West Bengal State Electricity Board (WBSEB, West Bengal, India) constructed a 220-kV double-circuit transmission line from Jeerat 400/220/132-kV Substation to Laxmikantapur 220-kV Substation, looping one circuit in and out of Kasba 220/132-kV Substation, situated in the eastern sector of Calcutta, India.

This 220-kV transmission line, designed with ACSR ZEBRA phase conductors and galvanized stranded steel wire (7/3.15 mm) earth conductors, is supported by barrel-type towers designed as per IS: 802-1977.

During conductor stringing of the line into Kasba Substation, WBSEB encountered a two-storied building that encroached the existing right-of-way. This situation demanded a minimum horizontal clearance of 12 ft (4 m) from the power conductors, resulting in a redesign of two transmission towers. The two towers in question were the terminal deadend tower at Kasba Substation and the preceding 30- to 60-degree heavy angle.

The transmission line towers were redesigned using iTOWERS Designer Software, developed by IMI Software Ltd., India. To solve this tower problem involving conductor clearance, the same design inputs were used, but the tension between the two towers was reduced.

The tower was redesigned with an auxiliary crossarm on the transverse face of the tower and each member have been checked for the additional loads due to the auxiliary crossarm. The redesign resulted in changes to sections in a number of tower members, but with introduction of the redundant members, the modifications required in the existing tower were minimized. The deflection of the tower at different nodes was viewed from the display of the software enabling the designer to conceive the load pattern geometry and behavior of the tower with more accuracy and confidence.
Circle 179 on Reader Service Card