Because most Utility distribution systems were not originally designed with the intent of interconnecting generating facilities, the impacts of such an interconnection, if not carefully managed, can be detrimental to the safe and reliable operation of the system. Unless specifically permitted by the Utility, generating facilities are not allowed to operate in an “islanded” condition (generating energy that flows onto the Utility system) with other Utility customers when the portion of the Utility system serving the generating facility is disconnected from normal Utility supply.
To facilitate the interconnection process for both the applicant and the Utility, these rules classify interconnections based on shared characteristics. Because smaller facilities with appropriate interconnection technologies are expected to have a much lower impact on the Utility’s system, expedited processes and standardized interconnection requirements are applied to these interconnections. Larger generating facilities using different generating and interconnection technologies can have more significant impacts on the Utility’s system, which may require a more in-depth review and necessitate additional technical requirements.
Tiers 1, and 2, listed below contain initial applicability tests that will determine which tier process an applicant and Utility will utilize, along with process descriptions, technical requirements and completion criteria for each Tier. Additionally, all facilities must meet the appropriate requirements of Section 6, General Terms, Conditions, and Technical Specifications, and the rules and standards adopted by reference in Section 8.
Note that the interconnection requirements listed are for protection of the Utility system. The applicant and Interconnection Customer are responsible for providing protection for their own equipment; typically, these are two very different sets of functions.
Tier 1: 1 to 25 kW
Tier 1 – Applicability
Interconnection of a generating facility will utilize Tier 1 processes and technical requirements if the proposed generating facility meets all the following:
- Uses inverter-based interconnection equipment which is certified to meet the requirements of UL1741 and IEEE 1547.
- Is single phase and has a nameplate rating of 25 kW or less.
- Is connected through a single phase transformer on a radial distribution circuit.
- Is proposed for interconnection at secondary voltages (600 Volt and below).
- Does not require construction of new or upgrade of existing Utility facilities, other than meter changes.
- If proposed to be interconnected on single-phase shared secondary, the aggregate generating capacity on the shared secondary, including the proposed generating facility, will not exceed the lesser of the service wire capability or the nameplate of the transformer.
- If proposed to be interconnected at 120VAC on a 120/240VAC service, its addition will not create an imbalance between the two sides of the 240-volt service of more than 5 kVA.
Tier 1 – Application Process
The following application timelines are intended to be consistent with, and not cause delays in, other service request applications of the Utility.
- Once a fully completed application has been received by the Utility, the Utility will make its best effort to approve, approve with conditions, or deny the application with written justification within 20 business days.
- The Interconnection Customer must interconnect and operate the Generating Facility within one year from the date of approval of the application, or the application expires, unless the Utility, at its sole discretion, grants an extension in writing.
Tier 1 – Technical Requirements
The purpose of the protection required for Tier 1 generating facilities is to prevent islanding and to ensure that inverter output is disconnected when the Utility source of electricity is de-energized. Inverters certified by an independent nationally recognized testing laboratory to meet the requirements of UL1741 and IEEE 1547 must use undervoltage, overvoltage, and over/under frequency elements to detect loss of Utility power and initiate shutdown.
- An interrupting device must be provided which is capable of safely interrupting the maximum available fault current (typically the maximum fault current is that supplied by the Utility).
- The generating facility must operate within the voltage and power factor ranges specified by the Utility.
- The generating facility must be equipped with a utility-accessible disconnect switch located between the Utility meter and the generating device or devices. This disconnect is provided for the safety of Utility personal and must be located near or adjacent to the electric meter and must not be locked or blocked. See example diagram in Exhibit A at the end of Section 5.
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- Generating facility shall include provision for the Utility to install a production meter between the generating device(s) and the required safety disconnect.
Tier 1 – Completion Process
The interconnection process is complete, the generating facility can begin operation, and the applicant becomes the Interconnection Customer if and only if:
- The applicant and the Utility execute an Interconnection Agreement.
- The certificate of completion showing inspection of the system by the electrical inspector having jurisdiction over the installation has been provided to the Utility.
- The witness test, if required by the Utility, is successfully completed.
- All requirements and conditions of the Interconnection Agreement have been satisfied and approved by the Utility and permission is granted by the Utility to proceed with commercial operation.
Tier 2: 26 to 100 kW
Tier 2 – Applicability
Interconnection of a generating facility will utilize Tier 2 processes and technical requirements if the proposed generating facility meets the following:
- It does not qualify for Tier 1 interconnection applicability requirements.
- Has a nameplate rating of 100 kW or less. Interconnection at 3-phase is required at 50kW and above.
- Is proposed for interconnection to either a radial distribution circuit, or to a spot network distribution circuit limited to serving one customer.
- Is proposed for interconnection to an electric system distribution facility operated at or below 38 kV class.
- If an inverter is utilized, the inverter must be certified by an independent, nationally recognized testing laboratory to meet the requirements of UL1741.
- Is not generation using a rotating device. Rotating devices using inverter interfaces with the utility are subject to Utility review and approval and must meet the requirements above.
- If it is proposed to be interconnected on a shared secondary, the aggregate generating capacity on the shared secondary, including the proposed generating facility, will not exceed the lesser of the service wire capability or the nameplate of the transformer.
- If single-phase is to be interconnected at 120VAC on a 120/240VAC service, its addition will not create an imbalance between the two sides of the 240-volt service of more than 5 kW.
- Any upgrades required to the Utility’s system must fall within subsection 1 of the Tier 2 Technical Requirements Section.
- The aggregated nameplate rating of existing and proposed generating facilities must not contribute more than 10% to the distribution circuit’s maximum fault current at the point on the primary voltage distribution line nearest the point of interconnection.
- The generating facility’s point of interconnection must not be on a circuit where the available short circuit current, with or without the proposed generating facility, exceeds 87.5% of the interrupting capability of the Utility’s protective devices and equipment. (Including substation breakers, fuse cutouts, and line reclosers).
Tier 2 – Application Process
The following application timelines are intended to be consistent with, and not cause delays in, other service request applications of the Utility:
- Once a fully completed application has been received by the Utility, the Utility will make its best effort to approve, approve with conditions, or deny the application with written justification within 20 business days.
- The Interconnection Customer must interconnect and operate the Generating Facility within one year from the date of approval of the application, or the application expires, unless the Utility, at its sole discretion, grants an extension in writing.
Tier 2 – Technical Requirements
In all cases, the interconnection facilities must isolate the generating facility from the Utility’s electric system when power is disconnected from its electrical system source, including but not limited to, before any reclosing (automatic or manual) takes place. The Interconnection Customer will prevent its generating facility equipment from automatically re-energizing the electric system. For inverter-based systems, this requirement is satisfied by compliance with UL 1741 requirements. For non-inverter based systems a separate protection package will be required to meet IEEE 1547 requirements.
- If the generating facility fails to meet the characteristics for Tier 2 applicability, but the Utility determines that the generating facility could be interconnected safely if minor modifications to the transmission or distribution system were made (for example, changing meters, fuses, or relay settings), then the Utility may offer the applicant a good-faith, non-binding estimate of the costs of such proposed minor modifications. Modifications are not considered minor under this subsection if the total cost of the modifications exceeds $10,000. If the applicant authorizes the Utility to proceed with the minor modifications and agrees to pay the entire cost of the modifications, then the Utility may approve the application using Tier 2 processes and technical requirements.
- For proposed generating facilities 50 kW and greater, three-phase connection is required.
- No construction of facilities by the Utility on its own system will be required to accommodate the Tier 2 generating facility except as allowed in subsection 1 of this section.
- For three-phase induction generator interconnections, the Utility may, in its sole discretion, specify that ground fault protection must be provided. Use of ground overvoltage or ground overcurrent elements may be specified, depending on whether the Utility uses three-wire or effectively grounded four-wire systems.
- The Interconnection Customer is required to operate and maintain the inverter in accordance with the manufacturer’s guidelines, annually test the performance of the inverter, and retain documentation demonstrating compliance. Interconnection Customer further agrees that in the absence of such documentation, and at the Interconnection Customer’s expense, to allow the Utility, at the Utility’s sole discretion, to test, or cause to be tested, the inverter to ensure its continued operating and protection capability. Should the inverter fail the performance test, the Utility may disconnect the generating facility without notice.
- The generating facility must be equipped with a utility-accessible disconnect switch located between the Utility meter and the generating device or devices. This disconnect is provided for the safety of Utility personal and must be located near or adjacent to the electric meter and must not be locked or blocked. See example diagram in Exhibit A at the end of Section 5.
- Generating facility shall include provision for the Utility to install a production meter between the generating device(s) and the required safety disconnect.
- Visible-break lockable disconnect:
- The generating facility must include a UL listed AC disconnect switch, accessible to Utility personnel at any time of the day, that provides a visible break, is lockable in the open position, and is located between the required production meter and the utility-supplied power source. Contact the Utility for other configurations. The disconnect switch shall be physically located next to the production meter. See example diagram in Exhibit A at the end of Section 5.
- The Utility will have the right to disconnect the generating facility at the disconnect switch to meet Utility operating safety requirements.
Tier 2 – Completion Process
The interconnection process is complete, the generating facility can begin operation, and the applicant becomes an Interconnection Customer, if, and only if:
- The applicant and the Utility execute an Interconnection Agreement.
- The certificate of completion showing inspection of the system by the electrical inspector having jurisdiction over the installation has been provided to the Utility.
- The witness test, if required by the Utility, is successfully completed.
- All requirements and conditions of the Interconnection Agreement have been satisfied and approved by the Utility with permission granted by the Utility to proceed with commercial operation.
Exhibit A
Typical Photovoltaic Inverter Interconnection
**Production meter shall be located no further than 30ft from utility meter and production meter shall be visible from the net meter location.