## 8 Application Example  
The ASI is an information analysis rather than a protection device which is located in an area of vulnerability. It cannot know everything that is going on in the system but is watching for signs of impending trouble as in the case of multiple contingencies which will now be described.  
Consider the IEEE 39-bus system shown in Fig. 3: The system is running at the expected day-before load and all bus voltages are satisfactory in the range of 1.02 pu to.98 pu. All required backup generation is in place and reactive power is of the required format such as capacitors or rotational apparatus is in service. As a result of numerous tests it has been decided to install two ASI's, specifically at Bus-1 and Bus-16, and they are set up in accordance with the concept at the end of Section 3. Generator G10 fails and is shut down. The regular telemetering will inform the System Operator of this. ASI-Bus-1 will detect a momentary flicker of voltage due to the momentary short circuit in G10 and a pattern similar to Fig 4 may develop due to the redistribution of currents to supply the loads from the remaining generators. But ASI-1 determines that the voltage is still within specification and registers Performance Level N (Normal) because the spinning reserve has been adequate. The System Operators know that this is contingency No. 1 and that eventually they will get a report from the powerhouse as to when G10 will be back on line.  
While this event is going on and the operators are coping with the loss of G10, a second contingency occurs and it happens to involve Bus-16, namely Line 16-17 which trips and locks out. The System Operators know about this via the regular telemetering. Now the shortfall of Bus-17 must be supplied by other far-away generators. ASI-Bus-16 is still very busy because it is receiving power from Bus-19, Bus-21 and Bus-24. It was distributing it to Bus-15 and Bus-17. The ASI is aware of the lockout on line 16-17 and will factor this into the stress analysis. It turns out that instead of thevoltage of Bus-16 rising, it falls to.95 pu, putting the bus into the verge of collapse region. This is the region where voltage-restraint-overcurrent relays may start to time out and drop the load. The low-voltage condition will be reported by the regular telemetering but the fact that the voltage is at a dangerous level may not be known to the Operators. To make matters even worse, the ASI has detected instability on lines 16-21 and 16-24. (See Figs. 4 and 5.) This fact will not likely be known because the relay information is not usually telemetered. The ASI-Bus-16 determines from a pattern similar to Fig. 5 that the instability is of small magnitude and there is adequate time for the operator to take corrective action so, instead of putting out an E (Emergency) or X (Extreme) warning, it puts out A (Alert). The stability problem is part of the message that goes with the Performance Level shown in Fig. 1. Meanwhile the system operators will know via the regular telemetering that this line lockout is a second contingency and will be treating it as Emergency. Without this local analysis the system operators might not know of the situation at Bus-16.  
It can be seen from the foregoing example that the ASI functions on having a supply of reference voltage patterns for various known situations which can be referenced to determine the Performance Level category, as accessed by the data mining algorithm. The example makes it clear that the ASI puts out warnings (Performance Levels) based on what it is sure is happening and it does not repeat status information that is sent via regular telemetering.  
It is also clear that operator training on the application of the ASI is essential for its successful operation.