TRANSIENT OPERATION USING PSCAD® GENERATED FILES
VERSUS “REAL WORLD EVENT”
This chapter will discuss in detail the PSCAD ® generated files and how injecting the COMTRADE files helped determine the microprocessor -based relay settings/logic to assist in designing an enhanced TPS. Laboratory test setups for relay operation and information about application of waveforms obtained from the PSCAD® for 2φ fault and 3φ faults are explained here as well. Also discussed is a brief overview of the “real world event.
The transient analysis software can generate testing files called COMTRADE files, so the user can test the TPS or system being analyzed. There are three (3) files associated with the generation of COMTRADE files:
1. *.hdr file 2. *.cfg file 3. *.dat file
The *.hdr file can be opened using a text editor, such a Microsoft Notepad®. In PSCAD®, the header file displayed the software/compiler used in simulation, date of simulation, time of simulation, length of simulation and other data specified by the software manufacturer. The configuration file also can be opened using a text editor. As stated by [3], the configuration files contain information needed by a computer program in order to properly interpret the data. Information includes items such as sample rates,
number of channels, line frequency, channel information, etc. displays the signals being taken from the simulation. The data file can also be opened with a text editor and
contains the sampled values for the currents and voltages for each simulation performed. The files for “stn 2” will also be shown in Appendix E of this manuscript.
The component in PSCAD®, shown in Figure 5.1, was used to record the currents and voltages in the simulation required a start and stop time for data recording.
Figure 5.1 Recorder in PSCAD® used to generate COMTRADE files
The COMTRADE files were then transferred using a portable media device and loaded on the human machine interface of the relay test equipment. Figure 5.2 shows detail of the test setup and briefly describes the control capability of the use. The simulated currents and voltages were then generated using the relay test equipment and injected into the microprocessor-based relay, shown in Figure 5.3.
Figure 5.2 Detail “A” of Oneline Test setup
Figure 5.4 Detail “C” of Commercially Available Microprocessor-based Protective Relay Detailed Information
The first and second event simulated were 2φ fault and showed very similar current magnitudes and dynamics as the real-world event. The third event was a 3φ fault and showed similar magnitudes. Figure 5.4 shows the microprocessor-based relay used in test and describes some of the capability. It allowed the Protection Engineer to program or set the relay and gather more information about an event.
To compare the simulations and the real-world event, the real-world event will be described. A large Utility experienced an event that resulted in an outage to a customer and both transmission lines feeding the customer. The general system topology is given in Figure 5.5. The customer experienced a failed manually operated gang switch at the 100kV Harmonic Filter shown in the figure. The fault was initially an AB fault. The first event data showed that approximately 6 cycles into the event ground was involved shown in Figure 5.6. After the fault was cleared by the TPS at both Station “A” and Station “B”,
Figure 5.7, causing another operation of the TPS. Because of reliability concerns to the other customers on the Transmission System, the High Voltage breakers at both Station “A” and Switchyard “B” reclosed back into the fault for a third and final time 29.8 seconds after the initial fault shown in Figure 5.8. This time the fault evolved into all 3φ showing fault current. The final alignment of the event was Station “A” High Voltage breaker was closed, Switchyard “B” High Voltage breaker was open, and all customers offline.
Figure 5.6 Real-World Event at T=0
Figure 5.8 Real-World Event at T=29.8
The comparison of the first event, 2φ fault, for both the PSCAD® generated and the real- world event showed similar magnitudes. The loading was slightly different and is shown in Figure 5.9 for the first event comparison.
The comparison of the second event file revealed similar dynamics, however the phase currents were 180° out of phase and magnitudes were slightly off, as shown in
Figure 5.10. This anomaly shown in the Real -World event was due to when the relay triggered. A comparison both 1st and 2nd Real World Events, both 2φ faults, also showed
these currents 180° out was also shown as in Figure 5.11. The 1st simulation versus the
Real-World event (T=0) comes presumably close to the simulation. The magnitude being slightly off was mostly due to the simplification of the model. In the final comparison of the Real-World Event versus the PSCAD generated System, showed the dynamics slightly different mostly due to the simplified system simulation. The final comparison also showed the magnitudes and phase angles being slightly off. This comparison is shown in Figure 5.12.
Figure 5.11 1st and 2nd Event Comparison from Real World
The analysis revealed the need to enhance the relay settings and relay logic but also the need to better understand symmetrical/non-symmetrical faults, specifically on Harmonic Filter Systems and Rectifier networks. The relay settings/logic scheme was enhanced with the time delay instantaneous elements removed from the customer station. This allowed the customer local protection to clear for faults at the 100kV bus first before going upstream to the Transmission Stations. Having the TPS designed this way will allow for the other customers to stay online while clearing for faults in the zone of protection, the selectivity of the TPS.