Earthing and short-circuiting sets — periodic testing per IEC 61230

The guide on the 5 safety rules covers when and why step 4 — earthing and short-circuiting — is applied when de-energizing an installation. This article covers a prior condition that is often skipped: is the earthing and short-circuiting set itself still reliable at the moment of use? IEC 61230 ("Live working — Portable equipment for earthing or earthing and short-circuiting") describes both the type test and the guidelines for periodic in-service checking of this set.

Why the set itself needs periodic checking

An earthing and short-circuiting set is the last barrier between the technician and an unexpected re-energization or induced voltage while working on a de-energized installation. If the set itself has an elevated transition resistance — due to corrosion, a loosened clamp contact, or damaged conductor strands — it may be unable to carry enough current during an actual fault, with the risk that part of that current still flows to earth through the technician. A set that looks visually intact therefore does not automatically guarantee a sufficiently low transition resistance.

Visual check before every use

Before every use, the complete set should undergo a visual check:

Clamps: check for corrosion, deformation or hairline cracks in the clamp body, and for a firm, complete bite on the conductor or rail being connected.
Conductor: check for broken strands, mechanical damage to the insulation, or oxidation at the clamp connection points — that is precisely where transition resistance first develops.
Completeness of the set: verify that all components (earth, phase, and any neutral clamp) are present and belong to the same, matched set — an improvised set assembled from loose parts of different sets has never been tested as a whole.

Periodic resistance measurement: clamp-to-clamp

Besides the visual check, IEC 61230 provides for a periodic, instrumented check: measuring the electrical resistance between the clamps, through the full conductor and both clamp connections.

Note: IEC 61230 does not set a fixed maximum resistance value that applies to every set. Instead, the measured value is compared against the reference value recorded when that specific set was first put into service. A significant increase relative to that reference value indicates corrosion, a loosened contact, or the onset of strand breakage in the conductor, even if the set still looks fully intact visually.

In practice, this means every earthing and short-circuiting set needs a recorded baseline measurement at first commissioning, without which a later periodic measurement provides no meaningful comparison.

Sizing: cross-section matched to the prospective fault current

An earthing and short-circuiting set must be able to carry the installation's prospective fault current for the clearance time of the upstream protection device (typically on the order of 1 second) without melting or overheating unacceptably. A set that is oversized for a smaller installation than where it is currently deployed can physically fail during an actual fault before the upstream protection has cleared — the cross-section of the set must therefore match the actual prospective fault current at the point of use, not a generic rule of thumb.

Storage: just as decisive as the test itself

A correctly tested set that is then stored incorrectly — kinked, with a clamp dragging on the floor, or put away damp — can still develop an elevated resistance or damaged insulation by the next use, despite a recent, valid test date. Storing it dry, unkinked, and protected from mechanical damage is therefore just as decisive a factor in the set's reliability as the periodic test itself.

Practical relevance

When putting together a permit to work for de-energized work where step 4 of the 5 safety rules applies, it is important to check not just that an earthing and short-circuiting set is present, but also that that specific set has a valid, traceable periodic test date and a cross-section matched to the prospective fault current of the installation it is being applied to.

Common mistakes

Using an earthing and short-circuiting set without a recorded baseline resistance at first commissioning, so a later periodic measurement provides no meaningful comparison.
Deploying a set with too small a cross-section relative to the prospective fault current at the point of use, risking physical failure during an actual fault.
Combining parts from different sets into an improvised assembly that has never been tested or certified as such.
Storing a set incorrectly (kinked, damp, unprotected), which can undermine reliability despite a recent test date.