Power Quality Total Harmonic Distortion (THD) and Sag/Swell OBIS Registers

[sarah_jenkins]

Class 3/4 OBIS Codes for Power Quality & Grid Health Monitoring

Modern smart meters incorporate power quality analyzers conforming to IEC 61000-4-30 Class S/A.

Standard Power Quality OBIS Mapping

Parameter	Phase A	Phase B	Phase C	Unit
Voltage THD	1.0.32.7.124.255	1.0.52.7.124.255	1.0.72.7.124.255	% (Enum 29)
Current THD	1.0.31.7.124.255	1.0.51.7.124.255	1.0.71.7.124.255	% (Enum 29)
Voltage Sag Count	1.0.32.32.0.255	1.0.52.32.0.255	1.0.72.32.0.255	Count
Voltage Swell Count	1.0.32.36.0.255	1.0.52.36.0.255	1.0.72.36.0.255	Count
3rd Harmonic Current	1.0.31.7.3.255	1.0.51.7.3.255	1.0.71.7.3.255	Amperes (A)
5th Harmonic Current	1.0.31.7.5.255	1.0.51.7.5.255	1.0.71.7.5.255	Amperes (A)

Tracking 3rd and 5th harmonics allows distribution grid operators to identify non-linear industrial loads (such as variable frequency drives and EV fast-chargers) degrading local power factor.

[david_miller]

For THD registers, remember that the scaler is typically -1 or -2 ($10^{-1} = 0.1%$ or $10^{-2} = 0.01%$ resolution). Always parse the scaler byte dynamically.

[carlos_mendez]

In a recent commercial park audit, reading 1.0.31.7.5.255 pinpointed a malfunctioning rooftop solar inverter generating 18% 5th harmonic distortion back into the transformer.