The transition away from SF6-based insulation in high-voltage equipment has accelerated interest in alternative gas mixtures with lower environmental impact. One such mixture is CO2/O2 (70%/30%), which is used as a carrier gas in C4-FN based mixtures but is also being explored for stand-alone insulation applications. To enable detailed characterisation of partial discharges (PDs) in such alternative gases, a high-bandwidth measurement setup was developed. The setup is based on a custom designed test compartment that uses a needle-to-plane electrode configuration to generate corona discharges and applies a high-frequency current transformer (HFCT) as a measurement impedance.
Initial measurements using a conventional IEC 60270 configuration revealed a resonance frequency of 3.5 MHz, which limited the effective bandwidth of the system. By eliminating the traditional coupling capacitor and instead using the inherent capacitance between the conductor in the bushing and the grounded enclosure as a coupling path, the resonance frequency was shifted to 144 MHz. Aside from the significant increase in bandwidth, this also improved sensitivity. The frequency response of each segment of the measurement circuit was characterised, allowing the derivation of the PD current from the measured voltage and enabling calibration-free charge estimation. The setup was used to study the PD behaviour in a CO2/O2 (70%/30%) mixture at pressures ranging from 0.2 to 0.4 MPa and voltages up to 1.5 times the PD inception voltage. A novel phenomenon was observed: certain PDs were rapidly followed by another discharge, after which a longer interval was required for the next event.
Multiple charge estimation methods were adapted to suit the measurement circuit. After evaluation, the modified frequency domain method demonstrated the strongest correlation with peak current, especially at low discharge magnitudes. These results demonstrate that the developed measurement setup is suitable for detailed PD analysis in alternative gases and that it is able to offer new insight into the behaviour of alternative gases.

One of the major challenges faced by future robotic and human missions to Mars and the Moon is the presence of atmospheric dust. The Lunar Zebro rover which is intended to walk on the Moon is powered by solar panel. Due to its surrounding terrain, which mostly consists of small particles, the rover may be a potential target for dust accumulation, which reduces its output power. For the longevity of any space mission, it is important to have a long-lasting source of energy. That is why during this project, an Electrodynamic screen is constructed which could remove dust from a 100 x 100 mm area without containing moving parts. One subgroup concentrated on building the electronics necessary to create a high voltage (~1.6kV) three-phase drive signal, the other group focused on the electrodes of the system and described the effects of an electric field on dielectric particles. These are mostly found on the Moon. Different electrode architectures are proposed, but the zigzag architecture was found to be the best suited for a possible dust removal system. Furthermore, the higher voltage applied to the electrodes, the greater the forces exerted on the particles are. Further research should be conducted for any possible implementation. It is recommended to also read the other thesis.