This was the central theme of our recent webinar, where Head of Electrical Design Stefano Nicoletti and Head of Engineering (EPC) Anastasios Katsaros shared practical insights on navigating the G81 submission process. Using their extensive experience, these two explained why so many applications encounter delays, rejections, and costly redesign cycles.
With 132kV connections requiring four phased design submissions, each one with a 20 working day review period and a requirement to demonstrate progressive compliance, understanding DNO expectations is the key to first-time approval.
G81 submissions are more complex than ever
As grid constraints tighten and project designs become more sophisticated, the engineering work behind a compliant G81 submission is only increasing. Our experts see this firsthand and receive comments on most design submissions.
This doesn’t always mean the design is wrong, but it does mean the DNO needs more detail, more clarity, and sometimes more justification. It’s a meticulous process, and small gaps often lead to significant delays.
One of the most difficult areas for developers to manage alone is agreeing the Main Protection and Control Diagram also referred to as the Key Line Diagram (MCP/KLD) with the Distribution Network Operator (DNO). Protection and control is a grey area, and is subject to interpretation and sometimes ongoing changes from the DNO. Managing that conversation well is key, otherwise you end up in cycles of endless comments and design modifications.
For many developers, that back-and-forth becomes the single greatest source of slippage in a project schedule.
The cost of rejected G81 submissions
A rejected submission can cascade into months of programme disruption. Even a “simple” request for additional details from the DNO can stall procurement, civil design, energisation dates, and ultimately revenue generation. Accurate submissions aren’t just a technical requirement, they’re a critical success factor.
A delay at the G81 stage can affect construction sequencing, energisation windows, and even financial returns. Getting it right the first time protects the entire project programme.
For capital-intensive renewable assets, especially hybrid systems combining solar and BESS, these delays can be incredibly costly.
Root causes of G81 submission delays
There are many reasons that your G81 submission may be bounced back or rejected, but our experience shows us that a few key issues come up time and time again, leading to a domino effect of cascading delays.
Poorly developed sites
We have successfully developed dozens of renewable energy sites, so we know how complex it can be. Missing studies, oversimplified assumptions, incompatible technology during the development stage, and dev-to-construction gaps can all lead to serious headaches. The impacts of mistakes or oversites during development can involve connection point changes, substation relocations, and even complete redesigns.
Supply chain volatility
Your supply chain can make or break your project. Discontinued models, tech evolution, component obsolescence, and of course high demand can all complicate your G81 submission. The result? Incompatible protection, interface mismatches, and compliance reassessment.
Planning rejections
Achieving planning permission for a project is a major achievement, but the process can take years and can affect your design. Technology changes, BESS integration, and increased power density are all potential outcomes of working towards planning permission. Of course, this has a knock-on effect on your G81 submission, due to changed grid parameters, substation and main equipment moves, and scope changes for construction teams.
Land & density pressures
Renewable energy projects are not immune to the adage of “location, location, location”! Land cost escalation can lead to pressure to increase energy density, resulting in the need to work in co-location strategies and new technologies in order to maximise your grid offer and ROI. The impact of this can be collection voltage increases, transformer & inverter optimisation efforts, and footprint constraints.
Grid complexity
Our grid is going through a major, and much-needed upgrade. But changing generation profiles and increasing electrification adds to grid complexity. Variable profiles, reactive power needs, and fault ride-through can all massively impact your project, and your G81 submission through dynamic compensation, protection complexity, and SCADA changes.
Constantly changing G81 libraries
G81 libraries are living, dynamic texts. Requirements differ across DNOs and can change at any time, so staying on top of these changes is paramount. Some DNOs allow you to set up notifications when policies change, but the only trustworthy way of avoiding using outdated standards is to internally verify the current version before beginning any submission.
For developers without dedicated grid teams, simply staying current requires time and oversight, something that many growing companies struggle to allocate.
Why developers are turning to specialists
G81 compliance is no longer something most developers can afford to treat as an internal side-task.
The process requires:
- deep knowledge of electrical design
- familiarity with DNO-specific requirements
- precise documentation
- ongoing communication with network operators
- and the ability to respond rapidly to technical queries
Without this expertise, submissions are more likely to be rejected, delayed, or endlessly revised.
It’s not that developers can’t do this; it’s that doing it right requires a lot of specialist knowledge, and the DNOs expect a level of technical detail and rigour that leaves little room for interpretation or error.
This is why more developers and asset owners are turning to specialist partners. Not just to secure approval, but to maximise export capacity, optimise site layout, and protect project economics, all while reducing delivery risk.
Ethical Power’s role goes far beyond producing compliant submissions. As a consulting and asset management partner, we assess grid strategy early, design infrastructure to unlock the highest viable export within the available footprint, and align technical decisions with long-term asset performance and profitability.
Our vertically integrated teams can take a project all the way from idea to operation and help ensure that the project you submit is the project you actually build. On time, on budget, and with the strongest possible commercial outcome.
If grid compliance is critical to your project’s value, it shouldn’t sit in isolation. Talk to Ethical Power about a joined-up approach to grid, ICP, and EPC delivery.