Q1. which standard shown HV Tie breaker normally open or normally closed?
Q2. what advantages or technical/operational benefits for Tie breakers normally open?
Q3. what advantages or technical/operational benefits for Tie breakers normally closed?
I don't know what standards will speak to this. But when we back-feed from our 2 available back-feeders, we leave all tie breakers open. This is done to reduce risk of cascading failure if a bus overload situation, or any associated fault, should occur. With a tie closed then both sides of the system will see the upset, or fault, and potentially trip the entire plant. With the tie open, any given bus failure will only affect that bus. It may take down half the plant generally but is controlled and coordinated that way.