Hello all,
I have few questions about three winding transformers and harmonics that I would like to get some help from you.
I have seen three winding transformers wye-wye-delta with the delta not connected to any load; the neutrals of the “wye” are grounded and these transformers are used to...
Hello all,
Currently I am looking at a 3-Phase 4-Wire system (208/120 V) which will be supplied from an Automatic Transfer System (ATS). This ATS does not have the typical Normal and Emergency sources one can find in regular ATS systems: step down transformer (Normal) and the generator...
Hello,
I have been looking at the Canadian Electrical Code Ampacity Tables for underground circuits, specifically for direct buried installations (Tables D12A to D13B), and I have not been able to find what soil thermal resistivity the calculations are based on.
I am working in a project (in...
Hi everyone,
The reason I am consulting you is to ask if you know if there is any limitation or restriction given by NFPA 20 or NFPA 70 (NEC) for the power supply configuration of an electrical driven fire pump; I mean if it matters if it is Wye solidly grounded or Wye grounded with a NGR.
I...
Hi everyone,
If I know the ampacity of a given cable directly buried, provided the conductor's temperature, thermal resistivity (RHO), soil temperature, etc, is it possible to calculate a factor in order to determine the new ampacity when only the RHO has changed? The rest of the parameters...
Hi everyone,
I have been doing some research on generator protection and I have found that in some protection schemes the distance function (ANSI 21) is used as a backup protection.
I am having trouble to understand its philosophy (e.g. where should CT's be placed: before or after the...
I have a question about the impedance value in percent that is found on transformers under IEC standards.
As I understand a 32/40 MVA ONAN/ONAF, 20/6.9 kV with and Z=12%, had its impedance refered to lowest power rating, 32 MVA in this case.
For ANSI transformers the previous is true, but I...
