Evaluation of Nigerian Transmission Grid Capacity and Technical Limitations under Different Load Conditions

Abstract

This paper presents performance-based study of the Nigerian Transmission Grid (NTG), having about 27 power stations, 50 transmission (330/132kV) stations and 150 bulk load centers (132/33kV). Power stations and transmission grid are designed to operate at a level close to installed capacities, to achieve high efficiency. However, due to some technical limitations and maintenance factors, not all the elements may be available at all operating times. Therefore, the available generations may not equal the installed capacity; also, the load demand (consumed) on the grid may not equal the installed transmission capacities. This study evaluates the capacity of the transmission grid considering the installed and available generation capacity and three components of transmission load: actual load demand (LD), transmission wheeling capacity (TWC) and transmission load capacity (TLC). Obtained system data were used to create virtual simulator for the transmission grid, using Power System Analysis software (NEPLAN), which uses Newton Raphson Algorithm. The results established that the power generation on the grid must be maintained at the level of installed capacity to deliver the TWC and TLC load component to mitigate the practice of rotational power transmission and distributions currently being adopted in electricity transmission and distribution in Nigeria. It was established that the transmission capacity of the current transmission network is capable of accommodating and delivering power more than the current installed generation capacity. It is recommended that efforts be geared towards improving the generation capability of the grid for efficient power transmission and distribution. Keywords: grid capacity, transmission grid, load, system collapse, voltage stability