Improving MHz - GHz partial discharge detection using high-gain low-noise amplifiers with modified cascade and cascode topologies

• The proposed LNA enhances PD detection sensitivity in high voltage equipment. • HBT-based cascode and cascade of cascode LNAs achieve high gain, wide bandwidth, and meet IEC standards. • LNAs improve PD detection, especially for detectors with higher noise levels. • LNAs amplify weak PD signals, ensuring accurate and reliable insulation defect detection for testing voltages near PDIV. This study proposes an implementation of Low Noise Amplifier (LNA) for Partial Discharge (PD) detection in high voltage equipment, particularly covering the frequency range of MHz to GHz. Ultra-High Frequency (UHF) antennas, which are commonly used for modern PD detections, provide higher sensitivity and better signal detection but lack the amplitude required to effectively display the PD signals. To further improve PD detection, two topologies of LNAs which uses Heterojunction Bipolar Transistor (HBT), cascode and cascade of cascode, is proposed. The proposed LNA testing results show that the Cascode LNA had a gain of 19.9 dB with a bandwidth (-3 dB) of 1.86 MHz to 3318.84 MHz, while the Cascade of Cascode LNA had a gain of 31.2 dB with a bandwidth (-3 dB) of 7.11 MHz to 3124.87 MHz. This difference in gain and bandwidth will affect the characteristics of partial discharge detection, which will be seen in the real PD test. In the PD test, using a Micro-Strip Antenna and a Cube Antenna as detectors, it was found that both LNAs were able to increase the number of PRPD points obtained, especially in the detector that had a higher level of background noise. Higher gain and wider bandwidth also improved the amount of PRPD points detected, particularly in cycles where PD was less detectable without LNA. Both LNAs also show improvements in the visibility of fall time. The use of an LNA is proven to be crucial in PD detection due to the weak nature of PD signals, typically in the millivolt range, and it meets the requirements of IEC60270 and IEC62478 standards for PD measurements. Overall, LNA will improve the accuracy and reliability of PD detection systems, and the experiments have further emphasized the importance of LNA for voltages near PDIV to amplify weak PDs.