Knowledge gained through experience has a lot more weightage than the theoretical one. Very small mistakes can at times, lead to great disasters which is normally termed as “butterfly effect” . This relates to the chaos theory and a lot of research is going on regarding it.
Coming to the real time problems, it is tough o guess where the actual problem lies. There was a seminar by a professor who explained the real time problems. That was very informative and i felt it would be good to share the same with everyone. It was as follows:
An instrumentation system was designed for controlling nuclear reactor control rods. The system was designed in such a way that if the values or the signals given exceed the threshold , the control rods are brought down and the reactor is shut down. But a problem arose from nowhere , though the signals were within the threshold the plant was shut down.
This is a safe failure as the shutting down of the plant hasn’t caused any damage or disaster. Unlike the situation wherein though the signal exceeded the threshold limit, plant wasn’t shut down. The latter would lead to a disaster and damage beyond one’s imagination.
The problem shocking was with the power supply which none can usually guess. People usually go for checking the design and the components ,assuming that the power supply would be alright as it is UPS. But the fact is that UPS will not give a perfect sine wave, it gives a square wave which is approximated to a sine wave . The output also, consisted of spikes due to the UPS . Spikes being the high frequency components cross the threshold though the signal is within the range causing the plant to shut down. This was solved after the detection using an “ISOLATION TRANSFORMER”.
This was outside the plant . Coming to the point as why there were spikes in the output of power supply it was found that the internal control unit used SCR(silicon controlled rectifier) for AC TO DC conversion. For this a perfect design of the commutator is necessary. If the design isn’t perfect , the voltage will be reverted back which form spikes in the power supply output. Therefore , if the commutatot design was perfect , the problem would not have arose at all!!