GIC Mitigation and Transformer Thermal Assessment Services by Keentel Engineering

A GIC is a quasi-dc current induced by geomagnetic disturbances that flows through transformers and ground paths in the power grid.

GICs are caused by changes in the Earth’s magnetic field during solar storms, which induce electric fields that drive current in conductive structures like transmission lines.

GIC can saturate transformer cores, generating harmonics, heating windings and metallic structures, and potentially damaging insulation.

TPL-007-1 requires entities to evaluate their systems against benchmark GMD events and implement mitigation if necessary.

These include a peak geoelectric field magnitude of up to 20 V/km, adjusted based on geomagnetic latitude and earth conductivity.

Tools like PSCAD, PowerWorld, and EMTP-RV support GIC modeling. Keentel uses validated software compliant with NERC procedures.

Earth conductivity affects how electric fields propagate. A 1D or 3D conductivity model determines surface impedance and field strength.

It’s derived from magnetic field measurements using FFT and Earth impedance models.

It refers to how deep magnetic fields penetrate the Earth; in GIC studies, it can range up to hundreds of kilometers.

Grounded-wye windings are most susceptible. Delta windings block GIC flow due to lack of ground connection.

It occurs when dc-like GIC biases the ac flux in the core, causing asymmetrical flux and increased losses.

These are local high temperatures in transformer windings or structural parts due to GIC-induced losses.

IEEE C57.91 suggests 180–200°C as emergency limits for metallic hot spots.

It’s a calculated value combining the GIC in different windings of an autotransformer, adjusted for turns ratio.

Using directionally scaled GICE and GICN values with real-time EE(t) and EN(t) electric fields.

Typically yes, as their impact on steady-state GIC is minimal.

Rdc is typically used for GIC modeling. Rac is slightly higher due to skin effects at power frequency.

Lower resistance paths increase GIC current into substations, emphasizing accurate ground modeling.

Equipment installed between transformer neutral and ground to inhibit GIC flow, often a resistor or capacitor.

Transformer design, insulation aging, oil moisture, and cooling mode all play roles.

Time it takes for transformer parts to heat up in response to GIC. Winding constants are typically 2–10 minutes.

A standard time series profile used for simulating GIC impacts, based on historic storms.

No, it’s usually single-phase with total GIC divided by three for per-phase analysis.

Lower latitudes experience weaker GICs; scaling ensures correct geographic representation.

By applying rigorous modeling, thermal simulations, and engineering judgment aligned with TPL-007-1 and IEEE guides.