Connection applications rarely fail because the network can’t take the load. They fail because something in the submission doesn’t stand up, and the applicant finds out six weeks later when the answer comes back.
Most of those reasons are avoidable before anything is sent. Here are the ones that hold projects up.
1. The Paperwork Doesn’t Match The Site
A wrong MPAN, a single line diagram that doesn’t reflect what’s being built, or an inverter type test certificate that has been superseded. Each one is trivial in itself, and each one sends the application back to the bottom of someone’s pile.
Network operators assess what you submitted, not what you meant. Therefore, an application describing 400kVA of load when the site will draw 600kVA produces an offer for a site that doesn’t exist, and correcting it later means a fresh assessment rather than an amendment.
2. The Equipment Isn’t Compliant
G99 requires generation to ride through network disturbances rather than trip off at the first dip, and it requires interface protection that disconnects your plant when the network goes outside defined limits. Inverters without fault ride through capability, or without current type test certification, won’t be accepted no matter how well the rest of the application reads.
This catches retrofits hardest. Equipment specified two years ago against a superseded certificate is still sitting in a warehouse somewhere waiting for an approval that isn’t coming.
3. The Protection Design Arrives Too Late
Protection is the part applicants treat as a commissioning detail, and operators treat as a condition of connection. The settings that disconnect your generation must be agreed, applied, and witness-tested before anything is energised.
Plant that’s mechanically complete can sit dark for weeks over relay settings nobody discussed at application stage. At Johnson & Phillips, we set protection and attend witness testing as a matter of course, and the projects that run smoothly are the ones where the philosophy was agreed with the operator months earlier rather than argued about on the day.
4. There Are No Real Land Rights
Operators now verify that applicants genuinely control the site, because speculative applications were holding capacity that real projects needed. Operators expect a signed letter of authority up front.
The same problem shows up later in the cable route. For example, land you don’t own needs a wayleave or an easement, and those negotiations run at their own pace regardless of the programme. Establishing the route and the ownership during feasibility is the difference between a delay you can plan around and one you can’t.
5. The Local Network Genuinely Can’t Take It
Every cause above comes down to something the applicant controls. This one doesn’t. The cables and transformers feeding your area are already at capacity, or the export you’re proposing would push power back past the grid supply point, and no amount of tidying up the submission changes that.
However, what you can control is finding out early. Most operators publish capacity heat maps showing where headroom exists, and a budget estimate costs a fraction of a full application while telling you whether reinforcement is on the table.
Although finding out at feasibility is an inconvenience, finding out after the programme is committed rewrites everything downstream.
Can You Submit A G99 Application Yourself?
For a small, fully type-tested installation, the forms are published, the process is documented, and plenty of people get through it without help.
It changes above roughly 50kW, and it changes completely at HV. At that point, the application needs a single-line diagram that reflects the final design, load characteristics the operator can model, a protection philosophy with proposed settings, and equipment certification that holds up. Those aren’t form-filling problems. They’re design outputs, and if the design isn’t settled, the application can’t be either.
The practical test is whether you can answer a technical query from the operator without going back to three other parties. If you can’t, the clarification rounds will cost more time than the help would have.
How Long The Application Takes
Operators work to published standards for issuing quotations, so you can hold them to a date.
The clock starts when the application is complete, which is the point of everything above. An application returned twice for clarification has burned three months before assessment begins.
When The Answer Is No
A rejection on capacity grounds isn’t always the end of it. Export limitation under G100 caps what you can push onto the network and removes the reinforcement that was blocking the connection. A flexible connection accepts curtailment at defined times in exchange for connecting sooner and cheaper.
Both change the asset’s economics, so the question is whether a constrained connection now beats an unconstrained one in three years. That’s a commercial decision, but it needs the engineering in front of it to be made properly.
Getting It Right Before You Apply
At Johnson & Phillips, we sit on the installation side of the connection point, which is where most of these problems originate. We design and build the HV intake arrangements and substations connections terminate in, manufacture the switchgear at our Newport works and supply the transformers behind it, so the single line diagram going to the operator describes equipment we’re actually installing.
We carry out protection and commissioning testing that operators witness before energisation, and we handle the network integration side of solar, wind, and storage schemes. Our own engineers do everything rather than subcontracting, which matters when an operator raises a query and the answer has to come from whoever did the work.
If an application has been rejected, or you want the engineering settled before one goes in, get in touch or call 0800 86 000 86.