Implementation of a Numerical Over-current Relay Using LabVIEW and Acquisition Card

Abstract

The project aims at the design and the construction of a numerical over current relay in PC using LabVIEW. It will acquire, sample and convert into digital form the analog current signals from a power system in real time using the NI USB-6009 acquisition card. When a current in a part of a power system exceeds a pre-set value due to a fault or a large overload, the relay will isolate the part through sending trip signal to a circuit breaker. In the developed laboratory model, a lamp board assembles the system.The overcurrent model is masked in a single subsystem (block) and a graphical user interface is provided where the user can select the type of overcurrent relay (Instantaneous, Time Definite or Inverse Definite Minimum Time IDMT). Furthermore, the user can select the different characteristic curves for IDMT overcurrent relay (Standard Inverse, Very Inverse, Extremely Inverse and Definite Time) and the relay settings (Current Set Point and Time Multiple Setting).