltage transformer area is influenced, and the normal use of user electric equipment is influenced in severe cases. The common management method is to monitor the operation state of the distribution transformer, perform data analysis on the collected voltage, current and other electrical data, and check abnormal events. Under the working mode, abnormal problems such as abnormal neutral point connection and the like are difficult to find quickly and timely, and the problems of low efficiency, high missing rate and the like exist depending on manual investigation of technicians.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a method for studying and judging the abnormal connection of a neutral point of a distribution transformer, which adopts the following technical scheme:
a method for studying and judging the connection abnormity of a neutral point of a distribution transformer comprises the following steps:
s1, acquiring a three-phase voltage curve and a zero-sequence current curve of the low-voltage side of the distribution transformer in the same day;
s2, forming a data set by the phase voltage values and the zero sequence current values at the same moment according to the three-phase voltage curve and the zero sequence current curve, and acquiring a plurality of data sets;
s3, respectively calculating zero sequence voltage amplitude values corresponding to the data sets;
s4, respectively calculating the unbalance degree of the three-phase voltage of each data set, and judging whether the three-phase voltage is balanced according to the unbalance degree;
s5, calculating the correlation between the zero sequence voltage and the zero sequence current, and judging whether the two have strong correlation according to the correlation;
and S6, if the three-phase voltage of the distribution transformer is unbalanced and the zero-sequence voltage and the zero-sequence current have strong correlation, the distribution transformer has abnormal connection of the neutral point of the electric line.
Further, in step S2, 96 data sets at different time instants are obtained, and data sets with incomplete data items or significantly erroneous data are eliminated.
Further, in step S3, zero sequence voltage phasorThe real part of (a) is a zero-sequence voltage amplitude, the zero-sequence voltage phasorThe calculation formula of (a) is as follows:
wherein U isA∠0°、UB∠120°、UCThe angle 240 degrees respectively represents A, B, C three-phase voltage.
Further, in step S4, if the proportion of the data group in which the three-phase voltage unbalance is located in the balance interval is greater than the balance determination threshold, the three-phase voltage of the distribution transformer is considered to be balanced, otherwise, the three-phase voltage is unbalanced; the calculation formula of the three-phase voltage unbalance epsilon is as follows: e ═ U0/220,U0Is the zero sequence voltage amplitude.
Further, in step S5, a Pearson correlation coefficient r of the zero-sequence voltage and the zero-sequence current is calculated, and if | r | is greater than a correlation determination threshold, it is indicated that the zero-sequence voltage and the zero-sequence current have strong correlation; the calculation formula of the Pearson correlation coefficient r is as follows:
wherein, I0,iAnd U0,iAnd respectively representing the zero sequence current and the corresponding zero sequence voltage amplitude of the ith data set, wherein n is the total number of the data sets.
Further, the balance interval is [0, 2% ], and the balance judgment threshold is 90%; the correlation determination threshold value is 0.6.
The invention has the beneficial effects that:
the method is simple and practical, is easy to convert into a software algorithm module, realizes batch automatic study and judgment of the abnormity, effectively improves the working efficiency and reduces the missing rate.
Drawings
FIG. 1 is a schematic flow diagram of the process of the present invention;
FIG. 2 is a three-phase voltage curve diagram of a low-voltage side of a distribution transformer at a certain day in an embodiment of the invention;
fig. 3 is a zero sequence current curve diagram of the low-voltage side of a certain distribution transformer at a certain day in the embodiment of the invention.
Detailed Description
The present invention will now be described in further detail with reference to the accompanying drawings.
In order to find the abnormality of the connection of the neutral point at the low-voltage side of the distribution transformer in time, the invention provides a method for studying and judging the abnormality of the connection of the neutral point of the distribution transformer, as shown in fig. 1, which mainly comprises the following steps:
And 2, acquiring 96 three-phase voltage values and zero-sequence current values corresponding to time points according to the voltage curve and the current curve to form 96 groups of data, wherein each group of data comprises four data items (namely the three-phase voltage values and the zero-sequence current values at the same moment), performing data inspection group by group, rejecting the data groups with incomplete data items or data obviously exceeding a reasonable range, and finally obtaining n effective data groups.
Step 3, respectively calculating the zero sequence voltage corresponding to each effective data setThe calculation formula is as follows:
wherein, UA∠0°、UB∠120°、UCThe angle of 240 degrees respectively represents A, B, C three-phase voltage and phasorThe real part of the zero sequence voltage is the amplitude value U of the zero sequence voltage0。
Step 4, respectively calculating the three-phase voltage unbalance epsilon of each effective data set, counting the proportion that epsilon falls in the interval of [0, 2% ], if the proportion is more than 90%, considering that the three-phase voltage of the distribution transformer is balanced, otherwise, unbalance; the calculation formula of the three-phase voltage unbalance epsilon is as follows:
ε=U0/220
step 5, calculating a Pearson correlation coefficient r of the zero-sequence voltage and the zero-sequence current, judging the correlation strength of the zero-sequence voltage and the zero-sequence current, and if the absolute value r is greater than 0.6, indicating that the absolute value r and the zero-sequence current have strong correlation; the calculation formula of the Pearson correlation coefficient r is as follows:
wherein, I0,iAnd U0,iZero sequence current and corresponding zero respectively representing the ith valid data setThe sequence voltage amplitude.
And 6, if the three-phase voltage at the low-voltage side of the distribution transformer is unbalanced and the zero-sequence voltage and the zero-sequence current have strong correlation, determining that the distribution transformer has abnormal connection of the neutral point of the electric line.
In order to explain the practice of the present invention in more detail, the following description will be made with reference to actual data.
And obtaining 96 effective data sets according to a voltage curve and a zero-sequence current curve (shown in figures 2 and 3) of the low-voltage side of the distribution transformer of a certain low-voltage transformer area at a certain day. Group-by-group calculation of zero sequence voltage at low-voltage side of distribution transformerAnd three-phase voltage unbalance degree epsilon, and only 12 groups of calculation results epsilon fall in 0,2 percent]And in the interval, the percentage is 12.50%, and the three-phase voltage on the low-voltage side of the distribution transformer is judged to be unbalanced. And (3) calculating a Pearson correlation coefficient r, wherein r is 0.96, and the condition that r is greater than 0.6 is met, so that the zero sequence voltage and the zero sequence current have strong correlation. In summary, it is considered that the distribution transformer low-voltage side height is suspected of causing a problem of an abnormal connection of the neutral point of the electric line. And (4) through field inspection, the wiring abnormality at the connection position of the zero line and the neutral line at the low-voltage side of the distribution transformer is found, and the analysis result is met.
The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention.
Claims (6)
1. A method for studying and judging the connection abnormity of a neutral point of a distribution transformer is characterized by comprising the following steps:
s1, acquiring a three-phase voltage curve and a zero-sequence current curve of the low-voltage side of the distribution transformer in the same day;
s2, forming a data set by the phase voltage values and the zero sequence current values at the same moment according to the three-phase voltage curve and the zero sequence current curve, and acquiring a plurality of data sets;
s3, respectively calculating zero sequence voltage amplitude values corresponding to the data sets;
s4, respectively calculating the unbalance degree of the three-phase voltage of each data set, and judging whether the three-phase voltage is balanced according to the unbalance degree;
s5, calculating the correlation between the zero sequence voltage and the zero sequence current, and judging whether the two have strong correlation according to the correlation;
and S6, if the three-phase voltage of the distribution transformer is unbalanced and the zero-sequence voltage and the zero-sequence current have strong correlation, the distribution transformer has abnormal connection of the neutral point of the electric line.
2. The method as claimed in claim 1, wherein in step S2, 96 data sets at different time are obtained, and data sets with incomplete data items or significantly incorrect data are eliminated.
3. The method for determining the abnormal connection of the neutral point of the distribution transformer as claimed in claim 1, wherein in step S3, the zero sequence voltage phasorThe real part of (a) is a zero-sequence voltage amplitude, the zero-sequence voltage phasorThe calculation formula of (a) is as follows:
wherein U isA∠0°、UB∠120°、UCThe angle 240 degrees respectively represents A, B, C three-phase voltage.
4. The method as claimed in claim 1, wherein in step S4, if the unbalance of the three-phase voltages is within the balance rangeIf the proportion of the data group is larger than the balance judgment threshold value, the three-phase voltage of the distribution transformer is considered to be balanced, otherwise, the three-phase voltage is unbalanced; the calculation formula of the three-phase voltage unbalance epsilon is as follows: e ═ U0/220,U0Is the zero sequence voltage amplitude.
5. The method as claimed in claim 1, wherein in step S5, a Pearson correlation coefficient r between the zero-sequence voltage and the zero-sequence current is calculated, and if | r | is greater than the correlation determination threshold, it indicates that the zero-sequence voltage and the zero-sequence current have strong correlation; the calculation formula of the Pearson correlation coefficient r is as follows:
wherein, I0,iAnd U0,iAnd respectively representing the zero sequence current and the corresponding zero sequence voltage amplitude of the ith data set, wherein n is the total number of the data sets.
6. The method for studying and judging the connection abnormality of the neutral point of the distribution transformer according to claim 4 or 5, wherein the balance interval is [0, 2% ], and the balance judgment threshold is 90%; the correlation determination threshold value is 0.6.
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Cited By (1)
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CN117471366A (en) * | 2023-12-27 | 2024-01-30 | 国网福建省电力有限公司 | Metering device neutral line contact failure studying and judging method based on least square method |
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