Earth fault protection using transient signals in non-solid earthed network

Research on adaptive tripping for single phase earth fault in neutral point non-effectively grounded system

“…CICED2012 Session 3 Page2/5 b) Procedure of capacitive reactive power direction Direction of capacitive reactive power is judged by below equation definition [5]:…”

“…With the development of line selection techniques, some line selection principles are studied such as first-half transient wave [2], signal injection [3], medium resistance method [4], special frequency band (SFB) [5] and that based on wavelet transform and other mathematic principles [6], corresponding devices are developed and put into uses on site. And the practices show that these methods are not affected by arc suppression coil and unstable arc and make most of collected signals originated from the fault point, the sensitivity and reliability are high in case of right connection polarity of PT and CT.…”

“…Authors propose the procedure of combination of line selection based on polarity of transient current, directions of transient capacitive reactive power, in the resonance grounding system. a) Current polarity comparative method Polarity of sequence current of any two feeders iOk ( t )and iO m ( t ) are compared by polarity coefficients[5]: Pkm = l. rr iOk (t)iOm (the iOk (t) and iO m (t) are same polarity. If not, reversed polarity.…”

The fault location technology using transient signals for single phase earth fault in non-solidly earthed network

“…Fig. 1 shows the traditional circuit of single-phase earth fault presented in [5][6]. Where, L 0 , C 0 are the inductance, capacitance of zero modulus, respectively.…”

Study on the Non-power Frequency Transient Fault Selection in Distribution Network with a Single-Phase to Ground Fault Based on Hilbert-Huang Transform

“…我国配电网均采用中性点不直接接地方式，被称为小电 流接地系统。小电流接地系统包括中性点不接地系统、中 性点经消弧线圈接地系统(又称谐振接地系统)、中性点 经电阻接地系统。配电网发生故障时，单相接地故障的几 率最高，可占总故障的80%左右。传统的小电流接地系统 的选线方法例如幅值比较法、极性比较法、群体比幅比相 法、零序电流无功功率方向法 [1] ，基本满足小电流不接地系 统的选线要求，但不适用谐振接地系统。随着配电网的迅 速发展，电网中电缆线路的比例迅速上升，缆线混合线路 越来越多，电网发生单相接地故障时，故障零序电容电流 很大，更增大了谐振接地系统的选线困难。为解决谐振接 地系统故障选线这一难题，许多学者进行了大量的研究， 并提出了多种选线方法。目前应用于经消弧线圈接地系统 的选线方法主要由有功分量比较法和谐波比较法 [2][3][4][5] 。有功 分量比较法主要包括故障电流有功电流分量的幅值和极性 比较法、有功电流方向比较法、有功功率方向比较法，但 由于接地电流有功分量小(一般小于1A)，可靠性不能满 足目前供电可靠性的要求。到目前为止在实际应用中,对于 中性点经消弧线圈接地系统，现有的故障选线原理效果不 理想，所以此问题还有必要进一步研究。在小电流接地系 统从故障前稳态到故障后稳态，存在一个明显的暂态过程， 该过程中暂态电流有大量的暂态分量存在，并且暂态电流 的分布不受消弧线圈的影响 [5][6][7][8][9][10][11][12] ，所以本文提出基于HHT 非工频零序暂态电流分量的配电网单相接地故障选线方 法，该方法既适用于电缆线路、架空线路、缆线混合线路 组成的谐振接地系统，也适用于不接地系统。…”