(A) Scope and purpose.
(1) This section is intended to describe the requirements of Luverne Electric Utilities regarding connection to its system of customer-owned distributed generation equipment. The guidelines are intended to develop the minimum requirements for connection of such equipment to the Luverne Municipal Electric Utility system, and are not intended to be exhaustive. Each installation will be reviewed by Luverne Municipal Electric Utility staff, and additional requirements may be placed on the installation under special circumstances.
(2) This document is intended to describe certain equipment that will be necessary in order to ensure that the level of service provided to Luverne Municipal Electric Utility's customers is not degraded by the installation of the proposed distributed generation equipment. It is also intended to ensure that safe operation of both the generation equipment and Luverne Municipal Electric Utility's existing distribution system are maintained.
(3) Since this is a rapidly developing and changing field, it is expected that these guidelines will be updated periodically to reflect new technologies or industry standards. Luverne Municipal Electric Utility reserves the right to require compliance with new guidelines should they be issued in the future.
(B) Standards. The requirements developed in this chapter are intended to comply with the following standards and regulatory bodies.
(1) Emerging IEEE Standard 1547.
(2) State and federal regulatory agency requirements.
(3) Requirements of Luverne Municipal Electric Utility's power suppliers and transmission agents.
(4) National Electric Safety Code (latest version).
(5) National Electrical Code (latest version), if applicable, IEEE Standard 519.
(C) Classifications of installation.
(1) Three types of distributed generation connections covered in this document are as follows:
(a) Open transition. An open transition involves the disconnection of the utility from the customer's load prior to transferring the load to the customer's generator. The customer experiences a momentary interruption of power while the transfer is being made. At no time is the customer generator attached to the Luverne Municipal Electric Utility's distribution system.
(b) Closed transition/short-term parallel. This arrangement allows a momentary connection of the customer's generator with the Luverne Municipal Electric Utility's system during the time the customer load is being transferred from the utility to the customer's generation equipment. Once the transfer is made, the Luverne Municipal Electric Utility system is disconnected from the customer load during the time the generator is operating. The length of time in which the generator and the Luverne Municipal Electric Utility system are connected is very short. In this arrangement, the customer does not experience an interruption of service while the transition to and from the generator is being made.
(c) Closed transition/long-term parallel. At this time, Luverne Municipal Electric Utility does not allow long-term parallel operation of a distributed generation installation.
(2) Protective equipment and interrupting devices vary depending on which of the above operating modes are present.
(3) Disconnecting device. Each generating installation shall have a three-phase disconnecting device of suitable voltage and current rating to allow disconnection of the generating facility from Luverne Municipal Electric Utility's system. The characteristics of this device are dependent on the proposed operating mode of the generation equipment.
(a) Open transition. For an open transition installation, a transfer switch or equivalent arrangement utilizing the “break before make" operating characteristics shall be provided. This device shall ensure that the local customer load bus is disconnected from Luverne Municipal Electric Utility's system prior to closing the connection to the generator.
(b) Closed transition/short-time parallel. A three-phase device suitable for protective relay operation shall be provided for any installation that involves paralleling of the generation equipment with the Luverne Municipal Electric Utility System. The required equipment for the utility side device shall be a three-pole circuit breaker suitable for interruption of load and fault current. The device shall be electrically operated such that protective relaying (described below) can initiate disconnection of the generator installation from Luverne Municipal Electric Utility's system when a fault is sensed on Luverne Municipal Electric Utility's system.
(D) Protective relaying.
(1) It is essential that the delivery of power from the generating equipment into Luverne Municipal Electric Utility's system, for however brief a time, be done in a manner to minimize hazards to adjacent property. It is essential that the generating facility be taken off line from Luverne Municipal Electric Utility's system immediately whenever a fault is detected on Luverne Municipal Electric Utility's system. Further, it is critical that the tie to Luverne Municipal Electric Utility's system be separated whenever Luverne Municipal Electric Utility's system experiences an outage (no "islanding" can be allowed).
(2) The protective devices listed below are intended to protect Luverne Municipal Electric Utility's system only. Protection of the generation equipment is the responsibility of the generation equipment owner.
(3) Various protective relaying functions are required for any arrangement that involves a closed transition or parallel operation of the generating unit with Luverne Municipal Electric Utility's system. The following are the minimum protective functions that must be present on the utility tiebreaker looking out onto Luverne Municipal Electric Utility's system.
(a) Phase over-current protection.
(b) Over-voltage protection.
(c) Under-voltage protection.
(d) Over-frequency protection.
(e) Under-frequency protection.
(f) Ground-fault protection.
(g) Reverse-power protection.
(4) Many of the above functions can be incorporated into a multi-function electronic relay. For all installations over 40 kW of nameplate-generated capacity, the relays must be utility grade (not industrial grade). Proposed equipment must be approved by Luverne Municipal Electric Utility.
(E) Auxiliary equipment. Luverne Municipal Electric Utility will review the proposed installation, and determine if modifications to its equipment are necessary. If Luverne Municipal Electric Utility determines that changes to its equipment are required to accommodate the distributed generation equipment, the changes will be made by Luverne Municipal Electric Utility, with all or part of the cost assessed to the customer. Luverne Municipal Electric Utility will provide an estimate of the cost prior to proceeding.
(Ord. 18, Fourth Series, effective 6-24-2021)