霍尼韦尔DCS卡件51403988-15051403988150霍尼韦尔DCS卡件51403988-15051403988150霍尼韦尔DCS卡件51403988-15051403988150-------------------------------------------------------------------------------------------------------------------变压器铁芯有两点及以上接点时，铁芯主磁通周围有短路匝存在，内将流过环流，其大小取决于铁芯正常接地点与故障点的位置，距离越远，包括的磁通就越多，环流也比较大，有可能高达数百安培，反之，环流较小。另外，环流也与金属接地或高阻接地有关。由于铁芯芯片间有绝缘电阻，铁芯自身也有电阻，当环流通过时，将会发热，而发热将使油温上升，变压器内部产气速率猛增，如不及时处理，轻则瓦斯继电器动作，严重者接地线烧断中进而出现放电故障，损坏固体绝缘和油质绝缘强度，造成严重后果。1.铁芯多点接地故障的危害变压器正常运行时，是不允许铁芯多点接地的，因为变压器正常运行中，绕组周围存在着交变的磁场，由于电磁感应的作用，高压绕组与低压绕组之间，低压绕组与铁芯之间，铁芯与外壳之间都存在着寄生电容，带电绕组将通过寄生电容的耦合作用，使铁芯对地产生悬浮电位，由于铁芯及其它金属构件与绕组的距离不相等，使各构件之间存在着电位差，当两点之间的电位差达到能够击穿其间的绝缘时，便产生火花放电，这种放电是断续的，长期下去，对变压器油和固体绝缘都有不良影响，为了消除这种现象，把铁芯与外壳可靠地连接起来，使它与外壳等电位，但当铁芯或其他金属构件有两点或多点接地时，接地点就会形成闭合回路，造成环流，引起局部过热，导致油分解，绝缘性能下降，严重时，会使铁芯硅钢片烧坏，造成主变重大事故，所以主变铁芯只能一点接地。2.铁芯接地故障的原因变压器铁芯接地故障主要有：（1）接地片因施工工艺和设计不良造成短路；（2）由于附件和外界因素引起的多点接地；（3）由遗落在主变内的金属异物和铁芯工艺不良产生毛刺，铁锈与焊渣等因素引起接地。3.铁芯故障的类型变压器铁芯常见的故障类型有下述六种：（1）铁芯碰壳、碰夹件。安装完毕后，由于疏忽，未将油箱顶盖上运输用的稳（定位）钉翻转过来或拆除掉，导致铁芯与箱壳相碰；铁芯夹件肢板碰触铁芯柱；硅钢片翘曲触及夹件肢板；铁芯下夹件垫脚与铁轭间纸板脱落，垫脚与硅钢片相碰；温度计座套过长与夹件或铁轭、芯柱相碰等。（2）穿芯螺栓钢座套过长与硅钢片短接。（3）油箱内有异物，使硅钢片局部短路。如山西某变电所的一台31500/110型电力变压器发生铁芯多点接地，吊罩发现在夹件与铁轭间有一把天柄螺丝起子；另一变电所一台60000/22O型电力变压器吊罩启发现有一根120mm长的铜丝；还有一个变电所台120000/220型电力变压器吊罩后在下夹件与铁轭之间找出一锅块；再如，东北某变电所的一台大型电力变压器发生铁芯多点接地，吊罩检查发现油箱底部有三段曲折型钢丝，钢丝的直径约0.31mm,长度分别为25、28、31mm.（4）铁芯绝缘受潮或损伤，如底沉积油泥及水分，绝缘电阻下降，夹件绝缘、垫铁绝缘、铁盒绝缘（纸板或木块）受潮或损坏等，导致铁芯高阻多点接地。（5）潜油泵轴承磨损，金属粉末进入油箱中，堆积在底部，在电磁引力作用下形成桥路，使下铁轨与垫脚或箱底接通，造成多点接地。（6）运行维护差，不按期检修。P0970BXP0970DCP0970DFP0970DGP0970EJP0970GWP0970HHP0970HSP0970HTP0970HVP0970HXP0970JAP0970JBP0970JDP0970JEP0970JGP0970JHP0970JJP0970JKP0970JLP0970JRP0970JWP0970JZP0970KEP0970KFP0970KGP0970KHP0970KJP0970KTP0970KUP0970KVP0970KWP0970LJP0970LKP0970LWP0970MMP0970MNP0970MUP0970MVP0970MYP0970MZP0970NGP0970NLP0970NMP0970NRP0970PAP0970PBP0970PCP0970PDP0970PEP0970PFP0970PJP0970PKP0970PLP0970PMP0970PNP0970PPP0970PQP0970PRP0970PSP0970PTP0970PUP0970PVP0970PXP0970PYP0970PZP0970QSP0970QTP0970QUP0970QVP0970QWP0970QXP0970QYP0970QZP0970RAP0970TEP0970UTP0970UYP0970VBP0970VCP0970VDP0970VEP0970VQP0970VSP0970WUP0970WVP0970WWP0970WXP0970WYP0970WZP0970XAP0970XCP0970XDP0970XEP0970XFP0970XGP0970XHP0970XJP0970XKP0970XLP0970XMP0970XNP0970XPP0970XXP0970YAP0970YBP0970YCP0970YDP0970YEP0970YFP0970YGP0970YHP0970YJP0970YKP0971AAP0971ABP0971ACP0971AJP0971AMP0971ANP0971ATP0971AUP0971BAP0971BBP0971BCP0971BJP0971BKP0971BMP0971BNP0971BQP0971BRP0971BUP0971BXP0971CFP0971CTP0971CVP0971CWP0971CXP0971DAP0971DBP0971DEP0971DFP0971DLP0971DMP0971DNP0971DPP0971DQP0971DRP0971DSP0971DTP0971DUP0971DVP0971DXP0971DYP0971DZP0971FBP0971FCP0971FDP0971FEP0971FFP0971FHP0971FJP0971FKP0971FLP0971FMP0971FNP0971FSP0971FTP0971FZP0971GDP0971GEP0971GFP0971GGP0971GHP0971GJP0971GKP0971GLP0971GQP0971GTP0971GXP0971JAP0971JBP0971JCP0971JDP0971JEP0971JFP0971JGP0971JHP0971JKP0971JLP0971JMP0971JNP0971JPP0971JQP0971JRP0971JSP0971JTP0971KTP0971LAP0971LBP0971LCP0971LDP0971LEP0971LFP0971LRP0971LSP0971LTP0971LZP0971MBP0971MCP0971MKP0971MLP0971MQP0971MXP0971MYP0971MZP0971NUP0971NVP0971PAP0971PBP0971PCP0971PDP0971PEP0971PKP0971PNP0971PSP0971PZP0971QLP0971QMP0971QPP0971QRP0971QTP0971QV)