A Critical Investigation Into Extra-High Voltage Transmission Line: Bangladesh Perspective

Bangladesh intends to build a 5 GW transmission super-highway from Moheshkhali to Madunaghat to Bhulta to evacuate a bulk amount of power. This study presents the particle swarm optimization (PSO) method for estimating line parameters. The optimum value for inductance is 0.3152 mH/km and capacitance is 3.57 × 10⁻² μF/km. A hexa-bundle conductors are designed using triangle properties. Three types of ACSR conductors such as Moose, Cardinal, and Tern are examined for the proposed EHVAC line. At 75°C, the line resistances of these three conductors are 0.0057, 0.0061, and 0.0074 Ω/km while line losses are 0.0006346, 0.0006791, and 0.0008238 MW/km. The conductor surface gradient is the permissible limit to suppress the audible noise. The value of surface gradient shows 7.4406 kV/cm for Tern conductor while using six conductors per bundle. The results indicate that the hexa bundle Moose, Cardinal, and Tern are promising for the proposed EHVAC line. The transmission capacity based on natural condition, normal condition, and emergency condition is examined for the proposed line. The natural loading (SIL) represents 6232.52 MW of the line for the optimal values of L and C. The corona loss is recorded as 0.422, 0.420, and 0.416 kW/km/phase when the line is made of Moose, Cardinal, and Tern conductors with subconductor spacing of 500 mm. The corona loss is insignificant in fair weather condition. The techno-economic analysis is presented using an economic model. The GDP-based long-term forecasting model is developed to compute the cost and benefit of the transmission system. Future cash flow is estimated using discounted cash flow method. The key economic parameters such as ENPV, EIRR, DPP ensure the economic viability of the high-voltage transmission line project. The life cycle cost of the proposed line is $1701.91 million, while the ENPV of the project is $1577.18 million. The results yield valuable information for the future 765 kV transmission line projects of Bangladesh Power’s grid.