Distributed Power Quality Monitoring using Wireless Sensor Networks M. Ramakrishnan Department of Electrical and Electronics Engineering, College of Engineering, Guindy, Anna University Chennai. P. Vanaja Ranjan Department of Electrical and Electronics Engineering, College of Engineering, Guindy, Anna University Chennai Abstract Nowadays power quality (PQ) is the major issue for both electrical utilities and consumers, as the deregulation of power market happens all around the world. In this context, power quality attracts the research interest of both academia and the industrial community. This paper deals with the design of distributed power quality monitoring using wireless Power Quality Monitoring Nodes (PQMN). The design of intelligent PQMN which does the data acquisition, signal processing and wireless information transfer is reported. The wireless PQMNs are connected to the Ethernet backbone network through the embedded gateway nodes. Keywords: Distributed Power Quality Monitoring, Wireless Sensor Networks, Embedded Web Server 1. INTRODUCTION In recent years research in power quality gets greater momentum and the term power quality itself gets significance among the electric utilities and industrial power consumers due to the deregulation of the power market. In this scenario, the consumer has an option to select the power suppliers not only according to the cost of power but also the reliability of the power (i.e.) Power Quality. According to the IEEE power quality monitoring standards Power Quality is defined as powering the sensitive equipment in a manner that is suitable for the operation of that equipment [1]. As far as the industries are concerned, power quality is getting the power with the contracted specifications without any interruption and any power disturbances from the utilities. The industries are subject to lose billions of dollars because of power quality problems [2]. Power quality disturbances can be broadly classified into the following categories [3]. i) Power frequency disturbances: They are low frequency phenomena that results in voltage sag and swells. ii) Power system transients: They are a fast short time duration event that provides distortions. iii) Power System Harmonics: It is the existence of multiple frequencies in the system. This happens due to the non linear load. Sometimes interaction of the harmonics with the power system parameters(R-L-C) make the harmonics to multiply, which leads to severe consequences. iv) Electro static interference and electro magnetic interferences are other power quality issues. The paper is organized as follows. Section II discusses about the various power quality monitoring systems reported in the literature elaborately and the section III describes the distributed wireless power quality monitoring architecture. Section IV and V discusses about the firmware design in the PQMN and the gateway node. And section VI gives the conclusion of this work. 2. RELATED WORK In the literature there has been lots of work done on distributed power quality monitoring system. Reference [4] discusses about the optimal number and location of power quality monitor in a power system to reduce cost and redundant data. Microcomputer acts as power quality info nodes (PQIN) and they are connected to each other through internet. In [5] an algorithm is also proposed to find the optimal number and location of Power Quality Monitor. An internet based power quality monitoring system is proposed in [5]. Reference [5] also deals about development of software modules to integrate various commercial power quality meter output. In reference [6] the usage of energy monitoring system is justified. The paper states that continuous monitoring will yield a better savings due to the preventive maintenance. It is also stated that the site engineer can plan for the expansion by doing load prediction from the continuous monitoring. In reference [7] power quality problems voltage swells and sags occurring in the field have been reported. The PQ information are drawn from the data collected over the years. Reference [8] proposes a combined metering system for various sites of the industry spread across the geographical area. It is also stated that the combination of continuous power and energy monitoring along with the power quality monitoring is an effective method of obtaining power system information to enhance the reliability of the manufacturing unit. In [9] S. R. IGabram et al are reported a theoretical approach for power quality monitoring using MEMS wireless current sensor. It is