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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...

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

Hello, Does 24VDC (ELV) require to be armoured or mechacnial protected in all sections of the cable run?

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...

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...

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...

Hi guys, We are using IP66 motors on our site and in some instances we have motors mounted vertically outside. Do these motors require rainhodos over the fan? These will be installed where there is a lot of rain per year. There are conflicting views in the office, some people say yes and some...

Hello, I have been getting myself extremely confused about earthing. We are doing a design for a mine which will be all cables. I have been reading up about step/touch/earth potential rise etc etc, worrying about how to achieve this on my project. My confusion is this: The standards require a...

Hello, We are looking at reducing the fault level on a new system in order to save costs on cables and MCC boards. The fault level is only an issue on the MV side. We do not want to put in reactors as it will increase the losses. We can’t increase the transformers impedance upstream as they are...

Can anyone tell me if cyclo-converters act in the same way as a VSD in preventing the fault contribution of connected motors onto the bus.

Hello, I am trying to determine load and diversity factors of various equipment. I have had a look on the internet and cannot find any information on load/diversity factors for the following equipment Agitator and Mixer Bucket Elevator Blower Crane Compressor Crusher Conveyer Dust Collector...

Hello, I am having a bit of trouble determining what CT burden I will need for a PFC unit which will be connected to a 415V MCC. I have read a bit of information on the requirements of standard PFC units and from what I can gather they require a Class 1 metering CT and 15 VA burden with 5A...