A Case Study of Voltage Transformer Failures: Solution Implementation in a Modern Data Center

While preparing a modern data center for startup, the commissioning process involved primary circuit switching that resulted in two voltage transformer (VT) failures. As a result, we conducted a comprehensive investigation of the VT failures. As the investigation proceeded, VT ferroresonance on circuit opening and high-frequency switching transients on closing emerged as possible root causes of the failures. After incorporating extensive transient simulations and three rounds of field transient measurements, we designed and implemented a complete solution that included the sizing of snubbers to overcome excessive switching transients and the development of a saturable reactor to protect VTs against the effects of ferroresonance. This article describes the root causes, simulations, field measurements, recommended solutions, and solution implementation for this event. The correlation between field measurements and simulation results shows the effectiveness of modeling the implemented solutions.