How To Rectify Supply When 3 Phase Supply Gets Reversed From Grid End?

It's a weird world, so stuff happens, Your answer is the best approach, a reversing contactor is mechanically interlocked, there's no risk of phase to phase short, but just to avoid simultaneous coil pull, the O.P. should allow a few mSec. between brake and make.

Why would the grid reverse a phase?

I was curious about that one too. Never heard of the grid reversing phase before. But I don't live where the op does.

The commercial units I found were from India, so I suppose that might be a problem there. Possibly phase reversals occur during repairs and it makes no difference if there are no users of all 3 phases.

http://www.saboindia.com/automatic-phase-sequence-corrector.html#automatic-phase-sequence-corrector

Supply authorities would be crazy to reverse phases. The amount of damage that could be done by motors going the wrong way round and possible health risks to people would put them out of business in a hurry?

So who is the grid supplier?

I worked in Beirut during the war where power lines were regularly damaged in the shelling. The repairs were ad-hoc and there was no guarantee that the phase rotation would be the same after repair. In addition if one phase was lost there would often be DIY repairs in the street which usually involved linking the dead phase to one of the other phases still present. It worked for the single phase consumers but caused havoc for three phase consumers like ourselves (the neutral current of a three phase transformer is spectacular under those conditions).

I had to build a protection system with a contactor and phase rotation relay (as well as over and under-voltage trips) which could detect and protect against these faults.

In some countries little attention is paid to the phase rotation when wiring or repairing the local power distribution system and both phase loss and rotation detection is needed.

http://dir.indiamart.com/impcat/phase-sequence-corrector.html

The place I served my apprenticeship at had its own power station dating from the 1930's. In the early 50's the newly formed national grid came to the area so it was decided to import power as the station was struggling with the ever growing demand.
Our plants had been running BYR since day one, the grid was RYB.
Simple enough, swap the phases at the intake sub. All our LV was 550V until the mid 60's when several new plants were built. These were to use 433V for the LV and some genius decided the phase rotation was to be RYB. Not really a problem as the new plants were stand alone.

The early 70's and I arrived on the scene. One of the first projects I got involved with was major alterations to an old plant. All the retained bits of the plant was to remain on 550V, all new bits were to be 433V. Do we make it BYR to match the old 550V parts of the plant or RYB to match the other 433V plants? We went with BYR as again this wasn't tied in to the other plants.

A few years down the line and the plants had spread out somewhat. Still not a problem until the idiots (management) wanted a new office block and IT centre mid way between.
I was asked to arrange the power feeds. 2 x 200A RYB from plant "A" and 2 x 200A BYR from plant "B".
Most of the plant electricians were totally oblivious to the different phase rotations and thought I'd taken leave of my senses when we connected the various feeds in.
I've got to admit, it did look strange.

In about ½ mile square you could run across

3.3KV BYR
3.3KV RYB
550V BYR
433V BYR
433V RYB

11KV was always BYR

Similar situation here in California. PG&E (Pacific Gas and Electric), the largest utility in Northern Calif., is ACB rotation. Southern California Edison (SCE) is ABC rotation, as is most OEM equipment, including portable generators, and it is the default rotation for VFD outputs. It causes no end of issues when people get new equipment or move it from an SCE service area to a PG&E service area and ASSume it was set for proper rotation . I've had some very interesting arguments with people in the field when I try to explain to them that it is all relative, they don't seem to understand, or don't want to I guess...