Introduction

In three-phase Alternating Current (A/C) systems, phase reversal and single phasing (i.e., phase loss) are the most commonly observed fault conditions. A phase-reversal fault generally arises from human errors during system installation or maintenance, while single-phasing faults are caused due to a broken wire or mechanical failure, worn contact, blown fuse or thermal overload. The consequences of these faults are unsafe conditions for system operation, which can lead to severe damage and failures to the systems, causing potential injury. Hence, a phase sequence and phase-loss monitoring unit is required for three-phase A/C systems. The monitoring unit detects the faults and notifies the system to take subsequent action to protect the load.

This application note describes the implementation of a phase sequence and phase-loss detection system for a three-phase A/C supply and demonstrates the detection of phase sequence and phase-loss faults on emulated three-phase A/C systems supply using the PIC18F56Q24 microcontroller. The demo is based on the PIC18F56Q24 Curiosity Nano development board, a Curiosity Nano Adapter board and MikroElektronika Click boards™. The supplemented firmware is developed with the PIC18F56Q24 microcontroller, using the MPLAB® Code Configurator (MCC) and MPLAB X Integrated Development Environment (IDE).

The PIC18-Q24 microcontroller family is equipped with a 10-bit Analog-to-Digital Converter with Computation (ADCC), Zero-Cross Detect (ZCD), Timers, Universal Asynchronous Receiver Transmitter (UART) and Serial Peripheral Interface (SPI) peripherals that are essential for the implementation of a phase sequence detection application. The combination of ZCD and the 10-bit ADCC peripherals offer a reliable, efficient and cost-effective alternative for the phase sequence detection solution, compared to conventional non-microcontroller-based solutions for multiphase A/C supply.