高压电力设备在线监测技术-第5章-电力电缆在线监测与诊断课件.ppt

1、第第五五章章 电力电缆在线电力电缆在线监测监测与诊断与诊断On-line monitoring and fault diagnosis for power cable1本章内容 概述 电缆绝缘的劣化和诊断内容 电缆绝缘的在线监测 电缆的故障定位方法25.1 概述3 3 什么是电力电缆？架空线电力电缆电力传输通道4 为什么使用电缆？输电通道小不受环境污染影响可靠性高对人身及周围环境干扰小特殊应用环境使用电缆的优点5制造工艺复杂造价高施工维修麻烦使用电缆的缺点6电力电缆发展简史7电力电缆的使用至今已有百余年历史。1879年 爱迪生首次使用电缆实现地下输电。1911年 德国敷设60kV高压电缆。19

2、13年 霍希施泰特研制成分相屏蔽电缆。1981年 研制成1000kV的特高压电力电缆。8XLPE电缆 结构简单 无敷设落差限制 安装维护方便 1952年：发明XLPE材料 1957年：GE制成XLPE电缆 50年代末：第一代工艺|湿法交联 70年代末：第二代工艺|干式交联 80年代中后期：第三代工艺|净化材料,自动控制9电缆的种类油纸绝缘电缆气体绝缘电缆塑料绝缘电缆10聚氯乙烯电缆聚乙烯电缆XLPE（交联聚乙烯电缆）塑料绝缘电缆11交联聚乙烯交联聚乙烯电缆电缆 XLPE，cross linked polyethylene 30余年历史 性能优良、工艺简单、安装方便 得到广泛应用12XLIE电缆

3、的基本结构13交联聚乙烯绝缘电缆结构示意图交联聚乙烯绝缘电缆结构示意图1、导体 2、导体屏蔽 3、交联聚乙烯绝缘 4、绝缘屏蔽 5、金属屏蔽 6、填充 7、内衬层 8、铠装层 9、外护套141.导电线芯：高导电率材料，绞线承圆形或扇形截面。2.绝缘层：高电阻率材料，tg、低而电气强度Eb高的油浸纸、橡皮或塑料。3.密封护套：保护绝缘线芯免受机械、水分、化学等的损伤，有时外部还有保护覆盖层。4.半导体层的作用：均匀电场，它可以克服电晕及游离放电，使芯线与绝缘层之间有良好的过渡。1516电缆敷设情况电压等级/kV电缆总长度/kmXLPE电缆所占比例/%1073,66498.23511,56995.

4、3110(66)05,30390.7220(330)00,52857.950000,05642.717电缆故障率按电压等级18电缆故障率按运行时间19编号电缆故障原因比例A外力破坏外力破坏58%B附件制造质量缺陷27%C敷设施工质量缺陷12%D电缆本体质量缺陷3%电缆故障原因5.2 电缆绝缘的劣化和诊断内容20水树枝劣化的监测方法：Detection of bridged water tree On-line diagnostic methods Detection of un-bridged water tree Off-line diagnostic methods024681051015

5、2025AC breakdown voltage(kV)No.of BD samples交联聚乙烯电缆的寿命额定额定电压电压电压寿命电压寿命极限极限劣化劣化条件条件3-6kVrmsRated highest voltage+a few years after bridged water tree initiation11kVrmsAfter bridged water tree initiation(1 year or more?)more than 22kVrmsImmediately after or before bridged water tree initiationBDV of c

6、able with bridged WT电压寿命极限Bridged water treeUn-bridged water treeBDV;10-20kVElectrical treeInsulation layerInsulation layer21根据现场运行经验，水树枝劣化特性如下：（l）仅发生在6kV以上的高压交联聚乙烯电缆中。（2）从投运到破坏的时间需要数年至十几年，大多数在10年以上。（3）贯通绝缘体的水树枝状劣化，大部分能维持正常工作电压以上的电压值，只有在发生脉冲电压等异常电压时才产生破坏。（4）环境温度高时，劣化进程加快。因此对电力电缆绝缘本体进行故障监测是可行的，也是必要的。

7、5.3 电缆绝缘的在线监测22 离线方法 直流法 工频法 低频法 综合判断法电力电缆监测和诊断方法电力电缆监测和诊断方法23对已运行油纸电力电缆的试验项目 项目周期标准说明测量绝缘电阻13 年一次绝缘电阻的标准自行规定1kV 以上者用2.5kV 兆欧表试验电压标准类型额定电压 U0（kV）试验电压15354 U0631102.6 U02202.3 U0油纸3302 U0直流耐压试验并测量泄漏电流主干线每年一次橡塑2352.5 U0加电压 5min,除塑料电缆外，三相泄漏电流的不平衡系数应不大于 2电缆油的耐压23 年一次运行中油不小于 45kV，新油不小于 50kV耐压试验用的标准油杯电缆油的

8、 tg23 年一次100 2时，运行中油不大于 1%，新油不大于 0.5%测 tg用的标准油杯+-24XLPE预试时不宜用直流耐压 运行后常有（电、水）树枝生成 直流耐压时沿树枝有电荷注入 XLPE电阻率极高，短路时电荷放不完 再加交流时电场畸变，更易击穿25XLPE几种停电预试方案 用超低频0.1Hz测tan及耐压 用交流（串联谐振）测tan及耐压 用振荡波试验耐压 测回复电压 测极化去极化电流 测损耗电流中的谐波分量26回复电压的测量方法27回复电压实例28Tettex 546229极化去极化电流测量原理30极化去极化电流典型曲线31PDC-ANALYSER-1MOD 32绝缘连接盒两侧接

9、成差分法以测量局放 33一种电缆检测系统34水树枝检测方法对象对象测量条件测量条件方法方法实用情况实用情况针对形成桥的针对形成桥的水树枝水树枝离线离线直流泄漏电流法直流泄漏电流法DC leakage current under DC high voltage application is measured.实际采用实际采用在线在线直流成分法直流成分法DC component current in service is measured.直流叠加法直流叠加法DC component current when low DC voltage is superimposed on rated volt

10、age is measured.交流叠加法交流叠加法1Hz current when low voltage of 2f+1 Hz is superimposed on rated voltage(f)is measured.低频叠加法低频叠加法7.5Hz loss current when low 7.5Hz voltage is superimposed on rated voltage is measured.针对未形成桥针对未形成桥的水树枝的水树枝离线离线残余电荷法残余电荷法Residual charge after DC voltage application is measured

11、.研究中研究中损耗电流法损耗电流法Harmonic component current in loss current is measured.试用中试用中DC leakage AC superposition LF superposition DC superposition DC component针对形成桥路的水树枝探测效果:35直流泄漏电流试验线路cableguard electrodeterminalDC power supply(buttery)recorder判断标准状态良好状态良好损坏或值得注意损坏或值得注意泄漏电流值泄漏电流值0.1A0.1-1A1A电流波形电流波形-Norm

12、alPI(=I1/I10)1Existence of kick-36直流泄漏电流(A)Un-bridged water treeBridged water treeApplied stress;1kV/mm0.0010.010.11Accumulation probability(%)10205090One bridged water tree can pass the DC leakage current of about 0.1 A.Un-bridged water trees can hardly pass the DC leakage current.直流泄漏电流37直流法直流法 直流

13、成分电流监测 直流叠加法 直流电桥法38直流直流成分法成分法机理机理 电缆中存在水树时，类似尖板电极具有整流作用。因此在工作电压下，电缆绝缘中将流过微小的直流电流。根据这一电流的数值，既可判断电缆中水树的发展状况。直流成分电流监测39 TR 配电变压器 GPT 接地保护用 电压互感器 M 直流微电流 检测装置 (nA级)回路中流通微弱的直流成分电流直流直流成分电流监测原理接线成分电流监测原理接线直流成分电流监测40 微电流测量装置 微电流测量仪 低通滤波器 衰减交流成分、检出直流成分 接地保护装置 保证试验人员和装置的安全直流成分电流监测41直流成分电流监测6 kV XLPE电缆交流击穿电压与

14、电缆交流击穿电压与直流分量的关系直流分量的关系42判断规则 直流成分电流 小于1 nA 绝缘良好 大于100 nA 绝缘不良 介于两者间 加强监测直流成分电流监测43护层与地之间有化学电势Es直流成分电流监测44 护层与电缆绝缘护层的绝缘电阻下降 M中将流过杂散电流 通常Es不超过 0.5 V 当护层绝缘电阻小于200500 M 杂散电流将影响诊断的可靠性45直流法 直流叠加法 借助电抗器将直流电压在线叠加于电缆绝缘测量直流叠加电流。46 防止影响GPT二次输出电压 直流电压不能很高，约1050 V 直流电压不高 电缆绝缘处于交流高压作用下 真实反映绝缘的实际状况直流叠加法47 6 kV XL

15、PE电缆 直流叠加电流 与 水树长度 的关系直流叠加法48 保证安全 L、C 调谐于50 Hz 杂散电流Es的影响 正、反向 叠加直流 电压消除直流叠加法49判断规则 测得绝缘电阻 大于1000 M 绝缘良好 小于10 M 绝缘不良 介于两者间 加强监测试验证明：用直流叠加法测得的绝缘电阻与停电后加直流高压时的测试结果很相近。直流叠加法50Test circuit直流重畳法絶縁抵抗（M）直流漏電流法絶縁抵抗（M）DC power supplyMeasuring equipmentcableDC 5-50V is superimposed on the high voltage in servi

16、ce.DC component in leakage current is measured.Resistance measured by DC superposition method(M)Resistance measured by DC leakage current(M)Relationship between DC superposition method and DC leakage current.DC Superposition MethodDC leakage current is highly sensitivity.51時間絶縁抵抗（M）時間絶縁抵抗（M）Resistan

17、ce(M)Resistance(M)TimeTimeTime change of DC superposition currentProblemThis method tends to be influenced by the stray current or corruption of the terminal.Measured value will change with measurement time or humidity very much.The trend management by on-line diagnosis is required.DC Superposition

18、Method52直流法 直流电桥法 测量电缆绝缘电阻的电桥接线53 电桥平衡 Rx=(E1-V4)R2/V4 设E1为20 V，V4为1 mV，R2为50 M Rx最大可测到100 000 M 防止直流电压对GPT的有害影响直流电桥法54 Es影响的消除 调节R4及E0 V0指示为零 其他设备的绝缘电阻与R3并联 R3之值并不参与计算 其他设备的绝缘电阻不影响测量结果直流电桥法55 加于电缆的电压信号(通过电压互感器取出)流过绝缘的电流信号(通过电流互感器取出)通过数字化测量装置 电缆绝缘的tg工频工频法法 介损介损因数法因数法56什么是介质损耗角 (tan)?time/sec010电压电流

19、=介质损耗角 tan =有功功率 无功功率CRCURU 122 57 0,0010,010,11100,0010,010,11101001000W.C.=0.18%W.C.=1.52%W.C.=2.12%W.C.=2.60%W.C.=3.51%Tan Frequency HzPaper with different moisture contentsTemperature ca.22C50 Hz60 Hz受潮对tan的影响580,0010,010,11100,0010,010,1110100100020 oC40 oC60 oC80 oCTan Frequency HzDry paper(0.

20、5%)at different temperatures50 Hz60 Hz温度对tan的影响59 6 kV XLPE电缆交流击穿电压与在线测得 tg 间的关系60 统计分析表明 tg大于1%绝缘不良61 如果满足以下条件，电缆状态正常:tan (2 U0)1.2 andtan (2 Uo)-tan (Uo)0.6 如果发生以下情况，则电缆处于故障状态(须立即更换）:tan (2 Uo)2.2 ortan (2 Uo)-tan (Uo)1.0 对于 XLPE 电缆这一标准是非常重要的。62工频法 局部放电法 试验分析证明 绝缘中的电树枝达到0.5 mm时 局部放电量约100 pC 由-q、-n

21、、q-n、或-q-n谱图 判断电缆状态 放电相位，q 放电量，n 重复率63 偏斜度s 在4个象限中 的分布 预测树枝的 延伸发展情况 P点进入第3象限 绝缘进入危险状态64 水树 流经电缆绝缘 的电流也含有 低频成分 根据频谱分析 频率在10 Hz,特别在3 Hz以下.低频法 低频成分法65 在电缆接地线中串接入测量装置 由测得的低频电流诊断绝缘 低频电流也是纳安级 对测量装置要求较高66低频法 低频叠加法 避免直流微电流测量上的困难 将7.5 Hz、20 V的低频电压 在线叠加于电缆 在电缆接地线中串接入测量装置 绝缘电阻值67 低频叠加法6 kV电缆绝缘电阻与工频击穿电压的关系68判断规

22、则 绝缘电阻大于1 000 M 性能良好 绝缘电阻小于1 000 M 性能下降 绝缘电阻小于400 M 电缆应立即更换69综合判断法综合判断法 绝缘状态与特性参数间的统计分散性 仅用一种方法诊断绝缘 漏判和错判的可能 采用几种方法，互相配合进行复合诊断 可提高诊断的正确性 采用包含直流叠加法、tg法和局部放电法的复合诊断 诊断的准确率高达95%以上70电缆故障的演变电缆故障的演变 早期电缆本体故障为主 近期电缆负荷过载性故障较多 目前电缆附件故障已成为重要故障原因。电缆终端或中间接头出现放电点电缆终端或中间接头出现过热点电缆外护层绝缘不良导致的环流故障71对电缆在线监测技术的要求对电缆在线监测

23、技术的要求 实时报警 故障精确定位 综合监测（温度、烟雾、放电等）72Among on-line diagnostic methods,the detection sensitivity to bridged water tree is high.This method is strong in a noise.High voltage work is unnecessary.AC Superposition MethodNoDC leakage current(A)AC superposition method(nA)adjust5kV10kV16kV10.010.020.0014.48X2

24、0.020.74-6.34X30.000.000.008.37OK40.403.10-17.79OK50.0210.5-76.72OK60.010.030.002.84OK70.000.020.006.43OK80.010.030.0021.30X90.010.190.2156.80OK100.102.80-34.13OK110.000.060.0727.79X120.3010.50.2517.62Ok130.000.000.003.03OK140.000.000.004.17OK150.000.000.0032.54X160.000.000.007.78OK170.000.000.002.7

25、1OK180.000.000.003.06OK190.000.000.001.19OK200.000.000.003.88OK21-0.8514.57OKOn-site measurement results左、充電式，交流重畳装置，測定器左、充電式，交流重畳装置，測定器左、充電式，交流重畳装置，測定器左、充電式，交流重畳装置，測定器Measuring equipmentsMeasuring time;20 min.Weight;40kgPower supply;50/60Hz 100V73Loss Current MethodHVCurrent which flows on a cable(

26、Loss current)(Capacity current)Test circuitOnly the waveform for loss current is observed by comparing a current phase with a voltage phase.The peak value I3 and phase difference angle 3 to the basic wave of the 3rd harmonics current wave are used as an index of a degradation judging.74The ac loss c

27、urrent wave is distorted by water tree.(The occurrence of harmonics)Harmonic current changes according to the growth of water tree.(I3:small large,3:0)The level of water tree deterioration is judged by harmonic.Short WT3：small3：LargeBDV:HighLong WT3：Large3：SmallBDV:LowLoss Current MethodNon degradat

28、ionRelationship between water tree degradation and loss current waveform75Loss Current MethodResult of diagnosis using removed cablesResult of diagnosisGoodDefectThe degree of degradation(Breakdown voltage)Small(100kV)46 samples(Correct)4 samples(Failure)Large(100kV)0 samples(Failure)3 samples(corre

29、ct)Rate of correct answers:92%The poor cable is not judged to be good.(The breakdown in service after diagnosis is avoidable.)76cableDC power supplyRAC power supplyLPFOutputSignalcableDC power supplyRAC power supplyLPFOutputSignalCableDC power supplyRAC power supplyLPFOutputSignalResidual Charge Met

30、hodTest circuitCharge(nC)Current(nA)Time(sec)Applied AC voltage patternCharge(nC)Current(nA)Time(sec)Applied AC voltage patternResidual charge signal1.Application of DC pre-stress voltage（）Charge is accumulated in the insulation layer including water tree.2.Short-circuiting(Earth)（）Accumulated charg

31、e in the insulation layer is discharged,but trapped charge in water tree region is not released.(The existence of residual charge)3.Application in steps of AC voltage（）Trapped charge is released from water tree region.DC component current by residual charge is measured.(DC component current)DC curre

32、ntProcedure of measurement77The highest voltage value that residual charge is detected is used as the index to estimate the degree of water tree deterioration.Residual Charge MethodProcedure of voltage applicationRelease of residual chargeTrapped charge in long water tree(heavy deteriorated water tr

33、ee region)requires a higher voltage application to be released.780510152000.511.52Residual Charge Method (kV)C課電電圧残留電荷量（）築港稲永線 (kV)C課電電圧 (kV)C課電電圧残留電荷量（）残留電荷量（）築港稲永線SampleSample C課電電圧(kV)C課電電圧(kV)残留電荷量(nC)0510残留電荷量(nC)0510 C課電電圧(kV)C課電電圧(kV)残留電荷量(nC)0510残留電荷量(nC)0510Measurement resultsof residual ch

34、argeRelationship between Er and EBDMax.released stress of residual charge,Er(kV/mm)AC breakdown stress,EBD(kV/mm)AC applied voltage(kV)AC applied voltage(kV)Residual charge(nC)Residual charge(nC)EBD decreases along with the increases in Er.79Residual Charge MethodPower amplifierMeasurement deviceTes

35、ting Tr.DC power sourcePower amplifierMeasurement deviceTesting Tr.DC power sourceSchematic diagramOn-site examinationDiagnosis is automatically performed by PC.Diagnostic result is displayed on PC for a short time.Total weight;4 ton or lessMax.load;1.4FPower source;200V/100V,10kVA or less 80Compari

36、son of On-line Diagnosis and Off-line DiagnosisDiagnosis technologyDetection purposeFeatureOn-lineAbnormalities of equipmentInformation for the scram of equipmentTrend management is possible.It is easy to be influenced of a noise.Initial cost:more expensive Running cost:cheaperAged degradation of eq

37、uipmentInformation for planned replacementInitial cost:cheaper Running cost:more expensiveOff-line81Effective Example of On-line DiagnosisOn-line degradation diagnosis of a XLPE cableData changes with measurement time a lot.In the case of fixed diagnosis,an incorrect judging may be carried out.(Meas

38、urement data needs to be trend managed.)時間絶縁抵抗（M）Resistance(M)Time時間絶縁抵抗（M）Resistance(M)Time82一些新型方法 分布式光纤温度传感器 基于Faraday效应的光磁场传感器 0.1Hz超低频余弦波耐压试验 高压电缆局部放电故障定位 使用噪声减轻系统进行电缆局部放电的故障定位技术83DTS安装 DTS 原理 230kV电缆表面温度848586Layout of laboratory test system实验室测试6.6kV/LV transformers(1MVA x 2)Cables under test

39、(Maximum current 2kA)Three phase 0-230V variac(75kVA)400V,100A supply876.6kV/LV TransformersCables in trenchThermocouples Thermocouple on cable surface and coreThe 3600 paperless temperature recorder88应用热点定位Located hotspot and site conditionsLayout of circuit installationS=0.15mS=0.15mnative soilcon

40、crete slabbackfill500MVA circuitDTSgroundH=1.5mH=1.0m250MVA circuitS=0.2m S=0.2m895.Conclusion 应用II 电缆负荷预测 With the optimised soil parameters,the cable rating under various emergency load conditions could be readily predicated:when the cables are subjected to the 120%,150%and 200%nominated loading c

41、urrent(1255A),the circuit can take 120%of emergency load for 26.8 hours,150%for 8.09 hours and 200%for around 2.77 hours.Predicated conductor temperature under different overload conditions5.4 电缆的故障定位方法90XLPE交联电缆离线测试系统局放测试加压过程92振荡交流电压法 DAC Process Control Unit Data Storage PD AnalysisDielectric loss

42、es estimationHV SourceHV Solid-State SwitchInductorTest Object:Power CableHV DividerPD Coupling CapacitorPD detectorCcLSProcess Control Unit Data Storage PD AnalysisDielectric losses estimationHV SourceHV Solid-State SwitchInductorTest Object:Power CableHV DividerPD Coupling CapacitorPD detectorEmbe

43、dded PC Data Storage PD AnalysisDielectric losses estimationHV SourceHV Solid-State SwitchInductorHV DividerPD Coupling Capacitoradaptive PD detectorCcLS200 MHz AD Converter Test Object:power cable频率范围：50500Hz93连续交流和振荡波法的局放参数很相似PDIV of several PD faults at 50 Hz AC and 600 Hz DAC 94新型振荡波测试系统 OWTS M 28 28 kV peak voltageOWTS M 60 60 kV peak voltage Thank youThank you95