Distributed Energy Resources (DER) Experiences at CenterPoint Energy 2/23/2015 Distributed Energy Resources (DER) Experiences at CenterPoint Energy by James Koinis & Aman Fatma Distribution Planners Approved by: Ed Briggs, P.E. Manager Distribution Planning Presented at SWEDE: 05/04/2018 CenterPoint Energy Proprietary & Confidential Information CenterPoint Energy Proprietary & Confidential Information

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Agenda Safety Share Historical Utility Operation What is a DER? Why are DERs connecting to the Utility Grid? CenterPoint Energy DER Experiences Distribution Planning Customer Interaction Metering and Telemetry Distribution Protection References Questions? CenterPoint Energy Proprietary & Confidential Information

Safety Share 2/23/2015 CenterPoint Energy Proprietary & Confidential Information CenterPoint Energy Proprietary & Confidential Information

Electricity Distribution Background 2/23/2015 CenterPoint Energy Proprietary & Confidential Information CenterPoint Energy Proprietary & Confidential Information

DER- Future of Electric Utility 2/23/2015 What is a DER? Distributed Energy Resource (DER) is an electrical generating facility located at a Customer's point of delivery (point of common coupling), 10 megawatts (MW) or less, and connected at a voltage less than or equal to 60 kilovolts (kV), which may be connected in parallel operation to the utility system. [1] Rate of interconnection. Currently CenterPoint Energy has approximately 261MW of existing DERs connected and expecting 189 MW in the coming year. Types of DERs. Renewable Solar Wind Hydro Landfill Gas Non-Renewable Diesel Natural Gas CenterPoint Energy Proprietary & Confidential Information CenterPoint Energy Proprietary & Confidential Information

CenterPoint Energy DER Installations 2/23/2015 CenterPoint Energy Proprietary & Confidential Information CenterPoint Energy Proprietary & Confidential Information

CenterPoint Energy Installed DER Types 2/23/2015 Diesel 43.1%, 113.5 MW Solar 9%, 23 MW Landfill Gas 6%, 13 MW Natural Gas 42.9%, 112.8 MW CenterPoint Energy Proprietary & Confidential Information CenterPoint Energy Proprietary & Confidential Information

Why are DERs connecting? 2/23/2015 ERCOT Emergency Response Service (ERS) Four Coincident Peak (4CP) response Load Zone-level wholesale price response in the Real-Time Energy Market Back up Generation Incentive Programs CenterPoint Energy Proprietary & Confidential Information CenterPoint Energy Proprietary & Confidential Information

Distribution Planning Customer Interaction Metering and Telemetry Our DER Experiences 2/23/2015 Distribution Planning Customer Interaction Metering and Telemetry Distribution Protection CenterPoint Energy Proprietary & Confidential Information CenterPoint Energy Proprietary & Confidential Information

Distribution Planning - DER Modeling 2/23/2015 CYME 7.2/8.0 for DER studies Features nested views: Interconnection application with detailed One-Line. CenterPoint Energy Proprietary & Confidential Information CenterPoint Energy Proprietary & Confidential Information

Distribution Planning - DER Modeling 2/23/2015 CenterPoint Energy Proprietary & Confidential Information CenterPoint Energy Proprietary & Confidential Information

Distribution Planning – Other Concerns 2/23/2015 Split Service Agreements For example, at the Point of Common Coupling (PCC): 12kV – 4MW 2pts of 2MW 35kV – 6MW 2pts of 3MW (*not an all inclusive list*) Voltage Concerns Load Rejection Overvoltage (LRO) Transient or Temporary Overvoltage (TOV) DER Customers not wanting to take kVARs Substation Capacitor Bank CenterPoint Energy Proprietary & Confidential Information CenterPoint Energy Proprietary & Confidential Information

Substation Capacitor Banks 2/23/2015 Substation Capacitor Banks Received DER customer complaints of tripping due to high voltage. Substation Cap Bank was turned on to provide VARs to the transmission section. DERs that are close to the substation are more prone to high voltage levels causing them to trip. CenterPoint Energy Proprietary & Confidential Information CenterPoint Energy Proprietary & Confidential Information

DER and Telemetry 2/23/2015 Need more telemetry to allow operators better understanding of the system. How do you get telemetry? What is the most economical way to obtain the telemetry? Who will pay for the equipment necessary to obtain the telemetry from the DER site? Although DERs are accounted for during Load Forecasting, our large DERs are modeled off because they have not been consistently running during peak load season each year. CenterPoint Energy Proprietary & Confidential Information CenterPoint Energy Proprietary & Confidential Information

 / Y-grounded to Y-grounded/Y-grounded 2/23/2015  / Y-grounded to Y-grounded/Y-grounded Due to potential High Voltage damage to equipment, had to change to Y-grounded/Y-grounded transformer for DERs at customer cost Additional Expense and Time CenterPoint Energy Proprietary & Confidential Information CenterPoint Energy Proprietary & Confidential Information

Customer Interaction Exporting kW Importing kVAR 2/23/2015 CenterPoint Energy Proprietary & Confidential Information CenterPoint Energy Proprietary & Confidential Information

Protection Experiences 2/23/2015 Why Transfer Trip (TT)? Unintentional islanding may lead to several problems in utility grid such as power quality, voltage and frequency stability, interference etc. How TT affects DERs Time and Money Reverse Power Trip Conditional TT CenterPoint Energy Proprietary & Confidential Information CenterPoint Energy Proprietary & Confidential Information

Reverse Power Trip Brought about by Customer Request 2/23/2015 Reverse Power Trip Brought about by Customer Request Goal is to have anti-islanding at a lower cost and faster processing time than Transfer Trip. Other Utilities using it in place of Transfer Trip How do you determine the trip set point? What are the risks to CNP or customer’s equipment? We are still in the evaluation phase. CenterPoint Energy Proprietary & Confidential Information CenterPoint Energy Proprietary & Confidential Information

Conditional Transfer Trip Operation 2/23/2015 Conditional Transfer Trip Operation Used to not trip critical care facilities unnecessarily. It was decided that an additional Meter CT would be used to determine if the generator was on or off. This information could then be used to determine when to trip breaker “A”. Customer’s Relay Generators Meter CT Main Service G B A Meter CT CenterPoint Energy Proprietary & Confidential Information CenterPoint Energy Proprietary & Confidential Information

References 2/23/2015 [1] “Distributed Generation.” ERCOT.com : Web. 18 April. 2018. <http://www.ercot.com/services/rq/re/dgresource>. [2] “Smiley Face Happy Thumbs Up.” Pixabay.com : Web. 18 April. 2018. < https://pixabay.com/en/smiley-face-happy-thumbs-up-thumb-147407/> CenterPoint Energy Proprietary & Confidential Information CenterPoint Energy Proprietary & Confidential Information

Questions? 2/23/2015 CenterPoint Energy Proprietary & Confidential Information CenterPoint Energy Proprietary & Confidential Information