Advanced line current differential protection with reduced channel requirements

Line current differential protection creates challenges for relay design and application. From a design perspective, the distributed nature of the line current differential system imposes limits on the amount of data that can be exchanged between the system terminals and calls for data alignment schemes to enable the differential protection principle. From the application perspective, line current differential schemes are concerned with current transformer (CT) saturation, particularly in dual-breaker applications; in-zone reactors and line-charging current; in-line and tapped transformers; security on channel impairments; application to multiterminal lines; and so on. This paper reviews technical solutions to the line current differential design and application, addressing the common design constraints and application needs.