23 / 2017-01-23 14:33:53

Design and Analysis of Coupling Device in Partial discharge Detection

12578,12579,12580

This paper presents design and construction of a coupling device which is used as a PD signal and AC Voltage signal measuring device in the conventional partial discharge testing according to IEC 60270:2000. The developed coupling device is capable to measure AC voltage up to 60 kVpeak at frequencies of 50 Hz and 200 Hz. Lower limit and Upper limit frequency of the developed device are 30 kHz and 1 MHz, respectively. That means the bandwidth of the coupling device is 970 kHz. The remarkable feature of the developed device is the accuracy in PD signal measuring and the ability in eliminating noise signal such as unwanted AC signal at PD measuring point and interference signal. Therefore, in the design procedure based on OrCAD computer program, two main parts being the AC signal measuring part and the PD Signal measuring part are considered. In the AC signal measuring part, the proper impedance was chosen to achieve appropriate voltage divide ratio and accuracy in PD signal measuring. In the coupling device, voltage surge protective device was installed to protect the oscilloscope. In PD signal measuring part, the value of the components in PD signal measuring circuit must be chosen properly to achieve the determined Upper and Lower limit frequency and consider the value of the matching resistance. In this part, noise signal elimination must be considered to gain less effect to PD signal, otherwise the PD signal waveform will distort. From intensive study, three different coupling device circuits were designed and each circuit has different advantage. The three different coupling devices were constructed and then, they were tested at 50 Hz and 200 Hz 60 kVpeak . The results of the three developed coupling devices are compared to that of reference coupling device in the HV laboratory of King Mongkut's Institute of Technology Ladkrabang. The developed coupling devices can be used in conventional PD testing according to IEC 60270:2000. The comparisons of the simulated and experimental results show that the performance of the only one of the developed coupling devices as same as the reference coupling device.