Static Capacitors for High-Voltage Use in Japan

Over 4,000,000 kilovars of static capacitors designed for power-factor improvement and voltage regulations have been manufactured in Japan. About half have been used for voltage regulation at primary substations in place of synchronous condensers and are directly connected to lines operating from 11 to 77 kv. The largest installation has a capacity of 80,000 kilovars. More than 60 per cent of the electric power in Japan comes from hydroelectric sources that are remote from their load centers and synchronous condensers are generally installed at the end of the long transmission lines for voltage regulation. This offers an excellent field for static capacitors. The development of a paper dielectric several times thicker than standard capacitor papers has permitted the construction of single capacitors rated as high as 500 kilovars. The cost of a comparable new unit is less than a third of that of a conventional unit of 30 kilovars, the largest generally made. This has made the static capacitor a strong competitor of the synchronous condenser. A number of technical difficulties have been encountered. Waveform distortion, in particular, has caused abnormal current flow resulting in false operation of relays and excessive vibration and noise in transformers. This distortion was found to be due to magnetic saturation of the transformer cores and could be avoided by inserting a suitable reactor in series with the capacitor. Another technical problem concerned the development of a switch for frequent operation in the range from 11 to 77 kv.