In another project we have an electrical room in which we have encountered breaker failures, we have verified the system condition at the time of failures ( system loading,etc) and found no issues. Enviromental elements were checked and due to the type of failures phase to phase and phase to...
We are have a large facility ( new) , this facility has multiple LV UPS systems made up of 750 kVA modules in parallel.
We are experiencing failures of the main output breaker of the switchboard that consolidates the UPS outputs and of the load bank breaker. The occurrence has not been...
We have a project were the engineer has requested to modify our 21kV transformer taps in order to achieve a secondary voltage level of 510V. I know motors have rating of +/-10% so it should be Ok. However I would like to understand other impacts
Is there any difference on locating VFD's close to their loads or can they be located +100' from their loads. I had read at one time that there was an issue when working with VFD'and the cable lenght,etc.
Is this correct or is this no longer applicable with new generation VFD's
We have some diesel units installed indoors within a building, this facility is located in areas with design day + 122F. So we would like to cool the fuel on the return path as to improve a bit our performance. Our project owner has asked us if the only way to cool the fuel is with a plate type...
Could someone provide some insight on the difference between active and passive synchronization.
I have a project with closed transition were everything was designed around "pasive" synchronization and the Generator vendor is stating that they cannot do that and they only do "active"...
Are diesel generator field acceptance tests under load limited by the duty of the unit. Can I do extended test runs to both machines or am I limited by the duty. I understand from NEMA MG standards that 1 hr of a continuous duty machine is not the same as standby duty machine
I have used meggering for 1 minute as stated in NETA for field cable installations below 1kV. However Southwire in their website identifies hipot test for LV cables and one of our cleints wants to have all LV cable above 250 kcMil hipotted. Can you explain were is Southwire geeting these values...
We are currently building a new computer room in an occupied facility. We have found during demolition activities and 600AMP bud duct running within the area of the future computer room.
As the room will have raised floor we are trying to determine if the server racks are going to be impacted...
I have a four (4) 2MW diesel gen-sets that have a small 50 gallon day tank that is connected to a 4,000 gallon main tank. The question has come up by the Caterpillar on site technician that the overflow port of the day tank should be connected to the main tank as a return line. This connection...
I am working at a data center project were we have 4-2MW (480V) gen sets tied to a paralelling gear, these are currently solidly grounded and will be energized in a couple of weeks. Now our customer is stating that they are thinking on 1) grounding these generators via reactors or 2) making the...
For MV power cables you can ground the cable shield as follows:
+ Single Point.
+At Both Ends
+Transposition
For single point grounding I have noticed that certain vendors refers to a safe value of 25V for the open end side of the cable circuit. So the side were shield is grounded the...
Usually I swap any two leads to correct a motor rotation issue during start up process.
In the case of a VFD I can only do this correction between the VFD and the motor, is this correct.
I have seen several installations were you have day tanks next to generators , these day tank are fed from bigger storage tanks. What is the real purpose of a day tank.
Can someone help me with information in how to size the signal reference ground grids usually installed in raised floor areas. IEEE and TIA conflict with each other in recommendations, but I would like to understand for example what factors do you use to size the perimeter ground for example.
I have the REA Substation design manual, does anyone know of other substations design documents published for purchase or available via the Web. I looked at some IEEE papers and some make mention "old" TVA documents and some ABB info. But I did not have luck seraching for these, maybe...
Does anyone have experience with paralelling a Cummins 1500 KW with a CAT of similar size and generator pitch.
The Cummins use the Power Commader PCC and the Cat has a Woodward governor.
Someone state that the use of Cummins ISLI card would make this paralelling achievable and glitch free...
When I energize a 34.5-6.9kV Power transformer unloaded, the voltage in the secondary is not exactly 6.9kV. Is that basically due to voltage drop across the Xtr Impedance?.
Can someone clarify this calculation for me.
