Design and Implementation of a Microcontroller-Based Automatic Changeover System for Transformers in Power Stations

Abstract

Currently, most critical industries in Kenya have employed conventional methods to effect changeover processes from one power source to another for ensuring uninterrupted and efficient supply of power to their plants. However, these methods are subject to many setbacks that include; strenuous operation, time wastage, high probability of fire outbreaks and frequent maintenance which is expensive. This study seeks to provide a solution to these power interruptions by giving automation to the changeover circuit in order to eliminate these setbacks. The circuit incorporates two transformers connected independently to specific loads. Current sensors are connected to the transformers to check for current availability and feed the output to Arduino ATmega microcontroller. A feedback loop is created by connecting the loads to the microcontroller in order to monitor load variations. Using the transformer and load inputs, the microcontroller instructs the relays to switch between the loads according to the specified transformer capacities and availabilities. Load shedding and load sharing are also executed by the microcontroller and the status of the transformers and loads displayed on the LCD display. Two sets of data are then obtained, for the effects of load variations on transformer performance before and after changeover and the other one based on the efficiency of the designed microcontroller based changeover system. The obtained results shows that whenever a load is applied on the secondary side of the transformer, the secondary current increases together with the primary current. It is also found that for two operational transformers, the changeover process does not require any time lapse. A program algorithm is used to achieve load shedding and load sharing through the microcontroller. A Minitab is used to display the outputs of the measured current, voltage, time and resistance. Proteus Ver. 8.6 software was also used to simulate the circuit and the results presented graphically.