270   WYE and DEL rms values

Created: 09 Dec 2005

Status: In Force (green)

Part: Part 7-3 (2003)


Page: 31

Clause: 7.4.5, 7.4.6


Category: Issue may impact interoperability of implementations of Edition 1


See tissue 256/part 7-4


Interpretation of magnitude (rms or phasors): If there is an angle present, the values are phasor values and attribute mag represents the maximum value of the sinusoidal wave form. If there is no angle present, the attribute mag represents an rms value.

Discussion Created Status
29 May 07 In Force (green)
a new TISSUE 504 has been created for part 7-4.

The impact of TISSUE 270 is, to modifiy the condition for the presence of ang.
15 Apr 07 Ballot Period
I agree with Thierrys suggestion. For backward compatibility the ClcTyp default value (if this optional DATA is missing) should then be "TRUE RMS", might be "Max Fundamental", if ang is supplied..... 25 Jan 07 Discussion (red)
I aggree with Bruce.
There is no way to know how the mag in CDC MV and CMV have been calcultated.
It's either:
1) TRUE RMS (unfiltered signal, i.e. includes all harmonics of the signal)
2) Max amplitude of Fundamental
3) RMS Fundamental, i.e. Max amplitude of Fundamental / (sqrt(2)).

Add Data Object "ClcTyp" in the Common Logical Node definition.
ClcTyp (INS) is an enumerated whose value specifies the calculation type for all the mags available in a Logical Node.
Enum: TRUE RMS, Max Fundamental, RMS Fundamental. (ClcTyp is similar to the ClcMth introduced in amendment statistical and historical data)

Note: ClcTyp specifies the calculation type only of mag.
For vectors:
1) if ClcTyp = TRUE RMS -> no ang shall be available,
2) if Max Fundamental, or RMS Fundamental, then ang is optional.

Note: with ClcTyp, the rms text can be removed from the MMXN definition (as well as from all other logical nodes).
10 Jan 07 Discussion (red)
I was not watching the list when this issue was "resolved" and I want to re-open the issue.
The effect of the proposal is to remove any certainty of every 3-phase measurement. If we retrieve the value 120.00 from a measurement MMXU[MX}.PhV.PhsA.cVal.mag, the we cannot tell if the peak voltage is 120.00 or 84.85 volts unless we first inquire whether there is a .ang attribute on that measurement.
61850 needs precise definitions for each attribute, definitions which be determined exclusively by the object name.
I suggest that we open this TISSUE again and resolve it by stating that the "mag" component of a vector always be the "RMS-equivalent" value. This MIGHT require that phasor measurement units scale their output(s) by (1/sqrt(2)) before transmitting them on a 61850 system. This would restore faith in the value of measurements.
Note: I cannot find in IEEE C37.118 any mention that phasors are not RMS-equivalent.
04 Jan 07 In Force (green)
27 Mar 06 In Force (green)
Editor phone conference, December 9, 2005
Accept proposal
09 Dec 05 Ballot Period


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