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AS 61869.4:2021 Instrument transformers Part 4: Additional requirements for combined transformers (IEC 61869-4:2013 (ED.1.0) MOD). This part of IEC 61869 applies to newly-manufactured combined transformers for use with electrical measuring instruments and electrical protective devices at frequencies from 15 Hz to 100 Hz. The requirements and tests of this standard, in addition to the requirements and tests of IEC 61869-1, IEC 61869-2 and IEC 61869-3 cover current and inductive voltage transformers that are necessary for combined instrument transformers. 2 Normative references Clause 2 of IEC 61869-1:2007 is applicable with the following modifications: A ddition. IEC 60028, International Standard of resistance for copper IEC 60038, IEC standard voltages IEC 61869-1:2007, Instrument Transformers — Part 1: General requirements IEC 61869-2:2012, Instrument Transformers — Part 2: Additional requirements for current transformers IEC 61869-3:2011, Instrument Transformers — Part 3: Additional requirements for inductive voltage transformers 3 Terms, definitions and abbreviations For the purposes of this document, the terms and definitions given in IEC 61869-1:2007, IEC 61869-2:2012 and IEC 61869-3:2011, as well as the following apply. 3.1 General definitions 3.1.401 combined instrument transformer instrument transformer consisting of a current and a voltage transformer in the same enclosure 3.1.402 error of voltage transformer ratio error of voltage transformer determined with disconnected current transformer 4 Normal and special service conditions Clause 4 of IEC 61869-1:2007 is applicable. 5 Ratings Clause 5 of IEC 61869-1:2007, Clause 5 of IEC 61869-2:2012 and Clause 5 of IEC 61869- 3:2011 are applicable with the following modifications: Additional subclause: 5.401 Additional requirements for measuring and protective combined transformer 5,401.1 General The error limits for measuring combined transformers shall correspond to the requirements for measuring current transformers, indicated in 5.6.201 of IEC 61869-2:2012, and to the requirements for measuring voltage transformers indicated in 5.6.301 of IEC 61869-3:2011. The limits of error for protective combined transformers shall correspond to the requirements for protective current transformers indicated in 5.6.202 of IEC 61869-2:2012, and to the requirements for protective voltage transformers indicated in 5.6.302 of IEC 61869-3:2011. 5.401.2 Mutual influence When operating the current transformer between 5 % of the rated current and the rated continuous thermal current, the voltage transformer shall not exceed the limits of voltage error and phase displacement corresponding to its class within the specified range of burden and between 80 % and 120 % of the rated voltage. When operating the voltage transformer between 80 % of the rated voltage and...

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