National Grid S.A. is the transmission system operator subsidiary of Saudi Electricity Company (SEC) responsible for the high-voltage transmission network in the Kingdom of Saudi Arabia. National Grid S.A. is the Saudi counterparty (alongside IPTO of Greece) in the 50/50 joint venture Saudi Greek Interconnection S.A., which is advancing a proposed HVDC electricity interconnector between Saudi Arabia and Greece. Not to be confused with the unrelated UK-based National Grid plc.