This paper presents the design specifications and features of the automation system that is currently being applied to the distribution network of Istanbul.
Design and Implementation of a Feeder Automation System for Distribution Networks N. Ozay
A. N. Guven, SM, IEEE Elecmcal and Electronics Eng. Department Middle East Technical University 06531 ODTU, Ankara, Turkey
Abstract - This paper presents the design specifications and features of the automation system that is currently being applied to the distribution network of Istanbul. This system as a whole (software and hardware) has been designed, implemented, tested and integrated using the highest technology available complying with relevant international standards. Most prominent feature of the system is the capability of automatic fault detection and isolation on medium voltage feeders, a function yhich became a necessity with the decision of voltage uprating in medium voltage distribution in Istanbul. The system also provides distribution SCADA functionalities by utilizing fiber-optic cables as the communication medium. Being developed with an open system approach, the system could easily be extended to include other distribution automation functions.
Keywords: Distribution Automation, Power Distribution, Feeder Automation, SCADA Systems, Graphical User Interfaces I. INTRODUCTION
Turkish Electricity Authority, recently, has decided to uprate the primary distribution voltage level to 34.5 kV from 10.5 or 6.3 kV in big cities of Turkey. The most obvious advantage of voltage uprating is that more load can be served by the feeder, which automatically brings in the reliability problem. If the 34.5 kV level is used, since the number of transformers on the feeder is more than tripled, the exposure length and therefore the number of faults would also increase in the same proportion. These feeders can no longer be operated manually, and therefore, some form of feeder automation covering fault detection and isolation must be implemented along with any voltage uprating. With these motivations, the required hardware (remote terminal units) and software for such a feeder automation system, with additional SCADA capabilities, has been designed, implemented, integrated and tested. This paper presents the t e c h c a l specfications and features of the system developed.
A. Buyuksemerci
M. Fettahlioglu TUBITAK-BJLTEN
Middle East Technical University 06531 ODTU, Ankara, Turkey fiber-optic cable. On each end of the incoming and outgoing primary feeders in a DTS, there ar, current transformers (of 1 kV class) and special overcurrent relays. Once the fault is located by the termmal unit in the substation, the faulted section is automatically isolated provided that the dxonnect switches at both ends of the line sections are remotely controllable. Using the same communication medium, the corresponding switches are ordered to open, whch makes it possible to reclose the feeder clrcuit breaker in the substation and thereby energizing the healthy portion of the system. In order to transfer the load behind the faulted section, the normallyopen switch on the feeder is closed. The whole operation can be done in less than a minute, reducing drastically the restoration time whch is about 2 hours at the time being. Through a multi-layered network topology and the fiber optic communication medium, all the data from DTSs and substations necessaq for the operation, analysis and planning of the system can be monitored and collected in control centers. In addition to SUN workstations, operators in a control center are provided with other decision support devices such as plotters, printers, projection devices, etc. Control center software (graphical editor, graplucal user interface, database, etc.) has been developed using Object Oriented Programming technique with more than 200,000 lines of C++ code. The operating system is Unix based and POSIX compatible. The user interface is developed on X-Windows using Open Look widget libraries. The software provides the operators all the essential functions such as display of single-line diagrams, dynamic line coloring, alarm processing, sequence of events file, remote control of circuit breakers and switches, manual or automatic detection of the faulted section and isolation, monitoring analog quantities in substations. The communication protocol utilized on the three level network architecture is based on the Distributed Network Protocol (DNP 3.0) of the Hams Controls. Distributed processing is implemented via socket based inter-process communication mechanisms on top of TCP-IP protocol.
m.CONCLUSIONS
II. DESCRIPTION OF THE SYSTEM As the 34.5 kV primary distribution system would start from fresh, then it would be possible to install fiber optic cables along with the 34.5 kV underground cables whenever these are laid, with no extra cost apart from the cost of the fiber optic cable. Since the medium voltage feeders are designed in loops but operated radially, in case of a fault, the current flows from the substation through the feeder up to the fault point. Hence, the determination of the fault location is easily achieved by interrogating the remote terminal units in distribution transformer substations (DTS) through the
The system developed has been tested according to international standards and is now being applied in Istanbul distribution network. The undergoing project includes the establishment of three regional control centers and the automation of 205 DTSs. The performance of the system in a pilot region with 40 distribution transformers in the last 4 months has been found to be very satisfactory. Finally, one of the most important features of the system is that it has been designed using an open system approach and could easily be extended to include other distribution automation functions.
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