Programmable Logic Controller (PLC) susceptibility to voltage sag

Abstract

Programmable logic controller or PLC is the most commonly used industrial automation technique in the world. It is universally applied for factory automation, from the creation of computerized versions of relay. It is used to control manufacturing systems. IEEE 1159-1995 Recommended Practice on Monitoring Electric Power Quality has defined voltage sags are a decrease in RMS voltage between 90% and 10% of the RMS nominal voltage. The duration, between 0.5 cycles and 1 minute, will categorize it in the instantaneous momentary or temporary time domains. PLCs can react quickly when voltage sags occur, shutting automation systems down for events as short as one cycle. Susceptibility of the power supply or misinterpretation of input or output signals usually causes the shutdown. In this thesis, it is focused onto the PLC susceptibility to the voltage sag and the mitigations ways to overcome the effects. Conduct a research to determine the level PLCs susceptibility to voltage sag by using a test set up including PLC, relays fluorescent and LED lamp. The experimental showed, at the 16% and below of nominal voltage sags affect to shutdown of the systems. The mitigations techniques such as using power conditioners for the AC source voltage or employing a robust DC control power source provide effective mitigation. The PLC is susceptibility to voltage sag.