Is this project for the protection of a 3-Phase-Motor or Machine ?
.

A couple of typical places, one is mandatory use in elevator circuits, also used in remote automatic/unattended pumping stations.
I have also seen it used on one manuf. of CNC M/C's.

 

I'm simply trying to get a full understanding of what is meant by "Sequence-Change-Indicator".

There are plenty of well know schemes for 3-Phase-Motor-Protection.

There is a very low likelihood of a 3-Phase Mains-Supply changing it's Phase-Rotation.

But I suppose there could be a questionable situation where a Portable-Motor is being
connected to an unknown Portable-Generator,
where the Phase-Rotation needs to be verified before energizing the Motor,
but I don't understand the utility of a permanently installed
"Phase-Rotation", or "Phase-Loss", "Indicator" device.
Or, is this supposed to be a hand-held-Tester of sorts ?

In other words .........
I wish the Thread-Starter would simply state the intended, basic purpose of his project,
and the exact nature of the problem that needs to be solved.
So far everything has been based off of assumptions.
.
.
.

 

I'm simply trying to get a full understanding of what is meant by "Sequence-Change-Indicator".

There are plenty of well know schemes for 3-Phase-Motor-Protection.

There is a very low likelihood of a 3-Phase Mains-Supply changing it's Phase-Rotation.

But I suppose there could be a questionable situation where a Portable-Motor is being
connected to an unknown Portable-Generator,
where the Phase-Rotation needs to be verified before energizing the Motor,
but I don't understand the utility of a permanently installed
"Phase-Rotation", or "Phase-Loss", "Indicator" device.
Or, is this supposed to be a hand-held-Tester of sorts ?

In other words .........
I wish the Thread-Starter would simply state the intended, basic purpose of his project,
and the exact nature of the problem that needs to be solved.
So far everything has been based off of assumptions.
.
.
.

Phase monitoring relays have been around longer than I have, but in older equipment they are not very common. In newer equipment they seem to be getting more popular, I see them more often. You have a point about permanently installed equipment but the counterpoint I suppose would be that they are cheap if they save the equipment from self destruction just that one time during install/commissioning then they have paid for themselves several times over.

For portable equipment, depending on type, they may pay for themselves every time the equipment gets plugged into a different outlet.

 

As I mentioned, accidental or intentional phase reversal detection is important for a few applications, elevators is the one prime example. In most jurisdictions it is mandatory.
The other I have been involved in is in the remote city water supply pumping applications.

 

A phase sequence detector requires to monitor all three phases.

Can you not get away with two phases if you know it's around 50 or 60Hz?