Development of Gapless Surge Arresters for Electric Power Systems

Gapless Surge Arrester for 66kV Electric Power System at Hayato Substation of Kyushu Electric Power Co. Inc.

Fig.1 Gapless Surge Arrester for 66kV Electric Power System at Hayato Substation of Kyushu Electric Power Co. Inc.

Functional Principle and Strong Merit of Gapless Surge Arrester ( ZnO Element )

Fig.2 Functional Principle and Strong Merit of Gapless Surge Arrester ( ZnO Element )

Technical problems of gapped arrester (SiC element)

Tbl.1 Technical problems of gapped arrester (SiC element)

In 1970s, Surge Arrester Technology couldn’t satisfy the user’s request (high reliability, high performance and downsizing). Consequently, the realization of reliable and economical supply of electricity was difficult for Electric Power companies. It was the common problem for most of surge arrester engineers in the world. In July 1967, one of the researchers of Matsushita Electric Industry Co. Ltd. (Panasonic Corporation, now) accidentally discovered the excellent varistor for electronic circuits during development of ZnO based semiconductor. Meidensha Corporation (MSA Co. Ltd., now) and Matsushita carried out the cooperative research for developing a high voltage ZnO element. The Gapless Arrester using this ZnO element could solve perfectly the all problems described in Table1. Fig.1 photo shows 66kV gapless surge arresters at Hayato substation of Kyushu Electric Power Co. Ltd. These arresters were the first commercial gapless arresters in the world and energized July 1975. Gapless Metal Oxide Surge Arrester (MOSA) was then accepted in the world and some major examples of the world records are as follows: 500kV MOSA for GIS (1979), 500kV ultra heavy duty MOSA for converter station in Manitoba, Canada (1979) and DC MOSA for 250kV AC-DC converter station for the Central Electricity Generating Board Dover Strait DC Power Transmission (UK in 1984).

As shown in Fig.2, resistive current through non-linear resistor of the gapped surge arrester element (SiC element) at normal line-to-ground voltage is around several tens to a hundred ampere. Therefore, the surge arrester using a SiC element needs to have series gap(s) to insulate the element from the line-to-ground voltage. While, the gapless surge arrester (ZnO element) at normal line-to-ground voltage is around several tens μA flows (practically, no follow current). Therefore, the surge arrester using a ZnO element needs no series gap(s). The ZnO element has better energy absorption capability than the SiC element has. Consequently, the gapless surge arrester (no follow current, compact) solves all problems described in Table1, technically and economically. And it has many strong merits as follows:

1. Reliable for multiple lightning owing to no follow current.

2. Excellent anti-pollution performance owing to no follow current.

3. Excellent performance for steep front impulse voltage owing to gapless.

4. Any arrester can be designed easily by combination of series or parallel ZnO elements.

5. The gapless ZnO arrester can be applied to any type of surge arresters, e.g., GIS type, oil immersed type, built-in type for equipment, polymer mould type.

Innovative gapless arrester having above merits was achieved economically. Today UHV (1.100kV) surge arrester for GIS/polymer type was developed.

A valve resistor type arrester (gapped arrester) composed of SiC elements and series gaps was the main stream of surge arresters in 1940s to 1960s. The series gap was simple spark gap(s) in early era and the new magnetic blow gap was developed in 1950s. Consequently, the follow current interrupting capability and low protective level were achieved. In 1960s the new current limiting gap was developed and became popular in the world. The current limiting gap type arrester was believed as an ultimate arrester at that time.

But, the intrinsic technical problems (Table1) of gapped arrester were not dissolved even with the current limiting gap type. Consequently, the requests (reliability, performance and compactness) of users were not satisfied and these technical problems were common issues which should be resolved by main arrester engineers in the world.

 In 1967 a researcher of Matsushita Electric Industry Co. Ltd. discovered a new excellent varistor for electronic circuits. Matsushita released the new varistor in the newspaper in 1975. Meidensha Corporation cooperated with Matsushita and developed a ZnO element of surge arresters for electric power systems. The new innovative gapless arrester using the ZnO element was a pure Japan oriented product and resolved the all problems described in Table1, economically.



Publications

[1] M. Kobayashi, M. Mizuno, T. Aizawa and K. Mitani、Development of Zinc-oxide Non-linear Resistors and Their Applications to Gapless Surge Arrester、1977、IEEE Transaction on Power Apparatus and Systems, 1977 Vol. PAS-77 No.4, July/Aug. 1978
[2] M. Kobayashi and M. Hayashi、The background and history of developing Gapless Metal Oxide Surge Arrester、2008、Research Repot of IEE Japan, HEE-08-19 ( in Japanese and English ) Dec. 2008

Related Researches

Category

Electricity & Electric Power
(Fundamental Technology)

Events in World

1978
Japan-China Peace and Amity Treaty was signed.
1978
Narita Airport was inaugurated.
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