| 1. |
- Zelalem Desta, Berhanu, et al.
(författare)
-
Analyses of unexplained faults in transmission lines in the power grid of Ethiopia
- 2024
-
Ingår i: Electric Power Systems Research. - 0378-7796. ; 231
-
Tidskriftsartikel (refereegranskat)abstract
- Ethiopian power transmission lines operating at 132 kV, 230 kV and 400 kV are encountering unacceptably high number of unexplained outages caused by external factors, which compromise the reliability of the system. It is therefore crucial to examine the characteristics and underlying causes of these outages through analyses of long- term records of the faults for identifying their probable causes for best targeting future mitigation measures. A method is presented to identify, in retrospect, the major possible root causes of unexplained outages that combines information on fault time-of-the day and time-of-the year records with flashover characteristic of known fault causes and local climactic and environmental information. The analyses are based on data covering an 8-year period from 2015 to 2022. A total of 8891 fault records were compiled and among them 4231 faults (47 %) were unexplained faults. Results show statistical variations in the frequency of unexplained faults with respect to spaciotemporal occurrence of the faults, voltage level and local climate. Moreover, the analyses indicate that out of the total number of 4231 unexplained faults, 787 faults could be attributed to lightning (19 %), 1135 faults to pollution events (27 %), 479 were fire related (11 %) and 1830 faults caused by external interferences (43 %).
|
|
| 2. |
- Zelalem Desta, Berhanu, et al.
(författare)
-
Investigation on Pollution-Induced Flashovers of In-Service Insulators in Ethiopian Power Transmission Lines
- 2024
-
Ingår i: Energies. - 1996-1073 .- 1996-1073. ; 17:9
-
Tidskriftsartikel (refereegranskat)abstract
- Power transmission lines in Ethiopia are experiencing an alarmingly high frequency of unexplained outages triggered by environmental factors, which significantly undermine the reliability of the country’s power system. This paper presents investigations aiming to identify those among the unexplained fault records that have been caused by pollution induced flashovers. An identification method is developed, which associates the contextual fault features, such as information about the characteristics of the fault, fault location, and time of day, as well as month of its occurrence with local meteorological/climatic and environmental conditions. A total number of 4231 unexplained faults, recorded between 2015 and 2022, were analyzed. Among them, 1045 faults (24.7%) were identified as being most likely caused by pollution induced flashovers. The entire network suffered from more than 130 pollution-induced flashovers annually with a frequency of about 0.8 faults/100 km/year. The fault frequency strongly differed among the grid regions, being highest in the Northeast and lowest in the Southwest region. Moreover, the performed analyses also concentrated on the evaluation of the pollution performance of various insulator types employed in the network. The results indicate that porcelain insulators have the highest pollution-induced flashover intensity of 1.47 faults/year/1000 units, followed by silicone rubber polymeric composite insulators and glass insulators with the respective intensities of 1.21 and 0.83 faults/year/1000 units. These results indicate that despite the high expectations towards the pollution performance of silicone rubber polymeric insulators, their use in the Ethiopian climatic and environmental conditions appears to be unsatisfactory.
|
|
