AN EMBEDDED 1/3 PHASE AUTOMATIC TRANSFER SWITCH WITH INTELLIGENT ENERGY MANAGEMENT

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International Journal of Computer Engineering and Applications, Volume IX, Issue V, May 2015 www.ijcea.

1 International Journal of Computer Engineering and Applications, Volume IX, Issue V, May ISSN AN EMBEDDED 1/3 PHASE AUTOMATIC TRANSFER SWITCH WITH INTELLIGENT ENERGY MANAGEMENT Department of Electronics & Telecommunication Engineering, Savitribai Phule Pune University Maharashtra, India ABSTRACT: An Automatic Transfer Switch (ATS) for a power generator has been designed to enable the automatic operation and transfer of power supply between a public utility supply and a power generator. The ATS which a switchgear control system, provide a functional system that provides an automatic switching of power supply between a primary source(public utility) and a secondary power source(generator). The methods employed in designing the ATS involve the use of relay, phase detection circuit, microcontroller as the main component of the system. Incorporated in the ATS is a 5V, 12V,d.c. power supply unit, precision rectifier unit, current transformer, potential transformer and microcontroller to convert the measured analogue alternating current(a.c.) voltage and current quantities to digital values for display on personal computer. The result of the automatic transfer switch demonstrates its ability to perform automatic power change over activities easily and with little or no human interaction. Key Words Automatic switching, Automatic transfer switch, Public utility supply, Relay. [1]INTRODUCTION The poor state of power supply in developing countries, calls for alternatives sources of power generation and automation of electrical power generation to back up the utility supply. Over time, automation of electrical power supply has become so vital as the rate of power outage is predominantly high [1]. As a result of this power outage, developing countries experience slow development processes in both the public and private sectors of their economy. Investors from foreign lands do not feel secure to come and set up business or industries - in spite of the large market made available in such populated nations, because of frequent power failures experienced. In addition, delicate processes and operations such as surgery cases in hospitals, transfer of money between banks, data and information transfer at data centers, require constant power supply in 9

2 AN EMBEDDED 1/3 PHASE AUTOMATIC TRANSFER SWITCH WITH INTELLIGENT ENERGY MANAGEMENT order to prevent the loss of life or data resources which could be very expensive to business operations. Therefore, it is for these reasons that change over or transfer switches were developed. Initially, these switches were designed for manual operations, but with an increase in the technological advancement of electrical power control and automation that, Automatic transfer switches (ATS) were created. It eliminates the element of manpower interaction in starting a generator and changing power supply from one source to another. An Automatic transfer switch (ATS) is an electrical/electronic switch that senses when the mains or public utility supply is interrupted and automatically starts up a secondary supply (i.e. a generator) if the utility remains unavailable. ATS also known as Generator Transfer Switches, has an additional circuit component which is normally in the form of a computer that monitors the incoming power supply. This circuit according to Silva and Kolo [2-3], also monitors the voltage sags, power surges, power spikes, or brownouts. It also initiates the changeover action when there is a complete power loss. Whenever a fault is been detected, the automatic transfer switch starts up the emergency power supply. The ATS is connected to both power supply sources and supplies the load with power from only one of the sources at any particular instant in time. In contrast to the manual change-over switch system that requires manual stress in starting the generator and switching over from public supply to generator and vice-versa, that, the need to develop a system that will effectively manage power supply between two sources (utility and a standby power generator) therefore influenced the motivation for this project work. According to [4] and [5], all automatic transfer switches for generators consist of three parts namely: Contacts to connect and disconnect the load to source of power A transfer mechanism to move the contacts from one source to another An intelligent or logic control unit to constantly monitor the condition of the power sources and so provide the brain necessary for switching and related circuit to operate correctly. The ATS monitors the supply of voltage from a single phase line and a generator supply, it then base its control operation on the availability or unavailability of power supply from either sources. It consists of a series of relays contactors and protective devices that help form the control circuit of the ATS. The block diagram of the working principle of the ATS is as shown in figure 1. Figure:1. Block diagram showing the working principle of the ATS

3 International Journal of Computer Engineering and Applications, Volume IX, Issue V, May ISSN [2] METHODOLOGY The system can be divided into five main functional blocks namely; Phase detection unit, voltage measurement unit, current measurement unit, temperature measurement unit, level measurement unit. The phase detection unit is designed for primary source i.e. mains as well as secondary source i.e. generator. Upon failure of mains power load is connected to secondary source and vice versa. The voltage measurement unit measures the voltage of load. If load voltage exceed from limit then it automatically disconnect load from power source. It prevents any possibility of back feeding from the load to the utility line which could damage utility equipment or hurt, kill any utility workers. Temperature measurement and level measurement unit measure temperature and level of diesel in generator respectively. The temperature of generator is exceeded or level of fuel is below designed value it automatically turns of the generator and send the message to customer. [3] DESIGN STAGES/COMPONENTS The Relay switching stage: This block consists of the combination relay which serves as sensor used to determine the availability or non availability of voltage supply from either power sources before triggering the control sections of the ATS. Phase detection circuit: The 230V AC is directly converted to DC.If there is MSEB power then LED is blinking and in front of LED, LDR is placed. The single ended op-amp is used in the comparator. The inverting input voltage is greater than non-inverting input voltage then fixed threshold voltage is given using 10K pot. So output of comparator is 0V. i.e. phase is detected. And pin number 1 of comparator is directly connected to microcontroller. Potential transformer: The 230V is converted in 6V AC RMS (9Vp-p). Bridge rectifier output is given to capacitor filter which convert pulsating dc to pure dc. 9Vp-p is converted to 3.3V using 10K pot. Current transformer: If we use bridge rectifier directly then diode cannot be ON. Because cut-in voltage of diode is 0.7V. Here we are using precision rectifier. The switching is carried out by diode AC converted to pulsating DC. The filter gives the output as the DC. Temperature sensing circuit: The input section for the signal conditioner card for temperature consists of the voltage regulator using IC7805. The PT 100, which is a temperature sensor, is connected in one arm of the bridge and resistors of rest of the arms are selected such that at 0 C the bridge is balanced and OV appear at the output of the bridge circuit.the resistance of the sensor changes with respect to temperature, widely specifying RTD is having positive temperature coefficient i,e as the temperature increases so the resistance of the sensor also increases and vice versa. Now depending on the application of temperature the resistance of PT-100 changes proportionally which gives further changes in the output voltage of the bridge circuit at 0 C the bridge will be in balanced condition but as the temperature of the PT 100 changes due to application of some temperature input, then the bridge circuit becomes unbalanced. This unbalance results in small diff voltage across the bridge output. Maximum diff voltage will be 11

AN EMBEDDED 1/3 PHASE AUTOMATIC TRANSFER SWITCH WITH INTELLIGENT ENERGY MANAGEMENT from 20 to 40mv. This small voltage is fed to the differential amplifier for the amplification purpose.

Level sensing circuit:level sensor is placed in drum. The resistance across two wire changes according to level of diesel.

4 AN EMBEDDED 1/3 PHASE AUTOMATIC TRANSFER SWITCH WITH INTELLIGENT ENERGY MANAGEMENT from 20 to 40mv. This small voltage is fed to the differential amplifier for the amplification purpose. The gain may be from 150 to 300 to adjust full scale o/p. The Output of differential amplifier is then further fed to the ADC to convert the signal from analog to digital. Level sensing circuit:level sensor is placed in drum. The resistance across two wire changes according to level of diesel. If the level below designed value, controller automatically gives command to disconnect generator and send the message to user. [4]RESULTS Various tests were carried out on this project which include relay switching test (this is done to be sure the relays can switch back to generator when the power is out and vice-versa), generator starting test and voltage variation test (this is done to be sure that the output voltage is within permissible limit) and the testing of the entire ATS. Figure: 2. Load connected to MSEB and inverter [5]CONCLUSION Automatic Transfer Switch has been designed and constructed. The prototype of the system worked according to specification and quite satisfactory. The automatic phase change-over switch is relatively affordable and reliable. It is easy to operate, and it provides a high level of power supply when there are power outages. Finally, it reduces stress associated with manual change-over. However, for future work on this project we recommend that an actuator for mechanical movement of the choke lever should be included for cases where single phase generators without automatic choke controllers are used for testing operations. REFERENCES [1] M.S Ahmed, A.S Mohammed and O.B. Agusiobo, Development of a Single phase Automatic Change-Over Switch, Department of Electrical and Computer Engineering, Federal University of Tec`hnologyMinna, Nigeria, July [2] R. Silva, How automatic transfer switches work, retrieved online from November, [3] J. G. Kolo, Design and Construction of a Single Phase Automatic Change-Over Switch,

5 International Journal of Computer Engineering and Applications, Volume IX, Issue V, May ISSN Department of Electrical and Computer Engineering, Federal University of Technology Minna, Nigeria, [4] ATS-01 Ver1.0, Automatic transfer switch control unit operator s manual: retrieved on December17, [5] B. Brown, P. E. Jay Guditis, Critical Power System Functional Block diagram. Critical Power Automation Transfer Systems-Design and Application: SchneiderElectric, 2006 pp [6] R. Boylestad, L. Nashelsky, P. Hall, Electronic devices and circuit theory,seventhedition,upper Saddle River, New Jersey Columbus, Ohio[n.d]. [7] An article on Energy conservation in India by Shri P M Sayeed, Hon ble Minister of Power s article on the occasion of Energy Conservation Day, on 14th December [8] Y.SungSong,K.DeokMoon. Home Energy Management System Based on Power line communication /10ieee2010. [9] Yong Hua Song and Allan T Johns Flexible ac transmission System The Institution of Electrical Engineers, London, Uniited Kigdom1999. [10] Hingarani, N.G. High power Electronics and Flexible AC Transmission System, Power Engineering Review, IEEE, Volume: 8.Issue:7, July1988, pages3-4. [11] Utopia Automation and control Pvt.Ltd. User operation manual. [12] Anoop R, Anup J Nambiar, Prathap R, Sridhar Divakar, Dr. T B Isha Condition monitoring of Diesel generator using PC. [13] Paper on Automatic transfer switch (ATS) based on a programmable logic controller (PLC), Mechatronics, 2004, ICM '04. Proceedings of the IEEE International Conference, Issue: 3-5 June 2004,pages: [14] High voltage high-speed vacuum automatic transfer switch (ATS), Harmonics and Quality of Power, 2000 Proceedings, Ninth International Conference, 2000,volume:3,pages:882. [15] Book entitled by Maintaining Mission Critical Systems in a 24/ Environment, Publisher: Wiley-IEEE Press, Pages: , Subject Categories: Power, Energy, & Industry Applications. 13

6 A NOVEL TERM WEIGHING SCHEME TOWARDS EFFICIENT CRAWL OF TEXTUAL DATABASES (PAPER TITLE) 14

Construction and Operation of an Electronic Automatic Transfer Switch (Ats)

Global Journal of Energy Technology Research Updates, 2015, 2, 1-5 1 Construction and Operation of an Electronic Automatic Transfer Switch (Ats) J.O. Olowoleni, A.U. Adoghe *, A. Ademola, A.O. Omadoye,