Takahiro Kase

Charging current compensation for distance protection

When a distance relay is applied to a long transmission line, the capacitance of the transmission line causes oscillation of the distance measurement, although the exact nature of the phenomenon has never been clearly defined. Our research has shown that the degree of oscillation can be reduced significantly by introducing charging current to the circuit model to be solved by the distance relay. In this paper, the undesirable influence of charging current on distance protection is introduced, after which the effect of charging current compensation for a distance relay is proven by practical simulations. Furthermore, the advantage of this method of charging current compensation as opposed to other methods is also explained.

Charging Current Compensation for Distance Protection

One difficulty of the application of line protections to long transmission lines is the influence of the large capacitance of the line. When a fault occurs on a long line, relatively large magnitude harmonic components of current and voltage are superimposed on the fundamental frequency component due to the large capacitance of the line. This harmonic component can cause oscillation of the distance measurement. It is difficult to remove the harmonic component completely because the order of the harmonic component varies with several conditions. Our research has shown that the degree of oscillation can be reduced significantly by compensating for the charging current in the impedance calculation. This proposed charging current compensation (CCC) method provides an excellent result under all conditions. In this paper, the calculation method of CCC is introduced and good performance of CCC for the application to long overhead lines and to the long cable line is proven based on Alternative Transient Program simulations.

A proposal for the standardization of WASA which complies with international standards

Recently the importance of Wide-Area Situational Awareness (WASA) is increasing as a basis for power system stabilization systems or as a part of a smart grid. While, in Japan, power system stabilization systems have been applied for many years and a significantly long experience has been established in the application of this technology. These stabilization systems have different system configurations and applications for their specific purpose, and they are classified and systematized in this paper. On the one hand, standardization of various communication interfaces and protocols have been discussed triggered by the introduction of the concept of the smart grid, and we discuss some of those international standards which are related to WASA. Although some standards have already been published, some are still under preparation and discussion prior to official publication. Consolidation of those standards for the stabilization system is important to the standardization of WASA, and we discuss the approach to standardization and introduce a typical WASA system.

Problems associated with zero sequence compensation applied to distance protection

Zero sequence compensation is one of the essential functions found within distance protection and is widely used all over the world. However, the application of this function can be problematic as it can cause complex and subtle effects. Often investigations into problems found with zero sequence compensation have not clarified whether or not a problem would have caused unwanted operation under very severe conditions. In this paper the undesirable effect of zero sequence compensation on the measurement of resistance and on the performance of Mho elements is investigated and described. These undesirable effects are explained using vector diagrams and equations in order that a general tendency of the effect can be understood. The explanation is confirmed by simulation using ATP. Finally, the problems are summarised and possible solutions are suggested