At RenSolv, we are specialists in performing ENA Engineering Recommendation (EREC) G5/5 compliance assessment studies. Our engineers have been delivering power quality and harmonics assessments for over 15 years across solar, wind, BESS, conventional generation, and co-located projects, supporting developers and asset owners to achieve grid connection approvals with minimum delay.
EREC G5/5 is the UK standard used to assess harmonic emissions from distorting installations and to demonstrate that harmonic voltage distortion at the Point of Common Coupling (PCC) remains within the applicable limits. In practice, it is one of the most important gatekeepers for grid connections, particularly at 33 kV and above where network impedance characteristics and resonance risk can materially influence compliance.
Harmonics are not a paper exercise. A compliant project must demonstrate that the harmonic impact of the installation is acceptable to the network, and that the project will not cause unacceptable distortion that could affect other network users or degrade equipment performance.
A G5/5 study therefore focuses on the PCC and demonstrates compliance against the relevant limits by assessing:
For many utility-scale plants, this provides the clearest view of power quality risk both at the grid boundary and within the project electrical system.
We perform a detailed compliance assessment and, where a potential non-compliance is identified, we propose practical mitigation measures to resolve the issue. We also work with clients and stakeholders to explore technically credible solutions that can reduce mitigation cost and programme risk.
Investigating harmonics with sufficient modelling detail is particularly important, because interventions such as harmonic filters can become materially more expensive if they are introduced late in the design and civil layout process.
A robust G5/5 compliance submission is designed to show that:
RenSolv structures that evidence clearly and professionally, in a format that is straightforward for both the client and the DNO to review.
RenSolv provides professionally written technical reports authored by specialist power system engineers with extensive power systems backgrounds and years of hands-on experience on real projects.
Our reports are designed to be clear for both the client and the DNO, demonstrating compliance against the relevant G5/5 limits through a structured narrative, potential mitigation measures, and unambiguous outcomes.
RenSolv provides G5/5 compliance assessment studies for a wide range of generation and storage developments, including:
Our studies support projects connecting at distribution voltages including 11 kV, 33 kV, 66 kV, and 132 kV.
As a recent example, we performed a G5/5 compliance assessment for a utility-scale solar farm with active power export limited to 35 MW, connected to the distribution network operator at 132 kV.
This is a typical example of the type of project where G5/5 compliance must be demonstrated clearly at the PCC, with appropriate consideration of both incremental and total harmonic voltage limits.
RenSolv engineers have supported renewable generation and energy storage projects across the UK transmission and distribution networks.
Further details on comparable projects supported by RenSolv can be found in our Project Experience section.
We bring specialist power systems expertise backed by years of practical experience in harmonics and power quality compliance. Our submissions are structured, technically robust, and aligned to the G5/5 evidence framework expected by network operators.
We work closely with developers, consultants, and stakeholders to identify issues early, evaluate credible mitigation routes, and keep the compliance process commercially realistic and technically clear.
Where needed, we attend meetings with project teams and network operators to support the project through to completion, helping resolve technical queries beyond the report itself.
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