Phase angle regulator

Its correct name is Power Factor Correcting Network.

Generally the load on power-lines is Indctive [lagging]. So capacitors [wkg values in KVR] are connected at different lacalities to bring it to Resistive; ie NO LAG/LEAD in phase angle [ideal, but cannot be attained].

Basically, a phase angle regulator is a simple "confused" transformer. it has the same input and output voltages, with a tap changer on one side. It is used most commonly at interconnects between 2 different utility companies and it's purpose is to be a great big megawatt shovel.

When you raise or lower the tap on the regulator, it allows more or less megawatts to flow into or out of the respective connections relative to what side of the PAR the tap changer is on, line or load side.

To know the function of the PAR in a 138/27kv substation or switch yard, you need to know the layout of the station, if the PAR is being used as protection for the transmission lines to prevent overload if one of the 138kv lines is lost.

If you give me more info of the layout, or what you are exactly looking for I can explain easier.

hope this helps.