Transcript DonohooGMDERCOTSeminar01132014

Geomagnetic Storm Effects
on Transmission Elements
Kenneth A. Donohoo,P.E.
Oncor Electric Delivery Co LLC
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:
recognize how a geomagnetic disturbance
can impact the grid …
be able to identify possible impacts and
take action 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
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
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 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 leadtime:
Long lead-time (1-3 days in advance, storm possible)
1. Increase situational awareness
1. Assess readiness of black start generators and cranking paths
2. Notify field personnel as necessary of the potential need to report to individual
substations for on-site monitoring (if not available via SCADA/EMS)
2. Safe system posturing (only if supported by study; allows equipment such as
transformers and SVCs to tolerate increase reactive/harmonic loading; reduces
transformer operating temperature, allowing additional temperature rise from core
saturation; prepares for contingency of possible loss of transmission capacity)
1. Return outaged equipment to service (especially series capacitors where
installed)
2. Delay planned outages
3. Remove shunt reactors
4. 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 leadtime (continued):
Day-of-event (hours in advance, storm imminent):
1. Increase situational awareness
1. Monitor reactive reserve
2. Monitor for unusual voltage, MVAR swings, and/or current harmonics
3. Monitor for abnormal temperature rise/noise/dissolved gas in transformers1
4. Monitor geomagnetically induced current (GIC2) on banks so-equipped3
5. Monitor MVAR loss of all EHV transformers as possible
6. Prepare for unplanned capacitor bank/SVC/HVDC tripping4
7. Prepare for possible false SCADA/EMS indications if telecommunications
systems are disrupted (e.g., over microwave paths)
2. Safe system posturing (only if supported by study)
1. Start off-line generation, synchronous condensers
2. Enter conservative operations with possible reduced transfer limits
3. Ensure series capacitors are in-service (where installed)
Actions Available to Operator
The following are possible actions for Transmission Operators based on available leadtime (continued):
Real-time actions (based on results of day-of-event monitoring):
1. Safe system posturing (only if supported by study)
1. Selective load shedding5
2. 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)
2. System reconfiguration (only if supported by study)
1. Remove transformer(s) from service if imminent damage due to overheating
(possibly automatic by relaying)
2. Remove transmission line(s) from service (especially lines most influenced by
GMD)
Return to normal operation
This should occur two to four hours after the last observed geomagnetic activity.
Questions