HORN-4 RELAY

[google2004]

HORN-4 relay is in use for a 22kV tie between two switchboards in our power plant.
I want to know
What is the purpose of this relay?
Where can I get the literature of this relay?
What relay is being used today as an alternative of this relay?
Thanks in advance.

 

[Aakhrinaam]

I know of a HORM relay which is basically diferential protection over pilot wire ( "Translay" protection).

I would try Areva /ALSTOM for confirmation that it is indeed that form of protection.