shivam.pandey
Member
- Location
- Chula Vista
- Occupation
- Solar design engineer
We are working on 5MWac community solar and have submitted IC drawing. Utility is asking us to show configuration on the 10kVA auxiliary transformer and specify if transformer configuration Delta : WYE G. We currently take two lines (L1 and L2, 600V) from three phase panelboard with 30A, 2P breaker for auxiliary transformer.
I am attaching the utility concern for your reference. FYI, utility is AEP Ohio. Secondary is 120/240V
What is best configuration for auxiliary transformer when service transformer configuration is WYE G: WYE G, 600V:12.47kV, 5MVA
Originally no winding configuration symbols was shown for the aux transformer on drawings.
Utility comment
what is required for each of the projects to avoid the loss of phase testing.
The main issue that arose from the drawing set was a lack of clarity surrounding how the auxiliary transformers were shown in the drawings. What our engineers wanted clarity on is if the auxiliary transformer is taking more than a single phase on the primary side, then how is the transformer wired? The use three phase transformers that are not configured as WYE-grounded : WYE-grounded is problematic due to the noted effect it has on the inverters to detect a utility loss of phase-it has been observed that if a delta transformer is wired in series or in parallel with the inverter systems, then the delta transformer has made it difficult for the inverters to fully detect a utility side loss of phase event, so they will continue operations when they should cease to energize. So if the auxiliary transformers are three phase, then our engineering team wants to ensure that they are wired in a way that will not cause an issue with the inverters to detect a loss of phase on the utility side and will cease to energize. The preferred configuration is WYE-grounded : WYE-grounded.
If the transformers are not 3 phase, then the engineering team wants to ensure that the proper primary side voltage of the auxiliary transformer is shown on the system. If the transformers are single phase, then please show the primary side voltage as 347 V (L-N voltage).
I am attaching the utility concern for your reference. FYI, utility is AEP Ohio. Secondary is 120/240V
What is best configuration for auxiliary transformer when service transformer configuration is WYE G: WYE G, 600V:12.47kV, 5MVA
Originally no winding configuration symbols was shown for the aux transformer on drawings.
Utility comment
what is required for each of the projects to avoid the loss of phase testing.
The main issue that arose from the drawing set was a lack of clarity surrounding how the auxiliary transformers were shown in the drawings. What our engineers wanted clarity on is if the auxiliary transformer is taking more than a single phase on the primary side, then how is the transformer wired? The use three phase transformers that are not configured as WYE-grounded : WYE-grounded is problematic due to the noted effect it has on the inverters to detect a utility loss of phase-it has been observed that if a delta transformer is wired in series or in parallel with the inverter systems, then the delta transformer has made it difficult for the inverters to fully detect a utility side loss of phase event, so they will continue operations when they should cease to energize. So if the auxiliary transformers are three phase, then our engineering team wants to ensure that they are wired in a way that will not cause an issue with the inverters to detect a loss of phase on the utility side and will cease to energize. The preferred configuration is WYE-grounded : WYE-grounded.
If the transformers are not 3 phase, then the engineering team wants to ensure that the proper primary side voltage of the auxiliary transformer is shown on the system. If the transformers are single phase, then please show the primary side voltage as 347 V (L-N voltage).
