Outdoor trench

[m sleem]

Can we have outdoor electrical trench with checker plate runs for ~ 1000 ft?, the electrical trench will include 13.8kv cables on 1000mm depth & LV cables on 800mm depth.

 

[ramsy]

From a design perspective, without structured-cable shielding, in close proximity of power-distribution lines during transients like lighting strikes, solar flares, faults, or typical harmonic noise and magnetic fields, the low-voltage equipment could be destroyed.

 

[Sierrasparky]

What is the voltage of the low voltage cables? 480v , 240?

 

[m sleem]

What is the voltage of the low voltage cables? 480v , 240?

Two circuits 400v

 

[Sierrasparky]

Two circuits 400v

At 480v I don't think you are worried about sensitive equipment as Ramsey implied. I think he was thinking LV being Comm and data cable and such.

 

[m sleem]

At 480v I don't think you are worried about sensitive equipment as Ramsey implied. I think he was thinking LV being Comm and data cable and such.

:slaphead: there are two comm and data trunks on top of the trench

 

[gadfly56]

:slaphead: there are two comm and data trunks on top of the trench

Are the comm and data trunks running in metallic raceway? If they are, they might be pretty well shielded to begin with.

 

[Sierrasparky]

Can we have outdoor electrical trench with checker plate runs for ~ 1000 ft?, the electrical trench will include 13.8kv cables on 1000mm depth & LV cables on 800mm depth.

Two circuits 400v

:slaphead: there are two comm and data trunks on top of the trench

Where did the comm cables come from ,,, that is a big oops.

 

[ramsy]

Where did the comm cables come from ,,, that is a big oops.

Another forum member NewtonLaw is more familiar with an Electromagnetic-Transient Program called Cyme

 

[m sleem]

Where did the comm cables come from ,,, that is a big oops.

But, i'm still meeting the requirements of 800.133(a)(2) since we have approx 500mm distance from telecom to 13.8kv feeders, may be i'm not meeting TIA/EIA where >600mm shall be maintained but it's ok from NEC requirements.

 

[m sleem]

Another forum member NewtonLaw is more familiar with an Electromagnetic-Transient Program called Cyme

Thanx, i'm going to send him private message & share with you the feedback or i'll ask him to join our thread.

 

[m sleem]

But, i'm still meeting the requirements of 800.133(a)(2) since we have approx 500mm distance from telecom to 13.8kv feeders, may be i'm not meeting TIA/EIA where >600mm shall be maintained but it's ok from NEC requirements.

Please advise, thanks in advance.

 

[ramsy]

But, i'm still meeting the requirements of 800.133(a)(2) since we have approx 500mm distance from telecom to 13.8kv feeders, may be i'm not meeting TIA/EIA where >600mm shall be maintained but it's ok from NEC requirements.

I don't believe Proximity to 13.8kv distribution voltages is addressed by this section, or anywhere else in NFPA-70.

I believe 800.133(a)(2) concerns proximity to "electric light, power" & Class-1 control circuits.

I believe "electric light, power" may be up to 277vac, while 725.41 A) Class 1 Power-Limited Circuits. are not more than 30 volts and 1000 volt-amperes.

 

[NewtonLaw]

CYME and EMPT

CYME and EMPT

Thanx, i'm going to send him private message & share with you the feedback or i'll ask him to join our thread.

Hello. We worked for a number of years with our local Public Utility Commission to revise their requirement to have one trench with all the utilities in it. This included Gas, water, phone and Data circuits and cable TV in vertical configuration with no requirement for separation between power system cables (any Distribution voltage) and phone/Data and Cable TV/Data cables. It did not take long before all the utilities responded with technical details as to why this was not a good idea. As mentioned in your threads, noise, ground currents, inductive interference, fault current coupling, etc. all provided various operational concerns. To be sure, these items are always a concern however, locating cables on long runs intentionally exacerbates these concerns to unacceptable levels not to mention the mechanical difficulties attempting to perform repair or cable locating services.

In any case, separation between power cables and most anything else remained in effect. As to your questions regarding transient analysis, two programs are available and are very well written to power system analysis. EMTP (Electro Magnetic Transient Program) ( see https://www.youtube.com/watch?v=P6k1X9T0ccs and https://www.epri.com/#/pages/product/1000366/ ). This is a powerful program that allows you to model your system and test the various operating scenarios for transient response and more. You will have a step learning curve but it is worth the effort. I believe version 4.0 is free if you are an EPRI member, may be free to the public.

The second program for power system analysis is CYME from Copper Power Systems now EATON. This software allows the user to analyze Distribution systems, Transmission systems, cable ampacity, coordination studies, grounding grid design, network load flows and includes EMTP. (see http://www.cyme.com/software/ )

These are the programs I used and have been very pleased with their results. Hope this helps.