Why is snow melting at the base of my substation structures?

Introduction

Air-core reactors are pieces of equipment that are commonly found in substations. The nature of their operation brings a distinct and challenging characteristic: large magnetic fields in the vicinity of the equipment. These fields can induce circulating currents in surrounding equipment and grounding systems. Our client observed melting snow at the base of several structures near the reactors and suspected magnetic induction as the cause, but desired validation before undertaking expensive mitigation measures.

Approach

The substation ground grid, relevant structures, and the reactors themselves were modeled in SES CDEGS HIFREQ. The magnetic fields predicted by the model would be compared against readings obtained in the field to provide validation. The model would then be used to explore mitigation options as needed.

Evaluation

SR3’s model predicted magnetic field values that were generally supported by the field observations, with some predictions nearly identical to the measured values. SR3 was also able to confirm that the circulating currents predicted by the model occurred in similar locations in the substation, with large magnitudes at the base of the problematic structures.

Results

The results of the model corroborated the suspicions and supported the decision to make physical changes to the substation ground grid or overall layout. The model was used to evaluate several mitigation options, and was ultimately used to validate a new physical layout provided by the client.