Need suggestion about lightening protection

[mikas_m]

Greetings,
I have a problem and hope you'll be able to help me.
I have one measuring circuit including power suppply unit 24V and two-wire transmitter (loop powered). From time to time, because of lightening either power supply unit or transmitter and sometimes even both burn out. Can you suggest me any typ of lightening protection? I don't have experience in this area and I'm interested to see what you would do in similar situations?
Thanks

 

[nonuke]

Phoenix Contact has the equipment for that type of protection.
It's called Trabtech

 

[mikas_m]

Thnaks, but can you give me an more details?
I have 24 V DC power supply which powers 2 wire transmitter. Basically I need to protect 4-20 mA loop and devices on it.
I have never used this type of protection before and not really sure how to chose appropriate.
P.S. does this protection element prevent burnout of equipment by acting like fuse or...?

 

[nonuke]

Please take a look at the pictura bellow.

 

[Norml]

These work well...


http://www.controrg.hu/MTL/MTLdoksik/SD/SD.pdf

 

[mikas_m]

Ok, thanks.Can you tell me if I made a good choice for 4-20 mA loop protection?

 

[nonuke]

I use the model 2856032+2856113
They are Phoenix part numbers

 

[mikas_m]

Thank you very much for your help guys. Just want to be sure about couple things:

1. For my application which includes transmitter and Power supply unit (220V AC -> 24 VDC) I'll need three surge protection devices according from the picture you pasted above nonuke (for transmitter, power supply and PSU's AC supply), but in this .pdf I see only one. What configuration Since I want to protect transmitter because it's much more expensive comparing with the PSU, I guess I'll need only one. Can you confirm this?

2. What is average cost of these devices?

Thanks

 

[Sheldn]

mikas m

what is the instrument measuring? (level, pressure, flow)
what is the instrument connected to? (tank, stand pipe, pipe)
where is the lightning striking?

 

[nonuke]

Hi Mikas m:
The 2 part numbers I posted are only for the protection of the transmitter. One code is for the Support (Base), and the other is for the Element.

 

[mikas_m]

Thanks for replies.
Sheldn,
we use transmitter to measure a level of water in a tank.
From the transmiter there are underground cable (cca 200 m length) to the control room, where instrument (4-20 mA) and power supply unit are.
I don't know where exactly lightning hits.
I think I'll need two deviced for surge protection, one to be placed on one end where transmitter is and other to be placed in control room to protect power supply unit.

 

[Sheldn]

If the tank is outside and metal and the transmitter process connection is metal and is connected directly to the tank say as a flange mounted transmitter with a diaphragm seal and the lightening strikes the tank and regardless of how well the tank is grounded, you can see stray voltage through the tank to the instrument housing through the signal .....

Is the instrument process connection a flange at the bottom of the tank? Or a threaded connection at the bottom of the tank?

Consider a device that uses a coated face such as plastic on the diaphragm seal process connection and make sure the transmitter is electrically isolated from the metal tank using a seal and make sure the bolts are isolated also. If the unit is threaded, then a plastic nipple can be considered with all other things considered such as freeze protection etc...

This is a typical scenario for towers/stand pipes in water distribution systems.

 

[mikas_m]

Sheldn,

tank is not directly outside. What I mean is that it is placed inside of a building. Tank is made of concrete, and we use level hydrostatic transmitter with stainless steel housing. Transmitter is placed at the bottom of the tank and it measure hydrostatic pressure of water which is directly proportional to water level.
I'm not sure where exactly lightning hits, but it's very likely that if there is a storm, there will be problems because of distroyed transmitter of supply units.
I'm plan to buy surge protection devices, and I'll try to order devices recommended by nonuke.

 

[Sheldn]

Then the path you are taking is good. I was concerned that after you installed all of the protectors, that the level transmitter would continue to be damaged. In your case the lightning strike appears to be coming through the power system or grounding or other place.

 

[mikas_m]

Hi Mikas m:
The 2 part numbers I posted are only for the protection of the transmitter. One code is for the Support (Base), and the other is for the Element.

So, when I'm making order, I need to order separately base element and protective plug, right?