After the official issue of standardization design specification of state grid

it is imperative to clear the differences between status quo of Hunan and the standardization design specification and to implement standardization design specification in actual work.This paper introduced the configuration of 220kV microprocessor-based bus protection of Hunan power grid

analyzed interrelation among bus differential

bus coupler malfunction and breaker malfunction protections

and enumerated the necessity and feasibility of canceling external starting loop in bus-coupler malfunction and the unattached voltage blocking device RCS-918A.Improved solutions for bus coupler malfunction and dead-time fault without protection during charging were also presented.