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Power plant tripped by lightning 2

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SA07

Electrical
Feb 22, 2018
365
Hi
Due to a lightning strike near our power plant, our 2 turbines tripped. We had several miniature breakers which tripped in a UPS supplying equipment in our 66 kV station which is in open air. In a panel for controlling breakers in the 66 kV station, 2 miniature breakers also tripped.
In an alternator panel, a miniature breaker tripped but could not be reset. After troubleshooting, an auxiliary contactor and a diode module were replaced.

We have lightning poles in our 66 kV Station. The lightning did not strike our 66 kV lines because no protection relays tripped.

It is the first time that we had such an incident.

Any idea what can be done to prevent such incident from happening again? Thanks
 
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They'd help . . .

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]
 
Having had to explain to a government official how to ensure lightning would never hit "redacted expensive machinery" once, there is no surefire cure for all possible lightning impacts (in this case we hired a lightning expert to write a report).

Bond and add surge protection in accordance with recommendations. The engineer (you?) will need to combine the effect of many documents containing recommendations:
[ul]
[li]NFPA 780 lightning protection,[/li]
[li]NFPA 70 National Electric Code,[/li]
[li]IEEE 998-1996 Guide for Direct Lightning Stroke Shielding of Substations, I[/li]
[li]EEE 62.23 IEEE Application Guide for Surge Protection of Electric Generating Plants,[/li]
[li]etc.[/li]
[/ul]
Surge protection devices may be part of your strategy, selection and placement with respect to sensitive equipment are important.

To bound the box a bit, you could focus on the failed and tripped locations and ask questions like:
Where was the strike?
How did the strike couple to the failed device(s).
From your description, the strike could have inductively coupled to something that related to the power feed to the failed devices or may have coupled to the ground bond system,

Attached "Technical Basis for Regulatory Guidance on Lightning Protection in Nuclear Power Plants" may provide some ideas to explore.
 
 https://files.engineering.com/getfile.aspx?folder=fcd77be4-92da-4620-babd-fdb7f6d80de6&file=ML053560387.pdf
A nearby lightning strike will inject a massive current into the ground. The current flows away from the strike point
most probably though a path offers the least resistance. Any ground electrodes, cables etc. etc. are in fact better
conductors than soil. As the current attempts to flow, dangerous over voltages occur across the equipment.
A known scenario is cattle get the shock (step voltage) and die when a ground flash hits near by.
Therefore, it is good to perform a "GROUNDING AUDIT" and make sure that your installation is fully BONDED & GROUNDED.
It will ensure that there are no difference in potentials during a nearby ground flash.
 
I'm going to second what FacEngrPE and really emphasize reviewing how the devices may have operated/failed as well as Kiribanda recommending the audit to verify your equipment is bonded and grounded. Sounds like you might be in an area outside north america, so earthing might be the better word and there are similar IEC standards compared to the NFPA/IEEE once listed above.

This Mitigating lightning Risks for PV plants webinar seems like it is exactly the right concepts to learn as you pursue this investigation. The presentation covers direct and indirect strikes.
 
Thank you for the advice, docs and links
 
This same problem comes up in other contexts. Under the influence of a lightning strike the earth is no longer the ground reference, but rather behaves more like the waves from a rock being dropped into a pond. A bonding grid system attempts to fix the step voltage problem during the influence of a lightning strike by helping the bonded items to have a relatively stable reference with respect to each other.

Some examples:
Local museum IT wiring between buildings run with hard wired CAT 5 cable.
Nearby lightning strikes (mostly off property) cause failures of computer and router com ports. As placing a grounding grid around a museum would be way outside their budget the recommendation was to replace the copper between buildings with fiber optic connections.

That problem could have been reduced (not eliminated) by having a gateway at each building with communications grade outside plant surge suppressors with the necessary bonding to the building structure and electrical distribution system.

I have attached "Eaton’s guide to surge suppression" which has current recommendations on this subject, which applies both generally and to some aspects of the utility substation control system protection.
 
 https://files.engineering.com/getfile.aspx?folder=ee1b2c32-3f1c-45bc-82d2-bde95449280e&file=sa01005003e.pdf
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