SyncGen Multiple Unit Selectivity for Stator Ground Faults Using a Sensitive Directional Element Design Proposal 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 synchronous machines RAI customer has multiple generators on ungrounded bus Traditional protection scheme detecting faults from neutral overvoltage Interested in a faster and more robust protection scheme for their system

Traditional Stator Protection

The Problem Multiple machines on a common ungrounded bus Fault seen on all machines Impossible to directly isolate the faulted machine from system measurements Units must be sequentially tripped until the faulted machine 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 CTs designed to detect zero sequence current flow Stator ground fault detection Directional analysis of current flow Detecting and isolating faulted units on the bus

Testing Test the method of stator ground fault detection from zero sequence current flow on the 14.9kW 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 machine will be unaffected Two SEL-351 relays with low ratio CTs will be used for the fault detection and tripping

Deliverables Create scalable equations based on values of relay sensitivity, CT ratios, 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 Supplies: Photocopying, posters, binders = $200 Two SEL-351’s = $7,060 (loaned) 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 Total Actual Cost: $200

Test System Configuration

Generator Specifications

Sub-coils of Stator Windings

Distribution Box

Relay Elements 59GN within 2-5% 50N1-50N6within +-1mA secondary 67N1-67N6within +-1mA secondary Induce 8V fault into stator Ground Resistance Ω

Example Relay Event

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

Overall Calendar

Spring Schedule

Major Items for Summer and Fall Testing – Completed July 26 Draft of Paper for WPRC – Aug 4 Review with sponsor/PPT development for WRPC – Aug 4 – Sept 15 Final Paper – Sept 15 Conference – Oct Senior Design Documentation

Questions?

Lab Connections