618 IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 61, NO. 3, MARCH 2012 A Compact Remote Monitoring System for a Three-Phase 10-kVA Energy-Efficient Switchable Distribution Transformer Hari Arief Dharmawan and Sam A. M. Ali Abstract—Remote monitoring has been implemented in many areas. This paper introduces its specific application to a three- phase 10-kVA energy-efficient switchable distribution trans- former. A designed embedded system and embedded Ethernet have been implemented to achieve a compact remote condition monitoring for the transformer. The embedded system performs acquisition of voltages, currents, and temperatures, controls the switching devices that connect the tappings of the transformer, and processes acquired data. Client and server applications were developed through the use of embedded Ethernet to enable remote monitoring through a local area network (LAN). Some protocols were developed as parts of software development of the whole system. Experimentation was done by applying the remote moni- toring system to the transformer connected to three-phase variable supply voltage and load. Results of the experimentation by using a LAN available in the school revealed that the system can handle remote monitoring and control tasks for the transformer. Index Terms—Embedded Ethernet, remote monitoring, switch- able transformer. I. I NTRODUCTION R EMOTE condition monitoring of transformers has al- ready been widely known and implemented with var- ious techniques [1]–[4]. The monitoring is mostly carried out to reveal significant parameters that reflect conditions of transformers, such as voltages, currents, and temperatures [5]. Further suggested monitored parameters are explained in [6]. In addition to applications for maintaining healthy operating conditions of transformers, condition monitoring might be im- plemented for classroom demonstration and exercises such as discussed in [7]. The existence of the Internet provides further flexible remote monitoring in many areas, including power transformers. Thus, many approaches are developed to perform remote monitoring throughout the world by using a network that is connected to the Internet. Manuscript received April 26, 2011; revised August 31, 2011; accepted September 8, 2011. Date of publication October 31, 2011; date of current version February 8, 2012. The Associate Editor coordinating the review process for this paper was Dr. Carlo Muscas. H. A. Dharmawan is with the Department of Physics, Brawijaya University, Malang 65145, Indonesia (e-mail: dhaha001@mymail.unisa.edu.au). S. A. M. Ali is with the School of Electrical and Information Engineer- ing, University of South Australia, Adelaide, S.A. 5095, Australia (e-mail: Sam.Ali@unisa.edu.au). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TIM.2011.2170497 Fig. 1. Three-phase 10-kVA switchable transformer. In relation to this project, remote condition monitoring was applied to a three-phase 10-kVA energy-efficient switchable distribution transformer (see Fig. 1). This transformer has been previously developed to show an increase in the efficiency through the use of special configurations of windings, called series and parallel. The series and parallel configurations con- secutively reduce losses of the transformer in low and high loads [8]. The configurations were made by the use of 18 switching devices and controlled by three microcontrollers (AT90CAN128). These microcontrollers were chosen because they have an internal peripheral that supports communications through a controller area network (CAN) bus. The remote monitoring system for the switchable trans- former is however quite unique because it includes measure- ments of switching devices’ temperature. Moreover, the system is useful not only in monitoring the parameters of the trans- former (such as voltages and currents) but also in controlling the switching devices and performing switching at appropriate timings [9]. A compact monitoring system was considered to be developed for this purpose as it requires less power and space and it is portable. To perform remote monitoring, a client/server system was implemented by using some embedded Ethernet boards (Ethernut 1.3 Board). The embedded Ethernet has been implemented in many areas involving data transmis- sions over a local area network (LAN) or the Internet [10]–[14]. 0018-9456/$26.00 © 2011 IEEE