Reliability of SESB Tawau distribution system obtained from LGBnet is compared with data obtained from IEEE Guide for Electric Power Distribution Reliability Indices (IEEE Std 1366-2003).

IEEE conducted three surveys on distribution reliability index usage. The purpose of the surveys was to determine index usage and relative index values. In 1990, 100 United States utilities were surveyed, 49 of which responded. In 1995, 209 utilities were surveyed, 64 of which responded. In 1997, 159 utilities were surveyed and 61 responded. Fig. 1 shows SAIDI value for 1990, 1995, and 1997 of the IEEE survey. The data shown in the Q1 column means that 25% of utilities have an index less than the value shown, followed by Q2; 50%, Q3; 75 % and Q4; 100%.

Data on distribution SAIDI at SESB Tawau from January 2009 to June 2009 from LGBnet is shown in Table 1. SAIDI data on Table 1 was compared with the IEEE Survey on SAIDI for 1990, 1995, and 1997. The maximum SAIDI value in Table 1 is 52.7 min and group into Q1 which have an index less than the value shown (54 min based on 1995 survey).

If SESB Tawau is a utility company that operate on its own, this result can be considered as excellence, but since only one zone (Tawau) of the utility company was represented the reliability of the whole distribution system still questionable. By totaling SAIDI from all distribution zones, then SESB distribution reliability can be determined.

Resources on SAIDI were limited to conduct the power distribution reliability analysis. A hypothesis concluded that the total SESB SAIDI may exceeds 200 min and group into Q4 since a single zone SAIDI already reach 52.7 min. This shows that reliability of power distribution system in Sabah is below average and need to be improved.