How does lightning protection in hydrostatic level sensors work

Many customer wonder why hydrostatic level sensors fail because of lightning strikes, even though they ordered a level 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 Steal , a special 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 in to the aftereffect of lightning storms on the instrumentation in reservoirs and the cabling to and from the website.
What lightning protection really means
The first thing to comprehend is that the result of a lightning strike is considerably different depending on how close to the pressure sensor the lightning strikes into the ground or installation. It really is fair to state that no level sensor will survive a direct or very close nearby lightning strike, where often the whole cabin including all installed electronics will be incinerated by direct hits.
However, more distant hits 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 particular level sensor may provide the shortest way for the raised voltage and current to earth. The energy will then dissipate in to the ground via the level probe and therefore destroy or damage its electronics. This might equally function as case when overhead wires take a hit.
So how exactly does lightning protection in level sensors work?
However, sensors can be protected from these lightning strikes by installing or integrating a transient voltage protection in to the hydrostatic level sensor. Due to the short nature of the voltage pulse, an element may be fitted 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 path to ground for the surge and protecting the electronics up to the utmost specified voltage potential.
The component would normally operate in a non-conductive state, but will undoubtedly 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 entire level of energy of the voltage pulse and fail.Which means protection is only as effective as the earth grounding provided 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 Amp of WIKAs submersible pressure transmitters LH-20 and LH-10.
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