1 Electrical Parameters Remote Monitoring, Using PLC and OPC Platform Valentin Dan ZAHARIA 1 , Călin MUREAN, Florin DRĂGAN 1 Department of Electric Measurements, Faculty of Electric Engineering, Technical University of Cluj-Napoca, Cluj-Napoca, Romania Abstract— Electric power measuring and management is a major issue in the current agenda of the electrical research community. In order to realize a real-time data acquisition system for monitoring electrical parameters in a wide-spread process, special hardware and software equipments have to be used. This paper proposes an experimental data acquisition system based on a Programmable Logic Controller (PLC), connected to a monitoring station via a pair of OPC Server/Client applications. The data collected are presented in real-time via an customized HMI application, and is also stored in a database for further calculations and analysis. Index Terms — data acquisition, database, interfacing, monitoring, programmable logical controller, system I. INTRODUCTION The concern for electric power metering has been in- creasing in recent times, for providers as users alike, as both categories are directly interested of both, the quantity and quality of electrical energy measuring precision. Another key concern in modern power metering is real-time access to field data. Modern data acquisition systems provide such real-time access to process data, as the hardware and software infra- structure is designed to fulfill this goal as good as possible. Data acquisition hardware devices (PLCs, DCSs, RTUs) consist of several analogue and digital inputs and outputs, having a limited amount of memory and processing power. Their main purpose is to collect the data in the field and to transmit it, as fast as possible, towards more complex ter- minals placed on higher levels in the hierarchy of a com- mand and control system, without subjecting it to complex operations. One approach for solving the matter of fast and secure data transfer would be the implementation of a classical SCADA (Supervisory Control And Data Acquisition) sys- tem, consisting of interconnected remote devices and a central control unit. Such systems are appropriate for moni- toring and control of a distributed process. However, as the number of command and control devices that have to be monitored increases, a basic SCADA system may be over- whelmed by the variety of the devices and the protocols needed to establish communication links between the sys- tem’s elements. In such systems consisting of devices pro- vided by different vendors or using different versions of communication software, communication needs to be sim- plified by implementing a unified architecture platform. Such a standard-based data-connectivity method can be supplied by using the OLE for Process Control (OPC) Specifications. The OPC Standard is used to overcome one of the automation industry’s biggest challenges – enabling various data access by establishing communication between devices, controllers and applications, regardless of their proprietary interfaces and protocols. [1] Measuring circuit Calculations Interfacing Storage Processing Unit Fig. 1 – PLC based SCADA system The generic system presented in figure 1 consists of mul- tiple Programmable Logic Controllers equipped with vari- ous input-output extension modules and special function blocks. The PLCs’ connection to the communication infra- structure is realized by various communication protocols implemented in the respective communication modules. In the following sections of this paper, a subsystem con- sisting of a PLC equipped with an analog to digital conver- sion module and connected via a Modbus communication module will be described, along with the measuring circuit, the user interfacing application and the data logging solu- tion. II. THE MONITORING SYSTEM The data acquisition system used in this paper is part of a larger scale SCADA system, based on FX3U Mitsubishi PLCs (fig. 1). The system’s measuring circuit uses a LA- 55P current transducer and a LV25-P voltage transducer.