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Dear Waross,dpc, Thanx for the detailed replies. I checked out the designs in adjacent Plants. The design is simple and I understand it is quite effective until now. Basically a Tripod consisting of 3 Mtr Copper rods are buried below ground at a depth of 1.5 Mtrs. The tripod is then connected...

Dear ALL, We have Class 1 Div 2 Group B,C,D Area in a part of the plant and the rest of the Plant is classified as Class 1 Div 2 Group C,D area. The specification states that ALL Conveinience receptacles(120V Single phase,Explosion proof type) shall be provided with Ground Fault Circuit...

Dear ALL, I checked out NEC for any such specs which specifies any minimum clearances required between Instrument Ground and Electrical Ground but could not find much. NEC clearly specifies that ALL grounding should be bonded together (whether Electrical or Instrument). But my Control Systems...

Dear ALL, Kindly advise the import of the following: 1)Instrument Reference Ground 2)Instrument Safety Ground We have Electrical Main Grounding grid of 70mm2 Copper conductor,but the entire Instrumentation system(DCS,etc) is connected to a Ground grid developed using separate tripods and...

Dear ALL, We have installed Neutral Grounding Resistors on the Neutral of a 34.5kV/480V Delta / Star Transformers. Its rated as 400A,10Secs. Kindly advise what is the sizing criteria for NGR's. What are the applicable Standards and codes for sizing NGR's. Can I get some reference materials for...

Dear ALL, Thank you for your useful insights. The manufacturer sent us revised data sheet( but no calculations!). SF is revised to 1. And manufacturer warrantied that the Motor can be treated "equivalent" to a Class F motor. Thanks all again. With Best Regards ksps

Dear All, Thanks so much for your advice. The change of Service Factor from 1.15 to 1 does give a Temperature Save(We observed it by experimenting here) i.e:Although the nameplate of the motor is stating SF=1.15, we want to change the Data sheet to limit the SF=1.0,so that the Operations team...

Dear ALL, We have a motor that is rated as Class B,Ambient=40Deg C,and Service Factor-1.15. My spec calls for all motors to be rated Class F, Ambient=50Deg C .Service Factor to be defined by Vendor Will the change of Service factor from 1.15 to 1 enable the motor to be rated for Class F and...

Dear ALL, Thanx for all your suggestions. The Battery is located based on the Building design. We cant get it closer because that would hamper access for DEG Maintenance. We plan to use 2 parallel runs of 150mm2 per terminal. 2 Nos of 150mm2 for +ve and 2 Nos of 150mm2 for -ve terminal...

Dear All, Thanx for all your support. The manufacturer recommends max 2V drop. Based on this i chose 2 runs of 120mm2 Thats 2 runs for +ve and 2 runs for -ve. Resistance of 120mm2 per meter=0.0002Ohms/mtr. Am I OK? Thanx

Hi All, I have a DEG whose Cranking motor current requirement at firing speed is = 1000A DC. How would I size the Cable for this? (Cable to be laid between the Battery terminals to the Cranking motor terminals). I plan to use XLPE Insulated 1 Core cables.I have sizes of 50mm2,95mm2,120mm2 and...

Dear All, Scotty-Thanx for the new method of calculation-i learned a few more things. I believe the impedances of the interconnects are causing the drop. Also my shorting link is 240mm2 copper cable.The connections of this cable at the busbar may also result in higher impedances. Secondly We...

Thanx all for your replies: The base condition is explained again: All Cables are 3Core + PE For eg: 3C(185mm2) + PE(50mm2),Copper conductors, XLPE Insulated,PVC Outer Sheath. The Cable Armor is 0.8mm thick. The PE Conductor is connected to the Grounding Bar at the Switchgear end and is also...

Dear Sir, Thank you for your reply. I am sorry about the few details I input in the thread. Test condition: 3 phase LV Winding is shorted. 3 phase 480V is applied to the HV Winding Below is calculation from one of the Nine total installed transformers-please review and advise me: Rating...

Hi All We are using Steel Wire Armored cable in our project. Cable Glands are used to fix the Cable to the Switchgear at the Switchgear end and at the Motor hub also. We use Brass earth tags to connect the Armor to Ground at the Switchgear end. Is it compulsory to Ground the Armor to Ground at...

Hi All, We have been doing Transformer Stability tests at our project. The System details are: Transformer - 34.5kV/.480kV,Delta-Star,3Ph,60Hz The Transformer Secondary Neutral point is connected to Earth through a High Resistance Ground Unit. A typical Transformer Differential protection...