Electricity: measuring and testing – Testing potential in specific environment – Voltage probe
Patent
1996-12-17
1999-07-27
Regan, Maura
Electricity: measuring and testing
Testing potential in specific environment
Voltage probe
324 72, 324509, G01R 2726
Patent
active
059296259
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to methods and apparatuses for monitoring anti-lightning protection equipment, in particular lightning rods and dischargers or lightning arresters.
Lightning rods comprise a metal rod or spike secured vertically on the roof top of a structure to be protected and connected to the ground via a grounding line. Because it is at ground potential, the metal spike captures lightning, and the grounding line conveys lightning to the ground where it is dissipated.
Since the amount of lightning energy captured by a lightning rod can be considerable, this energy may possibly damage the grounding line, or more commonly it may dry out the ground at the interface between the ground and the grounding line. When this happens, the resistance between the ground and the spike of the lightning rod becomes greater than normal.
Consequently, the grounding line that runs up the height of the structure to be protected can then be raised to electrical potentials that are very high when lightning strikes the lightning rod. These potentials can in turn propagate through the structure of the building and may cause fire to break out, or may at least severely disturb the operation of electrical equipment or electronic equipment contained in the structure to be protected.
To avoid such accidents, the quality of the electrical connection between ground and the lightning rod is therefore checked from time to time.
Such checking may be performed either at regular intervals, however that runs the rise of checking being pointless if lightning has not struck the lightning rod since the previous check, or of being too late if lightning happened to damage the lightning rod shortly after said previous check.
That is why lightning rods are sometimes monitored by counting the number of times they have been struck by lightning since the preceding check. When the number reaches a predetermined value, then the quality of the electrical connection between ground and the lightning rod is checked.
Usually, such counting is performed by means of a device that comprises a magnetic circuit that forms a closed loop around the grounding line of the lightning rod, and an electrical circuit including at least one turn wound around the magnetic circuit so that lightning current passing along the grounding line induces current in said turn, the turn being connected to a relay which causes a mechanical counter to advance by one step on each occasion that it closes.
Nevertheless, that method of monitoring a lightning rod suffers from the drawback of not taking into account the magnitude of each lightning strike received by the lightning rod.
A predetermined number of low energy lightning strikes will not produce any damage to the grounding line, and will cause relatively little drying out of the ground at the interface between the ground and the grounding line, whereas a single lightning strike of exceptional energy runs the risk on its own either of destroying or damaging the grounding line or else of severely drying out the ground at the interface between the ground and the grounding line.
The same drawbacks apply to methods of monitoring other anti-lightning protection equipment, in particular dischargers or lightning arrestors, if they operate merely by counting lightning strikes. With dischargers or lightning arrestors, a single high-energy lightning strike runs the risk of damaging not only the connection to ground, but also, and above all, the discharger or arrestor itself.
A particular object of the present invention is therefore to propose a method of monitoring equipment for providing protection against lightning, which method avoids the above-mentioned drawbacks and makes it possible to trigger checking of said equipment as soon as it is liable to have been damaged or to have suffered any deterioration in its electrical characteristics.
To this end, the invention provides a method of monitoring anti-lightning protection equipment that includes a grounding line, the method being essentially characterized in that a "lightning"
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Lewiner Jacques
Smycz Eugeniusz
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