sizing neutral grounding reactors for dg plant
sizing neutral grounding reactors for dg plant
(OP)
i am currently designing a dg plant utilizing 6 2500kva generators at 15kv. this plant will parallel with the grid at a municipal electric incoming sub. the sub is 15mva 69kv to 5kv. the muni proposes to upgrade the muni feeder to 15kv in the near future and cut the 69kv feed. i am proposing to use a 15kv/5kv transformer on the generation, close transition to the 5kv muni side of the sub to put the system in operation until they up grade to 15kv. i am proposing reusing the 5kv ucb after their up grade. my problem is how do i size reactors for my generator sets so they can be used on the 5kv system near term and reutilized on the 15kv system after the muni upgrade to their distribution?






RE: sizing neutral grounding reactors for dg plant
If one impedance value won't work, you can look at getting a reactor that is tapped or buy 2 different reactors. Somtimes getting a tapped reactor adds a good bit of $, so getting 2 different reactors may be cheaper/better technically in the end.
RE: sizing neutral grounding reactors for dg plant
RE: sizing neutral grounding reactors for dg plant
Talk to the utility re their system grounding plans - the reactors will still limit the ground fault current contributed by the generators, but the level of ground fault current available for generator internal faults will be decided by the utility grounding method. Usually, you would want to minimize the current level for internal faults, to avoid extensive generator iron damage that could require extensive rebuilding rather than rewinding.
RE: sizing neutral grounding reactors for dg plant
A useful reference may be: IEEE C62.92.2-1989 Neutral Grounding in Electrical Utility Systems Part II—Grounding of Synchronous Generator Systems
RE: sizing neutral grounding reactors for dg plant
RE: sizing neutral grounding reactors for dg plant
RE: sizing neutral grounding reactors for dg plant
The 5kV side of transformer, if connected in wye, could be grounded by the high resistance system grounding method, depending on the outcome of the grounding calculations.
The 15kV generator is suitable for the medium resistance system grounding method, although the reactor system grounding method might be applied too. It appears that a concentration on the appropriate system grounding methods would be preferable to saving a relative negligible amount of money.