Date post: | 21-Dec-2015 |
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SyncGenMultiple 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
a
b
c
V Meter(Relay)
3 phase Synchronous Machine
Stator Ground Fault Detection from neutral
overvoltage
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 Students @ 10 hours a week * 24 weeks =
$36,000• Dr. Johnson @ 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%
• 50N1-50N6 within +-1mA secondary
• 67N1-67N6 within +-1mA secondary
• Induce 8V fault into stator
• Ground Resistance 15-1000Ω
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 17-19
• Senior Design Documentation
Questions?
Lab Connections