摘要
针对西北750kV电网官亭、武胜两站空载变压器合闸(简称合空变)导致800km外的青藏直流系统闭锁故障进行了分析。合空变过程中可能产生大量谐波,其中包括明显的2次分量;从合空变位置看入西北电网的阻抗特性中存在接近二倍频的谐振频率;西宁—日月山—海西—柴达木750kV线路长度接近二倍频下电磁波的1/4波长,容升效应显著;柴达木末端电网在二倍频下呈大阻抗特性;青藏直流系统交流侧电压中负序2次谐波将在直流侧引起3次谐波。以上多个因素导致合空变产生的2次谐波电压沿线放大,并引起直流系统谐波保护动作。研究结果阐明了合空变过程产生的谐波远距离传输特性及对直流系统的影响,为研究直流谐波保护问题提供了理论依据。
This paper focuses on the blocking of Qinghai-Tibet DC system caused by energizing of no-load transformers located over 800 km away at Guanting and Wusheng,in northwest China 750 kV grid.Frequency response characteristics of the network are analyzed.There are zero and pole around 100 Hz in the frequency spectrum of the impedance seen from the energizing position.With the length of near quarter wavelength of electromagnetic wave at 100 Hz,capacitive effect of this line is significant.As such,second harmonic voltage is amplified along the 750 kV line.The equivalent impedance at 100 Hz of Chaidamu subtransmission network is large.Also in Qinghai-Tibet DC system,150 Hz harmonics will appear at DC side if negative 100 Hz harmonics exist at AC side.All these lead to amplification of harmonics and blockage of the DC system.Research results elucidate the transmission characteristics and influences on DC system of harmonic caused by energizing of no-load transformer,and provide theoretical evidence of research on harmonic protection problems in DC systems.
出处
《电力系统自动化》
EI
CSCD
北大核心
2013年第10期129-133,共5页
Automation of Electric Power Systems
关键词
直流输电
合空变
谐振频率
谐波
容升效应
DC transmission system
blocking of no-load transformer
resonant frequency
harmonics
capacitive effect
