Probabilistic Design of Distribution & Reticulation Systems juxtaposed with Traditional Design Software E. Chikuni 1 , S. Arendese 2 , O.I. Okoro 3 C.C. Awah 3 , O Dzobo 4 1 Department of Electrical Engineering, University of Zimbabwe, 2 City of Cape Town, South Africa 3 Department of Electrical and Electronics Engineering, Michael Okpara University of Agriculture, Umudike, Nigeria 4 Department of Electrical Engineering, University of Johannesburg echikuni@ieee.org, shannon.arendse@yahoo.com, odzobo@yahoo.com, oiokoro@yahoo.co.uk, ccawah@ieee.org Abstract.A residential development design using the Herman Beta method based on a widely used software package ReticMaster for low voltage and DIgSILENT for medium voltage (which is also used for more complex analysis and higher voltage design). The design was done to meet the requirement according to National Energy Regulator of South Africa (NERSA) standards. Cost comparisons were carried to determine materials best suited for the design. The Herman-Beta method is a departure from other probabilistic methods, in particular those based on Gaussian assumption. It applies to the South African distribution systems which have less customers per distribution point, typically less than 30 [2].. Keywords: Low voltage; medium voltage design; Herman-Beta method; distribution system and residential development design, system reliability. 1 Introduction The power system which supplies electricity to the consumer consists of a generation, transmission and distribution system. In this paper only the distribution system will be discussed. The distribution system is divided into a medium voltage (e.g. 11kV) and a low voltage (eg. 400V). A distribution system consists of feeders, distributors and service mains. In the past the radial system was used, but to ensure continuity of supply the ring-main distributor system is used. Distribution substations’ main function is to step-down the voltage to the required level. Low voltage distribution planning involves the placement of miniature substations at strategic areas to provide optimal supply to consumers. The low voltage distribution system is the final stage in ensuring quality of supply to the consumer [1]. According to the South African National Rationalization of Standards document NRS034-1, the voltage drop for low voltage cables should not be higher than 10% [2]. Therefore the voltage drop is the main constraint which determines the size of cable required [2]. According to the NRS guidelines [5] voltage drop limits must comply with the following maximum limits: MV distributor 3% LV feeder 8% 191 ACRID 2017, June 20-21, Victoria Falls, Zimbabwe Copyright © 2017 DOI 10.4108/eai.20-6-2017.2271003