CN102998323B - Method for evaluating aging degree of crosslinked polyethylene cable based on nuclear magnetic resonance - Google Patents
Method for evaluating aging degree of crosslinked polyethylene cable based on nuclear magnetic resonance Download PDFInfo
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- CN102998323B CN102998323B CN201210502477.0A CN201210502477A CN102998323B CN 102998323 B CN102998323 B CN 102998323B CN 201210502477 A CN201210502477 A CN 201210502477A CN 102998323 B CN102998323 B CN 102998323B
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Abstract
The invention relates to a method for evaluating aging degree of a crosslinked polyethylene cable based on nuclear magnetic resonance. The method comprises the following steps of: testing and comparing a molecular structure of the crosslinked polyethylene cable under different aging degrees through a nuclear magnetic resonance analyzer, and obtaining a proportional relation among the crosslinked polyethylene aging degrees, the temperature and the time, thus obtaining an aging state and residual service life of the crosslinked polyethylene cable to be evaluated according to the proportional relation. According to the method, the aging performance of an insulating material is detected from a micro perspective.
Description
Technical field
The present invention relates to a kind of method twisted polyethylene cable degree of aging assessed based on nuclear magnetic resonance principle, be specifically related to the relation of twisted polyethylene cable micro-property and its degree of aging.
Background technology
Crosslinked polyethylene (XLPE) cable is very important equipment in electric power power transmission and transformation, it has the restrictive function of bottle-neck to electric load safety, stable transfer, the designed life of XLPE cable is approximately 30 years, the cable that more domestic Utilities Electric Co.s come into operation in early days is close to tenure of use, cable is due to lack of standardization and weather and the artificial origin of constructing, cable running environment is caused to worsen, such as, the filling etc. of the accumulation of cable, ponding, mud, rubbish.Research shows the change of running environment in cable tunnel, and the temperature of cable can be caused to raise, the degree of aging aggravation of cable.Except affecting the life-span of cable self, also can cause the impact on operation of power networks stability.Because cable running environment is destroyed and the overlap of cable, the heat dissipation channel of a lot of cable is destroyed, thus cable operationally easily produces the faults such as local overheating, comprising: the mechanical damage that local overheating, humidified insulation and construction aging and lack of standardization cause.
Because running environment is severe, the underground cable in a lot of city is in order to ensure the safe operation of cable, and all run in low load condition, the utilization ratio of cable is low, and operating cost is high.In order to improve the economical and power supply reliability that cable runs, national grid has started to carry out the assessment of assets life-cycle.Therefore, under the prerequisite of safe operation ensureing cable, improve operational efficiency and the utilization factor of cable, the operating cost reducing cable is the problem that Utilities Electric Co. needs solution at present badly.
The methods such as current thermal lifetime appraisal procedure such as conventional method, differential scanning calorimetry (DSC), Weibull distributed model method.But conventional method and Weibull distributed model method just consider the change situation of a certain performance parameter of insulating material, have certain difference with actual conditions.DSC method cannot set up theoretically information that this method provides and material function lost efficacy between relation.Particularly because twisted polyethylene cable is laid and the complicacy of running environment, the impact of the factors such as electricity, heat, chemistry and water can be subject in actual motion, cause it aging, main from macroscopic perspective at present, its running status and serviceable life are assessed in change according to a certain performance of crosslinked polyethylene, the impact that its aging action brings can not be considered comprehensively, cause assessment result and actual conditions to have certain difference.
Summary of the invention
The object of the invention is to overcome the deficiency assessing the existence of twisted polyethylene cable degree of aging according to a certain bulk parameter, a kind of method of the micro molecule structural appraisal twisted polyethylene cable degree of aging according to insulating material is provided.When insulating material occurs aging, its molecular structure or polymer sequence can change, thus cause material microstructure to change, molecular structure is as shown in Figure 1 under normal circumstances for it, because the main composition of crosslinked polyethylene is c h bond, when occurring aging, molecular structure will change.And nuclear magnetic resonance is as a kind of method of detection material micromechanism, can distinguish preferably different structure sequence in the chemical composition of macromolecular material and composition of the same race, there is provided one from microcosmic angle to characterize crosslinked polyethylene aging conditions, the ageing state assessing twisted polyethylene cable can be convenient to so the present invention is based on nuclear magnetic resonance principle.
The feature of nuclear magnetic resoance spectrum (as the width of spectral line, shape and area) can characterize nuclear character and residing environment, and determines molecular structure.Nuclear magnetic resonance spectroscopy is carried out to sample and after inverting, we can obtain the parameters such as chemical shift (relaxation time), peak area, and them can be utilized to determine the change of molecular structure.Insulating material in ageing process due to macromolecules degradation, deterioration etc., material molecule structure can change, first by magnetic nuclear resonance analyzer test insulating material molecular structure situation under normal circumstances, and test the molecular structure situation of insulating material in ageing process, the degree of aging of crosslinked polyethylene and the relation of its micro-property can be obtained, its degree of aging can be assessed more accurately.
The technical solution used in the present invention is, a kind of twisted polyethylene cable degree of aging appraisal procedure based on nuclear magnetic resonance, comprises the following steps:
1) nuclear magnetic resonance is utilized to obtain the molecular structure of normal twisted polyethylene cable
Get the insulating layer material of normal twisted polyethylene cable, along the sampling of insulation course axial direction, and be cut into particle of uniform size, take 1.2 grams as normal specimens, utilize magnetic nuclear resonance analyzer to analyze normal specimens, obtain the peak area SP of normal twisted polyethylene cable
0and longitudinal relaxation time RTL
0; Magnetic nuclear resonance analyzer optimum configurations is as follows: centre frequency is 22MHz, and deviation frequency is 584.347825 KHz, and the pulse train repetition time is 2000us, and repeated sampling number of times is 16.
2) aging test carried out to normal twisted polyethylene cable and sample
Get normal twisted polyethylene cable, be cut into some sections of stub cables, every section of stub cable grows 15 ~ 20 centimetres, utilize air thermal aging oven under 90 DEG C, 110 DEG C and 130 DEG C of three temperature, carry out aging test to stub cable, sample 7 times at each temperature, the time interval of every sub-sampling is geometric ratio relation; By the stub cable after aging test respectively along the sampling of insulation course axial direction, and be cut into particle of uniform size, take 1.2 grams as aged samples.
3) nuclear magnetic resonance spectroscopy is carried out to aging twisted polyethylene cable characteristic quantity
Utilize magnetic nuclear resonance analyzer to step 2) in each aged samples analyze, obtain the peak area of twisted polyethylene cable and the relation SP of aging temperature and digestion time
t,t, and the relation RTL of longitudinal relaxation time and aging temperature and digestion time
t,t, subscript T and t represents aging temperature and digestion time respectively.
4) twisted polyethylene cable to be assessed is got, along the sampling of insulation course axial direction, and be cut into particle of uniform size, take 1.2 grams as testing sample, utilize magnetic nuclear resonance analyzer to analyze testing sample, obtain the peak area SP of twisted polyethylene cable to be assessed
objand longitudinal relaxation time RTL
obj.
5) the relation SP of the peak area in step 3) and aging temperature and digestion time
t,tand the relation RTL of longitudinal relaxation time and aging temperature and digestion time
t,tin, find out the peak area SP with twisted polyethylene cable to be assessed
objand longitudinal relaxation time RTL
objthere is the cable aging temperature under identical peak area and longitudinal relaxation time and digestion time, remember that this aging temperature and digestion time are T respectively
s, t
s.
6) the aging temperature T that air thermal aging oven obtains in step 5) is utilized
sunder, carry out aging to normal twisted polyethylene cable, until insulation not up to standard, note cable be aged to insulation not up to standard time digestion time be t
se.
7) time that twisted polyethylene cable to be assessed can also use under original load and running environment is:
In formula:
for the time that twisted polyethylene cable to be assessed can also use under original load and running environment;
for the time that twisted polyethylene cable to be assessed had used before being detected.
The good effect that the present invention produces owing to adopting said method is very significant, namely by the molecular structure of magnetic nuclear resonance analyzer test and comparison twisted polyethylene cable under different degree of aging, obtain the proportionate relationship between insulating material degree of aging and temperature and time, achieve ageing state and the residual life of assessment twisted polyethylene cable.
Accompanying drawing explanation
Fig. 1 is twisted polyethylene cable molecular structure;
Fig. 2 is nuclear magnetic resonance inverting spectrogram;
Sample peak area and thermal aging time graph of a relation when Fig. 3 is 90 DEG C;
The graph of a relation of sample peak area and digestion time when Fig. 4 is 110 DEG C;
The graph of a relation of sample peak area and digestion time when Fig. 5 is 130 DEG C;
Fig. 6 be under different temperatures peak area relative to the change amplitude figure of normal crosslinked polyethylene;
Fig. 7 is crest 1 longitudinal relaxation time and digestion time graph of a relation under different temperatures;
Fig. 8 is crest 2 longitudinal relaxation time and digestion time graph of a relation under different temperatures.
Embodiment
The inventive method is see following steps.
1) nuclear magnetic resonance is utilized to obtain the molecular structure of normal twisted polyethylene cable
Get the insulating layer material (crosslinked polyethylene) of normal (newly dispatching from the factory) cable sample, along the sampling of insulation course axial direction, and be cut into particle of uniform size, take 1.2g as normal specimens.
Magnetic nuclear resonance analyzer is utilized to analyze normal specimens, magnetic nuclear resonance analyzer optimum configurations is as follows: centre frequency (SF1) is 22MHz, deviation frequency (O1) is 584.347825 KHz, the pulse train repetition time (TR) is 2000us, repeated sampling number of times (NS) is 16, and accompanying drawing 2 is the sample nuclear magnetic resonance inverting spectrograms obtained under this optimum configurations.
By nuclear magnetic resonance spectroscopy, obtain the peak area SP of normal twisted polyethylene cable
0and longitudinal relaxation time RTL
0, this peak area SP
0with RTL
0as the foundation of twisted polyethylene cable degree of aging assessment.
2) aging test carried out to normal twisted polyethylene cable and sample
According to IEC6-811-1 standard, get normal (newly dispatching from the factory) twisted polyethylene cable, be cut into some sections of stub cables, every section of section stub cable length is 15 ~ 20 centimetres, utilize air thermal aging oven to carry out aging test to stub cable under 90 DEG C, 110 DEG C and 130 DEG C of three temperature grades, sample 7 times under each test temperature.
Under different temperatures grade, raise 10 DEG C according to temperature, the sample life-span can reduce 1/2 ~ 1/3 to calculate the digestion time under different temperatures grade, and under same temperature grade, the time interval of sample should be geometric ratio relation, is namely geometric ratio relation between every sample aging period.Some stub cable sampling methods after aging are still sampled along insulation course axial direction, and is cut into particle of uniform size, every sub-sampling 1.2g.For the sample sampling three times of different degree of aging, each nmr experiments is sampled 3 times, can the fully impact that brings of Elimination test error.
3) nuclear magnetic resonance spectroscopy is carried out to aging cable characteristic quantity
Utilize magnetic nuclear resonance analyzer to step 2) in each aged samples analyze, obtain the peak area of twisted polyethylene cable and the relation SP of aging temperature and digestion time
t,t, as shown in accompanying drawing 3 ~ 5, and the relation RTL of longitudinal relaxation time and aging temperature and digestion time
t,t, subscript T and t represents aging temperature and digestion time respectively, as shown in accompanying drawing 7 ~ 8; 90 DEG C of aging peak areas of 120 hours are such as adopted to be expressed as: SP
90,120.
4) twisted polyethylene cable to be assessed is got, along the sampling of insulation course axial direction, and be cut into particle of uniform size, take 1.2 grams as testing sample, utilize magnetic nuclear resonance analyzer to analyze testing sample, obtain the peak area SP of twisted polyethylene cable to be assessed
objand longitudinal relaxation time RTL
obj.
5) the relation SP of the peak area in step 3) and aging temperature and digestion time
t,tand the relation RTL of longitudinal relaxation time and aging temperature and digestion time
t,tin, find out the peak area SP with twisted polyethylene cable to be assessed
objand longitudinal relaxation time RTL
objthere is the cable aging temperature under identical peak area and longitudinal relaxation time and digestion time, remember that this aging temperature and digestion time are T respectively
s, t
s.
6) T is adopted
s, t
scarry out aging to the twisted polyethylene cable of normal (newly dispatching from the factory), until insulation is not up to standard, note cable be aged to insulation not up to standard time digestion time be t
se.
7) therefore can show that the time that twisted polyethylene cable to be assessed can also use under original load and running environment is:
In formula:
for the time that twisted polyethylene cable to be assessed can also use under original load and running environment;
for the time that twisted polyethylene cable to be assessed had used before being detected.
Below with 110kV twisted polyethylene cable for the application process of example to technical scheme of the present invention is described further.
1) peak area obtaining normal cable is 6925.45
, the longitudinal relaxation time at peak 1 is 20.6663ms, and the longitudinal relaxation time at peak 2 is 144.278ms.
2) at 90 DEG C, 110 DEG C, 130 DEG C according to the aging cable of IEC60811 standard, and obtain the peak area of each aged samples and the curved line relation formula of longitudinal relaxation time.
3) carry out nuclear magnetic resonance spectroscopy to cable to be assessed (2 years being 17200h), obtaining its peak area is 5583.18
, the longitudinal relaxation time at peak 1 is 17.7387ms, and the longitudinal relaxation time at peak 2 is 127.5420ms.
4) find in the curve map obtained and cable peak area to be assessed and the identical temperature spot of different peaks longitudinal relaxation time and time point, be 130 DEG C herein, 240h.
5) acquisition is carried out aging with a collection of cable that newly dispatches from the factory at 130 DEG C, is 2000h to failure of insulation (the insulating not up to standard) time.
6) residual life obtaining this cable is 2000/240*17200-17200=14.40.
Simultaneously in order to further illustrate the feasibility of the method, according to the experimental formula of generally acknowledging in the world, namely cable is in certain operating temperature range, and the relational expression most cases of life-span and temperature meets following experimental formula:
Wherein R is gas law constant, is 8.314, energy of activation
be the characteristic quantity characterizing insulating material degree of aging, data are by experiment obtained
obtain with being tested by IEC60811 Standard circuits length growth rate
contrast, according to IEC60811 standard carry out cable insulation breaking elongation experiment time, test specimen is take from step 2 equally) in same batch sample, obtain energy of activation
for 130.181kJ/mol, with the energy of activation obtained by magnetic nuclear resonance method
128.35kJ/mol close, carry out cable insulation failure test again, can solve variable a, the life formula that the life formula namely obtained by nuclear magnetic resonance principle and IEC60811 standard are obtained is close, and the accuracy in the method assessment twisted polyethylene cable life-span is described.
The method of the assessment twisted polyethylene cable degree of aging based on nuclear magnetic resonance principle provided by the invention, can be applicable in high voltage insulating materials Aging Assessment, achieves from the detection of microcosmic angle to insulating material ageing properties.Particularly fast-developing at the current extra-high voltage grid of China, and when high voltage insulating materials aging conditions is serious, the present invention provides effective ways for assessing insulating material.
Claims (2)
1., based on a twisted polyethylene cable degree of aging appraisal procedure for nuclear magnetic resonance, it is characterized in that, comprise the following steps:
1) nuclear magnetic resonance is utilized to obtain the molecular structure of normal twisted polyethylene cable
Get the insulating layer material of normal twisted polyethylene cable, along the sampling of insulation course axial direction, and be cut into particle of uniform size, take 1.2 grams as normal specimens, utilize magnetic nuclear resonance analyzer to analyze normal specimens, obtain the peak area SP of normal twisted polyethylene cable
0and longitudinal relaxation time RTL
0;
2) aging test carried out to normal twisted polyethylene cable and sample
Get normal twisted polyethylene cable, be cut into some sections of stub cables, every section of stub cable grows 15 ~ 20 centimetres, utilize air thermal aging oven under 90 DEG C, 110 DEG C and 130 DEG C of three temperature, carry out aging test to stub cable, sample 7 times at each temperature, the time interval of every sub-sampling is geometric ratio relation; By the stub cable after aging test respectively along the sampling of insulation course axial direction, and be cut into particle of uniform size, take 1.2 grams as aged samples;
3) nuclear magnetic resonance spectroscopy is carried out to aging twisted polyethylene cable characteristic quantity
Utilize magnetic nuclear resonance analyzer to step 2) in each aged samples analyze, obtain the peak area of twisted polyethylene cable and the relation SP of aging temperature and digestion time
t,t, and the relation RTL of longitudinal relaxation time and aging temperature and digestion time
t,t, subscript T and t represents aging temperature and digestion time respectively;
4) twisted polyethylene cable to be assessed is got, along the sampling of insulation course axial direction, and be cut into particle of uniform size, take 1.2 grams as testing sample, utilize magnetic nuclear resonance analyzer to analyze testing sample, obtain the peak area SP of twisted polyethylene cable to be assessed
objand longitudinal relaxation time RTL
obj;
5) the relation SP of the peak area in step 3) and aging temperature and digestion time
t,tand the relation RTL of longitudinal relaxation time and aging temperature and digestion time
t,tin, find out the peak area SP with twisted polyethylene cable to be assessed
objand longitudinal relaxation time RTL
objthere is the cable aging temperature under identical peak area and longitudinal relaxation time and digestion time, remember that this aging temperature and digestion time are T respectively
s, t
s;
6) the aging temperature T that air thermal aging oven obtains in step 5) is utilized
sunder, carry out aging to normal twisted polyethylene cable, until insulation not up to standard, note cable be aged to insulation not up to standard time digestion time be t
se;
7) time that twisted polyethylene cable to be assessed can also use under original load and running environment is:
In formula:
for the time that twisted polyethylene cable to be assessed can also use under original load and running environment;
for the time that twisted polyethylene cable to be assessed had used before being detected.
2. a kind of twisted polyethylene cable degree of aging appraisal procedure based on nuclear magnetic resonance according to claim 1, it is characterized in that: magnetic nuclear resonance analyzer optimum configurations is as follows: centre frequency is 22MHz, deviation frequency is 584.347825 KHz, the pulse train repetition time is 2000us, and repeated sampling number of times is 16.
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| CN103558518B (en) * | 2013-11-02 | 2015-11-25 | 国家电网公司 | The sample aging degree pick-up unit of insulator |
| CN103558241B (en) * | 2013-11-02 | 2016-03-30 | 国家电网公司 | The sample aging degree detection method of insulator |
| CN104914123B (en) * | 2015-05-04 | 2017-09-29 | 西安近代化学研究所 | A kind of method of assessment NEPE propellant storage lives |
| CN105547972B (en) * | 2015-12-08 | 2018-05-08 | 国网山东省电力公司电力科学研究院 | A kind of shaft tower coat of metal corrosion residual life appraisal procedure |
| CN105352879B (en) * | 2015-12-08 | 2018-05-18 | 国网山东省电力公司电力科学研究院 | A kind of japanning shaft tower coating corrosion residue lifetime estimation method |
| CN106908468B (en) * | 2017-03-03 | 2018-06-12 | 西安近代化学研究所 | Gel state cloud detonator cross-linked state changing rule detecting system under high temperature |
| CN108287174B (en) * | 2018-01-25 | 2020-10-23 | 西华大学 | Bus duct service life prediction method based on thermal service life loss at variable temperature |
| FR3081554B1 (en) | 2018-05-23 | 2021-05-21 | Electricite De France | NON-DESTRUCTIVE CONTROL PROCESS OF ELASTOMERIC INSULATING SHEATH OF CABLE, DEVICE AND PROGRAM |
| CN109324077B (en) * | 2018-08-14 | 2022-03-29 | 中国石油天然气股份有限公司 | Method and device for determining thermal stability of polymer crosslinked gel |
| CN110618160B (en) * | 2019-11-05 | 2023-01-10 | 重庆航天职业技术学院 | Magnetic resonance sensor for aging detection of cable insulation layer material |
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| CN102628906B (en) * | 2012-04-24 | 2014-04-02 | 国家电网公司 | Aging test device of cross linked polyethylene (XLPE) medium voltage cable water tree |
| CN102735706B (en) * | 2012-07-18 | 2014-12-10 | 重庆大学 | Nuclear magnetic resonance sensor used for nondestructive aging resonance of umbrella skirt of composite insulator |
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Inventor after: Pan Xiubao Inventor after: Luo Hanwu Inventor after: Yang Fan Inventor after: Gao Bing Inventor after: Zhong Jie Inventor after: Guo Xingye Inventor after: Ran Wei Inventor before: Yang Fan Inventor before: Gao Bing Inventor before: Zhong Jie Inventor before: Guo Xingye Inventor before: Ran Wei |
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Effective date of registration: 20161123 Address after: The western part of Tongliao city the Inner Mongolia Autonomous Region 028000 Huolinhe Street No. 2080 Patentee after: STATE GRID EAST INNER MONGOLIA ELECTRIC POWER COMPANY LIMITED Patentee after: Chongqing University Address before: 400044 Shapingba District Sha Street, No. 174, Chongqing Patentee before: Chongqing University |