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 a level sensor with integrated lightning protection. Focusing on how the lightning protection works and how lightning strikes affect hydrostatic level sensors is essential in resolving this confusion.
When submersible pressure sensors, a special type of hydrostatic level sensors, were first installed into reservoirs and lakes to monitor level, the sensor would become burned or destroyed after a lightning storm or bad weather periods. This prompted much research into the effect 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 comprehend is that the effect of a lightning strike is considerably different based on how close to the pressure sensor the lightning strikes in to the ground or installation. It really is fair to state that no level sensor will survive a primary or very close nearby lightning strike, where often the whole cabin including all installed electronics will undoubtedly be incinerated by direct hits.
However, Painless is only going to improve the Voltage differential by for instance 1500 Volts. If a local lightning strike raises the electric potential of a reservoir, the level sensor might provide the shortest method 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 might equally be the case when overhead wires have a hit.
So how exactly does lightning protection in level sensors work?
However, sensors could be protected from these lightning strikes by installing or integrating a transient voltage protection into the hydrostatic level sensor. As a result of short nature of the voltage pulse, an element may be suited to or integrated 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 up to the maximum specified voltage potential.
The component 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 is not good enough or no lightning protection is integrated within the hydrostatic level sensor, then your electronics will take the entire quantity of energy of the voltage pulse and fail.Therefore the protection is only as good as the earth grounding provided by the user.
In outdoor applications, where submersible pressure transmitters are generally used, WIKA offers 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 a mix of protection within the instrument and an excellent low impedance earth grounding.
Take a look at the profiles of WIKAs submersible pressure transmitters LH-20 and LH-10.
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