denvar
Member
- Location
- Nairobi Kenya
Hi, am designing a small hydro plant 800 KVA (two 415V generators using a single step up transformer) to be connected to the distribution system at 11KV. Am facing a challenge deciding which kind of step up transformer (0.415/11 KV) to use since local supply (30 KVA) both single and three phase is required. Am evaluating the following options:
a) (a) Use star-star step up transformer which enables connection of single phase loads easily but will have risk of imbalance, will pass zero sequence faults and will suffer third harmonic problems.
b) (b) Use delta-star step up transformer which is the most convenient for protection purposes but then connect another yyn0 isolation transformer on generator bus bar to supply the 30 KVA load.
c) (c) Use delta-star step up transformer but then use another 11/0.415 KV step down transformer for local supply.
Since cost is a major issue am leaning towards option (a) but am not sure the effects of using a y-y transformer especially if there are unbalanced loads. Kindly assist.
a) (a) Use star-star step up transformer which enables connection of single phase loads easily but will have risk of imbalance, will pass zero sequence faults and will suffer third harmonic problems.
b) (b) Use delta-star step up transformer which is the most convenient for protection purposes but then connect another yyn0 isolation transformer on generator bus bar to supply the 30 KVA load.
c) (c) Use delta-star step up transformer but then use another 11/0.415 KV step down transformer for local supply.
Since cost is a major issue am leaning towards option (a) but am not sure the effects of using a y-y transformer especially if there are unbalanced loads. Kindly assist.