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Geomagnetic Disturbance Risk Mitigation Services

June 20, 2017
Doble Engineering Co. has released its Geomagnetic Disturbance Risk Mitigation Services.

Doble Engineering Co. has released its Geomagnetic Disturbance Risk Mitigation Services. The new program is designed to help customers comply with the North American Electric Reliability Corporation (NERC) Standard TPL-007-1 and determine if their transformers are susceptible to geomagnetically-induced currents (GIC) triggered by solar storms. Doble’s program helps applicable transmission and generation owners conduct initial and ongoing assessments of the potential impact of severe geomagnetic disturbances and develop targeted mitigation plans.

“Geomagnetic disturbances (GMDs) caused by solar storms can create problems for the power grid by inducing currents in long conductors near the Earth’s surface,” said Dom Corsi, senior transformer engineer at Doble. “This can destabilize the electric system and potentially damage transformers. Adequately preparing for these events is required by NERC regulation and is essential to avoid costly damage to power equipment and disrupted power supply.”

How does space weather impact transformers?

GMDs occur naturally and cause quasi-DC current flow through wye-grounded transformer windings. While the result is not always catastrophic, certain factors influence the degree of risk to the grid and power system equipment, like geomagnetic latitude, ground resistivity, network topology, storm duration, loading and equipment design.

Depending on the transformer, a given GMD event may impact your equipment differently. The key is to know which equipment presents the greatest risk and understand how to best prepare should the so-called ‘perfect storm’ of space weather hit.

Some of the potential impacts of GIC flow to transformers include: increased current harmonics; increased reactive power absorption; hot spot heating of transformer windings due to harmonics and stray flux; hot spot heating of non-current carrying transformer metallic members due to stray flux; increased vibration and noise level; and system voltage instability.

Meeting regulatory requirements

The threats posed by space weather have become a focal point for regulatory bodies. Protecting the bulk electric system from the impact of GMD events is a motivation of the new NERC standard TPL-007-1. To adhere to the standard, utilities must conduct both initial and ongoing assessments of the potential impact of a “1-in-100-year” benchmark GMD event on their equipment and the bulk power system as a whole including:

  • GIC Disturbance Vulnerability Assessment for the system’s ability to withstand a benchmark GMD event without causing a wide area blackout, voltage collapse or transformer damage.
  • Transformer Thermal Impact Assessment to ensure that all high-side, wye-grounded >200kV transformers can withstand thermal transient effects associated with a benchmark GMD event.

The standard also requires corrective action planning to protect against instability and cascading failures.

To prepare for these kinds of issues, Doble’s Geomagnetic Disturbance Risk Mitigation Services start with an engineering study to establish power transformer capabilities while under GIC, according to the IEEE C57.163-2015 Guide.

“The industry is taking this threat seriously, and we are seeing independent system operators setting quickly approaching compliance deadlines for receiving the first set of information from their generation and transmission owners,” said Paul Griffin, vice president of consulting and testing services at Doble. “Our Geomagnetic Disturbance Risk Mitigation Services will help them meet regulatory requirements for collecting GIC modeling data and conducting thermal impact assessments, taking away the uncertainty associated with the impact of space weather and helping avoid potentially devastating consequences for the power grid and customers.”

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