We have an Oil Type/Medium Distribution 1000kVA Transformer at a site. There is a situation where the predicted / expected load on one transformer will be around 948kVA. As we understand that if the load is known or can be predicted, it is better to choose a transformer that will be loaded to about 75% of its nameplate rating; whereas the NEC maximum allowable continuous load on a transformer is 100% of its rating.
Could you please advise us pertaining to the loading of the transformer as per the below specifications of the transformer. This is important because the manufacturer instructions supersedes as NEC states, that if you do not follow the manufacturer recommendations then you would fall into a code violation of 110.3 (B) for not following manufacturer instruction.
Year of Manufacture : 1992
Application : Distribution Transformer
Basic Transformer Concept : oil-immersed, hermetically sealed
Number of Phases : 3-phase
Type : KTMP 18HC 1000
Rated Power : 1000 kVA
Method of Cooling : ONAN
Voltage Ratio - HV/LV : 13800 / 231 V
Tapping Range : +-2x2.5%
Frequency : 60 Hz
Connection : Dyn11
Load Losses (Pk) : 9482 W
No-load Losses (Po) : 1382 W
Standards : IEC 60076
Total Weight : 2930 kg
Weight of Oil : 585 kg
Looking forward for an earliest response, please.
The transformer is designed for 100% continuous load at specified ambient conditions according to IEC standard. It’s safe to use the transformer at 100% load considering that transformer protective devices are wired and in use and they are not giving any alarm/trip signals.
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