Harmonic Distortion (G55)

The ENA G5/5 Stage 3 harmonics assessment supersedes the G5/4 standard for connections starting from the 17th of June 2020. Under this new standard, all new 33 kV or above connections must comply to the specified total harmonic distortion and incremental limits allowed by the Distribution Network Operator (DNO).

In addition, the DNO is responsible for providing the actual background distortion up to the 100th harmonic order, which is typically measured or estimated at the Point of Common Coupling (PCC). The DNO also supplies the local operating characteristic impedances profile, which represents a set of feasible operational conditions of the grid upstream. These parameters are crucial in assessing and determining the harmonic behaviour and compatibility of the connection with the existing grid infrastructure.

We work with our clients to ensure accurate electrical models are created using actual equipment data, such as cables, transformers, loads, and harmonic emission elements installed on the new site.

To meet the requirements of the Distribution Network Operators (DNOs) and provide a detailed report to the client, our team has been working on automated tools. We are utilising the DIgSILENT Power Factory package for system modelling and harmonic simulation integrated with Python Programming Language.

Figure 1 demonstrates the operating points provided by the DNO at the Point of Common Coupling (PCC) for harmonics ranging from 58th to 78th orders. Subsequently, our software creates the R,X points to be simulated, as shown below in Figure 2. The aim is to maximise the number of points while staying within a computationally feasible capacity.

A picture containing diagram, line, text, plot

Description automatically generated

Figure 1 – Loci provided by the DNO


Figure 2 – Points to be simulated within the Loci area

The next step involves simulating along the impedance locus and obtaining the harmonic distortions for each harmonic order. Figure 3 displays the total harmonic distortion, with the areas exceeding the imposed limits highlighted in red.

A picture containing text, diagram, plot, line

Description automatically generated


Figure 3 – Total voltage harmonic distortion at PCC

In addition to discussing the distortion along the loci impedances, the report also presents the worst‑case scenarios for each harmonic order. Furthermore, it explores how the incremental and total distortion relate to the provided limits.

In the event that the limits are reached for one or more harmonics, we analyse potential solutions and provide guidelines for the next steps, if they are deemed necessary.  The heat maps should be reviewed by the DNO to ensure the loci areas that are exceeding limits are legitimate network configurations.