These voltage and current sensors which use a different measuring approach can transmit signals greater distances without losing high accuracy levels. These signals can be generated and transmitted without the high heating losses of traditional measurement devices. The secondary outputs for these type of sensors are in the millivolt (mV) range.
With the availability of these new current and voltage sensors, it is possible to build switchgear in a better way: using fewer materials, while being more reliable, more energy efficient and safer for operators than ever before. The time for change is now.
The control systems in switchgear have traditionally been based on using electromechanical devices, these electromechanical protective relays many times had high power requirements (burdens) that needed very large high accuracy current transformers in order to function properly. Today’s modern microprocessor based relays have multifunction, communication, and data logging capabilities (to name a few) all with very low energy burdens requiring only a small amount of energy. This opens up brand new possibilities with respect to the current and voltage measurement devices that can be used. Microprocessor based relays that are compatible with sensors have Low Energy Analog (LEA) inputs. Most sensors can meet these new requirements in a much smaller and less costly footprint. The main criticism of the low power sensors is that they are unable to drive multiple devices. This disadvantage can be eliminated by using Sampled Values data sharing following the IEC 61850-9-2 standard.