With everything Ok , the only risk of connecting the tertiary to Station auxilliariesv are : ( a ) The loading of the other secondary winding are to be reduced otherwise the feding winding will be overloaded . (b) The trnasformer may fail due to any fault ( voltage or current ) in the load connected to the tertiary ( c ) Besides (a) Power factor correction ( b ) Unbalaced load ( c ) Harmonic suppresson ( d ) Connecting to Auxilliary loads the tertiary winding can also be used for ( e) electrical isolation ( f ) Feed back system for voltage regulation ( g) Higher Zero sequence impedence