in fact a wellrun system requires adequate primary secondary and tertiary reserves the different reserve levels refer to the different time frames at which operators need to inject or withdraw load into or from the system in order to balance electricity demand at all times in addition good control strategies are required for electricity this means constant frequency and voltage controls and for natural gas constant pressure and flowrate control while not very glamorous equally vital are well designed maintenance strategies encompassing preventive predictive and corrective interventions including the scheduling and coordination of planned outages while indeed the adequacy and competent management of power transport systems are essential for ensuring the security of power supplies they should in principle not be an issue for policy making remaining interruptions would then be due to bad luck incompetence or extreme weather events none of which is very responsive to policy changes