Geomagnetic Storm Effects on Transmission Elements Kenneth A. Donohoo,P.E. Oncor Electric Delivery Co LLC NERC Planning Committee Member NERC GMDTF Chairperson

Introduction Space weather can affect the power system Large areas and multiple facilities can be affected Can happen at any time, not just at high sun spot activity Not just a northern latitude issue and can adversely impact ERCOT Higher voltage networks are more at risk Potential adverse impact on transformers, SVC’s and HVDC ties

Objectives At the completion of this course of instruction you will: identify how a geomagnetic disturbance can impact the grid Identify possible impacts and actions to prevent outages

Definitions Coronal Mass Ejection (CME) is a massive burst of solar wind and magnetic fields rising above the solar corona or being released into space Geomagnetic Disturbances (GMD) are caused by intense solar activity that impacts the Earth’s geomagnetic field Changes to the geomagnetic field creates a voltage gradient and induces a Ground Induced Current (GIC – quasi DC) through any conductor

The Sun CME typically take 1 to 3 days to arrive on Earth May not head toward Earth

Sunspot Cycle Large GMD Storms can and do occur at anytime in the sunspot cycle and not just around the Sunspot peaks

Space Storm

Interactions

Possible Interactions If the intensity and duration of a disturbance is sufficient, these abnormal electric currents may reduce system voltage and in the worst case, cause a widespread power outage. In the extreme, severe GIC can overheat transformer cores and lead to equipment damage or failure. Transformer harmonics increase Consume more reactive power, voltage decrease Trip capacitor banks, SVC’s, HVDC, etc… Relay misoperation

Some Storm History 19th century first effects observed on compass needle Sept 1859, largest recorded, Carrington Event 18 hours to reach Earth Telegraph wires shocked operators and caused fires March 1989, Hydro Quebec Only took 92 seconds to blackout system Seven SVC’s tripped within 59 seconds of each other leading to voltage collapse 25 seconds later Six million people without power for nine hours Northern lights seen as far south as Texas

What is a K Factor? The K-index quantifies disturbances in the horizontal component of earth's magnetic field with an integer in the range 0-9 with 1 being calm and 5 or more indicating a geomagnetic storm. Recent Storms K Factor 7 or higher: 10/01/12 03/09/12 09/26/11 08/06/11 08/05/11

ERCOT Procedures ERCOT Operating Procedure Manual Transmission and Security Desk Section 3 Review and Analyze System Security Section 3.5 Geo-Magnetic Disturbance Notification Procedure Purpose: To provide notification and increase situational awareness when a GMD storm is advancing. WHEN: Notified by the Shift Supervisor that a K-7 or higher GMD storm is expected; THEN: Issue an Advisory by making a Hotline call to TOs Post message on MIS Public Notify Real-Time operator to make hotline call to QSEs

How do I find out about a solar storm? Information and Indications The following are triggers that could be used to initiate operator action: External to your company: NOAA Space Weather Prediction Center http://www.swpc.noaa.gov/ or other organization issues: Geomagnetic storm Watch (1-3 day lead time) Geomagnetic storm Warning (as early as 15-60 minutes before a storm, and updated as solar storm characteristics change) Geomagnetic storm Alert (current geomagnetic conditions updated as k-index thresholds are crossed)

How do I find out about a solar storm? Information and Indications (continued) Internal to your company: System-wide: Reactive power reserves System voltage/MVAR swings/current harmonics Equipment-level: GIC measuring devices Abnormal temperature rise (hot-spot) and/or sudden significant gassing (where on- line DGA available) in transformers System or equipment relay action (e.g., capacitor bank tripping)

Actions Available to Operator The following are possible actions for Transmission Operators based on available lead-time:  Long lead-time (1-3 days in advance, storm possible)  Increase situational awareness Assess readiness of black start generators and cranking paths Notify field personnel as necessary of the potential need to report to individual substations Safe system posturing Return outaged equipment to service (especially series capacitors where installed) Delay planned outages Remove shunt reactors Modify protective relay settings based on predetermined harmonic data corresponding to different levels of GIC (provided by transformer manufacturer).

Actions Available to Operator The following are possible actions for Transmission Operators based on available lead-time (continued):  Day-of-event (hours in advance, storm imminent): Increase situational awareness Monitor reactive reserve Monitor for unusual voltage, MVAR swings, and/or current harmonics Monitor for abnormal temperature rise/noise/dissolved gas in transformers1 Monitor geomagnetically induced current (GIC2) on banks so-equipped3 Monitor MVAR loss of all EHV transformers as possible Prepare for unplanned capacitor bank/SVC/HVDC tripping4 Prepare for possible false SCADA/EMS indications if telecommunications systems are disrupted (e.g., over microwave paths) Safe system posturing Start off-line generation, synchronous condensers Enter conservative operations with possible reduced transfer limits Ensure series capacitors are in-service (where installed)

Actions Available to Operator The following are possible actions for Transmission Operators based on available lead-time (continued):  Real-time actions only if indicated: Safe system posturing Selective load shedding Manually start fans/pumps on selected transformers to increase thermal margin (check that oil temperature is above 50° C as forced oil flow at lower temperatures may cause static electrification) Possible System reconfiguration only if needed Remove transformer(s) from service if imminent damage due to overheating Remove transmission line(s) from service

Actions Available to Operator The following are possible actions for Transmission Operators based on available lead-time (continued): Return to normal operation This should occur two to four hours after the last observed geomagnetic activity.

Internet Links NOAA Space Weather Center http://www.swpc.noaa.gov/ NERC GMDTF 2013 http://www.nerc.com/comm/PC/Pages/Geomagnetic-Disturbance-Task-Force-%28GMDTF%29-2013.aspx NERC GMDTF 2011 & 2012 http://www.nerc.com/comm/PC/Pages/Geomagnetic%20Disturbance%20Task%20Force%20%28GMDTF%29/Geomagnetic-Disturbance-Task-Force-GMDTF.aspx NERC Standard Project 2013-03 Geomagnetic Disturbance Mitigation http://www.nerc.com/pa/Stand/Pages/Project-2013-03-Geomagnetic-Disturbance-Mitigation.aspx

Questions ? ?

Geomagnetic storms have a potential adverse impact on ___________, __________ and HVDC ties.   transformers SVC’s 345kV switches Both a and b Both b and c

Changes to the geomagnetic field creates a __________ gradient and induces a ground induced current through any conductor.   ferroresonance voltage high exceptional

In the extreme, severe GIC can __________ transformer cores and lead to equipment damage or failure.   overheat ground over rate increase capacity

Which of the following safe system posturing actions for long lead time (1-3 days in advance) are possible for transmission operators?   Return outaged equipment Delay planned outages Remove shunt reactors All of the above

Which of the following safe system posturing actions for day of the event (hours in advance) are possible for transmission operators?   Start off-line generation Enter conservative operations with possible reduced transfer limits Ensure series capacitors are in-service All of the above