Protection of the Blinding Area in Active Distribution Network by Multi-Function Relays

The overcurrent relay (OCR) is the major device to protect the distribution network feeder. The OCR issues increase with distributed generation (DG) embedded in active distribution networks (ADN). In addition, high impedance fault (HIF) has been challenging to properly detect the fault in the power systems. The blinding areas lead to a delay or non-tripping in the OCR. The typical method to cover the blinding area is the increasing sensitivity of relay settings. Changes in the settings of the protective relays may cause challenges to protect ADN. Most of the modern protection relays are digital multifunction. The relays can activate multiple protections, simultaneously. This paper presents a simple and economical solution to protect the fault in blinding areas by the OCR and thermal overload relay. The blind possibility points are determined in a case study by changing the fault impedances and DG presence. The case study is based on a real distribution network that includes two CHP generators with 4 MW capacity. The simulations are carried out on a realistic case study using DIg SILENT software. The results show the proposed method can cover the blinding zones with the thermal overload and OCRs.