Application of 77 kV Overhead Insulated Cables

The overhead cable laying method requires a smaller construction scale, resulting in higher

CAPEX efficiency, shorter construction period, and reduced environmental impact (such as less deforestation, land alteration, and disposal of contaminated soil). Specifically, compared to the underground cable laying method, approximately 60% cost reduction, about 30% shorter construction period, and a significant decrease in excavation volume were confirmed.

Additionally, a reduction in CO2 emissions from heavy machinery due to less excavation can also be expected.

From a technical perspective, measures such as adopting mechanically strong wire-shielding sheaths and copper protective pipes were implemented to address the increased weight associated with enlarging cable sizes and to protect against ground faults in joint boxes. Straight through joint without earthing is adopted to prevent back flashover events from the earth.

In terms of resilience, although recovery time is almost equivalent to that of the underground cable laying method, the overhead cable laying method allows flexible installation of joint boxes, providing superior response during outage for the repair work.

On the other hand, there are problems such as difficulties in co-installation with other companies’ cables due to domestic laws, the need for new poles due to insufficient load-bearing capacity of existing ones, and the risk of damage to support structures, and potential damages from vehicle collisions and typhoons. Taking those aspects into account, it can be considered that under specific conditions, the overhead cable laying method demonstrates superiority in terms of cost, construction period, and environmental impact.