Preliminary design of an interconnection transmission line between Nova Scotia and New Brunswick

The objective of the 160 km 345 kV transmission line project was to interconnect the provinces of Nova Scotia and New Brunswick, in order to contribute to their decarbonization.

As part of the 345 kV interconnection project between New Brunswick Power (NB Power) and Nova Scotia Power Inc (NSPI), CIMA+ was entrusted with the overall front-end engineering.

The first step consisted in defining the design criteria, which enabled CIMA+ to establish all the subsequent parameters such as the type of conductors, the geometry of the steel structures and the permissible spans.

CIMA+ then coordinated and carried out an aerial LiDAR survey of the 160 km corridor of existing transmission lines. The corridor studied included two existing transmission lines in New Brunswick and one in Nova Scotia. Using this data, CIMA+ modelled the existing lines in PLS-CADD, a 3D design software package specifically designed for transmission lines. This initial modelling of existing structures and conductors is of crucial importance to the 345 kV interconnection project, as it determines the context in which the new transmission line will be located.

CIMA+ also carried out the selection of the conductor and optical ground wires (OPGW), as well as the preliminary design of the steel towers and their foundations. Structure distribution, quantity and construction data lists, and a feasibility study were completed to establish a Class 3 cost estimate (AACE) and a construction schedule.

Analysis of environmental constraints enabled us to distribute the structures over the entire 160 km, while considering cable sagging.

Following preliminary design and establishment of the distribution table, an experienced transmission line estimator performed a detailed Class 3 cost estimate, accompanied by a feasibility and constructability study. The estimate was presented and discussed with a group of contractors and stakeholders specializing in overhead transmission lines, to validate and confirm the assumptions and methodology used by the CIMA+ team. Several suppliers were also involved in the process to obtain costs and delivery times based on current market realities.

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