Total Rated-Current Distortion and ION 8650 Meters

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TRD is Total Rated-Current Distortion and is the total root-sum-square of the current distortion components (including harmonics and inter-harmonics) created by the DER unit expressed as a percentage of the DER rated currenting capacity (Irated). As defined in IEEE 1547-2018. The term is also being adopted in IEEE 2800P with a slight difference. These standards are for monitoring Distributed Energy Resources and Inverter-Based Resources on the Transmission System. 

First, what are the differences in TRD between the 2 standards;

%TRD = √(I_rms² – I₁²) /I_rated * 100%

In IEEE Std 1547 where;

I₁             is the fundamental current as measured at the reference point of applicability (RPA).

I_rated         is the distributed energy resource (DER) rated current capacity (transformed to the RPA when a transformer exists between the DER unit and the RPA)

I_rms          is the root-mean-square of the DER current, inclusive of all frequency components, as measured at the RPA.

In IEEE Std P2800 where;

I₁             is the fundamental current as measured at the reference point of applicability (RPA).

I_rated         is the inverter-based resource (IBR) plant rated current capacity based on IBR plant MVA rating at the RPA (calculated based on the interconnection request) without any shunt devices installed as part of the installed project.

I_rms          is the root-mean-square of the IBR plant current, inclusive of all frequency components up to the 50^th order, as measured at the RPA.

The main difference between the two standards is how RMS is defined. Since, 1547 defines I_rms as inclusive of all frequency components it is possible to calculate TRD in the 8650C, 8650B, and 8650A models. For, 2800P as defined above, will require an 8650A meter to perform the calculations.

What is needed to calculate TRD per 1547?

• I_rms can be obtained from the Power Meter module output registers. Values are in primary amps.
• I_rated can be entered using an External Number Register. Enter value in primary amps.
• I₁ is obtained from the Power Harmonics Module (8650A/B/C) or Harmonic Measurement Modules (8650A). Values are in primary amps.

How to execute?

Create an arithmetic module to be used for the calculations.

Input Registers	Setup Registers	Output Registers
Source 1: I arms	ART Formula 1: (sqrt(S1^2-S2^2)/S7 * 100	ART Result 1: I a %TRD
Source 2: I a1	ART Formula 2: (sqrt(S3^2-S4^2)/S7 * 100	ART Result 2: I b %TRD
Source 3: I brms	ART Formula 3: (sqrt(S5^2-S6^2)/S7 * 100	ART Result 3: I c %TRD
Source 4: I b1
Source 5: I crms
Source 6: I c1
Source 7: Irated

What is needed to calculate TRD per OP2800?

• I_rms can be obtained from the Power Quality Analyzer module output registers. Values are in primary amps, and you can select 150/180 cycle or 10m values.
• I_rated can be entered using an External Number Register. Enter value in primary amps.
• I₁ is obtained from the Harmonic Measurement Modules (8650A). Values are in primary amps and will be 150/180 cycle or 10m value depending on Aggregation method of the module.

How to execute?

Create an arithmetic module to be used for the calculations.

Input Registers	Setup Registers	Output Registers
Source 1: I arms	ART Formula 1: (sqrt(S1^2-S2^2)/S7 * 100	ART Result 1: I a %TRD (150/180 Cycle or 10m)
Source 2: I a1	ART Formula 2: (sqrt(S3^2-S4^2)/S7 * 100	ART Result 2: I b %TRD (150/180 Cycle or 10m)
Source 3: I brms	ART Formula 3: (sqrt(S5^2-S6^2)/S7 * 100	ART Result 3: I c %TRD (150/180 Cycle or 10m)
Source 4: I b1
Source 5: I crms
Source 6: I c1
Source 7: Irated

Once, you have the values calculated you can connect them the in a data recorder or incorporate in other frameworks.

For more information reach out to your Schneider Electric Utility Account Executive, Regional Manager or local Sales Representative.