IEC 61850 Enabled Automatic Bus Transfer Scheme for Primary Distribution Substations

Automatic bus transfer scheme (ABTS) is the practice of transferring a load bus to an alternate source when the normal power supply fails or is tripped thus ensuring continuity of supply. This paper comprehensively reviews existing schemes and implementations of ABTS especially for motor bus. To limit the fault levels, during certain situations, the transformers supplying a primary distribution substation can be run in split instead of parallel operation. This is because during outages if one transformer is lost, overloading of remaining transformers, if it occurs, can be managed. This paper proposes an ABTS for a primary distribution substation for a utility facing such a situation and present details of its implementation. In the proposed scheme which is enabled by digital communications, if a transformer is lost, the bus section circuit breaker (CB) will be closed automatically after the incomer CB trips. The proposed ABTS has been implemented in the bus section relay for a new 11 kV switchboard where inter-relay communication is based on the IEC 61850 suites of standard. The contribution of this paper is that it shows how to use a standard automation scheme smartly to defer network reinforcements and manage fault levels in primary distribution substation.