Usually have fairly good electrical supply here but over the past week, we have had two brown outs after local lightning strikes and wind and these brownouts have lasted over 8 hours. Voltage is running 170-190 volts so have had to unplug the pump, fridge, and AC. Our power line comes directly from a large 3 phase transformer connected to what appears to be the local 3 phase (7KV perhaps) buss.

Most countries have fault detection on transmission lines that shut off the system if there is a dropped line, but it doesn't appear that way in Thailand. Any power transmission engineers out there want to explain how these faults occur and can stay this way for this long?

I assume the fault stayed that way for that long because that's how long it took their techs to fix the bits that got fried by the lightening

As for most countries having some sort of low voltage cutoff - the 3 I've spent a reasonable amount of time in (Thailand, USA, Australia) have all given me brown outs before.

Never saw anything like this in the USA. I worked at a hydroelectric dam for a while and just the slightest fault and the HV transmission lines were all down to protect the rest of the grid. Losing a phase means unbalanced currents that can cause some serious grid problems so that is why I am hoping some power engineer can chime in on what happens.

You are probably right that they are still trying to repair the damage from last nights storm. We had a lot of strong local lightning strikes.

Strongly suspect one phase of local transformer was blown and caused the two remaking phases to supply low voltage. Normally takes one to three hours to get fixed here in Bangkok if reported and not too much workload. Did take almost five hours first storm of season this year as most of city had problems and ours was late call. As most things still run at 170 volts often it is only those on the fuse blown line making reports and if at work may be delay.

Strongly suspect one phase of local transformer was blown and caused the two remaking phases to supply low voltage. Normally takes one to three hours to get fixed here in Bangkok if reported and not too much workload. Did take almost five hours first storm of season this year as most of city had problems and ours was late call. As most things still run at 170 volts often it is only those on the fuse blown line making reports and if at work may be delay.

Sound likely. Just heard from friends living three miles away and they are experiencing the same thing. So.... Must be the transformer upstream from our local buss if it is affecting a large area. We have had two weeks of unusually strong thunderstorms up here so I am sure the power companies have their hands full.