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单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,第,五,章 电力电缆在线,监测,与诊断,On-line monitoring and fault diagnosis for power cable,1,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,2,5.1,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。,1913,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。,8,XLPE,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,铜量,/1000t,50,100,150,66,70,74,78,82,86,1,2,3,1.,电力电缆合计,2. XLPE,电缆,3.,油纸电缆,11,交联聚乙烯,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,12,XLIE,电缆的基本结构,13,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,14,导电线芯：高导电率材料，绞线承圆形或扇形截面。,绝缘层：高电阻率材料，,tg,、 低而电气强度,E,b,高的油浸纸、橡皮或塑料。,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。,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。,15,16,电缆敷设情况,电压等级,/ kV,电缆总长度,/ km,XLPE,电缆所占比例,/ %,10,73,664,98.2,35,11,569,95.3,110 (66),05,303,90.7,220 (330),00,528,57.9,500,00,056,42.7,17,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,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 methods,交联聚乙烯电缆的寿命,额定,电压,电压寿命极限,劣化,条件,3-6kVrms,Rated highest voltage,+,a few years after,bridged water tree initiation,11kVrms,After,bridged water tree initiation,(1 year or more ?),more than 22kVrms,Immediately after or before,bridged water tree initiation,BDV of cable with bridged WT,电压寿命极限,Bridged water tree,Un-bridged water tree,BDV; 10-20kV,Electrical tree,Insulation layer,Insulation layer,21,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。,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,23,对已运行油纸电力电缆的试验项目,24,XLPE,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,25,XLPE,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,28,Tettex 5462,29,极化去极化电流测量原理,30,极化去极化电流典型曲线,31,PDC-ANALYSER-1MOD,32,绝缘连接盒两侧接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,测量条件,方法,实用情况,针对形成桥的水树枝,离线,直流泄漏电流法,DC leakage current under DC high voltage application is measured.,实际采用,在线,直流成分法,DC component current in service is measured.,直流叠加法,DC component current when low DC voltage is superimposed on rated voltage is measured.,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,7.5Hz loss current when low 7.5Hz voltage is superimposed on rated voltage is measured.,针对未形成桥的水树枝,离线,残余电荷法,Residual charge after DC voltage application is measured.,研究中,损耗电流法,Harmonic component current in loss current is measured.,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,cable,guard electrode,terminal,DC power supply(buttery),recorder,判断标准,状态良好,损坏或值得注意,泄漏电流值,0.1A,0.1-1A,1A,电流波形,-,Normal,PI (= I,1,/ I,10,) 1,Existence of kick,-,36,直流泄漏电流,(A),Un-bridged water tree,Bridged water tree,Applied stress ; 1kV/mm,0.001,0.01,0.1,1,Accumulation probability (%),10,20,50,90,One 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,成分电流监测,直流叠加法,直流电桥法,38,直流,成分法,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,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,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,E,s,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,E,s,不超过,0.5 V,当护层绝缘电阻小于,200,500 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,10,50 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 XLPE,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,E,s,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,50,Test circuit,直流重畳法絶縁抵抗（,M,）,直流漏電流法絶縁抵抗（,M,）,DC power supply,Measuring equipment,cable,DC 5 - 50V is superimposed on the high voltage in service.,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 S,uperposition Method,DC leakage current is highly sensitivity.,51,時間,絶縁抵抗（,M,）,時間,絶縁抵抗（,M,）,Resistance (M),Resistance (M),Time,Time,Time change of DC superposition current,Problem,This 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 S,uperposition Method,52,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,R,x,= (,E,1,-,V,4,),R,2,/,V,4,设,E,1,为,20 V,，,V,4,为,1 mV,，,R,2,为,50 M,R,x,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,E,s,影响的消除 调节,R,4,及,E,0,V,0,指示为零,其他设备的绝缘电阻与,R,3,并联,R,3,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,法,介损,因数法,56,什么是介质损耗角,( tan,d) ?,time/sec,0,10,电压,电流,=,介质损耗角,tan,=,有功功率,无功功率,57,受潮对,tan,的影响,58,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,d,(2,U,0,) ,1.2,and,tan,d,(2,Uo) -,tan,d,(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,d,(2,Uo),2.2,or,tan,d,(2,Uo) -,tan,d,(Uo),1.0,对于,XLPE,电缆这一标准是非常重要的。,XLPE,的,tan,d,标准,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,、,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,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,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,实时报警, 故障精确定位,综合监测（温度、烟雾、放电等）,72,Among 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 Method,No,DC leakage current (A),AC superposition method (nA),adjust,5kV,10kV,16kV,1,0.01,0.02,0.00,14.48,X,2,0.02,0.74,-,6.34,X,3,0.00,0.00,0.00,8.37,OK,4,0.40,3.10,-,17.79,OK,5,0.02,10.5,-,76.72,OK,6,0.01,0.03,0.00,2.84,OK,7,0.00,0.02,0.00,6.43,OK,8,0.01,0.03,0.00,21.30,X,9,0.01,0.19,0.21,56.80,OK,10,0.10,2.80,-,34.13,OK,11,0.00,0.06,0.07,27.79,X,12,0.30,10.5,0.25,17.62,Ok,13,0.00,0.00,0.00,3.03,OK,14,0.00,0.00,0.00,4.17,OK,15,0.00,0.00,0.00,32.54,X,16,0.00,0.00,0.00,7.78,OK,17,0.00,0.00,0.00,2.71,OK,18,0.00,0.00,0.00,3.06,OK,19,0.00,0.00,0.00,1.19,OK,20,0.00,0.00,0.00,3.88,OK,21,-,-,0. 85,14.57,OK,On-site measurement results,Measuring equipments,Measuring time; 20 min.Weight; 40kgPower supply; 50/60Hz 100V,73,Loss Current Method,HV,Current which flows on a cable,(Loss current),(Capacity current),Test circuit,Only the waveform for loss current is observed by comparing a current phase with a voltage phase.,The peak value,I,3,and phase difference angle,3,to the basic wave of the 3,rd,harmonics current wave are used as an index of a degradation judging.,74,The ac loss current 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 WT,3,：,small,3,：,Large,BDV : High,Long WT,3,：,Large,3,：,Small,BDV : Low,Loss Current Method,Non degradation,Relationship between water tree degradation and loss current waveform,75,Loss Current Method,Result of diagnosis using removed cables,Result of diagnosis,Good,Defect,The degree of degradation,(Breakdown voltage),Small,(100kV),46 samples,(Correct),4 samples,(Failure),Large,(100kV),0 samples,(Failure),3 samples,(correct),Rate of correct answers : 92%,The poor cable is not judged to be good. (The breakdown in service after diagnosis is avoidable.),76,cable,DC,power,supply,R,AC power,supply,LPF,Output,Signal,cable,DC,power,supply,R,AC power,supply,LPF,Output,Signal,Cable,DC,power,supply,R,AC power,supply,LPF,Output,Signal,Residual Charge Method,Test circuit,Residual charge signal,1.Application of DC pre-stress voltage,（） ,Charge is accumulated in the insulation layer including water tree.,2.Short-circuiting (Earth),（） ,Accumulated charge 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 current,Procedure of measurement,77,The highest voltage value that residual charge is detected is used as the index to estimate the degree of water tree deterioration.,Residual Charge Method,Procedure of voltage application,Release of residual charge,Trapped charge in long water tree (heavy deteriorated water tree region) requires a higher voltage application to be released.,78,Residual Charge Method,Sample,Sample,Measurement resultsof residual charge,Relationship between Er and E,BD,Max. released stress of residual charge, Er (kV/mm),AC breakdown stress, E,BD,(kV/mm),AC applied voltage (kV),AC applied voltage (kV),Residual charge (nC),Residual charge (nC),E,BD,decreases along with the increases in Er.,79,Residual Charge Method,Schematic diagram,On-site examination,Diagnosis is automatically performed by PC.,Diagnostic result is displayed on PC for a short time.,Total weight ; 4 ton or less,Max. load ; 1.4F,Power source ; 200V/100V, 10kVA or less,80,Comparison of On-line Diagnosis and Off-line Diagnosis,Diagnosis technology,Detection purpose,Feature,On-line,Abnormalities of equipment,Information for the scram of equipment,Trend management is,possible.,It is easy to be influenced of,a noise.,Initial cost : more expensive,Running cost : cheaper,Aged degradation of equipment,Information for planned replacement,Initial cost : cheaper,Running cost : more expensive,Off-line,81,Effective Example of On-line Diagnosis,On-line degradation diagnosis of a XLPE cable,Data changes with measurement time a lot.,In the case of fixed diagnosis, an incorrect judging may be carried out. (Measurement 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),Time,82,一些新型方法,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,83,DTS,安装,DTS ,原理,230kV,电缆表面温度,84,85,86,Layout of laboratory test system,实验室测试,6.6kV/LV transformers,(1MVA x 2),Cables under test,(Maximum current 2kA),Three phase 0-230V variac,(75kVA),400V, 100A supply,87,6.6kV/LV Transformers,Cables in trench,Thermocouples,Thermocouple on cable surface and core,The 3600 paperless temperature recorder,88,应用,热点定位,Located hotspot and site conditions,Layout of circuit installation,S,=0.15m,S,=0.15m,native soil,concrete slab,backfill,500MVA circuit,DTS,ground,H,= 1.5m,H,= 1.0m,250MVA circuit,S,=0.2m,S,=0.2m,89,5. 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 current (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 conditions,5.4,电缆的故障定位,方法,90,XLPE,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 Analysis,Dielectric losses,estimation,HV Source,HV Solid,-,State Switch,Inductor,Test Object: Power Cable,HV Divider,PD Coupling Capacitor,PD detector,C,c,L,S,Process Control Unit,Data Storage,PD Analysis,Dielectric losses,estimation,HV Source,HV Solid,-,State Switch,Inductor,Test Object: Power Cable,HV Divider,PD Coupling Capacitor,PD detector,Embedded PC,Data Storage,PD Analysis,Dielectric losses,estimation,HV Source,HV Solid,-,State Switch,Inductor,HV Divider,PD Coupling Capacitor,adaptive PD detector,C,c,L,S,200 MHz AD Converter,Test Object: power cable,频率范围：,50,500Hz,93,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 voltage,OWTS M 60,60 kV peak voltage,Thank you,95,
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