Doshisha University (Private)

Modeling
Insulation levels in electrical power systems are dictated by the voltage of switching surges generated by breakers and lightning
surges caused by lightning. It is therefore important to predict overvoltage precisely when designing economical electrical power
systems. To do this, we first need very precise numerical analysis models to represent power equipment. Our laboratory develops
models of different equipment used in electrical power systems.
The primary components of transmission and distribution systems are the overhead power lines and cables, which are
distributed-parameter lines. In overhead power lines with considerable length, which are affected by earth, wave propagation
characteristics have frequency characteristics. In cables, sheaths are thin, so their propagation characteristics also are a function of
frequency. Our laboratory has devised numerical analysis models that consider the frequency dependence of these homogeneous
lines with great precision. We are also developing a finite-length line model that considers grounding and vertical conductors, as
typified by steel towers, which must be treated as non-homogeneous lines. When developing these models, we conduct theoretical
electromagnetic field analysis and develop functional approximation method suited to represent line models; we then conduct
measurements using scale models to confirm the precision of the analytical model. We are also developing devices that measure
high voltages precisely without contact by applying the induction characteristics of multi-phase distributed-parameter lines.
Substations are built by organically combining an array of equipment such as transformers, bus lines, breakers, and arrestors.
Models of these are widely available for low-frequency domains, but we are developing the broadband numerical models needed for
surge analysis. Since this equipment has nonlinear voltage-current characteristics, these characteristics must be adequately
expressed in model development. For breakers, it is particularly necessary to consider arc characteristics, which are a discharge
phenomenon. The model developed by our laboratory can take these characteristics into account with an extremely simple function
and has notably short calculation times. The model developed by our laboratory was also improved jointly with Mr. Ichiro FUJITA of
the Plasma Application Laboratory, and we developed a discharge lamp model that has achieved good results. A paper on this
model was presented and awarded a prize at a conference.