AS 61869.13:2021 – Instrument transformers Part 13: Stand-alone merging unit (SAMU)(IEC 61869-13:2021(ED.1.0)MOD)
AS 61869.13:2021 – Instrument transformers Part 13: Stand-alone merging unit (SAMU)(IEC 61869-13:2021(ED.1.0)MOD).
For a SAMU mounted inside an outdoor cabinet, the maximum temperature for very hot climates shall be increased to .55 C. In the most demanding applications, temperatures up to +70 C may be specified.
5.3 Rated Insulation levels
5.3.2 Rated primary terminal insulation level
Subclause 53.2 of IEC 61869-1:2007 is not applicable because a SAMU does not have high-voltage primary terminals. Insulation requirements for analogue inputs connected to instrument transformer secondary circuits are given in 5.3.1301.
5.3.3 Other requirements for primary terminals insulation
Subclause 5.3.3 of IEC 61869-1:2007 is not applicable because a SAMU does not have high-voltage primary terminals.
5.3.4 Between-sectIon Insulation requirements
Subclause 5.3.4 of IEC 61869-1:2007 is not applicable because a SAMU does not have high-voltage primary terminals.
5.3.5 InsulatIon requirements for secondary terminals
Subclause 5.3.5 of lEG 61869-6:2016 and of lEG 61869-1:2007 ‘S not applicable because a SAMU does not have high-voltage instrument transformer secondary terminals.
The SAMU output is Ethernet based and in case of optical implementation does not have insulation requirements- In case galvanic interlace is used (e.g. RJ45 based communication port), insulation requirements shall be in accordance with lEG 60255-27. It is recommended not to use galvanic interface. When present, the galvanic interface shall not be used for distances above 10 m.
5.3.1301 Insulation requirements for inputs from Instrument transformers
Analogue inputs connected to instrument transformer secondary circuits shall be rated for a minimum working voltage of 300 V. pollution degree 2. overvoltage category Ill, in accordance with IEC 60664-1.
When overvoltage above category Ill is expected (e.g., gas insulated substation installations and direct connection to low-voltage mains systems), overvoltage category IV should be considered in accordance with IEC 60664-1:2020. Annex B. See Annex 13B for GIS switching and lightning surge voltages examples.
Minimum insulation requirements for analogue input terminals are summarized in Table 1301. Requirements apply from the input terminals to any grounded part, and between independent circuit terminals. Insulation voltage rating also depends on the circuit configuration (e.g. insulation voltage for analogue inputs connected to open delta VT circuits is multiplied by a square root of three).
5.5 Rated output
Subclause 5.5 of IEC 61869-6:2016 and of IEC 61869-1:2007 is not applicable.
5.6 Rated accuracy class
Subclause 56 of lEO 61869-6:2016 Is applicable with the following additions:
Accuracy classes for SAMU instrument transformer channels are given in 5.6.1301 and 5.6,1302, Accuracy class specifications apply between the device analogue input terminals and the digital output quantity contained In the corresponding digital stream. SAMU accuracy class specifications include all errors introduced by the device and apply throughout the ambient temperature range stated on the device rating plate. When protection rated channels are present, the manufacturer shall declare separate temperature ranges for measurement channels and protection channels,
Channels with common function shall have a common accuracy class designation (for example set of three phase voltages or currents) For this purpose, channels are arranged in channel groups and listed jointly on the device rating plate (see 6.13.1302),
SAMU Output is expressed in SI units (V. A) and represents the power system primary quantibes as specified in IEC 61869-9. To accomplish this task, the SAMU shall support settings for the external instrument transformer ratio (see 5.61305).
SAMU accuracy specifications directly incorporate all errors associated with lime synchronization. Time synchronization requirements are described in IEC 61869-9:2016. 6.904.
With regards to accuracy classes. SAMU current channels shall be classified as:
• measuring channels.
• protection channels.
In accordance with IEC 61869-9, all protection-capable current channels shall be specified with dual accuracy class ratings. Dual rating is intended to document the measuring and protection accuracy class applicable to a given current channel, Dual rating means that protection rated current channels shall also meet all measuring specifications including the frequency response defined in PEC 61869-6:2016. Table 6A.2 and the anti-aliasing requirements specified In IEC 61869-6:2016, Clause 6A.1. Measuring accuracy classes 3 and 5 are not allowed in the SAMU.Output current channels rated for quality metering shall meet the frequency responsespecified in lEC 61869-6:2016,Clause 6A.3.