@lovelylovely
First, I would urge you to contact KESC and complain about this. Usually this happens because your neighborhood's powerlines aren't in order. This is particularly likely as people enjoy stealing the neutral cable and sell the copper.
If you just want protection, you can get an under/over voltage relay installed at your main line. That's basically a fancy breaker where no power comes into your house if the incoming voltage exceeds the limits you've set. So if power from the mains is too low (ie a blackout), then it'll trip. Conversely if the power is too high, it'll cut the power to your house. There's also a time element...so if the voltage exceeds your limits for 0.1s continuously, then it'll trip. Of course this is all adjustable with a simple screw, but just to give you an idea.
It's a little complicated to install, so you definitely need to find someone qualified to do it for you, but that's basically what you're looking for.
The relays themselves cost ~10k, but all the supporting equipment can get a little expensive; so look at around 40k per connection.
Hope that helps, good luck