Backup protection requirements in future low-inertia power systems

The content of this paper will illustrate how, in the future, the power transmission system in Great Britain (GB) may be much "weaker" than it is at present, and will describe the potential impact that this could have on the voltage profiles during faults, and how the operation of backup protection system operation, if required, needs to be considered carefully to ensure system integrity in the future. The potential for future problems associated with generators’, converter-interfaced infeeds’, and HVDC interconnectors’ potential inability to “ride through” during slow/backup protection operations, and the consequent risk of complete system collapse, will also be highlighted. The paper also contains a description of ongoing and future work concerned with investigation of the use of wide-area communications systems, which may already be in existence and used for other purposes, to enhance backup protection performance and possibly offer an alternative and improved solution compared with existing schemes. It is shown how such a system could potentially be "settings-free" and establish and maintain an image of the connectivity of the network from either SCADA data and/or analysing current flows during normal operation. Example results of simulations are included to demonstrate the concept of identifying fault locations and protection failures using measured voltages from phasor measurement units (PMUs). This may act as a foundation for a future backup protection scheme and this is discussed in the conclusions and future work sections.