Design and Analysis of Selective Cross Tripping Protection Scheme on 250 MVA (220/132kV) Auto Transformer

Abstract

This research explores protecting electrical systems from overload, a common issue when transmission lines or equipment face excessive loads. It focuses on forced tripping, vital in power management at transmission substations and power plants. Overloading can cause cascade tripping, leading to extensive shutdowns. In literature, the solution proposed is cross-trip scheme, which protects healthy transformers from unnecessary overloading and tripping when operating in parallel, preventing total network disruption. A significant disadvantage is that the cross-tripping scheme often lacks selectivity. It may cause tripping of healthy or non-overloaded components due to an issue in a parallel circuit, which can lead to inefficiencies and potential damage to equipment. The study's innovation lies in introducing the Selective Cross Tripping scheme, a method that uses transformer load to decide which circuits to trip. It incorporates a unique device that trips circuits based on the transformer's load, thereby enabling proactive power load management. This scheme avoids system overload, one of the most damaging events in power system operation. It isolates circuits based on transformer load, preventing the need to entirely shut down the system or trip unaffected circuits, saving significant operational and financial costs. The study also highlights how the Selective Cross-Trip device can reduce revenue loss by maintaining the power system's integrity and ensuring uninterrupted operation of unaffected parts. This method balances the need to protect the system's hardware and minimize financial losses. The study also compares the Selective Cross Tripping scheme with the standard Cross Tripping scheme, demonstrating the superior efficiency of the former. It significantly outperforms the latter by ensuring continuity of unaffected parts, reducing revenue loss, and maintaining power system integrity.