Harmonic Assessments

What is G5/5?

The Energy Networks Association Engineering Recommendations G5/5 (also known as ENA EREC G5/5 or simply as “G5/5”) was introduced on 17th June 2020, superseding the previous recommendations G5/4-1, which were in place since 2001.

The main purpose of G5/5 is to provide a set of design ‘limits’ for harmonic voltage levels that ensure the actual IEC compatibility limits are not exceeded when new or additional load is connected.  

In other words, if the system is designed within the harmonic levels prescribed in G5/5, then harmonic voltage levels should be well within the IEC compatibility limits.

Some connections pass with flying colours; others require harmonic mitigation (eg. Active Harmonic Filtration) to be installed before a connection can be agreed.

Ultimately, the decision on whether to allow connection of the new load or not is that of the Network Operator – but in our experience if the proposed load passes the G5/5 Assessment (with or without mitigation), then connection is usually permitted.

Why do we need G5/5 Assessments?

With the ever-increasing proliferation of harmonic producing equipment, it is essential that within the design of any new electrical installation, whether it be additional load to an existing supply or a completely new installation, there are no detrimental effects for other consumers.

These consumers may be internal or external to the installation, but regardless, it is essential that they must be provided with an electrical environment within which their equipment can function without operational issues.

Simply put, G5/5 Assessments are essential to protect all parties from poor electrical environments; whether that’s for the benefit of your own electrical supply, other consumers connected to the same supply point or the Network Operator – if we all design systems within these recommendations then we’ll all have fewer electrical issues.

How is G5/5 implemented?

G5/5 adopts the same three stage approach to harmonic assessment as G5/4, however G5/5 has dropped the explicit harmonic current limits from within Stage 2 of the assessment process.

It’s a more pragmatic approach to the harmonic assessment process, involving limiting the allowable rating of converter equipment based on:

  • Equipment technology.
  • The fault level at the point of common coupling (PCC).
  • The headroom between the existing levels of voltage harmonic distortion and the G5/5 design limits.

The use of the predicted harmonic current injection for the new load will only be required if a harmonic voltage assessment is required (Stage 2C, LV and MV), which will only occur if the assessment fails Stages 1A / 2A and 1B / 2B.  

The failure of Stage 2C will result in a full harmonic flow modelling being carried out in Stage 3 which can often be more expensive than simply implementing harmonic mitigation measures to ensure passing Stages 1 / 2.

How we can help

PureSine can carry out the full G5/5 assessment process including assisting the collation of the information necessary to carry out the G5/5 assessment, carrying out measurements of pre-existing voltage harmonic distortion if this is not available from the DNO, and the actual G5/5 assessment itself – including the presentation of a report detailing the results of the assessment.

PureSine are also happy to converse with the relevant connection approval bodies (usually DNO) and equipment manufacturers, should any queries relating to the assessment arise.

Feel free to complete the below form or call 01440 564890 to schedule a free initial consultation, where we can discuss your project in greater detail.

Or, for a more in-depth look at the G5/5 assessment process please enquire about our very own Guide to G5/5.

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