Corridor of EEIC, The University of Tokyo

High voltage and high current engineering, insulation of electrical apparatus, plasma physics：Akiko Kumada

Towards Advanced Power System

With the need to build a zero-carbon society, the power system is undergoing major changes. In addition to upgrading the conventional AC grid, there is an urgent need to develop fundamental technologies for the DC grid. Our research focuses on developing new sensors and clarifying the phenomena of discharges, current interruptions, and electrical conduction in solids based on the understanding of the physics of physics. I direct HV lab. in collaboration with Project Prof. Takashi Fujii and Assistant Prof. Masahiro Sato.

Current interruption technology with VCB

Switchgear technology is an important fundamental technology in power systems.
In order to improve the environmental friendliness of power grid, it is necessary to raise the voltage class of vacuum circuit breakers and to realize compact and low-cost DC circuit breakers. In order to understand the physics of the breakdown and arcing phenomena in vacuum circuit breakers, we are investigating the mechanism of the breakdown caused by small particles, the improvement of the flashover voltage, and the characteristics of vacuum arc under DC interruption (through the measurement of plasma temperature, electron density, and neutral particle density).

Treeing phenomena in insulating material

When voids or cracks exist inside a polymer insulating material or at the interface with a conductor, a partial discharge occurs and electric tree is generated, which propagates through the insulating material and eventually leads to breakdown.
In recent years, it has been shown that nanocomposite fillers in epoxy resins can suppress the generation and propagation of tree. By optical microscopy and X-ray phase imaging techniques, the tree-suppression mechanism of nano fillers is investigated.
Silicone gel is used as an encapsulant of power modules, which are the key component of AC/DC converters. We have also measured the characteristics of the electrical tree propagation phenomena under PWM waveforms with repetitive surges and have proposed methods to improve the dielectric strength of the power module for higher operating voltages and higher operating frequencies.

Electro-optic sensors for measuring high-voltage phenomena

There is a strong demand to measure electric field with electrical discharges or with non-linear materials. Sensors based on electro-optic effect (Pockels effect, Kerr effect) are suitable for the measurement of high voltage and discharge phenomena due to their wide applicable frequency, electromagnetic non-inductive properties and the possibility of using only insulators. Our laboratory has been developing sophisticated electro-optical sensors for many years, increasing their applicable voltage, sensitivity, application as a surface potential probe, use of electromagnetic waves with long and short wavelengths, and the expansion of application.