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Inspection, Analysis And Restraining Of DC Transmission On Power Grid Equipment

Posted on:2006-03-21Degree:DoctorType:Dissertation
Country:ChinaCandidate:D Z KuaiFull Text:PDF
GTID:1102360155958683Subject:Detection Technology and Automation
Abstract/Summary:PDF Full Text Request
Along with the general ploicy "West to east power transmission, North-south power exchange and Nationwide interconnection",the HVDC is the main selection of long distance transmission, but HVDC link has influence on the traditional electral network device.Since the 500kV DC transmission project was put into service by monopolar link in Dec. 2002, noises of the 500kV main transformers around WuNan increase significantly (about 21 DB). This thesis discussed the impact of ground direct current produced by DC monopolar link upon equipment in AC system. It includes:i) Through field testing, analyzed characteristics of underground direct current distribution of Jiangsu Power Grid, and built corresponding direct current system models.ii)Direct current bias will cause rapid increase of transformer excitation current and result in overheat, noises and vibration increase in magnetic circuits. In the case of direct current bias, there appear significant odd harmonic noises in the spectrum of transformer noises, the problems caused by which may make the related components in the transformer loose, then threaten the operation security of transformers.iii)Both HVDC monopole to ground operation and the switching of filters in coverter stations will cause wide-range increase of grid harmonics, especially the latter. The playback wave of filter switching in the DC converter station didn't cause mis-action of protective devices. The protective devices act correctly when superposing grid faults.iv)The moniter device was mounded on the neural side of main transformer, It could detect the influence on transformer by DC transmission and solar storm. The device was put on operation. The inverse current injection method at the neural points of transformers can possibility restrict DC current at transformer neutral point on principle. These measures are available in engineering implementation.
Keywords/Search Tags:DC transmission, Harmonic, DC magnetic biasing, Transformer, Current Transformer, Relay Protection, Grounding network
PDF Full Text Request
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