Power quality: reducing risk and maintaining compliance

Challenge

UK Distribution Network Operators are required to manage power quality across their network and ensure compliance with the Engineering Recommendation G5/5 standard under their license conditions. This includes assessing the potential impact of new connections (such as large industrial loads or generation schemes) on network harmonics. This is a regulatory obligation, and failure to manage harmonic distortion could lead to network issues, non-compliance and risks to both equipment and customer operations.

Carrying out these G5/5 Stage 3 assessments involves complex network modelling, specialist software and detailed analysis to produce harmonic limits and specifications for customers.

One UK DNO needed a reliable and efficient way to deliver accurate results within a tight timescale to ensure new projects could proceed without delay, while keeping the network within statutory limits.

Solution

Ricardo’s Clean Power experts provided a structured process combining network modelling expertise, advanced software and close collaboration with network planners.

• New connections were reviewed to confirm the point of connection and its position within the DNOs master network model. A background harmonic measurement for at this point of connection is produced using either direct monitoring where available, or by simulating conditions using measurements taken from the surrounding network. 
• An updated network model tailored for the connection was then produced to allow an impedance scan of the network to be carried out. 
• Preliminary outage scenarios captured the full range of potential running arrangements which were validated with the DNO planning team to ensure the model reflects operational reality. The validated scenarios are then linked to three standard loading conditions: daylight minimum, GB maximum and GB minimum, to provide a robust basis for analysis. At this stage the model is fully set up for harmonic analysis.
• Using a suite of automated scripts, Ricardo carried out impedance scans, generated impedance loci and calculated harmonic limits. The outputs are carefully reviewed before being compiled into a final harmonic specification for the customer. 

This strategic approach ensures every assessment is accurate, efficient and regulatorily compliant, enabling the DNO to provide customers with clear harmonic limits while safeguarding the performance and resilience of the wider network.

Customer benefit

The DNO was supported by a dedicated team with deep expertise in harmonic analysis and network modelling. This specialist capability acts as a critical resource, ensuring every G5/5 Stage 3 assessment is handled by experienced engineers who understand both the technical complexity and the regulatory importance of the work. The client can be confident in the resourcing continuity for important core services and licencing conditions can be met on time, keeping projects on track and meeting compliance obligations. 

With a dedicated focus on these critical assessments, Ricardo reduces risk, protects network integrity and provides confidence that every new connection is assessed to the highest standard.