The General Electric (GE) company is developing an advanced plasma switch that will make a conversion of high-voltage DC to high-voltage AC more efficiently, enabling reduced-cost transmission of long-distance power. Additionally, substations along the power route will reduce the voltage of AC current to low-voltage before it reaches consumers’ devices.
We use low-voltage alternating current (AC) to power everything inside our homes and offices. However, when we need to transport the electricity for longer distances – for instance, transportation from sources such as hydropower or solar generating plants – using direct current (DC) is more efficient. Then, we need bulky and expensive switches to transform it back to AC.
The company has an idea to use a tube filled with plasma as conversion devices. This plasma switch could be able to operate with a voltage up to 300 kilovolts and last for years. Such a unite, alone, will be able to substitute current solution – the assemblies of power semiconductor switches along transmission lines.
Firstly, the GE team tested a high-voltage plasma switch and found out that it is slow and expensive. Then, they tried to demonstrate how the high current affects the helium gas (used inside the plasma tube by modeling the switch. This led to producing new insight into the physics of the process.
However, this was mostly focused on studying the lower-voltage breakdown of gases, and GE is dealing with a much higher voltage. The low-pressure and high-voltage breakdown mechanism has been poorly understood because of the need to consider new mechanisms of gas ionization at high voltages, which is what the team did.
Three different breakdown regimes were identified by the findings. They are very important when a high voltage is used to transform helium into plasma. There, electrons, ions, and fast neutral atoms start the breakdown by bouncing off the electrodes through which the current flows. Previously, models considered only the impact of electrons on the ionization process.
According to the leader of the project, Timothy Sommerer, the potential applications of the plasma switch depend on its maximum possible voltage. He and his team have already experimentally demonstrated that a plasma switch can operate at 100 kilovolts and there is space for improvement (300 kilovolts).