可控并联电抗器的功能和调节

根据超、特高压长线路无功平衡的条件,列出了并联电抗器的可控调节方式,可使全线始终处在最佳运行工作状态。并联电抗器抑制工频过电压的机理,在于缩短空线的等效长度,从而削弱电容效应,基于这一特点,可控电抗器应有高速响应能力,使在形成空线的瞬间立即恢复到全补偿工作状态。在切空线过程中,线路残余电荷通过并联电抗器的低频泄放显著延缓开关恢复电压的上升速度而致避免重燃。在叙述中性点小电抗对抑制谐振和潜供电弧的重要作用的同时,指出它不应做成可控形式,其大小应根据主电抗的最大容量选定,以免显著限制后者的功率调节范围和造成对自身与主电抗中性点的过高的绝缘要求。

Function and Regulation of Controllable Shunt Reactor

With the rapid development of EHV systems and construction of UHV lines in China, controllable shunt reactors are expected to be put into operation in the near future as one of the important electro-apparatus. They have the ability to compensate for the dynamic capacitive power of transmission lines smoothly, suppress the power frequency overvoltage effectively, and avoid the overvoltage in the case of empty line interruption. They are also be able to prevent the power frequency resonance and impel the secondary arc to suppression when a small power inductance is connected to the neutral of reactors. These functions have been partly presented in the open literature. This paper will develop some further insights into the functions of the controllable reactors from different viewpoints of the mentioned problems. From the conditions for reactive power balance in long EHV and UHV lines, the regulation mode of shunt reactors was presented in this paper for optimal operation of the lines. It was realized that the suppression of the power-frequency overvoltage through using a shunt reactor was due to the weakened capacity effect resulted from the reduction of the equivalent length of the empty line. This requires a quick response from the controllable reactor in order to recover its full capacity immediately in the presence of empty line. When the empty line is interrupted, residual charges on the isolated lines will discharge with low frequency oscillation.,this delays the rise of the recovery voltage between the contacts of the breaker and thus avoids restrike. While the neutral inductance of a shunt reactor plays an important role in restraining resonance phenomenon and secondary current, our research in this paper reveals that the value of neutral inductance should be determined according to the maximum degree of the compensation of the shunt reactor, implying that this value should not be set in controllable form, which narrows the range of the power regulation of the shunt reactor and requires high level of insulation of the neutral itself.