Networked loads in the distribution grid

Central utility services are increasingly networked systems that use an interconnection of sensors and programmable logic controllers, and feed data to servers and human-machine interfaces. These systems are connected to the Internet so that they can be accessed remotely, and the network in these plants is structured according to the SCADA model. Although the physical systems themselves are generally designed with high degrees of safety in mind, and designers of computer systems are well advised to incorporate computer security principles, a combined framework for supervisory control of the physical and cyber architectures in these systems is still lacking. Often absent are provisions to defend against external and internal attacks, and even operator errors that might bypass currently standalone security measures to cause undesirable consequences. In this paper we examine a prototypical instance of SCADA network in the distribution network that handles central cooling and heating for a set of buildings. The electrical loads are networked through programmable logic controllers (PLCs), electrical meters, and networks that deliver data to and from servers that are part of a SCADA system, which has grown in size and complexity over many years.