Is anyone aware of the origin of the term Pallet relay? We use multip

[woodseng]

I am trying to find out where the term Pallet Relay comes from. I see it on several older drawings from one of the Utilities here in Canada.

It appears to be the smae as a multiplying relay, but I'd like to be sure.

 

[busbar]

Are you sure you don’t mean ‘pilot relay’? See

http://www.gedigitalenergy.com/multilin/notes/artsci/art15.pdf

 

[woodseng]

Thanks for responding. The word is pallet for sure. Here is an exerpt from a 1922 text:

"For this reason it is necessary that the tripping circuits be opened by an auxiliary pallet switch or contacts fastened to the circuit breaker in such a manner that the opening of the breaker automatically opens the tripping circuit."
from [PROTECTIVE RELAYS THEIR THEORY, DESIGN, AND PRACTICAL OPERATION BY VICTOR H. TODD. 1922]

This makes it sound more like a MOC (mechanism operated contact).

 

[DiscoP]

I don't really know the origins, but pallet is the only term people use at the company I work for when talking about CB auxiliary contacts (52a and 52b). Never heard of it before joining !

 

[woodseng]

I am hoping that someone (perhaps on the IEEE 37 committee?) can chek out my assumtions:

Referring to IEEE 37.20.1 defnitions:

I see MOC (mechanism operated contact) as the auxillary contacts, directly operated by the breaker mechanism itself BUT mounted on the STATIONARY housing (ie. not on the draw-out portion with the breaker).

There are also contacts (usually 2NC and 2NC) built right inside the breaker called Auxilary 52a and 52b.

The TOC (truck operated contacts) are also mounted on the stationary housing and are closed when the breaker is in Test or drawn out position, and open when the breaker is in the connected position. This provides a "permissive" for other functions(and is sometime referred to as a "69" contact per IEEE/ANSI protective device numbering (though this is not used in Stand 37.20.1.