So how exactly does lightning protection in hydrostatic level sensors work

Many customer wonder why hydrostatic level sensors fail due to lightning strikes, even though they ordered an even sensor with integrated lightning protection. Understanding how the lightning protection works and how lightning strikes affect hydrostatic level sensors is important in resolving this confusion.
When submersible pressure sensors, a particular kind of hydrostatic level sensors, were first installed into reservoirs and lakes to monitor level, the sensor would become burned or destroyed following a lightning storm or bad weather periods. This prompted much research into the aftereffect of lightning storms on the instrumentation in reservoirs and the cabling to and from the site.
What lightning protection really means
The first thing to understand is that the effect of a lightning strike is considerably different depending on how near to the pressure sensor the lightning strikes into the ground or installation. It is fair to state that no level sensor will survive a primary or very close nearby lightning strike, where usually the whole cabin including all installed electronics will be incinerated by direct hits.
However, more distant hits will only improve the Voltage differential by for instance 1500 Volts. In case a local lightning strike raises the electric potential of a reservoir, the particular level sensor may provide the shortest way for the raised voltage and current to earth. The power will then dissipate in to the ground via the level probe and therefore destroy or damage its electronics. This may equally function as case when overhead wires have a hit.
How does lightning protection in level sensors work?
However, sensors could be protected from these lightning strikes by installing or integrating a transient voltage protection in to the hydrostatic level sensor. As a result of short nature of the voltage pulse, an element may be fitted to or built-into the sensor that acts on rising differences in voltage potential. If the voltage goes above say 50 Volts, this lightning protection can short-circuit the electronic circuit to ground, allowing a way to ground for the surge and protecting the electronics around the maximum specified voltage potential.
Jeopardy would normally operate in a non-conductive state, but will be conductive for a voltage transient, allowing the voltage spike to flow harmlessly to ground. If the connection to earth isn’t good enough or no lightning protection is integrated within the hydrostatic level sensor, then your electronics will take the full amount of energy of the voltage pulse and fail.Which means protection is only as good as the earth grounding supplied by the user.
In outdoor applications, where submersible pressure transmitters are generally used, WIKA provides an optionally integrated lightning protection in the level sensors. The sensor electronics will be protected from local power surges and transient high voltage. Lightning protection is really a combination of protection within the instrument and an excellent low impedance earth grounding.
Check out Outlawed of WIKAs submersible pressure transmitters LH-20 and LH-10.
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