Improvement of Power Supply Reliability of Port Harcourt Zone 4 Network, Nigeria.

The availability of stable and reliable electric power supply is the prerequisite for determining the socio-economic and technological development of any country. However, interruptions which are largely unavoidable contribute to the unavailability of power and thus prevent power system from being stable and reliable. Hence, it is necessary to determine the major cause of unavailability of power in the distribution system. To achieve this, the study examined the reliability of existing Port Harcourt Town (Z4) distribution system. The distribution system consists of six (6) 33kV medium voltage feeders. The network is designed in Electrical Transient Analyzer Program software (ETAP19.1) and simulation performed for single contingency level using Newton-Raphson load flow technique. The result obtained from base case simulation shows that the feeders with highest annual outage time are UST 927.6 hr/yr, followed by Secretariat 717.7 hr/yr and Borokiri 631.1 hr/yr. Also the feeders availability to serve its customers calculated and the value for three (3) least available feeder are UST feeder (0,75867 p.u) followed by Secretariat (0.82823 p.u). The result when compared with IEEE ASAI standard of 99.99989 for distribution substation availability, shows that the substation availability is low. However, the result obtained when a DG of 3MW is installed in the network, shows an improved reliability of the network. The result obtained in the improved case shows that the feeders with highest annual outage time are UST 278.28 hr/yr, followed by Secretariat 215.31 hr/yr and Borokiri 189.33 hr/yr. Also the feeders availability to serve its customers calculated and the value for three (3) least available feeder are UST feeder (0.98744 p.u) followed by Secretariat (0.99177 p.u) and Borokiri (0.99192 p.u) and when compared to IEEE ASAI standard of 99.99989 for distribution substation availability, shows a high substation availability. From the result obtained, the proposed DG impacts significantly in the improvement of the distribution network reliability