IEC61850-9-2 Process Bus implementation on IEDs

The Process Bus is based on two types of multicast messages, the GOOSE (defined in IEC61850-8-1) and the Sampled Values (SV, defined in IEC61850-9-2). This paper focuses on the SV messages and their influence on the IEDs. Devices working with SV, coming from the Merging Units (MU) or from the non-conventional CTs (NCCT), have to cope with issues not considered with conventional IEDs: resampling, frequency tracking, counter-measures to be taken during loss or delay of SV, etc. The paper explains the issues found during the development of an IED based on SV, describing the adopted solutions. Interpolation algorithms are used for resampling and for lost SV estimation. The frequency tracking algorithm is reviewed. Tests results for different conditions are included.