Message Board Thread - "Substation abnormal temperature on bolts?"

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Substation abnormal temperature on bolts? Oskarstz 2/15/2011
Hi,
I need some help understanding the picture i uploaded here. We have 110 kV substation switchyard and disconnector with six bolts on top. Yesterday i manage to take infrared picture and saw with my camera Flir T425 using auto settings that one of the bolts is very hot. U can see the pictre one is near 200 C and the others are like 60-70 C. Is there any explanation of this "focused" hot spot on the bolt?
Reggards
 
Re:Substation abnormal temperature on bolts? IRJay 2/15/2011
This resembles the pattern of a connection where the current is mostly passing through that bolt and the others are poor or worse connections. This transition connection would need some attention if this is truly 200C. The problem is that if this part of the connection fails or worsens through heating and the oxidation increases then the current may get passed to the other parts that are worse and the connection "self corrects".
 
Re:Substation abnormal temperature on bolts? Oskarstz 2/15/2011
Thanks for the reply.
The bolts are in very bad condition.(mostly rusted)
200 C is very high temeprature for this connection. Today or tomorrow we will switch off the bus disconnector and repair the connection.
Today i saw the same thing on other substation.
The question is why are the other bolts not hot.. they are like two centimetres from each other.
Look at this picture. This is Curcuit breaker 110 kV and u can observe the same effect.
 
Re:Substation abnormal temperature on bolts? sretend 2/16/2011
Hi,
Interesting images, but unfortunately very often on HV equipment. I do not know
much experience you have on this application, but you must take care about a lot of
things… Reflected apparent temperature, load, different materials with different emissivity etc.
Generally, there are problems, big problems. Of course, I agree with IRJay, and my English is not so good for longer post. Here is one of many images from 110 kV substations.

 
Re:Substation abnormal temperature on bolts? Oskarstz 2/17/2011
Hi.
My experience with the camera is poor but i learn fast. Your picture have the same effect called by reading old posts here in this comunity Magnetic heating. So if we use ferous bolts on busbar equipement the effect is present. Yesterday the old and rusted bolts were replaced with new and the problem is gone. No more glowing hot spots.
Emissivity is set to rusted iron (0,69) or aluminium 0,83.
Reflected temperature is set to 20 C, load is normal threee phase load simetric 238A,237A,239A.
 
Re:Substation abnormal temperature on bolts? sretend 2/17/2011
Hi,
It’s me again. There are no magnetic heating, it’s just a loosen bolts. All bolts are the same, same material. If is not the case, a whole substation will glow like Las Vegas.
 
Re:Substation abnormal temperature on bolts? Oskarstz 2/21/2011
Hi,
Thanks for the information.
 
Re:Substation abnormal temperature on bolts? CARLOS CASTRO 3/3/2011
It may be the bolt loose.
May be the cable that is not reaching the entire connection.
May be that the load is concentrated only on the bolt overheats due to problems in connection with the other bolts.
 
Re:Substation abnormal temperature on bolts? Demetrio Flores 3/3/2011
Oskarstz wrote:
anks for the information.
I find it strange that I do not see a thermal gradient in the terminal, if the temperature is 200 ° C as you say, that temperature should be transmitted by conduction to the entire terminal, but not, I can only see hot pin
 
Re:Substation abnormal temperature on bolts? DR@Gallatin 3/4/2011
I think it depends on how much oxidation you have going on at the connection. If only the hot bolt is severely oxidized, then it may have a different emissivity than the other bolts. The conduction of heat is taking place, but due to the different emissivities only the one bolt is being displayed as a (relatively) higher temperature.
 
Re:Substation abnormal temperature on bolts? EMinor 3/4/2011
DR@Gallatin wrote:
it depends on how much oxidation you have going on at the connection. If only the hot bolt is severely oxidized, then it may have a different emissivity than the other bolts. The conduction of heat is taking place, but due to the different emissivities only the one bolt is being displayed as a (relatively) higher temperature.
We've had this problem in our subs and every time it has been a loose connection. Upon inspection of the plates, we always find evidence of micro-arcing which is the cause of the hot spot. We believe the heat dissipates quickly from micro-arcing which is why the entire assembly is not hot. As the micro-arcing increases, the entire assembly will become hot.
 
Re:Substation abnormal temperature on bolts? Demetrio Flores 3/4/2011
Demetrio Flores wrote:
I find it strange that I do not see a thermal gradient in the terminal, if the temperature is 200 ° C as you say, that temperature should be transmitted by conduction to the entire terminal, but not, I can only see hot pin
good answer, but if it is true, with a simple visual inspection you can find the problem, I think this isn't case
 
Re:Substation abnormal temperature on bolts? Thermax IR 3/6/2011
Oskarstz wrote:
for the reply.
The bolts are in very bad condition.(mostly rusted)
200 C is very high temeprature for this connection. Today or tomorrow we will switch off the bus disconnector and repair the connection.
Today i saw the same thing on other substation.
The question is why are the other bolts not hot.. they are like two centimetres from each other.
Look at this picture. This is Curcuit breaker 110 kV and u can observe the same effect.
Hello.
I have seen this often in the substation equipment you depict here.
It is caused by induction heating with in the bolt. Not all bolts are the same. some are more ferrerous than others, although we trust that the supplier has a quality control program to prevent that. If you are ion a third world country you suffer from junk been dump in your location. With the bolt heating there will be more corrotion on the bolt, so the emmisivities will not be equal on all the bolts, hense the delta T measured will not be accurate. The reason a thermal gradient is not seen in the image is due to the thermal tuning. It will become evident if tuned differently.
 
Re:Substation abnormal temperature on bolts? Oskarstz 3/16/2011
Hi this is the result after we changed the bolts and cleaned the connection.
 
Re:Substation abnormal temperature on bolts? Pete 4/11/2011
Sorry, I am a day late and a dollar short. Simple answer: "Focused" hot spot = High resistance connection. This is fairly common in switchyards, especially ones located on the coast. Think about electrical theory: I squared(R). Resistance = heat.

Possible causes for that are: Loose, galled, corroded bolting. Ferrous bolting can also cause circulating eddy currents which create heat.

On a piece of equipment that is a large heat sink, such as the bolt pad, you probably won't see alot of transmitted heat to the surrounding surfaces.

Thermax IR is correct: If you change your tuning, you would probably see more heating on the bolt pad. Either way, nice catch. At our plant, a Delta T. that large would require clearing the equipment and repairing ASAP.
 


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