SyncGen Multiple Unit Selectivity for Stator Ground Faults Using a Sensitive Directional Element Snapshot Presentation

Team SyncGen Sponsor – Lawrence Gross Relay Application Innovation Advisor – Brian Johnson Webmaster / Client Contact – John Trombetta Team Contact – Robert Schloss Documentation Manager – Jason Panos

Background Research and testing of stator ground protection methods for high speed synchronous generators RAI customer has multiple generators on ungrounded bus using traditional protection scheme detecting faults from neutral overvoltage Interested in a faster and more robust protection scheme for their system

Traditional Protection

The Problem Multiple generators on a common ungrounded bus Fault seen on all generators Impossible to directly isolate the faulted generator from system measurements Units must be sequentially tripped until the faulted generator is isolated Non-faulted machines must be restarted if tripped in the detection process Leads to large disturbances in the system

The Solution New microprocessor relay algorithms and low ratio CTs designed to detect zero sequence current flow Detect stator ground faults from zero sequence current flow Zero sequence current flows into the faulted unit and away from non-faulted units Faulted unit easily isolated so other units on the bus unaffected

Testing Test the method of stator ground fault detection from zero sequence current flow on the 20kVA generator in the model power system Induce faults in the stator to determine how far into the winding faults can be detected A second generator on the ungrounded bus will allow us to prove the non-faulted generator will be unaffected Two custom SEL-351 relays with low ratio CTs will be used for the fault detection and tripping

Deliverables Equations for the level of selectivity that can be achieved on a system based on values of relay sensitivity, CT ratios, generator impedances, and relay settings Level of stator protection obtainable Relay settings, test cases, test bed Fault simulation results Compare results to the traditional scheme Presentation paper for WPRC in October

Constraints Operational limits of laboratory generators Limit to the level of faults we can safely induce without damaging the machine IEEE standards of protection Ratio of CTs in the SEL-351

Budget Hardware and Supplies: Model Power System, instruments, CT’s, laptop, MathCAD, photocopying, supplies, posters = $200 Two SEL-351’s = $7,060 (loaned) Facilities: Shop $25 per hour (We do not believe we will need any.) Engineering Time: Three 10 hours a week * 24 weeks = $36,000 Dr. 2 hours a week * 24 weeks = $7,200 Total Estimated Cost: $50,460

Schedule / Time Line Accelerated Time line Want to present findings at WPRC Testing completed by July 26 to finalize draft Rough draft of paper complete by August 4 if accepted for WPRC

Major items for Spring Semester IPS – Completed Abstract for conference – In progress Lab familiarization – Apr Begin Testing – May 1

Major Items for Summer Testing – Completed July 26 Draft of Paper for WPRC – Aug 4 Review with sponsor/PPT development for WRPC

Major items in Fall Semester Final Paper – Sept 15 Conference – Oct 17-19

Questions?