Protection and measurement systems in switchgear have always relied on analog current and voltage signals from traditional instrument transformers (current transformers and potential transformers).
Traditional instrument transformers use a ferromagnetic circuit with secondary outputs that are proportional to the primary current and voltage being measured – 1 A or 5 A for current transformers and 110 VAC for voltage transformers.
The Digitalisation of Analog Signals
Digital switchgear, on the other hand, uses low power output signals from current and voltage sensors which are inherently safer for personnel. These sensors are often referred to as non-conventional instrument transformers (NCITs) or low power passive current or voltage transformers as per IEC 61869.
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.