We know that for underground ducts (in concrete), with arrangement as per Fig.310.60(C)(3), with MV cables, we use the Tables 310.60(C)(77)till (80).However, as detailed in Handbook, the term "electrical ducts" refers to nonmetallic conduits. Does this mean these tables pertain to non-metallic...
Recently read an article in EC&M from 2007 which said:
When correcting conductor ampacity for elevated ambient temperature, the correction factor used for THHN conductors is based on the 90°C rating of the conductor, based on the conductor ampacity listed in the 90°C column of Table 310.16...
We have a situation where the transformer (dry type) is rated at 1500/1770kVA (85/115degC). The secondary side current @ 480V for 1770kVA is 2129A. As per NEC Article 450.3(A), the secondary side OCPD needs to be sized at 125% of FLC i.e 2661A. If we choose to use 100% rated breaker (UL 1066 for...
Recently I came across the versatile Savitzky-Golay filter on a different forum. The creator for the code Conrad Hoffman has kindly shared the code, as below.
This filter is very useful for smoothing data which is voluminous and has too many spikes. Try it.
Sub SG_five()
'5 Point...
We have a project in Mexico, where the client has insisted on ungrounded (delta-delta connection of Transformer) system for Low voltage (480V). From the design basis, it is clear that the purpose is to maintain power to process loads, which cannot be shut down without proper supervision and...
How may of you have actively derated breakers from their test certificate (IEC 62271-100 HV breakers)which are tested at standard time constant of 45 ms? What method did you employ? Did any of you use the CIGRE Technical Brochure No.304 OR the ENA Engineering Recommendation G89 (2011)? If you...
This is regarding Oil filled Transformer derating for ambient higher than 30degC as per IEEE C57.91.
The specified values are 1.5% for each deg C rise above for Self Cooled and 1% for each deg C rise for Forced air Cooled.
If I have a 60/80 MVA ONAN/ONAF Xmer, and the average max is 45degC...
