Switchgear Automation

IEC61850 model for GIS with Non Conventional Instrument Transformers (NCIT)

  • The IEC 61850 8-1 standard applies to station bus.
  • The IEC 61850 9-2 LE standard relates directly to NCIT sensor communication.

Ethernet optical communication driver is essential
and results from the use of glass core fiber optics as a physical medium.
Given the low level of output signals from a NCIT metering element, it is essential that a ‘Primary Converter’(PC), which is an electronic converter with signal filtering(low pass filter), signal digitization(CAN) and signal processing, be positioned in immediate proximity.
The PC calculation capacity is used to communicate with a piece of equipment called a Merging Unit(MU) by proprietary protocol.
The MU gathers the inputs coming from different PC and has several output ports intended for communication with different equipment using the measurements like the protections, the bay controller or the metering devices.
In order to obtain the best possible metering accuracy, the level of sensitivity of the metering element should be related to the level of background noise(lowest possible) of the printed circuit board.
In figure show IEC61850 communication protocol with NCIT for GIS

CIGRE article

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