Prevention of voltage collapse on the Nigerian 330 kV grid network using under-frequency load shedding scheme

Abstract

Study on use of UFLS scheme in the prevention of voltage collapse on Nigerian 330 kV network. The network was modelled using PSS/E. Three simulation cases were considered: case one determined the network convergence status, case two considered AC contingency study to see the network weak points and case three dealt with the situation of voltage collapse as occurred on the grid on 27th May, 2013 and the effect of using UFLS scheme on the network to prevent the collapse. The results obtained showed that the network frequency declined to 49.2 Hz and the voltages at the various buses without UFLS relays fell below 0.8 pu while with the use of UFLS scheme, the network was stable after shedding 15% of the load at each load bus, this was reflected on the bus voltage magnitudes which rose above 0.9 pu and the network frequency was restored to 50 Hz.