New to the forum and i apologise if this post is in the wrong topic, I am studying a circuit from a Summation Transformer that is used in an aged HV protection relay system called SOLKOR, the summation transformer in my basic understanding compares a 3 phase output current/voltage of 3 bar primary current transformers fitted into HV switchgear, and induces a single phase voltage for the relay to act upon and to transmit down a pilot wire. Its probably a basic circuit for you chaps, but could anyone explain to me the role or any possible roles of the capacitor that the arrow points too. The circuit is fully AC and the capacitor is across the two terminals that outputs the single phase voltage to a pilot wire that is connected to a similar transformer and the other end of a high voltage feeder,