Solar City H6 Hybrid inverter DC volts on AC line?

Recently finished install of 12kw array feeding two Solar City H6 Inverters. We were going thru start up of the inverters as per the manual. Utility guy was out to start everything and noticed there was about 30vdc per inverter (total of 60 vdc) on the AC line after the DC disconnects were closed. This was with no AC supplied to the inverters and the AC disconnect off. The dc voltage gradually decreased to zero over about a minute after the DC disconnects were opened. Inverters appeared to boot up normally after DC discconnects were closed. Both inverters performed the same way. Looking for an explanation as the utility guy did not want to energize the inverters until this was explained. Thx in advance to anyone that can provide info. mark in MN