Client-side aplications in software system for electrical power systems management.

Moraru, Sorin Aurel ; Danila, Adrian ; Perniu, Liviu 等

Abstract: Being provided by different vendors, there is a problem of managing the applications, developed using various technologies and running on different environments, implying administration problems and many security aspects. The information is spread into many places, this making it difficult to have a global view on the enterprise's resources. The solution is to have a single software system that provides functionality for all the enterprise, into a unified manner. Our distributed software applications architecture comes to deal with the problems presented above. The technology used for developing this system is web-oriented.

Key words: software system, power management, applet, web.

1. INTRODUCTION

Distributed applications systems allow very easy access to the information, by simply using a web-browser (such as internet explorer), from any computer that can communicate, through LAN or Internet, with the application servers that manage all the information into a unified manner.

Our solution uses a 3 level architecture, with a driver that communicate with the equipment, a server gathering all the data from the data sources, processing and storing it into the database, and client applications, including the user-interface. This paper presents in detail the client-side applications.

2. STATE OF THE ART

The subject is approached in IEEE publications such as:

* IEEE Transactions on Power Delivery--In the paper (Carullo & Nwankpa, 2005) the authors develop a model of an electrical power system, which is referred to as an "information-embedded power system" to emphasize the inclusion of information variables that represent measurements that have been delivered across the communication system and observed at a control center.

* IEEE International Symposium on Communications and Information Technologies--The paper (Paiva et al., 2006) emphasizes that the industrial motors energy monitoring is very important currently, making possible to the electrical energy efficiency be analyzed. The measured data were stored in a database developed in MySQL.

* IEEE Power Engineering Society General Meeting, 2006--In order to acquire data about the actual conditions of power consumption, an electric power energy monitoring system is developed in (Nagata, 2006), describing the system configuration and the surveillance results.

* Proceedings of the IEEE--Several example novel control and communication regimes for the needed new infrastructure accordingly to the present time are given in (Tomsovic et al, 2005). In (Birman et al., 2005) the authors give answers to the new control and monitoring requirements for restructuring of the electric power grid, for which classical technologies may be inadequate.

3. OUR SOLUTION FOR CENTRALIZED MONITORING OF ENERGY CONSUMPTION

3.1. Our implementation allows the monitoring of a set of electric measures acquired by electronic-cells counters (SEPAM and PECA type) connected to the power consumers (6.4 and 0.4 KV), at two big cement factories of a big transnational company.

These measures are the phase voltages and currents, frequency, power factor, active energy and reactive energy. The monitoring can be done on instant values or recorded values.

Our system does the on-line information publishing (on any computer from LAN, using a simple web-browser), and archiving and storing into a MySQL database (Moraru et al., 2005) for later viewing, over a period of years, having different sampling periods, depending on the measurement time.

3.2. System reliability and error detection

The server is highly reliable, meaning that it has a built-in expert error detection system, which automatically detects errors and signals them to all the users concerned by the problem. It allows more drivers and clients to connect and disconnect, without the need of stopping or restarting. So, because of the way it is built, the server allows viewing different measures with different criteria, at the same time by many users, each using a different computer.

The image in the Fig. 1 presents a screen capture taken with the client application that shows the phase currents evolution for a group of counters. The red rectangle informs the user that the counter 5 is not working properly. This system can be used very well as an error detection system, along its main functionality--monitoring the variation of electrical measures.

4. RESULTS

4.1. The Client application

The technology used for implementing the Client application, further called applet, is Java Applet.

This technology allows an easy access, from anywhere, to the component that interacts mostly with the users. The applet is an application that runs into a web-page and is being accessed with an Internet browser (Internet Explorer, Netscape, etc). Accessing is easy, just as if you would enter a normal web-site.

The first page in the client application is the login page. This allows restricted access to the monitoring system. Only the persons who have a user account and a password can enter the system through this way. After login, the applet shows a table into which appear the measured data from the electric-cells counters network. This table is updated every 2.5 seconds. Close to the table also appear some buttons. This table presents a list with all the counters recorded into the database. For each counter, on the columns are presented the values recorded for the monitored measures. These values are updated each 2.5 seconds. In this table, the information is accompanied by the validity status for each measurement.

[FIGURE 1 OMITTED]

In the case when an electric-cell counter does not send any information to the server within a 10 seconds interval elapsed from the last update, this counter is marked as invalid. Like this, when the applet gets the updated information regarding the measured values, it also gets the status for each counter, marking visually the validity status for each counter (cell).

The applet connects to the server at startup and maintains this connection over all its run time. On the main applet page, in the lower-left corner appears an indicator that shows the server connection status. The normal status is "Connected". In this status, the indicator will have a green color. This indicator can also be used to control the connection status, meaning that the user can connect or disconnect from the server by just clicking.

The most complex part of the applet is represented by the Graphics panel, which presents the time evolution for the measured values acquired by the monitoring system. The access to this panel is done by clicking the "Variation over time for measures" button, which is located on the main applet panel. From the Graphics panel you can return the main panel by clicking "Back to the table". You can choose what kind of monitoring you want to see (instant values or history) in the combo-box from the bottom of the panel. You can also see measures for all the counters, for a group of counters or even for an individual counter by making the appropriate selections in the two middle combo-boxes. The measure to be monitored can be selected from the "Choose measure" combo-box.

When you choose one of the three options corresponding to the history graphs, the time selector becomes active. When you move the mouse over the selector, a red thick vertical line appears at the mouse position. This line is used to mark the first end of the interval. When you make the first click, the thick line is fixed into position and is shown as a thin line. The space between this fixed line and the moving end is filled with yellow until you make the second click. The second click definitively marks the interval and it becomes colored. The "History" button now becomes active.

For better viewing the graphs in various cases, we provided tools for changing the graph's look and functionality. So, you can shrink or enlarge the graph, by changing the number of pixels per sample, or you can change the frequency of the major gridlines, or even eliminate them. There is implemented an "AutoSnap" feature too. When AutoSnap is on, the ruler automatically snaps on the real measures, avoiding so to view interpolated values.

4.2. The Graphchart

The Graphchart is the most impressive tool from all the client applications created by us. It provides a wide range of information to the user. When the mouse pointer is over it, a ruler appears. A vertical line and a horizontal line comprise this ruler. On the vertical line appears the value on the "y" axis at which the line is located. On the horizontal line appear three types of information:

* The timestamp--this is the exact moment of time at the place where the vertical line is;

* The interpolated values of the three graphs--at the upper part of the chart, near this line, are printed the three values corresponding to the time marked by the position of this line on the chart

* The identifiers for the counters that have invalid values, if necessary.

The Fig. 1 presents also the Graphchart and the ruler. The horizontal axis is placed on at the 54.6 Amperes, and the vertical line is placed at 13:31:19. At that time, the values for the currents are: i1 = 27.7, i2 = 31.4, i3 = 39.7. The counter having the ID 5 has invalid values.

The graphs generated in the Graphchart are time dependent. This means that even if the sampling period is 2.5 seconds, the whole system is asynchronous. So, the values arrive at periods around 2.5 seconds; if no data arrives for 10 seconds for example, this is clearly illustrated in the graphs. In the middle of the graph will be a large gap between the samples. This means that the time between the two distant measures is proportional with the distance on the screen (about 25 seconds).

5. CONCLUSION

The concept of industrial enterprise resource planning is getting shape, as such a system will provide the means to have all the information centralized and processed as a whole. We are facing a new revolution in the industrial control systems, which is not guided by the technological improvements, but by the integrating power of distributed software applications.

The security of enterprise resources is improved by being unified into a single system, more accessible and easier to use.

6. REFERENCES

Birman, K.P. et al. (2005). Overcoming Communications Challenges in Software for Monitoring and Controlling Power Systems. Proceedings of the IEEE, Vol. 93, Issue 5, pp. 1028 - 1041, ISSN 0018-9219.

Carullo, S.P. & Nwankpa, C.O. (2005). Experimental Validation of a Model for an Information-Embedded Power System. IEEE Transactions on Power Delivery, pp. 1853 - 1863, ISSN: 0885-8977.

Moraru, S.A.; Pelcz, A.; Bujdei, C. & Perniu, L. (2005). Web-oriented Applications of Databases Used in Electrical Domain. The 14th International Scientific and Applied Science Conference Electronics' 2005, Sozopol, Bulgaria, book 3, ISBN 954-438-519-3.

Nagata, T. (2006). An Electric Power Energy Monitoring System in Campus using an Internet. IEEE Power Engineering Society General Meeting, 6 pages, Digital Object Identifier: 10.1109/PES.2006.1709008.

Paiva, H.S.; Marciel, N.S.; Silva, R.D.S. & Tostes, M.E.L. (2006). Software Project Development for Industrial Motor Systems Simulation. IEEE International Symposium on Communications and Information Technologies, ISCIT 2006, pp. 327 - 331, Digital Object Identifier: 10.1109/ISCIT.2006.340057.

Tomsovic, K.; Bakken, D.E.; Venkatasubramanian, V. & Bose, A. (2005). Designing the Next Generation of Real-Time Control, Communication, and Computations for Large Power Systems. Proceedings of the IEEE, Vol. 93, Issue 5, pp. 965-979, ISSN 0018-9219.