Grid connected PV system : Transformer winding configuration

[SS_EE]

I am working on a rooftop grid connected system of 3 inverters of 2 X 100kVA and 1 X 60kVA and the wiring configuration for 400V is 3 phase, 3 wire system, and for the utility side its 240V 3 phase, 3 Wire system. in this case can I use a delta-delta winding transformer or will I still need a wye with neutral point grounded on the 400V side (PV inverter side)?

appreciate a quick answer in this regard

 

[electrofelon]

Your location says Philippines so there may be standards and practices I am not familiar with, but typically here in the states we would use a delta on the utility side and wye on the PV side. Many/most inverters need the neutral connection, but even if they dont, we would still use a wye because it provides for easy grounding. We dont like ungrounded systems here, and there is no advantage to going ungrounded or corner grounded. which would be your choices with a delta.

 

[SS_EE]

Thanks for your quick response.
The inverter we are using states only 3W + PE for 400V.
During the operation what would be the potential risks involved if we still use delta? (if any)

 

[Carultch]

Many/most inverters need the neutral connection, but even if they dont, we would still use a wye because it provides for easy grounding.

To add to this, even if the inverter doesn't even require a neutral, it may still require a WYE grid with a grounded neutral on the inverter side (secondary), so that the voltage-to-ground is kept below what the inverter requires.

 

[electrofelon]

Thanks for your quick response.
The inverter we are using states only 3W + PE for 400V.
During the operation what would be the potential risks involved if we still use delta? (if any)

Ungrounded would need ground detectors. People would need to know how to install them and what they mean. Most of us here have never even seen them in the wild I think. Besides that and being a bastard system in the low voltage world, arcing Faults can generate higher voltages than the system was designed for. Corner grounded is a possibility and I have done that in a pinch a few times. Also rather unusual. would want good labels on everything.
May require more expensive circuit breakers (not the common slash rated ones) . Voltage to ground would be higher or course compared to a grounded wye so probably a bit more dangerous to work on live from a shock and arc standpoint (but no one works live of course). So essentially there is just no reason to go Delta, unless maybe you already have the transformer.....

 

[GeorgeB]

I am working on a rooftop grid connected system of 3 inverters of 2 X 100kVA and 1 X 60kVA and the wiring configuration for 400V is 3 phase, 3 wire system, and for the utility side its 240V 3 phase, 3 Wire system. in this case can I use a delta-delta winding transformer or will I still need a wye with neutral point grounded on the 400V side (PV inverter side)?

In much of the world, "standard" power is 415Y240, also known as 400Y230. It is likely your inverters (what brand and model?) are designed around that.

 

[kingpb]

The "PE" means it requires a earthed conductor.