POWER April 2017 - 40

OPERATIONS & MAINTENANCE
2. A magnetizing effect. Geomagnetic
disturbances due to solar activity can lead to
geomagnetically induced currents (GICs) in
power system networks. These GICs are quasi-DC
in nature (0.01 Hz to 0.5 Hz) and could
saturate the core of a power transformer. The
saturation of the core due to these currents
may spur increased magnetizing currents,
peaking beyond the nominal current of the
unit. This image illustrates a sample exciting
current magnetizing pulse due to GIC events.
Courtesy: Trafoexperts
Table 1. Significant deadlines for compliance with the North American Reliability
Corp.'s " Transmission System Planned Performance for Geomagnetic
Disturbance Events " reliability standard (TPL-007-1). Source: Doble Engineering
Date
Jan. 1, 2017
July 1, 2017
Reliability standard takes effect
Identify roles and responsibilities within utility
Aug. 1, 2017 Completion by network planners of geomagnetically induced current (GIC) models
Jan. 1, 2019
Jan. 1, 2021
Jan. 1, 2022
Transmission and generation owners complete GIC thermal impact assessments
Transmission and generation owners complete corrective actions such as monitoring or
refurbishment
3. Transformer armor. Armor steel
shielding of transformers and power equipment
is part of the " hardening " process to
provide components with advanced ballisticlevel
protection against physical attack. ABB's
AssetShield solution is designed to safeguard
and protect large power transformers and
other substation equipment. Courtesy: ABB
mal impact assessment on their high-side,
wye grounded transformers of more than
200 kV based on a maximum effective GIC
value-which, according to the standard, is 75
amperes per phase or greater. If, per that assessment,
these transformers cannot withstand
thermal transient effects associated with the
benchmark GMD event, transmission owners
and generators must implement corrective
action plans developed by coordinators and
transmission planners.
September 2016 approved a reliability standard
submitted in January 2015 by interstate
grid security monitor North American Reliability
Corp. (NERC) that, for the first time,
establishes mandatory requirements for grid
entities to guard against GMDs.
The standard, TPL-007-1, essentially applies
to power transformers with windings
on the high-voltage side that are connected at
200 kV or higher in a wye configuration and
have a grounded neutral connection. Every 60
months, network planning coordinators and
transmission planners must assess and report
how vulnerable their system is to geomagnetically
induced current (GIC) disturbances, and
whether their system can withstand a " 1-in100-year "
benchmark GMD event without
causing a wide-area blackout, voltage collapse,
or transformer damage.
Additionally, it requires that transmission
owners and generators conduct a ther40
Corsi
noted that the timeline for NERC
compliance kicked off on January 1, 2017.
After network planners determine full GIC
parameters as required by January 2019, transformers
identified as vulnerable to GIC disturbances
would need to complete thermal impact
assessments by January 2021 (Table 1).
Companies like Doble can help utilities
meet the NERC standard by performing an
engineering study on transformers older than
20 years (whose design review documentation
may not be readily available) to establish
power transformer capabilities while under
GMDs, following guidelines established by
the IEEE Standards Association, specifically,
IEEE C57.163-2015. This guide specifies parameters
and performance characteristics and
evaluation techniques for power transformers
to help minimize risks and impacts when GIC
is present in the power system.
A Physical Approach
Physical threats to high-voltage transformers
are another emerging worry that has engulfed
transformer owners and legislators alike. Because
they are behemoths-a typical 345-kV
unit can weigh up to 435 tons-they are easily
identifiable alongside power plants, or in
network substations. Transformer experts assert
that a bad actor with basic knowledge of
transformer design could inflict irreparable
damage. Such attacks can cause massive electrical
short circuits and oil fires that would destroy
a transformer and damage surrounding
infrastructure.
The vulnerability of individual transformer
substations was demonstrated most promiwww.powermag.com
nently
by a rifle attack in April 2013 at Pacific
Gas & Electric's 500-kV substation in Metcalf,
Calif., where multiple individuals reportedly
shot at high-voltage transformer radiators
with .30 caliber rounds, causing them to leak
cooling oil, overheat, and become inoperative.
In November 2014, FERC approved a
NERC-submitted physical security reliability
standard (CIP-014-1), which went into effect
in January 2015. Essentially the standard requires
transmission owners and operators to
identify and protect substations and associated
primary control centers. It calls on them
to perform initial risk assessments to identify
critical facilities, and to evaluate potential
threats and vulnerabilities of a physical attack
on those facilities by November 2016.
Operational measures that could make critical
equipment more secure include reinforced
perimeter fencing with opaque bulletproof
walls, multiple fencing layers, and electronic
motion sensors on fencing with multiple system
triggers. Metalax's expanded metal security
fencing solution, for example, offers
smaller openings, a rigid design, and ballistic
resistance compared to typical chain-link
fencing. Other measures include enhanced
lighting systems and remote surveillance.
Zurich-based technology firm ABB also
recommends equipment and substation hardening
using cooling resiliency solutions and
porcelain-free dry bushings (which it makes),
which could eliminate the risk of explosion or
fire. The company also recommends bulletresistant
technology. In November 2015, it
rolled out its AssetShield ballistic protection
solution (Figure 3), and it has since bagged
three orders from major U.S. utilities for the
impact and fragmentation-protective system
designed for transformers, switchgear, circuit
breakers, and capacitors. The solution's
optimized combination of coating and steel
reduces the kinetic energy of the bullets and
reduces spalling after impact, it said.
(An extended version of this article is
available online at www.powermag.com.) ■
-Sonal Patel is a POWER
associate editor.
POWER | April 2017
Network planners to provide transmission and generation owners with GIC flow information,
which specifies transformers that are subject to the GIC disturbance benchmark event
Requirement

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POWER April 2017

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