To use the IEEEA RTS as an example, a SCADA system must be designed for it. Aligned with the intention of looking at area architectures of SCADA the IEEE RTS is split into two areas. An area control center is located at the site of buses 8, 9, 10 & 11 and a national control center somewhere. Then using the communication availability categories defined. In addition to this routing information is also needed to specify allowable connection paths through the system of SCADA between the Operator position and the HV busses.
It is normal for system availability to be specified as a single number such as 99.8%. This availability type specification does not cover how the overall target should be apportioned to the many system components of SCADA. For instance the reliability model is defines a realistic master station model and establishes that a single figure is inadequate. However in order to preserve some relationship to traditional targets availability, 99.8% has been used as the combined figure for the lumped back end components.
The analysis algorithm requires a DC load flow model of the power system. This is derived from ignoring reactive loads and power generation. Also we are concerned with reliability at individual busses a load shedding philosophy is also required. The philosophy chosen for the IEEE RTS is defined by the load shedding weight, loads with the lowest weight will be shed first if possible.
These weights are critically important to this analysis. To illustrate this consider the extreme example of assigning a high weight on all busses of the IEEE RTS. This would cause a disproportionate number of load curtailments to occur at area 2 busses which in turn would result in a lower probability significantly of a joint failure event. The sensitivity of joint system minutes to back end availability was also calculated as well as calculating the system reliability at normal component availabilities.