Evaluation of GIC Thermal Capability of Power Transformers ― Part I: Core Form Transformers

Abstract

Recently, evaluating the GIC Thermal Capability of power transformers has become an important item requested by Specifications of new power transformers, especially, in North America. Also, the TPL-007 Standard [1]** requires evaluation of GIC Thermal Capability of installed power transformers expected to be subjected to certain levels of GIC under specific Benchmark and Supplemental GMD Scenarios. The objective of this paper is to demonstrate that the GIC Thermal Capability of a transformer is a strong function of the design of that transformer and that the GIC Thermal Capability of transformers of the same core type vary from a low value to a much higher value. Additionally, the paper presents impact of Load and duration of GIC pulses on the GIC Thermal Capability of transformers. In performing the studies reported in this paper, heating of structural parts of transformers was used for the thermal evaluations. This is since the thermal impact on the structural parts has been found to be much greater than that on windings [2]. Part I of this paper deals with GIC Thermal Capability of Core form Transformers while Part II deals with GIC Thermal Capability of Shell form Transformers.