Copyright © SEL 2017

Understanding Design, Installation, and

Testing Methods That Promote Substation

IED Resiliency for High-Altitude

Electromagnetic Pulse Events

Tim Minteer, Travis Mooney, Sharla Artz,

and David E. Whitehead

Schweitzer Engineering Laboratories

Analyze HEMP Effects, Assess the Risk, Assist Policy Makers and Grid Operators

1 High-altitude nuclear explosion creates

gamma rays…

…which strike molecules, releasing

electrons.

…creating an EMP, which may

disrupt electronic systems.

2

4

High-Altitude Electromagnetic PulseHEMP

Earth’s magnetic field aligns

electrons…

3

Three Stages of EM Waveforms From a HEMP Event: E1, E2, E3

|E|

100 mV/m

1000 s

100 mV/m

100 V/m

100 kV/m50 kV/m

E1 + E2

E1

E2 |E3|

1 s1 ms1 ms1 ns1 ps

Time

Only E1 Waveform Has Potential to Damage Substation IEDs

EM Waveform (HEMP)Duration Similarity to

Natural Phenomena

Concern for

Substation IEDs

E1: Short-Duration Electrostatic Discharge Yes

E2: Intermediate-Duration Lightning No

E3: Long-Duration Geomagnetic Disturbance No

The Unknown Effects of RF E1 Concerned Some Policy Makers and Grid Operators

E1(t

) (k

V/m

)

0

20

30

40

50

10

0 10 20 30 40 50 60

Time (ns)

2.5 ns

rise time

23 ns

• 100 kHz – 100 MHz

AM: 535 – 1700 kHz

FM: 87.5 – 108 MHz

• Thousands of times

greater than EMC

RF immunity levels

MYTH: “HEMP Could Cause a Protracted Nationwide Blackout”

FACT: Robust, Substation-Hardened IEDs Are HEMP Resilient in Substation Control Houses

IEEE and IEC Standards Mitigate EMC Effects

IED

IED

IED

Yard

Equip.

Yard

Equip.

H1

E1Protect cables originating

from beyond the

substation yard fence

Shielded transformers and

transient protection

attenuate > 40 dB (IEEE 1100)

H1

E1

Control houses constructed from

concrete panels with metal liners

attenuate > 20 dB

Route internal

signal wiring

along grounded

structures

Use substation-

hardened IEDs

H1

E1

Conducted

disturbance

on shields

Substation Control House

Signal wires routed in metal conduits or shielded cables grounded at

both ends and ≥ 4/0 wires with multiple ties to ground grid (IEEE 525)

Similar Mitigation Techniques of Hardened IEDs

IC

IC

ICEN, USB,

EIA-232,

4–20 mA...

PTs, CTs,

I/O

Substation engineers route signal wires along metallic

grounded framework inside the control house reducing loop area

H1

E1

Shielded, grounded

cables protect low-level

signals (IEEE 525)

Fiber-optic cables provide

IED serial communication

outside the control houseH1

E1

Substation-Hardened IED

Chassis and metal

shields attenuate

the RF E1 waveform

Ground planes

and multiple

ground points

minimize all

EMC effects

Transformers and

isolation barriers

protect integrated

circuits

MIL STD 188-125A Is Not an Appropriate Standard

Applies to Military Facilities Performing Critical Time-Urgent Missions

Use IEC Standards to Assess Substation IEDs

Power substations, power generation facilities, and electrical and electronic

equipment intended for use indoors

IEC Subcommittee 77C

High Power Transient

Phenomena of human

origin (including HEMP)

21 Publications

1996 – present

IEC Substation EMC Immunity Levels Exceed HEMP Resiliency Levels

Electrical Fast

Transient / BurstSurge

Damped

Oscillatory Wave

HEMP EMC HEMP EMCHEMP(fast)

EMC (slow)

I/O2 kV 4 kV

—

4 kV 2 kV 2.5 kV

Power (dc) 1 kV

Serial Comm 1 kV 2 kV — 2 kV 1 kV 1 kV

Evaluation of Existing Substation Designs Concluded That Substation-Hardened IEDs Are

HEMP Immune in Legacy Substations

Substation Designs That Provide Lightning Resiliency Also Provide HEMP Resiliency

Lightning EMP RF E1 Waveform

Electric Field 100 kV/m 50 kV/m

Rise Time / Pulse

Width10 / 350 ms 2.5 / 23 ns

Energy 250 mJ 0.7 mJ

IEEE Standards Form the Basis of Legacy Substation Design Practices

IED

IED

IED

Yard

Equip.

Yard

Equip.

Cables originating beyond the substation

yard fence have always been well-

protected from severe EM effects

H1

E1

Control house material

provides 0–20 dB of

attenuation

Routed internal

signal wiring

along grounded

structures

H1

E1

Substation-hardened IEDs

withstand conducted

disturbance on signal wires

Substation Control House

Signal routing in trenches within a few feet of the ground grid reduces

coupling and induced voltages

H1

E1

Mother Nature Doesn’t Read Standards –Margin Testing Ensures EMC Immunity

Substation-Hardened IEDs Exceed ESD Immunity Requirements

Air ESDContact

ESD

HEMP 8 kV —

EMC 8 kV 6 kV

S-H 15 kV 8 kV

Most Regions Will Experience Less Than E1 Max

Nuclear Environment Survivability

U.S. Army. Report AD-A278230 (1994)

50.0 kV/m

25.0 kV/m

37.5 kV/m

25.0 kV/m

12.5 kV/m

5.0 kV/m

Signal Wire Alignment, Incident Angle, Monopole Height, and Wire Length Affect Coupling

E1

H1

y

F Ground Plane

Coupled Transient Voltages From the RF E1

Waveform Are Statistically Less Than 4 kV

Pro

ba

bili

ty D

en

sity (

% / k

V)

0

20

30

40

10

0 4 8 12 16 20

IED Signal Wire Terminal

Peak Transient Voltage (kV)

Random variables

• Location under burst

• Signal wire alignment

• Monopole height

• Signal wire shielding

IEDs Have an Implied HEMP Withstand 3x Greater Than Their Rated Impulse Withstand

IED Withstand

Voltage Limit

Percentage of Installed IED Signal Wire

Terminals Exceeding Withstand Limit

23 kV (Post 2013 Withstand) 0 % (Withstand > 20 kV Maximum Peak Transient)

16 kV (Pre 2013 Withstand) 0.003 %

8 kV 1.6 %

4 kV 14.3 %

2 kV 40.6 %

Five Immunity Type Tests Demonstrate HEMP Resiliency of IEDs

Immunity Type Test

(IEC 61000-6-6)

EMC Requirement

(IEC 60255-26)

Radiated Pulse (2.5 / 25 ns) IEC 61000-4-25 Not Required

Fast Damped Oscillatory Wave IEC 61000-4-25 Not Required

Air ESD (8 kV) IEC 61000-4-2 IEC 61000-4-2

EFT/B (5 / 50 ns) IEC 61000-4-4 IEC 61000-4-4

Surge (1.2 / 50 ms) IEC 61000-4-5 IEC 61000-4-5

Third-Party Testing Confirms Substation-Hardened Relay Immunity to HEMP RF E1 Max

Third-Party Testing Confirms Relay Printed Circuit Boards Immunity to HEMP RF E1 Max

• IEC 61000-6-6 provides the framework for

demonstrating HEMP resiliency of substation IEDs

• Substation-hardened IEDs are HEMP resilient in legacy

and new substations as demonstrated by

Fast Damped Oscillatory Wave testing

HEMP immunity to 50 kV/m, RF E1 pulse

HEMP survivability using air ESD margin testing at 30 kV

followed by impulse withstand testing

Conclusions

• New substation designs provide HEMP resiliency for

IEDs meeting IEC EMC and Safety requirements

• Further testing of similar substation-hardened IEDs is

not recommended

• The effects of HEMP on substation IEDs should no

longer concern policy makers, grid operators, and

others

Conclusions

“The grid is tougher than you think.”– Edmund O. Schweitzer, III

Contact InformationTravis_Mooney@selinc.com