Temperature Reduction in the Clamping Bolt Zone of Shunt Reactors: Design Enhancements

This paper presents design improvements to lower the temperature in the clamping bolt (CB), in a single-phase extra-high-voltage (EHV) shunt reactor. Laboratory temperature measurements, under overload and nominal load conditions, were performed in the middle of the two top main air gaps inside one of the slots drilled in the CB using commercial fiber-optic temperature sensors. 3-D finite-element (FE) simulations were performed to calculate fringing losses in the CB. Subsequently, the fringing losses were employed as a heat source for static-steady thermal analysis using 3-D FE simulations. Convective heat-transfer coefficients were selected with a methodology that leads to a close match between measured and simulated temperatures. Two practical design enhancements to diminish temperatures in the CB are analyzed using measured and simulated data. These alternatives improve design and reduce potential failures and, hence, increase the EHV shunt reactor lifetime.