Harmonic Analysis Study for High-voltage Distribution Equipment on Power Factor

Dielectric loss factor measurement is an important index in accessing the insulation performance of power equipment. With the development of the condition-based maintenance and smart grid, more attention has been paid to online diagnostic technologies for the dielectric loss factor measurement. Various methods have been developed in this field in which harmonic analysis (HA) is prevalent due to its performance of resisting disturbance and stability superior to others. When performing the HA method on the sampled data, the non-simultaneous sampling and the lack of synchronization between sampling rate and the signal period are believed to be the main source of error in the measurement of the magnitude and the phase of the signals. To improve the effectiveness of the HA method, measures were taken by means of the designing online monitoring system. The basic principle of the HA method is presented in this paper and an online monitoring system based on DSP technology is developed accordingly. At last, this paper analyses the on-line monitoring results resulted from the online monitoring system on a substation. To ensure the safe and reliable operation of a power system it is necessary to monitor periodically the insulation condition of HV apparatus. This may be accomplished through measuring partial discharge levels, dielectric loss factor and capacitance using conventional well-established time based maintenance method. To implement these routine tests require removal of equipment from service, however, the measure and continuous monitor may be carried out directly if on-line monitoring method is adopted. These on-line dielectric loss factor measuring methods detect the current flowing through the test object and the voltage signal applied to it. The various techniques reported in the literature differ from each other in the manner how the signals are acquired and how the gathered data are handled. In the work reported in this paper a distributed on-line monitoring system has been developed based on