Modelling of Analog to Digital Converter for Merging Unit of Optical Current Transformer

Evolution in technology in substation automation provides engineers with numerous new challenges. These advancements in technology are defined in the IEC 61850 standard. This standard depicts the communication mapping for substation automation. The primary problem is to switch out outdated protective relays with reliable, newly developed microprocessor-based relays. These are called intelligent electronic devices (IEDs) in the automation field. The analog to digital converter is a crucial merging unit (MU) component. In order to meet the application of the requirements, an analog signal with an input frequency of 50 Hz, a current of 0 to 2 amps, and a voltage of 0 to 5 volts into a digital format with a high resolution of 14 to 16 bits. In the current scenario, the merging unit is placed near the substation where relay control panels are located. This merging unit takes analog signal from the CT through the cables which are running from the CT to the merger unit control box. This paper proposes a design of SAR ADC for a decentralised merging unit, a small unit which will be installed in the CT base. Furthermore, this will directly give a digital output that complies with IEC 61850. An optical fibre will send that signal directly by a wired or wireless control system.