Shunt Trip Recommendation

[Raam_Solar]

We are working on a C&I rooftop solar project and are looking for suggestions on shunt trip for our main breaker. We have a customer owned transformer that is a Delta:Wye configuration, with Delta on the utility side at 13.2 kV and Wye on the customer side at 480V. Utility got back to us and requested that we add a shunt trip in the main breaker to detect any phase loss on the primary, Delta side of the transformer.

We understand their concern and we are looking at options. We are running into issues as the phase loss detection has to happen on the 13.2 kV side. Has anyone come across similar situation and does anyone have any recommendation? For anyone who is curious, this will be a 750 kW DC/480 kW AC system with 4 x SolarEdge 120s.

 

[ggunn]

We are working on a C&I rooftop solar project and are looking for suggestions on shunt trip for our main breaker. We have a customer owned transformer that is a Delta:Wye configuration, with Delta on the utility side at 13.2 kV and Wye on the customer side at 480V. Utility got back to us and requested that we add a shunt trip in the main breaker to detect any phase loss on the primary, Delta side of the transformer.

We understand their concern and we are looking at options. We are running into issues as the phase loss detection has to happen on the 13.2 kV side. Has anyone come across similar situation and does anyone have any recommendation? For anyone who is curious, this will be a 750 kW DC/480 kW AC system with 4 x SolarEdge 120s.

Your DC:AC ratio will be greater than 1.5; will SolarEdge allow that? Where is the revenue meter? Will the POCO install the phase loss detection if it would be on their side of the meter?

 

[Raam_Solar]

Yes our DC: AC ratio is higher than 1.5 and SE allows up to 1.75. We try to stay at around 1.3-1.4 but we have an interconnection limit and AC size above 500 kW triggers further additional protection mechanism.
From the overhead pole we feed the CT cabinet + meter socket at 13.2 kV, and then to the 13.2 kV Delta to 480V Wye transformer. So the phase loss detection installation will be on the customer.

 

[pv_n00b]

You are looking at a basic 27 relay, like a Basler BE1-27, to trip the breaker on low phase voltage. You will need a PT to get the voltage down to the voltage the relay uses. You don't say if the utility service is 3 wire or 4 wire. It can be hard to detect loss of phase on a 3 wire ungrounded service since open delta looks pretty much like closed delta.

 

[Raam_Solar]

You are looking at a basic 27 relay, like a Basler BE1-27, to trip the breaker on low phase voltage. You will need a PT to get the voltage down to the voltage the relay uses. You don't say if the utility service is 3 wire or 4 wire. It can be hard to detect loss of phase on a 3 wire ungrounded service since open delta looks pretty much like closed delta.

Sorry missed that detail. We have an ungrounded 3 wire service here. Looks like this might make it a bit tricky. We have asked the utility to provide any reference or even point to the exact product they would like us to add here, but they weren't confident that they can give us solutions