it's old, but i have to add something.
the overload isn't cause by sagging voltage because of too much use from neighbor, but from overvoltage sent by TNB.

you can easily check by a multimeter. you need a logging meter to get the voltage pattern, but a multimeter is good enough for initial measurement.
usually the voltage sag will happen around 8-10pm and during midday during 12-2pm. check what's your voltage during that time, preferably at all 3 phase.

tnb can't supply more than 260v by regulation. my lab usually get 235 and sometimes 255v, which a power transmission engineer mentioned to me before, is perfectly normal with tnb.
if your neighbor is using more power than usual, or if you're one of the last people in the chain, you could see the voltage swing from 190-ish to 210v within a minute. if you're further up the chain you could see quite high voltage around 230v. if you frequently get >250v especially during the high usage time (refer above) then there's a high chance you're at the top of the chain and there's higher possibility overvoltage will happen to you and bump the voltage over >260v and burn your equipment.
in which case if it happens you could claim from TNB for damages.

i've successfully forced TNB to rewire the line to my parents house (and to half of the village) because it's at the end of the line and voltage sags below <200v causing lights to dim and sometimes can't be started at all. took quite an effort.

it's -6% to +10%. which means from 216v - 253v.
the standard is available from suruhanjaya tenaga's website.

so if you get lower voltage that sags below 215v, report to TNB and if there's no action for a few months, escalate to suruhanjaya tenaga. might need to submit proper documentation and evidence though, as the voltage sag will never happen during off peak time.

it took me nearly 6 month, 4 reports, threat to escalate to suruhanjaya tenaga and direct phone number of the TNB's pengurus bahagian bekalan.
now the voltage is stable at 235v-238v, up from 195v during 8-10pm

wait you're totally right. forgot about that. the current will compensate the decrease in voltage.

other than paying more for the increase in current, i reckon not all equipment will be affected.
electronics such as TV, radio, computers doesn't run on AC. they all run on regulated DC so they decrease in AC voltage won't have much effect to them.

but other electrical items that run on pure AC like washing machine, non-inverter aircond, fans, florescent lamp, incandescent lamp etc will be affected. some will run at reduced speed, some won't even start.
6 month of sagging voltage doesn't damage any electrical item at my parents house. only the bill shot up to over RM200. and some lamps can't start.

separate the phase will not give you cleaner power.