Phase monitor relay

[Jraef]

Just thinking about it in 40 years I’ve used phase failure relays twice.

Each time it was due to external control supplies. Each time it could have ended in a fatality. I’d get called in after the event to sort the mess out.

With proper design and there’s no need for PFR’s

I had an entire sawmill in Washington State get fed reversed phases after transmission lines 50 miles away went down in a storm. So much damage it was almost impossible to determine it, but the PoCo settled at $3 million.

The most valid applications for them are portable equipment and things with back-up portable generators. Around here, PG&E is ACB sequence, all the other utilities in this state are ABC. So people who have portable equipment and don't know this get in trouble when they plug in at a jobsite fed by a different utility. A lot of sewer utilities have back-up generator receptacles and the generators are sometimes brought in by the fire dept., who might have different sequencing than the sewer dept. service trucks.

 

[Tony S]

The OCPD and cable are not the issue, it is the smoke leaking from the motor windings.

Keep in mind out many currently used motor OLs do not protect against single phase conditions.

How can the cable and OCPD be a non issue? I suppose an outbreak of localised Volt Drop is a non issue.


Thermal or magnetic dash pot?
In 40 years I’ve never come across thermal O/L’s that can’t detect single phasing. Some of the old thermal relays from the 40’s to early 60’s were a bit dodgy.

 

[Tony S]

I had an entire sawmill in Washington State get fed reversed phases after transmission lines 50 miles away went down in a storm. So much damage it was almost impossible to determine it, but the PoCo settled at $3 million.

The most valid applications for them are portable equipment and things with back-up portable generators. Around here, PG&E is ACB sequence, all the other utilities in this state are ABC. So people who have portable equipment and don't know this get in trouble when they plug in at a jobsite fed by a different utility. A lot of sewer utilities have back-up generator receptacles and the generators are sometimes brought in by the fire dept., who might have different sequencing than the sewer dept. service trucks.

Where I served my time was BYR. OK until the company was connected to the “national grid”. A bit of juggling phases around at the intake sorted that. Because of our own power stations we wanted 11.4KV and not 11KV

Quarry men can be awkward *****