Sensing methods and systems for transformers, and the construction thereof, are described herein. Example transformer systems and example methods for constructing a core for the system are disclosed. The example system includes a core with a bottom plate, two or more limbs mounted to the bottom plate and a top plate enclosing the core. At least one of the bottom plate, the limbs and the top plate is formed with a sensing component therein. The sensing component can be mounted to a spacer layer assembled within a stack of laminated layers. The sensing component can be mounted within a path defined within the spacer layer, for example. Methods for detecting operating conditions within the transformer are also disclosed.