Micro Processor Based Bus Protection System Using IEC 61850 Process Bus (9-2) Sampled Values

摘要

A novel, phase segregated bus differential protection scheme, which utilizes independent multi-principle advanced protection algorithms, such as, differential percent slope, delta phase directional comparison, rate of change of differential (ROCOD) currents, delta phase directional comparison on zero sequence current differential, fast CT saturation detection, second harmonic blocking and a check zone to secure the electrical bus bars up to three zones (two main and one transfer bus) will be discussed. The proposed microprocessor based bus protection scheme has the ability to measure the conventional CT currents within the protection unit, and will share / distribute the corresponding sampled values using IEC 61850, 9-2 technique, acting as Merging Unit, with other protection units in the system to perform the overall differential protection. Each protection unit therefore acts as a processing (subscribing sampled values) and as well as a Merging Unit (publishing sampled values). The scheme can be scaled to support up to 24 bays (24 sets of three phase CT current inputs) and a three phase PT voltage input by means of 4 individual relay protection units (6 sets of three phase CT current Inputs per relay) working together as one protection scheme, in a very compact electrical panel (4x3U rack units). For time synchronization, additional inputs, and outputs, an I/O unit is used to collect breaker status, isolator status, and any other inputs into the bus protection scheme.