electro mechanical relays

[NewbieButTrying]

What is the difference between a HCB relay, and a PMA relay? Don't the both monitor pilot wires between substation?

 

[RalphChristie]

Download:

HCB:

http://library.abb.com/GLOBAL/SCOT/...03AC1256EC900560A63/$File/HCB_IB41_971_3M.pdf

(copy and paste whole address)
The type HCB relay is a high speed pilot wire relay designed for the complete phase and ground protection of two and three terminal transmission lines.

PMA:

http://library.abb.com/GLOBAL/SCOT/...85256EAF005A47C2/$File/IB41-973.5r RM.pdf

(copy and paste whole address)
Type PM and PMA Monitoring Relays provide continuous monitoring of a pilot-wire circuit to detect open circuits, short circuits, grounds, and wire reversal.



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[electricpete]

We used to have that type of electromechanical pilot wire relay setup. I think we had HCB and PM-1. Presumably PM-1 is similar to PMA.

If memory serves me right, you need both an HCB and a PM-1 at each end (4 relays). I remember the HCB takes the input of the three phase currents at one end. The PM-1 somehow helps with the interface and transfer trip function.

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