Hi I am after a single phase,self powered overcurrent relay, preferably with definate time.
I want to use this to measure the current on the earth connection of a 13.8kV zigzag transformer. It is in a remote area and dont have (or dont want) to have auxilary power.
The self powered relays I...
Hi Krisys,
250.187 - states:
250.187 Impedance Grounded Neutral Systems. Impedance grounded neutral systems in which a grounding impedance, usually a resistor, limits the ground-fault current shall be permitted where all of the following conditions are met:
(1) The conditions of maintenance...
Thankyou for that.
Do all ungrounded systems require earth fault detection?
Would a 13.8kV ungrounded system require one?
Also can someone provide a link or brand/model of equipment that has ground fault detection at MV
Hello,
Everywhere I read on the net it says that Ground Fault Detection is not required on Low Resistance Grounding Systems only it is required on High Resistance <25A
However NEC 250.187 implies differently.
Can anyone help? What is the NEC requirement for Ground Fault Detection on low...
Hello,
Can someone please tell me if an ungrounded 13.8kV system is allowed by the NFPA/NEC requirements.
I have read the NEC code but cannot find any definite answer.I may be missing something ofcourse.
Can anyone please advise and hopefully point to the specific article.
Thanks
Hi,
I have an application where the prospective fault level is 10kA. The CT ration is 200/1 5P20. So the max current before CT saturates and larger inaccuracies start is around 4kA.
My settings are such that the pickup will occur at 2kA.
Will this CT pose a problem with the high fault level...
Hi Can someone please tell me the following:
1) When doing an engineering design of a plant is an Arcflash assessment required by NFPA? If so can someone please tell me the article to look for?
2) When doing an engineering design of a plant and purchasing equipment is an Arcflash labeling...
Hello,
We have situation where we are feeding a large load aprox 20MW 5km over 33kV Overhead powerline. The load is such that the volt drop is aprox 12% at 33kV.
I understand that I have a few options for voltage regulation:
a) PF correction, however I have calculated that at 0.98 it will...
Hello,
Does anyone know if the NEC/NFPA allows:
1) The use of a 4 core cable for a 3 phase supply (such as a motor) and use the 4th (unused core) as the earth. (i.e full sized earth). The 4core, which is usually white will be taped green for identification.
2) The use of Steel Wire Armour...
Hello,
Can someone tell me if there are any good MCC manufacturers or board builders in the USA or Mexico?
I was hoping for a board builder more than an ABB or Eaton or GE type.
Are there such companies that design and build a board to suit your requirements?
Regards
UKgrad
Hello,
We are looking at purchasing some helical rotor pumps. The vendor has offered an RTD installed into the casing of the pump which will monitor the stator temperature. We can of course take this into our PLC or motor protection unit at trip at a desired setpoint.
We have also previously...
Hello,
We are looking at purchasing some helical rotor pumps. The vendor has offered an RTD installed into the casing of the pump which will monitor the stator temperature. We can of course take this into our PLC or motor protection unit at trip at a desired setpoint.
We have also previously...
You can use either.
It is simply a feeder to the VSD. The VSD may have some signals it requires to go back to the upstream feeder contactor or breaker for protection of the VSD itself.
Thanks KuanYau,
In response to your comments please see below:
1)You are correct its a 3MVA Transformer. It is a TN-S system. The intention was to place the CT on the PE wire for earth fault protection.
2)I agree my first statement was misleading
3)There will be no earthroad near the equipment...
Hello,
I have an application where we have a 3MV Delta/Star transformer. The star system will be solidly earthed. We want to put a CT on the earth connection of the transformer for earth fault protection.
The transformer is for industrial uses and generally balanced as it is mainly running...
Thanks for the feedback.
There is nobody at my workplace that can help on this. I have read NESC standard and its talking in mm. As Desrod 22 said I would have thought you need space for a boom truck. I was thinking of allowing 10m between powerlines, but I am not sure if this is reasonable...
Hello,
I am working on a project where we need multiple overhead circuits running in parallel. On each pole there will be 2 circuits (one on either side of the pole). Further to this we need 4 powerlines running in parallel for approx 800m.
I have searched everywhere for rules and standards...
