26-07-2012, 12:59 PM
Micro controller based distribution transformer Monitoring and Protection system
transformer Monitoring.doc (Size: 423 KB / Downloads: 98)
ABSTRACT
The aim of the project work is to protect the distribution transformer or any other transformer, burning due to the overload, over temperature and input high voltage. Normally transformers are burning because of these three reasons and by incorporating this type of monitoring and control circuits, life of the transformer can be increased.
For monitoring the load current continuously a current transformer is used, similarly for monitoring the transformer body temperature or oil temperature (Basically all the distribution transformers are oil cooled transformers) LM35 temperature sensor is used. For monitoring the transformer primary voltage, for high voltage sensing, a step-down transformer of 6V secondary is used.
For simulation of the faults, in the demonstration unit a step-down transformer of 12V, 1Amp current rating is used, this is known as ‘TUT’ (Transformer Under Test) and the above parameters are carried over this transformer and the corrective action is initiated when the parameters crosses its limits.
INTRODUCTION
This project report describes on the design, development and fabrication of one demonstration unit of the project work “PC Based Transformer Failure Preventor”.
Nowadays, with the advancement of technology, particularly in the field of computers, all the activities in our day to day living have become a part of information and we find computers at each and every application. Thus, the trend is directing towards computer based project works. However, in this project work the basic signal processing of temperature, load current and input high voltage parameters related to the distribution transformers are monitored with analog electronics only. Subsequently after analog processing, these signals are converted into digital signals using analog to digital converter, then the decisions are taken with the help of computer and associated software. A relay is connected at the output of computer, which energizes or de-energizes automatically according to the condition of the parameters. This relay contact is used to break the supply to the load, hence by incorporating this kind of monitoring and control system, transformer failures can be minimized and the life of transformer can be increased.
General Description
The LM35 series are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius(Centigrade) temperature. The LM35 thus has an advantage over linear temperature sensors calibrated in° Kelvin, as the user is not required to subtract a large constant voltage from its output to obtain convenient Centigrade scaling. The LM35 does not require any external calibration or trimming to provide typical accuracies of ±1/4°C
at room temperature and ±3/4°C over a full -55 to +150°C temperature range. Low cost is assured by trimming and calibration at the wafer level. The LM35’s low output impedance, linear output, and precise inherent calibration make interfacing to readout or control circuitry especially easy. It can be used with single power supplies, or with plus and minus supplies. As it draws only 60 µA from its supply, it has very low self-heating, less than 0.1°C in still air. The LM35 is
rated to operate over a -55° to +150°C temperature range, while the LM35C is rated for a -40° to +110°C range (-10°with improved accuracy). The LM35 series is available packaged in hermetic TO-46 transistor packages, while the LM35C, LM35CA, and LM35D are also available in the plastic TO-92 transistor package. The LM35D is also available in an 8-lead surface mount small outline package and a
Plastic TO-220 package.
Monolithic IC voltage regulator:
A voltage regulator is a circuit that supplies a constant voltage regardless of changes in load currents. Although voltage regulators can be designed using op-amps, it is quicker and easier to use IC voltage regulators. Furthermore, IC voltage regulators are versatile and relatively inexpensive and are available with features such as programmable output, current/voltage boosting, internal short-circuit current limiting, thermal shutdown and floating operation for high voltage applications.
LCD display
LCDs can add a lot to your application in terms of providing an useful interface for the user, debugging an application or just giving it a "professional" look. The most common type of LCD controller is the Hitachi 44780, which provides a relatively simple interface between a processor and an LCD. Inexperienced designers do often not attempt using this interface and programmers because it is difficult to find good documentation on the interface, initializing the interface can be a problem and the displays themselves are expensive
CONCLUSION
Apart from these three parameters, various other parameters, such as line frequency, power factor, power leakage, Energy measurement etc; can be incorporated in this project work. Apart from using computer, Microprocessor or micro-controller also can be used. The advantage of using PC is, the parameters not only monitored, but also periodically the data can be logged and the same data can be stored. So that details of the parameters can be monitored on the screen. There by this data can be used for taking suitable decisions.