Technology / Engineering guide
Wind Power Meter CT Ratios & Data Scaling
A current-transformer ratio and a data multiplier describe parts of a measurement chain. A meter may already report primary quantities, while another export may contain secondary-side or encoded values. Identify where scaling occurs before applying another multiplier.
Prevent an unrecorded multiplier from changing the result.
Nameplate ratios, meter configuration and software decoding are separate records that must describe the same chain.
01 / Ratio meaning
Retain the primary and secondary definitions.
A current-transformer ratio relates stated primary and secondary current ratings under its documented conditions.
A current-transformer ratio relates stated primary and secondary current ratings under its documented conditions. Record both rated quantities and units from the actual identity information; a label such as CT ratio without its basis is incomplete.
Schneider’s CT reference illustrates that a ratio has defined construction and use assumptions. This guide does not instruct changes to those assumptions or describe CT handling. No current transformer or ratio is confirmed for a MARSTON package.
02 / Primary or secondary
Identify what the meter already represents.
Determine whether a displayed or exported quantity is already referred to the primary measurement boundary.
Determine whether a displayed or exported quantity is already referred to the primary measurement boundary. A meter can apply configured ratio information before reporting a value, but the actual instrument documentation must establish that behaviour.
Applying the same ratio again would duplicate a conversion. A reading should therefore carry its units, primary or secondary basis and source field definition. A plausible-looking result is not evidence that the multiplier was applied in the correct place.
03 / Data decoding
Separate engineering scaling from encoding factors.
A digital field can have a scale factor used to represent decimals or units.
A digital field can have a scale factor used to represent decimals or units. That encoding scale is not necessarily the current-transformer ratio. Retain both definitions and the order in which they are applied.
In a hypothetical field, raw 1250 with an encoding factor of 0.01 represents 12.5 of the defined unit. Whether that value is primary current or another quantity remains a separate definition. This is not an actual MARSTON field or CT rating.
04 / Chain completeness
Include other contributors to the reported quantity.
A power or energy result depends on more than a current ratio.
A power or energy result depends on more than a current ratio. Identify the voltage-measurement basis, phase/path scope, signs and relevant instrument calculation. Do not infer every kWh multiplier from the CT label alone.
Use the power-quantity guide to retain the distinction between current and power. Instrument and sensor uncertainties also remain separate from numerical decoding or a correct nominal ratio.
05 / Change history
Keep effective dates and affected fields.
A changed instrument, ratio setting or software map can divide a dataset into segments with different interpretations.
A changed instrument, ratio setting or software map can divide a dataset into segments with different interpretations. Retain the old and new definitions, effective time and affected outputs from existing change records.
Do not retroactively rescale a complete history without evidence of what the original values represented. The counter guide addresses discontinuities in cumulative readings; scaling history explains the quantity basis within each segment.
06 / Review record
Make the calculation path reproducible.
A useful scaling record identifies sensor and meter, rated ratio, actual documented meter configuration, exported field, encoding scale and final engineering unit.
A useful scaling record identifies sensor and meter, rated ratio, actual documented meter configuration, exported field, encoding scale and final engineering unit. It also states which stages already refer quantities to the primary boundary.
Compare the assembled record with the applicable documents and retain unresolved fields. This is a data-interpretation review, not a CT selection, connection, polarity check, open-circuit operation or live measurement procedure.
Continue the review with Wind Energy Counters, Resets & Interval Totals.
Continue the review with Active, Reactive & Apparent Power in Wind Projects.
Continue the review with Wind Sensor Analogue & Digital Signal Interfaces.
General background: Schneider Electric: current-transformer ratio assumptions. These references explain industry concepts; they are separate from the applicable MARSTON product and project documents.
Prepare the information for this review.
Use the checklist to organise the project information. Mark unavailable items and retain document references.
| Review item | Information to provide | Purpose |
|---|---|---|
| Chain identity | Actual sensor, meter, channel and measurement boundary | Locate the quantity source. |
| Ratio basis | Primary/secondary ratings, units and documented conditions | Interpret the nameplate. |
| Existing scaling | Meter-reported primary or secondary basis | Avoid applying a ratio twice. |
| Encoding factor | Raw type, scale, unit and final quantity definition | Separate decoding from CT ratio. |
| Change record | Effective dates, fields and prior interpretations | Keep historical values reproducible. |
Engineering questions.
Should every exported meter value be multiplied by the CT ratio?
No. Determine whether the instrument already reports a primary quantity.
Is a register scale factor the same as the CT ratio?
Not necessarily. They describe different transformations.
Does a current ratio alone define all energy scaling?
No. The full meter calculation and measurement chain must be understood.
Can a scale change affect earlier data interpretation?
Yes. Retain effective dates and the original field definitions.
Is a specific CT rating confirmed for MARSTON equipment?
No. No real transformer or ratio is asserted here.
Does this page provide CT installation or handling instructions?
No. It reviews existing identity and data records only.
Technical enquiry
Bring your project information to the discussion.
A current-transformer ratio and a data multiplier describe parts of a measurement chain. Share the available information and the equipment scope you want reviewed in a technical quotation.