Superimposed current components contain effective information, which can be employed to enhance the dependability and security of busbar protection relays. This study aims to investigate the use of the slope degree of grey incidence analysis model to design a methodology for busbar protection. A grey‐based busbar protection criterion has been established to inspect the similarities of the superimposed currents measured by nearby CTs inside busbar protection zone. It is concluded that fault is internal if all of the superimposed currents are similar, otherwise, fault is external. It is shown that in all of the simulated cases, the authors’ methodology can make reliable discrimination between internal and external faults. Moreover, the results demonstrated that the protection indexes of the proposed scheme including security, dependability, sensitivity, and selectivity, are satisfactory for different conditions including fault type, fault resistance (to 500 Ω), fault inception angle, simultaneous faults, evolving faults, faults during transformer energization, CT saturation and normal operating switchings and white noise. Besides, the improvements noted in our algorithm are achieved with a low computational burden and sampling rate. Also, the scheme can be implemented in digital relays. It means that the existing busbar protection scheme can be replaced by the proposed scheme.