We use electricity knowing that it is dangerous. We feel safe, because we have installed protection devices such as circuit breakers and fuses, that ought to disrupt power in case of risk to human life or property. We trust these protection systems with our lives. I am asking you – are they enough?
How often do you see a nuisance tripping of your circuit breaker? The circuit breaker trips, you turn it back on and circuits are working just fine. I am sure you have experienced it. We all have. I must warn you if you are experiencing nuisance tripping frequently it's certainly not a good sign. You should have your electrical network examined. It could also mean that your circuit breakers are getting old and need to be changed. But, this is by far better, in comparison to a circuit breaker not tripping in case of a power failure. How is that possible you might ask me. I am about to share my experiences from the morning of 23rd February 2014.
I started observing issues with my electrical supply the evening prior. I came back home and wanted to watch the football match but the set-top box kept turning off randomly. A closer examination revealed sparking at the spike guard and intermittent supply from the power adapter to the set-top box. I assumed that there a problem with the adapter. Everything else worked fine for the moment. Later, close to midnight one of the lights near the same set-top box started to flicker. Since the supply to the rest of the house seemed fine, I thought its too late to bother. I switched off the lights and went to bed. While I was sleeping, close to about 5am I heard a sound, like somebody was knocking at the bedroom door. I woke up, checked the bedroom door and nobody was there, just then I heard the knocking sound again. This time I realized the spark appearing at the power outlet where my cellphone was charging. I suspected a short circuit. I switched off all the devices in my room and went to the distribution board, with my phone working as the torch. I did not see any tripped circuit breakers. OK. Now, what?
I figured let me turn on a few devices elsewhere in the house to see what happens. I was close to the distribution box and at a worse case I would trip some circuit breakers. Cautiously, I started switching one appliance at a time in my living room. The first switch was for a tubelight, it worked, but output was low. The next switch was for a fan -- that didn't work. Next I tried one of the halogen spotlights in the passage close to my bedroom, and BOOM – a small explosion!!! The bulb exploded. No breaker tripped. Fortunately, no other damage. This time the sound was enough to wake up the rest of my family. I turned off the main circuit breaker and then went to ask the others if they noticed anything odd. My father complained, that the AC in his room stopped working and the fan started operating really fast. My brother too had an issue with the AC not working and smelt some burnt electronics in his room, perhaps his phone charger.
Sparking, fans operating at high speeds, bulbs bursting all indicated overvoltage. But, nobody else in the building seemed to be complaining. The problem was local to us. How could ours be the only flat in the building receiving a higher voltage. We do have a three phase supply at home. It was possible that we were receiving a Phase-to-Phase voltage of 415V at the appliances/outlets, instead of Phase-to-Neutral of 240V. I did not have my voltage meter and could not be sure. But, I still had some lingering thoughts. What was the cause of the Phase-to-Phase voltage? It would have to suggest a Phase-to-Neutral Short. Which should have tripped the circuit breakers on the shorted branch. And what about the low light output, flickering, random switching off the set top box – all indicated an undervoltage condition or an intermittent power supply.
A few hours later, at a more decent time in the morning morning I went down to the meter room with our local electrician. He measured the incoming supply to the meter and confirmed it was alright. However, the outgoing neutral from the meter was open, i.e. there was voltage between Phase-to-Phase but no voltage between Phase-to-Neutral. The antiquated meter installed in 1981 had a connection in the neutral path that had failed, and about time. The meter had outrun its lifetime. Certainly, that was an oversight on our part. But it certainly created an rather scary situation for us in retrospect. We were observing a floating neutral. With a floating neutral, the voltage observed at different appliances could be anywhere from 0V-415V, but most probably somewhere in between. The rather precarious situation it creates arises from the fact that one phase would experience a higher voltage whereas another phase would experience a lower voltage, it depends on the voltage the neutral would “assume” in the network, based on the loads on the respective phases. This clearly explains why some of the devices were observing a higher voltage and other devices on another phase were observing effects related to low voltage levels. It also confirms why none of the circuit breaker tripped. There wasn't any high current flowing through the network. The problem was high voltages. Enough to damage appliances in the house and even fire if not monitored. Understanding the gravity of the situation I was just happy that with good fortunes and Gods grace we avoided a major calamity. But after it sunk it, I realized that the circuit protections that we use, rely on, and trust are just not good enough. Their theory of application is fundamentally flawed. We simply cannot expect current based protection systems to protect against voltage failures. Its time we changed the old guard and added voltage based protection as part of our electrical networks at home.
It makes we wonder how many of the recent fires making daily headlines could have been averted with better more sound protection devices.
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