Nemanja Milojčić - Electrical Engineering Institute "NIKOLA TESLA"
Dušan Joksimović - Electrical Engineering Institute "NIKOLA TESLA"
Goran Mandić - Electrical Engineering Institute "NIKOLA TESLA"
In modern power systems, the main sources of electrical energy are synchronous generators. The power of the generators ranges from a few kilowatts in small power plants to upwards of 1.5 GW in modern thermal plants. Synchronous generators can be coupled with different types of hydro turbines in hydro power plants or steam turbines in thermal and nuclear power plants.
Excitation winding is connected to an excitation system and at the heart of every synchronous machine. In principle, an excitation system includes the regulated source of direct current needed to form an excitation electromagnetic field, which produces voltage at the generator’s terminals, in a synchronous machine. It is crucial for scientists and operators to monitor, record, analyze, and study the transient processes that can occur during power production in these systems.
As a designer and manufacturer of complete excitation systems for synchronous generators, the Electrical Engineering Institute Nikola Tesla implemented a solution to monitor the behavior of our system and generator to determine the precise response of our excitation system and generator during normal operations and when failures occur. Using data acquisition systems that are independent from all control signals in excitation systems allows for experimentation without endangering primary equipment and normal plant processes.
Hardware and Software Configuration
We built the monitoring system with NI data acquisition modules on an NI CompactDAQ platform. The main elements include the NI cDAQ-9172 chassis, an NI 9203 analog input module, an NI 9245 digital input module, an industrial 15 in. touch panel PC, and signal conditioning equipment. In addition, we selected LabVIEW graphical system design software for its ease of use and seamless integration with NI CompactDAQ hardware.
We built our rack with isolated voltage and current sensors for signal conditioning equipment. We also conditioned the voltage and current signals so that output signals would be within voltage levels suitable for NI CompactDAQ analog input modules. The main goals during the application development process were to retain linearity in the range of measurements and acquire signals within 10 kHz bandwidth. We took digital input signals from I/O relays in a relay scheme of the excitation system control cubicle. Figure 1 demonstrates the control cubicle with NI CompactDAQ equipment and Figure 2 presents the software front panel for the system at the Nikola Tesla A plant in Obrenovac, Serbia.
We programmed the application using LabVIEW, which provides a real-time view of the entire system on a primary screen and a live view of all analog values displayed as VIs. LabVIEW also provided the flexibility to display all analog signals in a graph and record them on demand and on external trigger. The system allows the operator to easily review recorded analog signals, adjust the triggering conditions, view all digital inputs in real time, and monitor changes.
We implemented our first monitoring system in the Nikola Tesla A thermal power plant on the new excitation system for generator No. 4 (308 MW). We installed a second monitoring system on a new excitation system for generator No. 1 (348 MW) in the Kostolac B thermal plant in Kostolac and plan to implement a third systems in the Potpeć hydro plant in Priboj for generator B (20 MW).
Continued System Development
The most recent addition to our NI CompactDAQ system involves the ability to monitor two important subsystems in the power plant: the generator synchronizer and a device for automatic reconnection of the power plant 6 kV self-supply. The system ensures that all relevant signals are recorded in every generator synchronization process as well as when changes occur in the 6 kV busbar system.
Future system plans include linking communication of our NI CompactDAQ monitoring system with supervisory control and data acquisition (SCADA) power plant control equipment and the ability to access all measurement data remotely via an Ethernet connection. Overall, the monitoring system based on NI hardware and software proved to be a highly flexible and easy-to-use solution for our application.
Electrical Engineering Institute "NIKOLA TESLA"
Koste Glavinića 8a
Tel: +381 (0)11 3691-447
Fax: +381 (0)11 3690-823