Ignition risk from MV, HV and EHV lines

[BPW363]

I need to assess the ignition risk from MV, HV, and EHV lines and transformers in the vicinity of wells producing hot oil and gas. Can you all comment on whether you think bare overhead lines, sub-stations, and transformers are a potential source of ignition and, if so, then direct me to any research carried out to determine safe separation distances.

I would also be interested in statistics for fires and explosions resulting from power lines and transformers.

Thanks

 

[BPW363]

I should point out that the scenario here is:

1. a well blowout
2. migration of a large, hot and flammable vapor cloud near the electrical equipment
3. potential liquid rainout

 

[bacon4life]

During normal conditions there is not normally arcing or extremely high temperature present for power lines. However, abnormal conditions such as loose hardware or bad connections could result in potential ignition. Also most mechanical switching will have some arcing during opening or closing as would distribution fuses.

Is the vapor conductive? If so it could reduce the insulation value between wires and result in a flashover.

 

[BPW363]

I realise this was somewhat an open question - but hope to get a few leads in the right direction.

I am not an electrical engineer but do understand flammability relatively well. The fluids are highly variable and start as bitumen and water with some CO2 and then end up as a variable mix of water, CO2, H2S, methane, ethane, propane, and right through to light oil. The compositions vary throughout the well production life-cycle and the temperatures generally increase up to around 700F.

The essence of my question is whether EHV, and MV power systems (lines, transformers, switchgear etc) pose a significant ignition risk and if so whether the safe distances specified in Code like IEC, ANSI or whatever are suitable for our particular application.

 

[dpc]

I think this will depend on the conductivity of the gasses as mentioned. Normally, air has sufficient dielectric strength to prevent arcing between the conductors. If the air is replaced with something with a much lower resistance, and an arc is created, you will ignite just about anything.

The other risk would be from an arc being initiated by something else and igniting the gas.

At distribution and transmission voltages, an arc to ground or between phases will be hot enough to ignite anything that will burn in air, including the shirt on your back.

 

[itsmoked]

What about the HV creating a spark between some ungrounded metal object and another object - induction/capacitance?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[dpc]

Good point - depending on the material involved, there could be static charge build up that could cause a flashover, I guess.

Flashovers often occur during brush fires that pass under power lines. (Just before the poles burn down!).

 

[Marmite]

This might be of interest.
Regards
Marmite

 

[stevenal]

I would assume any overhead line could be an ignition source, due to insulator tracking, arrester operation, fuse operation, switch operation, faulty connections, and line faults.

 

[stevenal]

How far away are you keeping other ignition sources, such as lit cigarettes, vehicle ignition systems, welding equipment, torches, open flames, etc.?

 

[TMD]

You might want to look at API RP-505. It defines zones around areas of piping, equipment, etc where flammable gas may escape. Once the zones are determined, that then defines the type of electrical equipment that can be located in that zone. Depending on the nature of the escape you have, you may need to use flameproof equipment in that zone.

 

[cranky108]

On the other hand, once a fire has been started in the area of a high voltage line, the fire itself can become a conductive path. This would make a gas or oil fire also into an electrical fire.
Also smoke from a fire can cause ash to collect on the electrical insolators which at some point can cause a flashover.

Normally, oil field equipment should not be in the right of way of the high voltage lines. Distribution lines have a smaller right of way, and maybe closer. But still if you are releasing that much gas into the air, you also have a breathing problem.

Any time there is a electrical equipment there is a potential of an ingition source (motors, lights, radios, etc). And there is special equipment made for explosive hazzard locations.

 

[BPW363]

Thanks Cranky -
You mention right of way - the question is whether the right of way width is suitable for our case. Do you know the basis on which the ROW was calculated and would it be appropriate to have a producing gas or oil well at 1000psi at the boundary of the ROW?