Understanding Geomagnetically Induced Currents and Their Impact on the Power Grid: Morgan Substation Neutral Isolation Device (NID) Mike Londo American Transmission Co LLC atcllc.com Wisconsin Public Utility Institute June 2019
Quick Review of where Geomagnetically Induced Currents (GIC) Come From atcllc.com 2
Geomagnetic Induced Currents EPRI Power Systems Dynamics Tutorial . EPRI, Palo Alto, CA: 2009. 1016042. atcllc.com
atcllc.com
Possible Effects of GIC on ATC System and Equipment • Transformer saturation – Additional heating in transformers--likely – Transformer aging/failure--unlikely • Additional VAR (Volts-Amps-Reactive) requirements on system – Depressed voltages--likely – Voltage collapse on system--depends • Harmonics – Relay misoperation--unlikely – Generator heating--possible but small – Power quality problems--likely but small atcllc.com
GIC Isolation Device at Morgan Substation atcllc.com
Morgan Neutral Isolation Device atcllc.com 7
Morgan Neutral Isolation Device cont’d atcllc.com 8
Sequence of Operation Normal Mode atcllc.com
Sequence of Operation Transitioning to GIC Isolation atcllc.com
Sequence of Operation In GIC Mode atcllc.com
Sequence of Operation Ground Fault in GIC Mode atcllc.com
Sequence of Operation Reset to Normal Mode atcllc.com
Critical Development The Transformation • Fail Safe Resilience – Spark Gap • Non consumable • Repeatable • Inspected after 10 events – Rogowski Coil (N-G path proof) Located on neutral bar heading to ground atcllc.com
Morgan NID in “By - Pass” Mode 10kv spark gap atcllc.com 15
Questions? atcllc.com 16
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