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

Geomagnetic Storm Effects on Transmission Elements

Kenneth A. Donohoo,P.E.Oncor Electric Delivery Co LLC

NERC Planning Committee Member

NERC GMDTF Chairperson

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IntroductionSpace 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 2

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

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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

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The Sun

CME typically take 1 to 3 days to arrive on Earth

May not head toward Earth5

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

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Space Storm

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Interactions

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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 increaseConsume more reactive power, voltage decreaseTrip capacitor banks, SVC’s, HVDC, etc…Relay misoperation

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Some Storm History19th century first effects observed on compass needleSept 1859, largest recorded, Carrington Event

18 hours to reach EarthTelegraph wires shocked operators and caused fires

March 1989, Hydro QuebecOnly took 92 seconds to blackout systemSeven SVC’s tripped within 59 seconds of each other

leading to voltage collapse 25 seconds laterSix million people without power for nine hoursNorthern lights seen as far south as Texas

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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:10/01/1203/09/1209/26/1108/06/1108/05/11

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ERCOT ProceduresERCOT Operating Procedure ManualTransmission and Security DeskSection 3 Review and Analyze System SecuritySection 3.5 Geo-Magnetic Disturbance NotificationProcedure 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 TOsPost message on MIS PublicNotify Real-Time operator to make hotline call to QSEs

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How do I find out about a solar storm?

Information and IndicationsThe 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)

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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)

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Actions Available to OperatorThe following are possible actions for Transmission Operators based on available lead-time:

Long lead-time (1-3 days in advance, storm possible)

1.Increase situational awareness1. Assess readiness of black start generators and cranking paths2. Notify field personnel as necessary of the potential need to report

to individual substations2.Safe system posturing

1. Return outaged equipment to service (especially series capacitors where installed)

2. Delay planned outages3. Remove shunt reactors4. Modify protective relay settings based on predetermined harmonic

data corresponding to different levels of GIC (provided by transformer manufacturer).

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Actions Available to OperatorThe following are possible actions for Transmission Operators based on available lead-time (continued):

Day-of-event (hours in advance, storm imminent):

1.Increase situational awareness1. Monitor reactive reserve2. Monitor for unusual voltage, MVAR swings, and/or current harmonics3. Monitor for abnormal temperature rise/noise/dissolved gas in

transformers14. Monitor geomagnetically induced current (GIC2) on banks so-equipped35. Monitor MVAR loss of all EHV transformers as possible6. Prepare for unplanned capacitor bank/SVC/HVDC tripping47. Prepare for possible false SCADA/EMS indications if telecommunications

systems are disrupted (e.g., over microwave paths)2.Safe system posturing

1. Start off-line generation, synchronous condensers2. Enter conservative operations with possible reduced transfer limits3. Ensure series capacitors are in-service (where installed)

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Real-time actions only if indicated:

1.Safe system posturing1. Selective load shedding2. 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.Possible System reconfiguration only if needed1. Remove transformer(s) from service if imminent damage due to

overheating2. Remove transmission line(s) from service

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Return to normal operation

This should occur two to four hours after the last observed geomagnetic activity.

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Internet LinksNOAA Space Weather Centerhttp://www.swpc.noaa.gov/

NERC GMDTF 2013http://www.nerc.com/comm/PC/Pages/Geomagnetic-Disturbance-Task-Force-%28GMDTF%29-2013.aspx

NERC GMDTF 2011 & 2012http://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

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QuestionsQuestions

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1. Geomagnetic storms have a potential adverse impact on ___________, __________ and HVDC ties.

a) transformersb) SVC’sc) 345kV switchesd) Both a and be) Both b and c

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2. Changes to the geomagnetic field creates a __________ gradient and induces a ground induced current through any conductor.

a) ferroresonanceb) voltagec) highd) exceptional

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3. In the extreme, severe GIC can __________ transformer cores and lead to equipment damage or failure.

a) overheatb) groundc) over rated) increase capacity

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4. Which of the following safe system posturing actions for long lead time (1-3 days in advance) are possible for transmission operators?

a) Return outaged equipmentb) Delay planned outagesc) Remove shunt reactorsd) All of the above

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5. Which of the following safe system posturing actions for day of the event (hours in advance) are possible for transmission operators?

a) Start off-line generationb) Enter conservative operations with

possible reduced transfer limitsc) Ensure series capacitors are in-serviced) All of the above

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

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