Earth continuity conductor

[Power0020]

In light of "withdrawn" IEEE Std. 565, I understand that EEC is required for single point bonded cables for the following reasons:

1- Equalizing sheath voltage at both ends to avoid transferred voltage issue.
2- Reduce the potential gradient around cable jacket for through faults esp. with high resistivity soils (I think a bare conductor will do better here!)
3- Reducing sheath returning current

the double point and cross-bonding don't require that; however, I think it will still suffer the voltage gradient issue in case of a fault return path nearby the cable.

Other issue is that sheath may be used as a path for fault currents / through faults.

Why ECC not required for double point and cross bonding cables?

 

[Power0020]

Correction : IEEE Std. 575,

any current replacement?

 

[ausphil]

Power0020, reason number one in your OP is essentially it.

with a cross bonded system, your have a continuous conductor bonding the two earth systems, which is your sheath. Any through fault current will return in the sheath and provide a low impedance path back to the source.

with a single point bonded system, you have no return conductor, as it is open circuited at one end (which is sitting on SVLs), hence to have a known low impedance return for through fault current, you need to put an ECC in, otherwise it will return through other cable sheaths, through numerous paths, and may provide a higher impedance to the fault current than otherwise wanted.

the issue with insulated or bare ECCs, I think you want to have them insulated because then you know where all you fault current is returning, rather than finding numerous paths back to the source through things you don't want them in. Also, there is a higher chance of producing unwanted voltages on hardware that is in the ground that could rise in potential due to the fault current in the ground inducing voltages, rather than being contained in a known system. Also, the insulation provides corrosion protection, so that you know you will have the full cross section of conductor to carry fault current when it is needed down the track (maybe up to 60 or 70 years later).

also, IEEE 575 has not been withdrawn, it has been revised on 12.6.2014. It still contains most of the wording from the original version, and has added some extra wording to do with ECCs, and most of the diagrams are nicer.

ausphil

 

[Power0020]

Thanks ausphil

The second point (voltage gradient due to through fault) will need a bare cable to:

1- capture the return current and divert it away from power cable.
2- avoid the voltage gradient near to cable jacket around the cable for out of circuit.

However, transferred voltage may be an issue.

Regardless of bare or insulated ECC, how to protect cable jacket from external voltage gradients in case of double point eathing or crossbonding?

would fault current return in the sheath cause any damage to the cable?