AS 61869.9 pdf download

AS 61869.9 pdf download.Instrument transformers
1 Scope
This part of IEC 61 869 is a product family standard applicable to instrument transformers with digital output. The product standard is composed of IEC 61 869-1 and IEC 61 869-6, in addition to this standard and the relevant product specific standards in the IEC 61 869 series (Part 7, Part 8, Part 1 2, Part 1 3, Part 1 4, and Part 1 5). This standard defines requirements for digital communications of instrument transformer measurements. It is based on the IEC 61 850 series, UCA international users group document Implementation guideline for digital interface to instrument transformers using IEC 61850-9-2, and the relevant parts of IEC 60044-8 that are replaced by this standard. It includes additional improvements including the IEC 61 588 network based time synchronization.
3 Terms and definitions
3.5 Terms and definitions related to other ratings For the purposes of this document, the terms and definitions in IEC 61 869-6:201 6 apply, with the following additions: 3.5.901 rated holdover time rated duration over which the merging unit continues to send samples maintaining the sample timing required for the measuring accuracy class following loss of the time signal 3.5.902 processing delay time t pd difference between the time encoded by the field SmpCnt in a digital output message and the time this message appears at the digital output 3.5.903 maximum processing delay time longest processing delay time (t pd ) under all rated operating conditions 3.5.904 free running mode operating mode where sampled values issued by the merging unit are not synchronised to an external clock to the degree required to meet the measuring accuracy class phase error limit Note 1 to entry: The values are based on an internal clock oscillator.
5 Ratings
5.6 Rated accuracy class Accuracy classes for electronic LPIT with digital output are defined in the applicable IEC 61 869 series product standards Part 7, Part 8, Part 1 2, Part 1 3, Part 1 4, and Part 1 5. Accuracy class specifications apply end-to-end, representing all errors introduced between the instrument transformer primary and the properly time-stamped message created at the digital output. Accuracy specifications directly incorporate all errors associated with time synchronization. Time synchronization requirements are as described in 6.904. With regard to accuracy classes, instrument transformers with digital output shall be classified in two groups: • measuring instrument transformers, • protection instrument transformers. To make best use of the dynamic range enabled by the 32-bit message format specified in this standard, all protection instrument transformers and protection capable SAMU channels shall be specified with dual accuracy class ratings. Dual rating is intended to precisely document the measuring and protection accuracy class applicable to a given channel. The dual rating requirement acknowledges the fact that protection rated instrument transformers are commonly also used for measurement and indication purposes. It establishes a proven, well understood method for documenting this performance. The protection instrument transformer accuracy class shall be given as a slash “/” symbol separated pair, with measuring accuracy class taking the first position and the protection accuracy class followed by the accuracy limit factor K ALF at the end. Dual specification shall be reported on the digital instrument transformer nameplate.5.901 Performance requirements Electronic LPIT with digital output shall meet all the requirements defined in IEC 61 869 specific product standards Part 7, Part 8, Part 1 2, Part 1 3, Part 1 4, and Part 1 5, if applicable. This requirement therefore extends to the merging unit component which is an integral part of the instrument transformer apparatus, and is therefore subject to the same environmental and EMC conditions. Depending on the device conformance class defined in 6.903.1 3, the merging unit component may be exposed to various levels of Ethernet network traffic. Although it is impossible to foresee all operating environments, the following recommendations are provided based on real life field experience: • merging unit behaviour should be well defined under all operating conditions; • if present, the test signal generating capability should be disabled by default; • all data included in the same ASDU (including quality bits) should be mutually consistent and represent the same time instant as required by the applicable accuracy class specification; • data shall be synchronized to a common time reference as described in 6.904. Merging units should have well defined behaviour under all operating conditions. This especially applies during power-up, power-down and self-diagnostic system failure indications (as required by IEC 61 869-6:201 6, 6.604). While the merging unit output (data stream) may become unavailable at any time (through component failure), when present, quality bits within the stream should faithfully represent the electronic LPIT operating state in accordance with the built-in self-check, diagnostic capabilities or external alarm inputs (when present). Quality bits are used by protective relays, and are relied upon to prevent protective scheme mal- operation.