CN103344808A - Method for detecting transformer neutral point current direct-current component - Google Patents

Method for detecting transformer neutral point current direct-current component Download PDF

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Publication number
CN103344808A
CN103344808A CN2013102476376A CN201310247637A CN103344808A CN 103344808 A CN103344808 A CN 103344808A CN 2013102476376 A CN2013102476376 A CN 2013102476376A CN 201310247637 A CN201310247637 A CN 201310247637A CN 103344808 A CN103344808 A CN 103344808A
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CN
China
Prior art keywords
current
neutral point
component
harmonic
mutual inductor
Prior art date
Application number
CN2013102476376A
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Chinese (zh)
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CN103344808B (en
Inventor
张红跃
熊章学
张振华
柳明
燕刚
宋红涛
胡晓静
路振宇
徐玉洁
Original Assignee
国家电网公司
许继集团有限公司
许继电气股份有限公司
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Priority to CN201310247637.6A priority Critical patent/CN103344808B/en
Publication of CN103344808A publication Critical patent/CN103344808A/en
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Publication of CN103344808B publication Critical patent/CN103344808B/en

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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/62Testing of transformers
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/0092Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02HEMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00Emergency 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
    • H02H7/04Emergency 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 transformers

Abstract

The invention relates to a method for detecting a transformer neutral point current direct-current component. The method includes the following steps: (1) according to experiments, building a corresponding relation library of the direct-current component in a saturation state and a third harmonic when a transformer neutral point alternating-current mutual inductor is saturated, and building a corresponding relation library of the direct-current component in a non-saturation state and the third harmonic when the transformer neutral point alternating-current mutual inductor is not saturated; (2) in actual operation, obtaining a value of a secondary side third harmonic of the mutual inductor through measuring and calculation; (3) judging whether the mutual inductor is saturated or not, inquiring the corresponding relation library in the saturation state and the corresponding relation library in the non-saturation state, and determining the value of the current direct-current component. The method has the advantages that when a direct-current mutual inductor is not arranged on a transformer neutral point, the direct-current component of the neutral point can be indirectly obtained due to the fact that the alternating-current mutual inductor measures the third harmonic.

Description

A kind of detection method of transformer neutral point current dc component
Technical field
The present invention relates to a kind of detection method of transformer neutral point current dc component.
Background technology
In recent years, extra-high voltage DC transmission system is swift and violent in China's development.Along with being constructed and put into operation in succession of HVDC (High Voltage Direct Current) transmission system, many problems have thereupon also been produced.DC power transmission line can be built up one pole earlier at initial operating stage usually and put into operation, just can finish bipolar operation afterwards, and when breaking down, affects greatly for preventing that circuit from stopping transport, and also can adopt the mode of one pole operation to continue transmission of electric energy.When DC transmission system is moved in one pole the earth mode, to there be very big DC current to be injected in the earth by direct current grounding pole, this a part of earth current will produce a very large impact near the transformer the earth point, because direct current grounding pole generally is positioned near the current conversion station, especially merit attention so converter power transformer institute is influenced.There is higher resistivity in soil generally speaking, huge earth current can the difference along with distance produce different DC potential near direct current grounding pole, this DC potential can produce a direct-current component at transformer neutral point and intrude into AC system, and DC current will form the loop by the alternating current circuit.Simultaneously DC current also can cause the DC magnetic biasing of transformer, and the excitation current waveform distortion intrudes into AC system thereby produce a large amount of harmonic waves, causes a series of harmful effect, causes transformer normally not move, when serious even can damage transformer.
Summary of the invention
The detection method that the purpose of this invention is to provide a kind of transformer neutral point current dc component, in order to solve transformer owing to the restriction of self structure, can't not measure the problem of neutral point current DC component in transformer neutral point installing DC current transformer.
For achieving the above object, the solution of the present invention is: a kind of detection method of transformer neutral point current dc component comprises the steps:
1) is determined by experiment: when the transformer neutral point AC current transformer is saturated, the corresponding relation of neutral point current DC component and described mutual inductor secondary side current third harmonic, set up state of saturation corresponding relation storehouse, when described mutual inductor is unsaturated, the corresponding relation of neutral point current DC component and described mutual inductor secondary side current third harmonic is set up undersaturated condition corresponding relation storehouse;
2) in the actual motion, calculate described mutual inductor secondary side third harmonic numerical value by measurement;
3) judge whether described mutual inductor is saturated, when saturated, query steps 2 in state of saturation corresponding relation storehouse) the corresponding current dc component numerical value of the third harmonic numerical value described in, when unsaturated, query steps 2 in undersaturated condition corresponding relation storehouse) the corresponding current dc component numerical value of third harmonic numerical value described in.
Adopt the waveform correlation coefficient method to judge whether described mutual inductor is saturated.
The invention has the beneficial effects as follows: do not install at transformer neutral point under the situation of DC current transformer, utilize the AC current transformer Measurement and analysis to obtain third harmonic, and obtain the neutral point direct current current component indirectly by the numerical value of Current Transformer Secondary side third harmonic, and then obtain the magnetic bias degree of transformer.
Description of drawings
Fig. 1 is an embodiment of the present invention realization flow block diagram;
Fig. 2 is neutral point direct current current component and mutual inductor secondary side third harmonic numerical relation figure under the current transformer undersaturated condition;
Fig. 3 is neutral point direct current current component and mutual inductor secondary side third harmonic numerical relation figure under the current transformer state of saturation;
Fig. 4 is that sampling gained one-period data are handled synoptic diagram.
Embodiment
The present invention will be further described in detail below in conjunction with accompanying drawing.
Set up the corresponding relation of transformer neutral point current transformer secondary side third harmonic numerical value and neutral point current DC component under undersaturated condition by experiment, 10 groups of data are got in this experiment altogether, obtain the numerical value of third-harmonic component under different DC component and set up state of saturation corresponding relation storehouse, this corresponding relation storehouse comprises corresponding tables and matched curve graph of a relation, and corresponding relation is as shown in table 1:
Table 1
Transformer neutral point direct current/A Mutual inductor secondary 3 subharmonic/A
11.47 1.59
21.11 2.72
31.16 3.64
40.90 4.34
50.86 4.89
60.89 5.31
70.97 5.60
80.72 5.79
90.47 5.89
100.23 5.91
Along with the increase of the DC component of transformer neutral point electric current, the content of third harmonic (absolute value) increases gradually as can be seen from Table 1.Utilize the data shown in the table 1, ' neutral point direct current current component-mutual inductor secondary side third harmonic ' drawn out in the described point match, and graph of a relation as shown in Figure 2.By Fig. 2 find the neutral point direct current component less than the 80A(transformer under the DC magnetic biasing situation, DC current can be greater than 80A) time, there are one-to-one relationship in third harmonic content and neutral point direct current component.Therefore only need measure the third harmonic numerical value of D.C mutual-inductor secondary side, just can draw neutral point direct current component under the mutual inductor undersaturated condition according to the correspondence that concerns of Fig. 2, thereby obtain the magnetic bias degree of transformer.
Set up the relation of transformer neutral point current transformer secondary side third harmonic numerical value and neutral point current DC component under state of saturation by experiment, 10 groups of data are got in this experiment altogether, obtain the numerical value of third-harmonic component under different DC component and set up undersaturated condition corresponding relation storehouse, this corresponding relation storehouse comprises corresponding tables and matched curve graph of a relation, and corresponding relation is as shown in table 2:
Table 2
Transformer neutral point direct current/A Mutual inductor secondary 3 subharmonic/A
11.47 0.25
21.11 0.43
31.16 0.57
40.90 0.68
50.86 0.77
60.89 0.83
70.97 0.88
80.72 0.91
90.47 0.92
100.23 0.93
Along with the increase of the DC component of transformer neutral point electric current, the content of third harmonic (absolute value) increases gradually as can be seen from Table 2.Utilize the data shown in the table 2, ' neutral point direct current current component-mutual inductor secondary side third harmonic ' drawn out in the described point match, and graph of a relation as shown in Figure 3.By Fig. 3 find the neutral point direct current component less than the 80A(transformer under the DC magnetic biasing situation, DC current can be greater than 80A) time, there are one-to-one relationship in third harmonic content and neutral point direct current component.Therefore only need measure the third harmonic numerical value of D.C mutual-inductor secondary side, just can draw neutral point direct current component under the mutual inductor state of saturation according to the correspondence that concerns of Fig. 3, thereby obtain the magnetic bias degree of transformer.
Be illustrated in figure 1 as an embodiment of the present invention process flow diagram, concrete sampling analysis flow process is:
Transformer neutral point is gathered one-period triple harmonic current Wave data with fixing sample frequency (the present embodiment sample frequency adopts 4800Hz); Analysis meter is calculated the third harmonic content (namely calculating mutual inductor secondary side third harmonic numerical value) of transformer neutral point electric current; Find out the third harmonic maximum of points; Be separation with the maximum of points, upset was designated as ordered series of numbers X about the maximum of points left data was carried out, and the former right side of maximum of points data are designated as ordered series of numbers Y, and disposal route as shown in Figure 4; Judge with the waveform correlation coefficient method whether mutual inductor is saturated: utilize following formula, ask correlation coefficient r XY,
r XY = Σ k = 1 15 ( X k - X ‾ ) ( Y k - Y ‾ ) Σ k = 1 15 ( X k - X ‾ ) 2 Σ k = 1 15 ( Y k - Y ‾ ) 2
In the formula, X kBe the array that the upset back is made up of sampled point about the waveform of maximum of points left side, be followed successively by sampled point X from left to right 1, sampled point X 2, Y kBe the array that former maximum of points right side sampled point is formed, be followed successively by sampled point Y from left to right 1, sampled point Y 2, Be all sampled point mean values of ordered series of numbers X, Be all sampled point mean values of ordered series of numbers Y, judge waveform correlation coefficient r XYWith default related coefficient criterion epsilon (0.9≤ε≤0.98) size, if r XYε, then the transformer neutral point AC current transformer does not reach capacity, if r XY≤ ε, then the transformer neutral point AC current transformer reaches capacity; At mutual inductor undersaturated condition query graph 2 curves or corresponding form, at mutual inductor state of saturation query graph 3 curves or corresponding form, find out the neutral point current DC component size of mutual inductor secondary third harmonic numerical value correspondence.

Claims (2)

1. the detection method of a transformer neutral point current dc component is characterized in that, comprises the steps:
1) is determined by experiment: when the transformer neutral point AC current transformer is saturated, the corresponding relation of neutral point current DC component and described mutual inductor secondary side current third harmonic, set up state of saturation corresponding relation storehouse, when described mutual inductor is unsaturated, the corresponding relation of neutral point current DC component and described mutual inductor secondary side current third harmonic is set up undersaturated condition corresponding relation storehouse;
2) in the actual motion, calculate described mutual inductor secondary side third harmonic numerical value by measurement;
3) judge whether described mutual inductor is saturated, when saturated, query steps 2 in state of saturation corresponding relation storehouse) the corresponding current dc component numerical value of the third harmonic numerical value described in, when unsaturated, query steps 2 in undersaturated condition corresponding relation storehouse) the corresponding current dc component numerical value of third harmonic numerical value described in.
2. the detection method of transformer neutral point current dc component according to claim 1 is characterized in that, adopts the waveform correlation coefficient method to judge whether described mutual inductor is saturated.
CN201310247637.6A 2013-06-20 2013-06-20 A kind of detection method of transformer neutral point current direct-current component CN103344808B (en)

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CN201310247637.6A CN103344808B (en) 2013-06-20 2013-06-20 A kind of detection method of transformer neutral point current direct-current component
PCT/CN2013/088471 WO2014201808A1 (en) 2013-06-20 2013-12-03 Method for detecting dc component of current at neutral-point of transformer

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WO2014201808A1 (en) * 2013-06-20 2014-12-24 国家电网公司 Method for detecting dc component of current at neutral-point of transformer
CN109103847A (en) * 2018-08-01 2018-12-28 西南交通大学 A kind of converter power transformer saturation protecting method based on DC component estimation
CN110389250A (en) * 2019-07-29 2019-10-29 武汉新电电气股份有限公司 A kind of device and method of for transformer D.C. magnetic biasing event early warning

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WO2014201808A1 (en) * 2013-06-20 2014-12-24 国家电网公司 Method for detecting dc component of current at neutral-point of transformer
CN109103847A (en) * 2018-08-01 2018-12-28 西南交通大学 A kind of converter power transformer saturation protecting method based on DC component estimation
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CN110389250A (en) * 2019-07-29 2019-10-29 武汉新电电气股份有限公司 A kind of device and method of for transformer D.C. magnetic biasing event early warning

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Inventor after: Xiong Yicheng

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