Lightning design for buried cables - really?

Lightning Protection Design

Lightning design for buried cables - really?

Continuing the theme for lightning design. I was having a technical discussion during a seminar in Germany. The question popped up regarding Lightning design on an AD plant (AD = anaerobic digestion) with long cable buried runs between plant areas - "What about the buried cables?" -

What do we do about Lightning protection for buried cables in Lightning design?"

The question was not aimed at surge protection, but at physical protection of the cables from a direct lightning strike.  And before you say 'what!!?' - Yes, buried cables are at risk from direct strike attachments! Read More

Why Rolling Sphere Method is best

Lightning Protection Design

Why Rolling Sphere Method is best

A common question on Lightning Protection Design that crops up time and again, is - "What is the rolling sphere method of protection?"

If you're looking for a convenient definition in BS EN 62305.  I can save you the hassle because there isn't one! The closest you will get to a conveniently packaged definition is in para E.5.2.2.2 ..

... the positioning of an air-termination system is adequate if no point of the volume to be protected is in contact with a sphere of radius, r, rolling on the ground, around and on top of the structure in all possible directions. Therefore, the sphere should touch only the ground and/or the air-termination system.

Hmmm, not exactly succinct or useful, right? Read More

Floating Roof Tank Earthing Strategies - Bypass conductors for lightning

Lightning Protection Design

Floating Roof Tank Earthing Strategies - Bypass conductors for lightning

Floating Roof Tank Fires are Common

There are some 15 to 20 known Floating Roof Tank (FRT) fires per year. Floating Roof Tanks are especially vulnerable to the direct and indirect effects of lightning. A direct or a nearby lightning strike can cause electrical current to flow across the tank shell and roof. When these lightning currents arc across the roof/shell interface, they can ignite any flammable vapours present with devastating effect. Read More

Standard earthing design - are they valid anymore?

Earthing Standards

Standard earthing design - are they valid anymore?

A number of organisations across the UK recommend a standard earthing design when building smaller scale substations. The key driver behind these is one of cost. Nobody wants to pay more than they have to. For an HV connection using a templated approach to meet Earthing Standards compliance kind of makes sense - or does it?

So, the question is - does installing a standard earthing design meet your obligations under the Electricity at Work regulations? Read More

Split factor revealed for Best Practice in Earthing Design

Earthing Designs

Split factor revealed for Best Practice in Earthing Design

I'm often asked about Reduction factors or 'Split factor' when looking at Earthing Designs.  So what do these factors refer to? Why are they necessary? And when should you apply them?

What is a Split Factor (or Reduction)?

In Earthing terms, the Split Factor can be defined as the 'split' or proportion of fault energy that chooses to use soil conduction as its preferred route back to the source, compared with how much of the energy takes alternative route(s).  Alternative routes could be the cable sheath arrangements, CPCs or any other conductive structures intentionally or unintentionally bonded. Read More

Codes that matter for Earthing Design Standards in Railways

Earthing Designs

Codes that matter for Earthing Design Standards in Railways

For the past few years. GreyMatters has been fortunate enough to support the rail electrification and upgrade programmes across the UK for Earthing Design. And maintaining a consistent approach across a building programme of this scale can be a massive engineering headache for all design teams concerned. Especially, when Earthing Design Standards touches on so many disciplines along the way - from civils, OLE (Overhead line equipment), signals, EMC, 3rd parties, ecologies, geophysical as well as the more obvious general E&B (earthing and bonding). Read More

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