CN102298109A - Determination method for circuit model for alternating-current voltage withstand test on power cable - Google Patents
Determination method for circuit model for alternating-current voltage withstand test on power cable Download PDFInfo
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Abstract
The invention relates to a determination method for a circuit model for an alternating current voltage withstand test on a power cable , which belongs to the technical field of a high-voltage test on the power cable. In the technical scheme, a cable model is established; in the model, the cable is not equivalent to one capacitor any longer, whereas the distributed parameters and the dielectric loss of the cable are considered; the cable model (3) is a parallel circuit formed by the equivalent capacitor (C1) of the cable and the equivalent conductor (R4) of the cable; and a circuit model for a series resonance test is formed jointly by the cable model, a reactor model (2) and an exciting transformer model (1). In the background art, the cable is ideally equivalent to one capacitor, thus, active loss is not generated. On the basis of considering the loss of the insulating medium of the cable, the novel cable model is disclosed, and the schematic diagram of a novel test return circuit is established, and on the basis, test parameters are calculated; and a calculated result is comparatively consistent with field test data, thus, the test is pre-controlled and controllable, and the test accuracy is improved.
Description
Technical field
The present invention relates to a kind of definite method of power cable AC voltage withstand test circuit model, belong to power cable High-Voltage Experimentation Technology field.
Background technology
The power cable AC voltage withstand test is because Test condition, more can reflect the situation of cable insulation and the defective in the discovery insulation near the operating condition of cable.Therefore, obtain that domestic and international authoritative institution is recommended energetically and in power industry, be extensive use of.In the background technology, the power cable AC voltage withstand test adopts the variable-frequency series-resonance method more, its test principle as shown in Figure 1, in theory, when the test loop produced resonance, the voltage on the test specimen was far above the output voltage of exciting transformer, therefore when the output voltage of exciting transformer is very little, voltage on the test specimen just can reach the testing requirements value, and power supply is required, and what provide only is the meritorious part that consumes of system.It is many that the power cable AC voltage withstand test relates to equipment, the voltage height, uncertain factor is many, test condition and peopleware are had relatively high expectations, development along with electric utility, the electric pressure of power cable is more and more higher, capacity is increasing, in length is tested apart from the high-voltage power cable voltage, it is unsuccessful usually to boost, can't finish the phenomenon of test, the important reasons that the problems referred to above take place is that test parameters determines inaccurate, the cable model of background technology is a perfect condition, it is equivalent to an electric capacity, the hookup schematic diagram that makes up also is a perfect condition, and it does not consider the insulating medium effects of distribution parameters, and result of calculation and field test data error are bigger, cause the preparation deficiency to test, the success of the test rate is lower.
Summary of the invention
The object of the invention provides a kind of definite method of power cable AC voltage withstand test circuit model, fully accomplish can be controlled in advance to testing, and improves the success of the test rate, increases work efficiency, improve the automatization level of test, solve the problems referred to above that exist in the background technology.
Technical scheme of the present invention is:
Definite method of power cable AC voltage withstand test circuit model, comprise following steps: make up cable model, this model no longer is an electric capacity with the cable equivalence, but the distribution parameter and the dielectric loss of consideration cable, cable model is: the equivalent conductance parallel circuit of the equivalent capacity of cable and cable; This cable model constitutes the series resonance test circuit model with reactor model, exciting transformer model.
Said structure cable model with the cable equivalence is: the equivalent capacity of cable is with after the equivalent conductance of cable is in parallel, the equivalent resistance of serial cable and the equivalent reactance of cable.
The invention has the beneficial effects as follows: in ac voltage withstanding, what background technology was desirable is an electric capacity with the cable equivalence, does not have active loss; Yet actual cable but exists certain active loss under the high-voltage alternating situation, this active loss be can not ignore in computation process; The present invention is on the basis of considering the cable insulation dielectric loss, new cable model has been proposed, made up new test loop schematic diagram, on this basis, test parameters is calculated, result of calculation is more consistent with field test data, and pre-control, controlled has been accomplished in test, has improved the test accuracy rate.
Description of drawings:
Accompanying drawing 1 is a background hookup precircuit synoptic diagram;
Accompanying drawing 2 is an embodiment of the invention hookup precircuit synoptic diagram;
Accompanying drawing 3 is an embodiment of the invention hookup model simplification circuit diagram;
Among the figure: 1 is the exciting transformer model, and 2 is the reactor model, and 3 is cable model, R
1Be the equivalent resistance of exciting transformer, L
1Be the equivalent reactance of exciting transformer, R
2Be the equivalent resistance of reactor, L
2Be the equivalent reactance of reactor,
Be the equivalent resistance of cable,
Be the equivalent reactance of cable,
Be the equivalent capacity of cable, R
4Be the equivalent conductance of cable, U1 is the output voltage of exciting transformer, and U2 is the test voltage on the cable.
Embodiment:
Below in conjunction with accompanying drawing, further specify the present invention by embodiment.
Definite method of power cable AC voltage withstand test circuit model comprises following steps: make up cable model, this model no longer is an electric capacity with the cable equivalence, but considers the distribution parameter and the dielectric loss of cable, and cable model 3 is: the equivalent capacity C of cable
1Equivalent conductance R with cable
4Parallel circuit; This cable model constitutes the series resonance test circuit model with reactor model 2, exciting transformer model 1.
Said structure cable model with the cable equivalence is: the equivalent capacity C of cable
1Equivalent conductance R with cable
4After the parallel connection, the equivalent resistance R of serial cable
3Equivalent reactance L with cable
3
With reference to accompanying drawing 2,
Be the equivalent resistance of cable, because core material normally copper or aluminium, so when flowing through electric current, certainly lead to voltage drop.Resistance
Resistivity for conductor material.In alternating circuit, because the influence of kelvin effect and " covering effect ", its resistance ratio direct current resistance is big, is called effective resistance.
Be the equivalent reactance of cable, the reactance of circuit is because portion and the outside alternating magnetic field that produces cause within it during by alternating current in the lead.The alternating magnetic field of lead inside is only relevant with the self-induction of lead, and the outside alternating magnetic field of lead is not only relevant with self-induction also relevant with the interactional mutual inductance of other lead on every side.
Be the equivalent capacity of cable, the susceptance in the circuit (holding) is determined by the electric capacity that reaches between lead and the earth between the lead.Through the three-phase circuit after the transposition, every mutually every meter equivalent capacity is
R
4Be the equivalent conductance of cable, it is that active power by in the medium causes that the electricity of circuit is led, and mainly is the active power loss that caused of insulating medium electric leakage and the active power loss in the insulating medium.The existence that electricity is led has increased the reactive loss in the process of the test, has also just improved the index request of every testing equipment, need give enough attention.
Generally speaking, R3, L3 is extremely small to the influence of result of calculation, can ignore.
With reference to accompanying drawing 3, accompanying drawing 2 is further simplified, wherein, U1 is the output voltage of exciting transformer, U2 is the test voltage on the cable.Convenient in order to use in the engineering, the spy will
Be defined as the apparent quality factor.
Then consider the influence of R4, the apparent quality factor of test are:
During resonance,
, because
So,
At this moment
Order
Bring following formula into, can obtain:
The quality factor of well-known theory are:
Then
Order
, then
Simple circuit model error calculated is bigger, in order to improve computational accuracy, is necessary to make up more rational circuit model, in advance analytical calculation is accurately carried out in test, and then is formulated reasonable test methods and means.The present invention has proposed improved circuit model on the basis of analysis-by-synthesis cable active power loss, this model is through case verification, and resultant error has better directive significance much smaller than the error of improving preceding model to test.
The 110kV of electric company is exchanged Polyethylene insulated cable carry out AC voltage withstand test, rated voltage is 64kV, and length is 0.15km, and design capacitance is 0.197 μ F/km.Electric pressure 110kV, trial voltage 128kV.
The testing equipment that uses in the test has: VFSR-P-1 type variable-frequency power sources, output frequency: 20～400Hz, rated capacity: 50kW, output voltage: 0～350V, output current: 0～571A; YD-50/15 type exciting transformer, frequency: 30-300Hz, rated capacity: 50kVA, voltage: 5-15/0.35kV, electric current: 3.33-10/142.9A; HVFR-650/130 type reactor, frequency: 20 ~ 300Hz, voltage: 130kV, electric current: 5A, inductance value: 125H.
With a reactor, simultaneously to the threephase cable pressurization, then
Adopt Fig. 2, circuit model shown in Figure 3 to calculate respectively, the parameter of each element is respectively among the figure: R1=20 Ω, R2=180 Ω, R4=800 k Ω, L2=125 H, C1=
F.
The embodiment of the invention, background technology, measured value are more as shown in table 1.
Table 1
As can be seen from the above table, the parameter value that uses circuit model of the present invention to obtain, the parameter value than the circuit model of background technology obtains more approaches actual measured value.
Claims (2)
1. definite method of a power cable AC voltage withstand test circuit model, it is characterized in that comprising following steps: make up cable model, this model no longer is an electric capacity with the cable equivalence, but considers the distribution parameter and the dielectric loss of cable, and cable model (3) is: the equivalent capacity (C of cable
1) with the equivalent conductance (R of cable
4) parallel circuit; This cable model constitutes the series resonance test circuit model with reactor model (2), exciting transformer model (1).
2. according to definite method of the described power cable AC voltage withstand test circuit model of claim 1, it is characterized in that said structure cable model, be: the equivalent capacity (C of cable the cable equivalence
1) with the equivalent conductance (R of cable
4) after the parallel connection, the equivalent resistance (R of serial cable
3) and the equivalent reactance (L of cable
3).
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| Application Number | Priority Date | Filing Date | Title |
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| CN2011102119581A CN102298109A (en) | 2011-07-27 | 2011-07-27 | Determination method for circuit model for alternating-current voltage withstand test on power cable |
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| CN2011102119581A CN102298109A (en) | 2011-07-27 | 2011-07-27 | Determination method for circuit model for alternating-current voltage withstand test on power cable |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103018573A (en) * | 2012-08-22 | 2013-04-03 | 浙江省电力公司电力科学研究院 | Field measurement system for dielectric loss value of crosslinked polyethylene power cable |
| CN104007354A (en) * | 2013-02-27 | 2014-08-27 | 上海宝钢工业技术服务有限公司 | Whole-group test circuit and method for 10 kV zinc oxide lightning arrester and cable |
| CN113625057A (en) * | 2021-08-11 | 2021-11-09 | 保定腾远电力科技有限公司 | Power cable dielectric loss testing device based on resonance characteristics |
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| CN201229390Y (en) * | 2008-07-30 | 2009-04-29 | 湖南省电力公司试验研究院 | AC cable voltage test device |
| US7705607B2 (en) * | 2006-08-25 | 2010-04-27 | Instrument Manufacturing Company | Diagnostic methods for electrical cables utilizing axial tomography |
| CN101788636A (en) * | 2009-12-30 | 2010-07-28 | 四川中鼎科技有限公司 | Resonance voltage resistant test system and voltage resistant test method of sample with large capacitance |
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| US7705607B2 (en) * | 2006-08-25 | 2010-04-27 | Instrument Manufacturing Company | Diagnostic methods for electrical cables utilizing axial tomography |
| CN201229390Y (en) * | 2008-07-30 | 2009-04-29 | 湖南省电力公司试验研究院 | AC cable voltage test device |
| CN101788636A (en) * | 2009-12-30 | 2010-07-28 | 四川中鼎科技有限公司 | Resonance voltage resistant test system and voltage resistant test method of sample with large capacitance |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103018573A (en) * | 2012-08-22 | 2013-04-03 | 浙江省电力公司电力科学研究院 | Field measurement system for dielectric loss value of crosslinked polyethylene power cable |
| CN104007354A (en) * | 2013-02-27 | 2014-08-27 | 上海宝钢工业技术服务有限公司 | Whole-group test circuit and method for 10 kV zinc oxide lightning arrester and cable |
| CN104007354B (en) * | 2013-02-27 | 2018-07-20 | 上海宝钢工业技术服务有限公司 | The total group test circuit and method of 10kV Zinc-Oxide Arresters and cable |
| CN113625057A (en) * | 2021-08-11 | 2021-11-09 | 保定腾远电力科技有限公司 | Power cable dielectric loss testing device based on resonance characteristics |
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Application publication date: 20111228 |