4.1 ERMUSR 02-13-2018 - Laserfiche WebLink

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SCHEDULE 3—INTERCONNECTION PROCESS,TECHNICAL REQUIREMENTS,AND OPERATING PROCEDURES 6. Protective Devices and Systems A)Protective devices required to permit safe and proper operation of the Area EPS while interconnected with customer's Generation System are shown in the figures at the end of this document. In general,an increased degree of protection is required for increased Distributed Generation size. This is due to the greater magnitude of short circuit currents and the potential impact to system stability from these installations. Medium and large installations require more sensitive and faster protection to minimize damage and ensure safety. If a transfer system is installed which has a user accessible selection of several transfer modes, the transfer mode which has the greatest protection requirements will establish the protection requirements for that transfer system. The Interconnection Customer shall provide protective devices and systems to detect the Voltage, Frequency, Harmonic and Flicker levels as defined in the IEEE 1547 standard during periods when the Generation System is operated in parallel with the Area EPS. The Interconnection Customer shall be responsible for the purchase, installation, and maintenance of these devices. Discussion on the requirements for these protective devices and systems follows: i) Relay settings (1)If the Generation System is utilizing a Type-Certified system, such as a UL listed inverter a Professional Electrical Engineer is not required to review and approve the design of the interconnecting system. If the Generation System interconnecting device is not Type- Certified or if the Type-Certified Generation System interconnecting device has additional design modifications made, the Generation System control, the protective system, and the interconnecting device(s) shall be reviewed and approved by a Professional Electrical Engineer, registered in the State of Minnesota. (2)A copy of the proposed protective relay settings shall be supplied to the Area EPS operator for review and approval,to ensure proper coordination between the generation system and the Area EPS. ii) Relays (1)All equipment providing relaying functions shall meet or exceed ANSI/IEEE Standards for protective relays,i.e.,C37.90,C37.90.1 andC37.90.2. (2)Required relays that are not "draw-out" cased relays shall have test plugs or test switches installed to permit field testing and maintenance of the relay without unwiring or disassembling the equipment. Inverter based protection is excluded from this requirement for Generation Systems<40kW at the Point of Common Coupling. (3)Three phase interconnections shall utilize three phase power relays, which monitor all three phases of voltage and current, unless so noted in the appendix one-lines. (4)All relays shall be equipped with setting limit ranges at least as wide as specified in IEEE 1547,and meet other requirements as specified in the Area EPS interconnect study. Setting limit ranges are not to be confused with the actual relay settings required for the proper operation of the installation.At a minimum,all protective systems shall meet the requirements established in IEEE 1547. (a) Over-current relays(IEEE Device 50/51 or 50/51V)shall operate to trip the protecting breaker at a level to ensure protection of the equipment and at a speed to allow Interconnection Process for Distributed GeneratASystems