Sensor technology in a medium-voltage switchgear for the US market applications
Predrag Milovac, Radek Javora, Veselin Skendzic · CIRED - Open Access Proceedings Journal · 2017
The traditional instrument transformers have limits in various aspects because their cores are made of ferromagnetic materials, and design requirement to deliver a high power output signal necessary to work with the electromechanical relays. Replacing the electromechanical relays with the digital microprocessor-based relays without upgrading instrument transformer technology created technological leap but with a set of engineering practices, which are sometimes not easy to implement. The more appropriate approach for the digital instruments is reduced input signal levels. Examples of such sensors are the Rogowski coil and the voltage divider that can provide not only a better and a more accurate signal, but they are also much smaller in overall dimensions, more standardised, safer, and less expensive products. Sensor use is especially appealing in medium-voltage (MV) applications. Over the years, sensor technologies rose to satisfactory performance level and are no longer considered as nonconventional, but are becoming devices of choice. New applications are growing as their use spread around the market, and it leads to an evolution of requirements and rules to be applied. The standardisation is in progress but not equally established across the regions. The sensor technology in MV switchgear design for the US market is discussed here.