Part of that work is electrifying 172km of track across the Valleys network, powered by renewable energy, a significant proportion of which will be sourced in Wales.
Rhan o’r gwaith hwnnw yw trydaneiddio 172 cilometr o drac ar draws rhwydwaith y Cymoedd, wedi’i bweru gan ynni adnewyddadwy, a bydd cyfran sylweddol ohono’n dod o Gymru.