Enhance Supply Reliability Research Articles

Reliability of stream flow in inter-basin water transfer under different climatic conditions using remote sensing in the Upper Tana basin

Inter-basin water transfer interventions are inherently prone to large-scale climate variability and droughts that may affect the reliability of the water supply to the recipient basin. This research evaluated the reliability of three streams of Maragua, Irati, and Gikigie in the Upper Tana basin to meet the proposed water transfers to Nairobi City in the Athi River basin. HEC HMS model was used to simulate the stream flows with NSE and R2 of 0.59 and 0.72 respectively in the validation period, using remotely sensed WaPOR ETa as input data. During the dry years, the reliability of Maragua, Irati, and Gikigie to meet the water transfer was 15 %, 23 %, and 33 % respectively. In normal years, the reliability increased to 45 %, 60 %, and 62 %; and to 83 %, 98 %, and 94 % in the wet years. This implies that the project will not meet its objective during the dry and normal years. The dry years had a 5 years cycle of occurrence while the wet years occurred every 10 years. Baker Flashiness index showed Irati and Gikigie flows to vary between 9 % and 25 % while Maragua flow, vary between 7 % and 44 % showing that the Maragua stream has higher variability thus lower reliability. The results showed the importance of considering water assessment of new infrastructural work on the cyclic nature of stream flows over traditional approaches that use long-average historical data. Inter-basin flood based systems coupled with storage reservoirs may enhance supply reliability thus reducing the hydrological risks of stream flow variability.

Positive Sequence Current Phase-Based Improved Reverse-Power Protection and a PV Hosting Capacity Assessment Method for Spot Networks

A spot network is a special low-voltage distribution network with multiple sources supplying it in parallel. It can significantly enhance supply reliability and is beneficial for integrating a distributed energy resource (DER). However, because traditional reverse power protection in spot networks cannot identify the reverse power cause, DERs, especially photovoltaic (PV) hosting capacity, are limited. Meanwhile, no uniform method exists for assessing the PV injection capacity in spot networks. Based on comparing the positive sequence current phase, this article presents an improved reverse power protection and PV hosting capacity assessment method for spot networks. Current variation is adopted to identify the reverse power cause, and a spot network equivalent model with PV is built. The positive sequence current phase relationship at the reverse power protection location is analysed when different types of short circuit faults occur. A short circuit fault section can be determined by comparing the positive sequence current phase. The influence of the PV output current on the improved reverse power protection performance is analysed. Then, a PV hosting capacity assessment method with improved reverse power is presented based on the PV influence on protection instead of on node voltage. A simulation model based on an actual project is constructed using PSCAD software. The simulation results show that the improved reverse power protection significantly enhances the ability to inject PV into the spot network and operates correctly under faults. The theoretical PV hosting capacity agrees with the simulation results.