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

2. 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

3. 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

4. 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

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

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

7. Space Storm

8. Interactions

9. 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

10. 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

11. 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

12. 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

13. 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 or other organization issues:
Geomagnetic storm Watch (1-3 day lead time)
Geomagnetic storm Warning (as early as minutes before a storm, and updated as solar storm characteristics change)
Geomagnetic storm Alert (current geomagnetic conditions updated as k-index thresholds are crossed)

14. 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)

15. 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).

16. 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)

17. 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

18. 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.

19. Internet Links NOAA Space Weather Center http://www.swpc.noaa.gov/
NERC GMDTF 2013
NERC GMDTF 2011 & 2012
NERC Standard Project Geomagnetic Disturbance Mitigation

20. Questions ? ?

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

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

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

24. 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

25. 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