Impact of decentralized transformer electronics on the protection relay design

Changes to the primary instrument transformers on the one hand affect the interface at the transformer (sensor) and on the other hand the entire structure of the measured value capturing on the substation secondary side. At the high voltage level the electronics are an integral component of the transformer. Communication to the bay units is implemented via a standardised interface. Guaranteeing synchronicity and accuracy of the sampled measured value is a core issue. By means of the proprietary interface between transformer and merging unit this is simply implemented by using re-sampling. Due to the random transmission characteristic of the Ethernet, synchronisation of the merging units must be achieved with an external clock. Further integration of functions is expected in future, which will result in a reduction of components and cost. A standardised Ethernet interface with integrated switch or other technology at the "transformer head" is already conceivable. A solution can for example be provided with a real-time-ethernet containing a built-in-1/spl mu/s time synchronisation.