Technology Development on Compact Mounting Structure for 500kV Transmission Line Arrester

The mounting structures of 500kV EGLA

Fig.1 The mounting structures of 500kV EGLA

Galloping test arrangement of 500kV EGLA

Photo.1 Galloping test arrangement of 500kV EGLA

About 70% of all electric outages in transmission lines are related to lightning strikes. And the external gapped line arrester (EGLA) shows an excellent performance to prevent lightning failures. However, the expensive installation cost of EGLA is an obstacle to expand the installation areas.
To solve this issue, we developed the compact mounting structure of EGLA for 77kV, 154kV and 275kV transmission lines, by replacing the existing arcing horn of insulator assembly with an arrester unit. This structure can reduce the installation cost because tower arm modification is not required.
On the other hand, it is difficult to apply this compact mounting structure to 500kV EGLA because of its longer arrester unit. Thus, we invented a new mounting structure, which consists of two arrester units by dividing the arrester unit into line and earth side. Then it is expected the rigidity of mounting structure and compactness. Table.1 shows the mounting structures of 500kV EGLA.
It is important to verify the corona characteristics of this structure, because an arrester unit is also installed on line side of the insulator assembly under high electric gradient. Moreover, it is necessary to verify its behavior against the aeolian vibration, and the influence to the mechanical reliability of insulator assembly. Based on this point of view, we carried out the following tests.
Electrical characteristics
We carried out various electrical tests in 500kV full-scale insulator assembly. Fig.1 shows corona characteristics test arrangement of 500kV EGLA. As a result, it was confirmed that a newly developed design has the equivalent performance compared to the previous one.
Mechanical characteristics
Since it is considered that Galloping is the severest mechanical stress for the compact mounting structure, verification test against Galloping was conducted in the 500kV test line of The Kansai Electric Power Co., Inc. Fig.2 shows Galloping test arrangement of 500kV EGLA.
It was observed that variation of external series gap length during the test was within the specified value. And the maximum mechanical stress on the pin of disc insulator unit was equivalent to that of the insulator assembly only, so it was confirmed that the compact mounting structure of 500kV EGLA did not affect fatigue characteristics of insulator assembly. Furthermore, any abnormal behavior was not observed in other mechanical tests such as aeolian vibration, swing of conductor and so on. Therefore, it is confirmed that this compact mounting structure has enough reliability against various mechanical stresses.
Based on these evaluation test results, it is concluded that a newly developed compact mounting structure for 500kV EGLA is applicable for practical use.

IEEJ praised the achievement of this development and awarded Masanori Ohnishi (The Kansai Electric Power Co., Inc.) and Toshiyuki Takagi (NGK Insulators, Ltd.) with prize of progress in 2010.


Publications

[1]K. Tsuge, and H. Yamada,“Application Technology of Lightning Arrester for 275kV Transmission Lines”,28th International Conference on Lightning ProtectionVol.ⅱ,pp1001-1006,2006

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Electricity & Electric Power
(Fundamental Technology)

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