Why do we Prefer to Close the Switch at 11 O’Clock and not at 12 o’clock?

  Synchroscope needle at 12 o'clock means the slip difference of sign waves and the voltage difference between the phases is minimum or nearly zero. If we close the switch at 11 o’clock because by doing so we are achieving nearly close to 12 o’clock position to compensate time taken for closing the synchroscope switch.