IEC 61850 as Digital Interface for Instrument Transformers

The CDV (Committee Draft for Voting) of IEC 61869-9: Instrument Transformers - Part 9: “Digital interface for instrument transformers” is out for ballot and comments until 2013-03-01.

This document will replace and extend the so-called “9-2LE” that defines the first profile (or subset) of IEC 61850 for voltage and current sensors (Merging Units).

The new standard is based on experience gained since the publication of “9-2LE”. There are a lot of new details in the configuration and description of the information models defined – in order to reduce the number of options.

The IEC 61869-9 standard will (when published):

• Replace IEC 60044-8 digital solution.
• Provide a product standard for instrument transformers with a digital interface according
  to 61850; similar to what IEC 62271-3 is doing for switchgear.
• Be backward compatible with the UCA International Users Group’s Guideline for Digital Interface to Instrument Transformers Using IEC 61850
• Use IEC 61588-Ed2 for time synchronization, with an option for 1PPS.
• Be applicable for AC and DC measurements.
• Be using 100 Mbit/s or 1 Gbit/s Ethernet.
• Specify 4.800 digital output sample rate with 2 sets of values per message (2.400 messages/s) for general measuring and protective accuracy classes, regardless of the
  power system frequency.
• Specify 14.400 digital output sample rate with 6 sets of values per message (2.400 messages/s) for quality metering accuracy class, regardless of the power system frequency.
• Specify 96.000 digital output sample rate with 1 set of values per message (96.000 messages/s) for DC instrument transformer applications [likely to using high speed Ethernet end-to-end].

Proposed conformance classes are (with detailed PICS in the draft):

• class a: the minimal set of services required to transmit MU data using sampled values;
• class b: class a capabilities plus the minimal set of services required to support GOOSE
  messages;
• class c: class b capabilities plus the implementation of the IEC 61850 series’ information
  model self-descriptive capabilities;
• class d: class c capabilities plus services for file transfer and either one or more of
  unbuffered reporting, buffered reporting, or logging.