EUSERC Training May 2017 Connecting Single phase 3 wire invertor to 3phase 4 wire utility service. Lessons learned - Customer Owned Interconnected Generation (COIG) such as Solar, Wind, Battery, Natural Gas, Diesel etc.

Plan Submittal and Plan Check Process Customer/ Contractor submits plans with Interconnection forms filled out. to Building Dept. and obtains a permit. Plans are sent to Electric Utility and Fire Dept.’s with permit number and necessary Utility Admin staff receives plans, verifies all forms are present and sends any comments to Utility Engineering staff. Utility Engineering Staff reviews plans for mitigate system wide impacts due to size of system/invertor type & connections to system etc. Utility Engineering Staff adds their comments to admin staff comments after which the comment sheet and plans are sent to Utility Metering Staff. Utility Metering Staff verifies the plans to ensure the proposed system meets the Utility Construction Standards (green book) for items such as: Accessibility (24/7/365) of Main service disconnect, NET meter, Dedicated PV breaker, 1st COIG AC disconnect, Production/Generation meter, 2nd COIG AC disconnect. Line of Sight, Distances (between equipment) & Signage Point of interconnection Disconnect type Panel compliance with EUSERC No customer loads on dedicated COIG (PV) back-feed circuit breaker, etc. When necessary a notice of resubmittal is required for to the customer/ contractor to address any deficiencies.

Scenario: Utility received a Solar COIG proposal to connect a Single Phase invertor to 3phase 4wire Utility provided service. Engineering thought this was a Typo on the submitted plans (because they did not think anyone would do this) therefore they did not include this to be corrected in their request for plan resubmittal comments. The plans were approved. The Contractor bought and installed as per submitted and approved plans. During inspection of installed system, metering team found this anomaly.

Resolution: After a lot of discussion inside the Utility and with the customer, the Utility decided it did not want to pay for the removal of the single phase invertor & the Purchase and installation of a 3phase 4 wire invertor system. Utility Engineering in consultation with Utility Metering agreed to grant a one-time variance from its standards. Because this was the only installation with this anomaly, the following was required for worker safety: Contractor to identify & connect the 2 the COIG system PV to the 2 highest loaded phases of the 3phase 4 wire system. Contractor at its cost to purchase & install Labels on the back-fed wires to identify the wires with “Solar Back Feed” labels inside all affected panels. Wires inside the transformer was labelled by Uitlity Utility purchased and installed “ABNORMAL CONDITION” label with white engraved lettering on Red Background. The “ABNORMAL CONDITION” label was placed by the Utility on the removable access cover of all affected 3 phase panel and the transformer.

Resources used to develop Utility Construction Standards. Utility Safety Manual FED & CAL OSHA State & Local Rules, Initiatives and Ordinances NFPA 70E & NESC ARC Flash Mitigation (special mitigation rules etc.) Reliability Standards, NFPA 70 B EUSERC, UL, IEEE NEC, NEMA