What happens when an HV fault is reported?

The power’s gone off on your site – what do you do?

It’s the last thing you want to have to think about, but a crucial scenario to prepare for. People will want answers quickly, work may grind to a halt, and you might not know where the problem is or who to call to get it sorted.

In this article, we walk you through the process step by step – from that first call, through to figuring out what went wrong. What helps is knowing who to call, what information to have ready, and what to expect once the fault is being investigated – you don’t need to diagnose the fault yourself.

1. Tell us what you know

The first call is about understanding the situation. Useful information includes:

• which areas have lost power;
• when the problem was first noticed;
• whether anyone saw or heard anything unusual;
• who is on site;
• how we can access the affected area.

If you have electrical drawings or site information available, let us know. If not, just tell us what you do know. Even a simple description such as “the warehouse has lost power, but the office still has electricity” can be useful. You do not need to work out the cause before calling.

2. Keep the area safe

Before the fault is investigated, the site’s existing electrical safety arrangements should be followed. High-voltage (HV) fault investigation should be left to the people authorised to carry out that work. What happens next will depend on the fault and the equipment involved. The priority is to keep people safe before work begins.

3. Find the fault

Some faults are easy to see. Others are not.

A damaged underground cable, for example, may be beneath a road, yard or other part of the site.

We can investigate and locate cable faults. If the cable needs to be uncovered, we can also coordinate the excavation needed to reach the fault. This can mean fewer separate contractors for you to organise during the fault.

4. Repair the fault and work towards getting the power back on

Once the fault has been found, we can identify the appropriate next step. Where the repair is covered by our agreed service scope, our team can carry out the work. If the issue falls outside our scope, we can explain where another responsible party may need to be involved.

The time needed will depend on:

• what has failed;
• where the fault is;
• how easy it is to access;
• the condition of the surrounding equipment.

That is why it is difficult to give a reliable restoration time before the fault has been investigated. The aim is to understand the problem properly and establish the appropriate route towards restoring the supply.

5. Understand why it happened

Getting the power back on solves the immediate problem.

But it can also give you useful information about the condition of your electrical equipment.

Sometimes the repair is all that is needed.

In other cases, the fault may suggest that something needs to be checked again, monitored more closely or included in future maintenance.

Repeated faults or signs of deterioration may also raise a bigger question about whether the equipment still suits the site.

That does not mean one fault automatically means replacement.

The next decision should depend on what failed, the condition of the equipment, whether the problem has happened before, how easy the equipment is to maintain and what the site will need from it in future.

We explore these decisions further in What happens after an issue is identified on an HV network? and When does an ageing transformer become an asset decision?

Know who to call before you need to

A fault is not the ideal time to work out who looks after the HV network or where important site information is kept.

Our maintenance contract options include 24/7, 365-day callout support, alongside planned maintenance and fault support.

If you manage several sites, having the same clear process across them can also make things easier for your team.

It is worth knowing:

• who should report a fault;
• who should be contacted;
• where site information is kept;
• what support is already in place.

Would your team know what to do if part of your site lost power?

If you want to review your current fault-response arrangements, we can help you look at what is already in place and where responsibilities could be clearer before a fault happens.