What is the reason for line voltage to drop from 240 vac to 198 vac?

Answer 1

If there is no problem with the incoming supply from the street, then such a high voltage drop could be caused by using a standard but relatively high-power kitchen appliance - like, say a 3 kilowatt electric kettle - on a branch circuit that is too long for the size of wire that was used to hook up the socket outlet that it is plugged into.

I have seen this happen many times in sheds or "garden offices" that are a long way from the main house because they have a small socket outlet fed by a length of thin cable that was meant to be used only on lighting circuits!

Or another example I have seen is someone who tried to run an arc welder using too long a length of thin flexible cable.

In both cases the current is not high enough to trip the circuit breaker but the cable gets warm because it's own resistance "steals" a lot of the supply voltage, which explains the the voltage drop, why the kettle doesn't heat up properly and why the arc welder refuses to start!

Taken to extreme you could easily end-up with the cable starting to smolder or even to catch on fire.

To avoid this problem you always have to use the right size of cable for the job. If you don't know how to find out the right size of cable to use then you must hire a licensed electrician to fix the problem for you or at least ask for advice on what you may be able to do yourself.

<><><>

As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized.

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.