This paper  addresses a new technology in maintaining power quality in electrical transmission and distribution it is an common concern for both generation grids and consumer to maintain standards in power quality, it is not an easy task to regulate the power flow on the secondary side of an distribution transformer when it is connected to an varying load, our project provides an sample model on micro controller based on-load tap changer for an power transformer in order to regulate the power flow under faulty conditions like over voltages, under voltages, voltage dips, voltage sags, induced harmonics.

The objective is to provide constant output voltage irrespective of load changes at the output terminals by using a tap changer; in order to overcome the present drawbacks of the manual tap changer having less operational speed with minimum accuracy, overheating, producing noise and arcs at the contact terminals,  the entire operation is controlled by the micro processor  automatically by sensing the load variations  and acts up on the situation by varying output contact terminal i.e. tap changing, an CMOS 8-bit, high performance, low power AT89C52 microcontroller with 8K bytes EPROM is used in this circuit as  logical central process control which process the input signal and produce an appropriate  output signal based on the programming that is stored in the RAM  of the micro processor, A/D Converter with 8-Channel Multiplexer is provide information regarding the varying parameters these parameters are displayed on the LCD screen at the output section.

The pin configuration with its performance characteristics are discussed below.

This sample circuit is tested and the practical results shows the capability of this device in eliminating the drawbacks of the conventional tap changing methods, and also improves the life time of the contact terminals, the response time is very less it is nearly 0.44s, it maintains constant output voltage in accordance to varying load by regulating the positions of the contact terminal, this device requires minimum maintenance and it is economical.

Download  Micrcotroller Based Semiconductor Tap Changer for Power Transformer Project Report.