With RMU solution (RM6 for example) you can have also more than one feeder, feeder in CB or disconnect+fuses you can also built a switchgear with some basic function. RMU is more compact and dedicated basic solution (for example for open loop in distribution) with basic or autonomous protection...
It's also a good idea to have a good distance between control and power cables, I have already see all in the same pipe, and it can generate some issues...
I am not use with distance relay, but have you any other back up relay in the protection panel who can help you to understand ? Maybe you can also try to have any OPG (curve capture) in order to see whats really happen at the trip time ? May be you can also test it with injection box to secure...
If the relay is not close to the CT's it's sometimes good to use /1A on secondary, it will allow you to save some VA in the wiring (RI²) most of the protective relays accept /1 or /5A.
I am agree that:
With an additionnal copper cable between the 2 site (with the good size) and if you also connect the existing cables shield (for power cables) on both side you will increase split factor, and by this way it will begin less dependent of the real value of the earth resistance. (as...
@Marmite
Some times it's not only "is sized to carry the full prospective earth fault current" but sized for phases short circuit current also. (especially if you have 2 earth fault on two different phases)on the same site.
If you can't improve easily the ground resistor you can try:
increase the value of the touch voltage by add surface material like washed granite similar to pea gravel,
to take in account the split factor in order to reduce the value of the current in the ground resistor who will allow you to...
Ok thanks for your explanations, I will read them carrefully and try to understand that better.
Maybe I will still need your help because the ground grid calculations could be very interrsting topic.
I am agree with electic in some case in the french NF C 13-200, les figures 41H et 41J it's admit that you can have a separate grounding loop for the fence (under conditions).
Anyway this separate grounding will be influence during a fault, but It may help you to limit the touch voltage in this...
Hello All,
I see that in the IEEE 80-2000 Curves to approximate the split factor Sf we have the choice between Transmission line and feeders for the curves.
I understand that transmission line is when you have only 3 phases (HV MV),
and feeders when you have 3 phases + neutral (LV).
It seems...
Hello All,
Why the split factor/current division is no more used in the ground calculation notes, most of the time it will allow to significatly decrease the value of current to the remote earth (from 0.9 for line to 0.1 for buried cables).
But in most of the calculation notes I have see it's...
Is it an additionnal request of your client ?
In most of the earthing ground calculation software you just have to fill table with your resistivity measures following depth and it automatically indicate if you are in one or several layers.
Anyway if you retrofit the old electromechanical relay by SEL, they will consume lower VA, additionnaly you can also increase the size mm² of the wiring between the CT's and the protective relay in order to decrease the VA consume inside wiring.
Following the distance between relay and ct's and...
