CN104237639A - Online monitoring method of insulation state of medium-voltage power cable based on impact impedance characteristic parameter - Google Patents
Online monitoring method of insulation state of medium-voltage power cable based on impact impedance characteristic parameter Download PDFInfo
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- CN104237639A CN104237639A CN201410548699.5A CN201410548699A CN104237639A CN 104237639 A CN104237639 A CN 104237639A CN 201410548699 A CN201410548699 A CN 201410548699A CN 104237639 A CN104237639 A CN 104237639A
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Abstract
The invention discloses an online monitoring method of an insulation state of a medium-voltage power cable based on an impact impedance characteristic parameter. The online monitoring method comprises the steps of switching a high-voltage capacitor at a cable joint to generate an operating overvoltage, converting a high voltage and a large current into a low voltage and a small current by use of a high-frequency voltage divider and a high-frequency current transformer, acquiring impact voltage and current by use of a high-speed data acquisition device synchronously, transmitting the acquired data to a computer and storing in the computer, and meanwhile, performing fast Fourier transform, dividing the frequency-domain voltage obtained through transform by the frequency-domain current to calculate the impact impedance, and then obtaining the minimum values of the amplitude frequency and the phase frequency of the impact impedance, respectively, comparing the minimum values with corresponding set values, wherein if one minimum value is lower than the set value, indicating degradation of insulation and outputting the online insulation state monitoring result, and finally, circulating all the steps and performing real-time online monitoring. The online monitoring method of the insulation state of the medium-voltage power cable based on the impact impedance characteristic parameter is capable of monitoring defects that cannot be exposed under low voltage and guaranteeing safe and reliable operation of the power cable.
Description
Technical field
The present invention relates to the state of insulation on-line monitoring method of the medium-pressure power cable based on impact impedance characteristic parameter, belong to power system insulation monitoring technical field.
Background technology
Power cable uses extensively in urban distribution network, and cable is aging due to the impact of the electricity between the operating period, heat, machinery and environmental stress, and monitoring cable state of insulation, guarantees that the task of cable running safety is more and more heavier.For the cable insulation condition monitoring of 10kV electric pressure, after mainly taking power failure at present, high direct voltage is applied to cable and carry out preventive trial.Because 10kV number of cables is huge, overload of power, be difficult to have a power failure, experiment work amount is huge, and cable insulation monitoring task has been difficult to.Traditional cable power failure preventive trial method test cycle is long, and can cause loss of outage.Current on-line monitoring method mainly contains flip-flop method, DC superposition method, tan δ method, AC superimposition method, low frequency method of superposition, harmonic component method and local electric discharge etc.The comparatively ripe and widespread use of the on-line monitoring method that XLPE cable is adopted be DC superposition method, tan δ method and local electric discharge, flip-flop method and the DC superposition method on-line monitoring cable insulation situation of Shanghai Electrical Cable Research Institute exploitation try the several years out, but not yet this proving installation are carried out commercialized running at present.Domestic Ge great colleges and universities research on-line monitoring of cable technology, comprises flip-flop electric current, insulation measurement, the measurement of dielectric loss angle tangent and shelf depreciation etc., achieves certain achievement.XLPE cable online test method in having developed both at home and abroad or having studied has multiple, but really enters the also more rare of applied generalization, but has had good application experience in some countries.Singapore is the international implementation reasonable country of state-detection, and its cable machinery measurement of partial discharge work has had good application experience, but for on-line monitoring technique, reliability still needs to be improved further.
Chinese patent CN201210199927.7 " crosslinking polyethylene-insulated cable insulation monitoring and life-span prediction method ", using the leakage current of twisted polyethylene cable, one of insulation resistance and dielectric loss angle as tested measurement, realizes the monitoring to cable insulation deterioration process by the mutation rate calculating detection limit in real time.The traveling wave electric amount that all cable lines that Chinese patent CN200910081348.7 " the power cable on-line insulation monitoring method based on traveling wave electric amount measurement " the same bus of Real-time Collection transformer station connects measure, monitor on all cable lines simultaneously and whether disturbance occurs, and carry out disturbance Time Calculation, with Preset Time comparison, draw cable insulation status monitoring result.Based on the insulation state monitoring under rated voltage, its voltage is lower, and defect is difficult to expose, and the insulation breakdown of cable is mainly under superpotential effect, therefore, is difficult to the time of day of accurately reflection insulation as the insulation parameter under rated voltage.
Summary of the invention
The object of the invention is the state of insulation on-line monitoring method that a kind of medium-pressure power cable based on impact impedance characteristic parameter is provided for the deficiencies in the prior art, be characterized in the superpotential (lightning surge or switching overvoltage) by occurring in monitoring cable and transient current, the impact impedance calculating cable judges to realize the on-line monitoring to cable insulation state by the insulation status of cable.The defect that it cannot expose under can monitoring low-voltage, thus the safety, the reliability service that ensure power cable.
State of insulation on-line monitoring method based on the medium-pressure power cable of impact impedance characteristic parameter comprises the following steps:
The first step: at cable splice place switching high-voltage capacitor;
Second step: the surge voltage obtained by high-speed data acquiring device synchronous acquisition high frequency voltage divider and HF current transformer and electric current;
3rd step: the data transmission gathered by high-speed data acquiring device also stores on computers;
4th step: the data of surge voltage and electric current are carried out fast fourier transform respectively;
5th step: the electric current of voltage divided by frequency domain utilizing frequency domain, obtains impact impedance;
6th step: ask for the amplitude-frequency of impact impedance and the minimum value of phase frequency respectively;
7th step: the minimum value of amplitude-frequency and phase frequency compared with respective setting value respectively, if one of them is lower than setting value, then this cable defectiveness, exports state of insulation on-line monitoring result, otherwise does not export, finally all will return the first step.
Feature of the present invention and beneficial effect:
By applying superpotential mode, the defect that cannot expose under can monitoring low-voltage, improves the safe and stable operation of power cable.Independently judged by the amplitude-frequency of impact impedance and phase frequency, and one of them minimum value is lower than setting value, the state of insulation on-line monitoring result of all exportable power cable, reliability is improved.
Figure of description
Fig. 1 is the FB(flow block) of medium-voltage power cable insulation state on_line monitoring of the present invention
1, switching high-voltage capacitor, 2, the collection of surge voltage and electric current, 3, transmit and store, 4, fast fourier transform, 5, calculate impact impedance, 6, obtain the minimum value of impact impedance amplitude versus frequency characte, 7, amplitude-frequency minimum value compares with setting value, 8, the minimum value of impact impedance phase-frequency characteristic is obtained, 9, phase frequency minimum value compares with setting value, 10, export state of insulation on-line monitoring result.
Fig. 2 is the schematic diagram that medium-voltage power cable insulation state on_line monitoring of the present invention is implemented
11, high-voltage capacitor, 12, fling-cut switch, 13, high frequency voltage divider, 14, HF current transformer, 15, power cable, 16, high-speed data acquiring device, 17, computing machine.
Fig. 3 a is the impact impedance amplitude-versus-frequency curve that zero defect occurs
Fig. 3 b is the impact impedance amplitude-versus-frequency curve that defectiveness occurs
Fig. 4 a is the impact impedance phase-frequency characteristic curve that zero defect occurs
Fig. 4 b is the impact impedance phase-frequency characteristic curve that defectiveness occurs
Embodiment
Be specifically described the present invention below by embodiment, what be necessary to herein means out is that the present embodiment is only used to further illustrate the present invention, but can not be interpreted as limiting the scope of the invention.The person skilled in the art in this field can make some nonessential improvement and adjustment according to the content of the invention described above.
Embodiment
As shown in Figure 1, switching high-voltage capacitor 1 is connected with the collection 2 of surge voltage and electric current, the collection 2 of surge voltage and electric current is connected with transmitting and store 3, transmit and store 3 and be connected with fast fourier transform 4, fast fourier transform 4 is connected with calculating impact impedance 5, calculate impact impedance 5 and the minimum value 6 obtaining impact impedance amplitude versus frequency characte, the minimum value 6 obtaining impact impedance amplitude versus frequency characte compares 7 with amplitude-frequency minimum value and setting value and is connected, amplitude-frequency minimum value and setting value compare 7 and are connected with output state of insulation on-line monitoring result 10, calculate impact impedance 5 to be connected with the minimum value 8 obtaining impact impedance phase-frequency characteristic, the minimum value 8 obtaining impact impedance phase-frequency characteristic compares 9 with phase frequency minimum value and setting value and is connected, phase frequency minimum value and setting value compare 9 and are connected with output state of insulation on-line monitoring result 10, export state of insulation on-line monitoring result 10 to be connected with switching high-voltage capacitor 1.
As shown in Figure 2, high-voltage capacitor 11 high-pressure side is connected with fling-cut switch 12, fling-cut switch 12 is connected with high frequency voltage divider 13 high-pressure side, power cable 15 input end, HF current transformer 14 is positioned at fling-cut switch 12, high frequency voltage divider 13 high-pressure side and power cable 15 input end junction, high frequency voltage divider 13 is connected with the input end of high-speed data acquisition equipment 16 with the output signal end of HF current transformer 14, and the output terminal of high-speed data acquisition equipment 16 is connected with computing machine 17 input end.
Power cable insulation state monitoring method based on impact impedance characteristic parameter comprises the following steps:
The first step: by controlling the switching-on phase of fling-cut switch, then at cable splice place switching high-voltage capacitor;
Second step: the surge voltage obtained by high-speed data acquiring device synchronous acquisition high frequency voltage divider and HF current transformer and electric current, the vertical resolution 12bit of high-speed data acquisition equipment, (vertical resolution is 10bit at least for sampling rate 20MHz, sampling rate is 10MHz at least), high frequency voltage divider is selected by its maximum voltage that may occur and by the nargin of 1.2, and the maximum current that HF current transformer may occur according to its circuit is also selected by the nargin of 1.2;
3rd step: the data that high-speed data acquiring device is gathered by data line transmission and store on computers;
4th step: the data separate software of surge voltage u and current i is carried out fast fourier transform respectively, i.e. FFT (u) and FFT (i), wherein FFT (u) comprises amplitude-frequency Amplitude (u) and comprises amplitude-frequency Amplitude (i) and phase frequency Phase (i) with phase frequency Phase (u), FFT (i);
5th step: the electric current of voltage divided by frequency domain utilizing frequency domain, i.e. Amplitude (u)/Amplitude (i) obtains the amplitude versus frequency characte Amplitude (f) of impact impedance, and Phase (u)-Phase (i) obtains the phase-frequency characteristic Phase (f) of impact impedance;
6th step: between frequency 500Hz-8.5MHz, asks for amplitude-frequency Amplitude (f) of impact impedance and the minimum value Amplitude (f) of phase frequency Phase (f) respectively
minwith Phase (f)
min;
7th step: by the minimum value Amplitude (f) of amplitude-frequency
mincompare with its setting value 80, the minimum value Phase (f) of phase frequency
mincompare with its setting value 0, as shown in Figure 3 and Figure 4, if one of them is lower than setting value, then this cable defectiveness, exports insulation state monitoring result, finally all will return the first step.
Claims (1)
1., based on a state of insulation on-line monitoring method for the medium-pressure power cable of impact impedance characteristic parameter, it is characterized in that the method comprises the following steps:
The first step: at cable splice place switching high-voltage capacitor;
Second step: the surge voltage obtained by high-speed data acquiring device synchronous acquisition high frequency voltage divider and HF current transformer and electric current;
3rd step: the data transmission gathered by high-speed data acquiring device also stores on computers;
4th step: the data of surge voltage and electric current are carried out fast fourier transform respectively;
5th step: the electric current of voltage divided by frequency domain utilizing frequency domain, obtains impact impedance;
6th step: ask for the amplitude-frequency of impact impedance and the minimum value of phase frequency respectively;
7th step: the minimum value of amplitude-frequency and phase frequency compared with respective setting value respectively, if one of them is lower than setting value, then this cable defectiveness, exports state of insulation on-line monitoring result, finally all will return the first step.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110161391A (en) * | 2019-05-07 | 2019-08-23 | 四川大学 | The method monitored on-line to cable insulation is inversely injected by low frequency signal |
| CN112881806A (en) * | 2020-12-21 | 2021-06-01 | 四川大学 | Medium-voltage cable insulation online monitoring method based on impulse impedance spectroscopy |
| CN113447537A (en) * | 2021-06-25 | 2021-09-28 | 海南电网有限责任公司电力科学研究院 | Oiled paper insulation frequency domain dielectric spectrum measuring method and device, storage medium and terminal |
| CN116643132A (en) * | 2023-07-26 | 2023-08-25 | 四川省机场集团有限公司成都天府国际机场分公司 | Cable insulation on-line monitoring method and device based on high-frequency signals |
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| EP0494656A3 (en) * | 1991-01-08 | 1993-01-13 | Seba-Dynatronic Mess- Und Ortungstechnik Gmbh | Circuit arrangement for locating high ohmic and intermittent cable faults |
| JPH05256892A (en) * | 1992-03-12 | 1993-10-08 | Fuji Electric Co Ltd | Method and instrument for measuring cable impedance |
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| CN101819233A (en) * | 2010-05-10 | 2010-09-01 | 中国人民解放军理工大学 | Impact grounding impedance measuring system and measuring method thereof |
| CN102565588A (en) * | 2012-01-14 | 2012-07-11 | 天津大学 | On-line monitoring method used for high-voltage XLPE (Cross Linked Polyethylene) cable |
| CN103499775A (en) * | 2013-08-29 | 2014-01-08 | 国家电网公司 | Method for detecting XLPE insulation degree based on partial discharge frequency properties |
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Patent Citations (6)
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| EP0494656A3 (en) * | 1991-01-08 | 1993-01-13 | Seba-Dynatronic Mess- Und Ortungstechnik Gmbh | Circuit arrangement for locating high ohmic and intermittent cable faults |
| JPH05256892A (en) * | 1992-03-12 | 1993-10-08 | Fuji Electric Co Ltd | Method and instrument for measuring cable impedance |
| CN1834673A (en) * | 2006-03-06 | 2006-09-20 | 西安交通大学 | Insulating state on-line monitoring method of cross-linked PE cable |
| CN101819233A (en) * | 2010-05-10 | 2010-09-01 | 中国人民解放军理工大学 | Impact grounding impedance measuring system and measuring method thereof |
| CN102565588A (en) * | 2012-01-14 | 2012-07-11 | 天津大学 | On-line monitoring method used for high-voltage XLPE (Cross Linked Polyethylene) cable |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110161391A (en) * | 2019-05-07 | 2019-08-23 | 四川大学 | The method monitored on-line to cable insulation is inversely injected by low frequency signal |
| CN112881806A (en) * | 2020-12-21 | 2021-06-01 | 四川大学 | Medium-voltage cable insulation online monitoring method based on impulse impedance spectroscopy |
| CN113447537A (en) * | 2021-06-25 | 2021-09-28 | 海南电网有限责任公司电力科学研究院 | Oiled paper insulation frequency domain dielectric spectrum measuring method and device, storage medium and terminal |
| CN116643132A (en) * | 2023-07-26 | 2023-08-25 | 四川省机场集团有限公司成都天府国际机场分公司 | Cable insulation on-line monitoring method and device based on high-frequency signals |
| CN116643132B (en) * | 2023-07-26 | 2023-10-13 | 四川省机场集团有限公司成都天府国际机场分公司 | Cable insulation on-line monitoring method and device based on high-frequency signals |
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Application publication date: 20141224 |