Fundamental Research of Power System Protection by applying Zone-Tune-Up Estimation Theory

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The purpose of this research is to develop the efficient estimation technique to eliminate the specified non-integer-harmonics (for instance, 3.7 harmonics and so on) with exponentially decay, which is included in the measured signal of the digital relaying system. Transient distortion of the signals becomes more severe with increase in the quantity of reactive compensation sources which usually increases with the size of EHV systems. Therefore, it becomes serious problem to estimate fundamental frequency component from the highly distorted measurement and to identify the fault location precisely in digital distance relay.Proposed algorithm in this research is based on the non-recursive type filter of which the coefficients are determined by minimizing the residue under the constraints, so-called 'vectorchain-rule'. 'Vector-chain-rule' is a phaser relation existing between the sequential sample data of exponentially decayed sinusoidal signal, which is newly introduced in this research. On the other hand, the frequency of transient harmonics depends on the location of fault. Therefore, the filter coefficient should be so carefully selected as the best identification of fault location is achieved around the boundary of protective zone. In other words, the filter coefficients should be tuned up the frequency of the transient hamonics at the protective zone. This zone-tune-up estimation technique is tested by using simulation model of EHV system. Result is compared with result by DFT (discrete Fourier transformation). When the measured data contains decayed transient component, the proposed algorithm shows excellent discriminative ability. The concept of surface protection for the grid-network system has been surveyed. The new idea is proposed for two-dementional identification of the fault location.