A method of evaluating reliability of SCADA system has been presented in other article. This provides an aggregate assessment of system reliability which can define reliability in absolute cost terms. This cost enables a quantitative, direct comparison of alternative SCADA system options.
In the two examples, alternative area architectures of SCADA were applied to the IEEE RTS reliability test system. The reliability analysis revealed that the centralized option was 5.5 time more expensive than the distributed option. The second example comprised a case study on an actual system implemented by Trans Power. In this case it was found that the annual reliability worth was relatively small. This suggests that Trans Power has incurred only a minor increase in liability as a result of changing area architectures of SCADA. However some reliability improvements would be justified, for instance duplicating low cost system components such as routers.
The validity of these conclusions is depending on the quality of the many assumptions made, many of which are the subjects of further study.
1. The analysis has considered only one category of reliability worth, cost of load curtailment resulting from failure of SCADA. In addition other categories could be considered such as:
• cost of routine maintenance
• repair failed component or sub system cost
• user and customer goodwill loss
• other revenue loss
2. 100% load shedding will regularly occur at low priority busses as implemented. In practice a more structured approach involving sheddable and firm loads.
3. The use of single power system load results in an exaggeration of the joint system minute figures. However including a full load profile also required a significant boost in computational performance.
4. The SCADA system model is simplified greatly.
5. The design availability figures need to be replaced or verified by real components availability data.