Short circuit analysis and harmonic studies on variable speed drives (VFD's) for mult-phase pumping systems installed on off-shore drilling platforms. Three types of VFD were analyzed for driving a submersible 1700 Hp motor-pump system through 1500 meters of cable. Fault conditions were studied for the system installed at a land-based test site and on the platform. Sub-transient and modified reactances of either the 69 kV supply on land or 6 synchronous generators on the platform with motor loads were used to select protective equipment into and out of the VFD. Equivalents were used in conjunction with current injection methods to determine filters needed to protect the supply system and to protect the cable-motor load.
Detection of partial faults (soft faults) or severe faults on power transmission networks. An expert system of a constraint relaxation type is used in conjunction with State/Parameter Estimation to detect the worst transmission line parameter fit to the power system data snapshot. Networks from 4 electric utilities were analyzed and parameter errors detected. For one utility, the detected errors were confirmed and corrected in their database. NASA plans to employ the methods of this research to monitor the dc power system of the forthcoming space station. One utility is beginning to apply the expert system method to its entire network to eliminate the + or - 25% errors in transmission line parameters. The utility expects to reduce losses by reallocating power flow, with a resultant cost savings.
Security programs for soft fault detection, verification and remedial corrective action. Real-time Ada computer codes developed to determine on-line topology, detect over-currents or abnormal voltages. Verification tools were State Estimation, Load Flow, Contingency Analysis, and network parameter estimation. All programs were designed to operate with the actual instrumentation hardware and to be installed on a hardware test bed representative of the space station.
For distribution-level circuits, software for three- phase load flow on unbalanced feeders. Short-circuits for single line, line-to-line, or three-phase faults on unbalanced feeders. An additional program to isolate faulted zones and re-connect dormant zones is available for stand-alone operation. Input data is spacing of distribution line conductors and wire types. Can be integrated with the man-machine interface and the SCADA system to operate in the real-time computer.
Harmonic filters for static VAR (volt-ampere-reactive) generators on power systems, rolling mill, and arc furnace applications. Factors taken into consideration are capacitor banks and system impedance on the high voltage lines and/or secondary circuits, the coupling transformer leakage and losses, and switching operations on the power system. Harmonics are generated by phased-back operation of delta- connected thyristor strings controlling current through inductors. Additional harmonics are also generated by arc furnaces or motor drives. Results were filter component specifications and ratings using minimum MVAR's to satisfy harmonic performance criteria.
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