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

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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