Numerical Quadrilateral Distance relay

This paper describes the development of quadrilateral distance relay characteristic for the protection of high voltage line using numerical technique. The characteristic of the relay is generated by the software designed in Visual Basic 6. The software estimates the magnitude of reactance and resistance by using differential equation principle. The analog voltage and the current signal are applied to the computer through Advantech Automation device. The software samples the input analog signals and estimates impedance for characteristic development. The characteristic of the developed numerical relay is adoptive with a provision for changing the relay parameter.