FERC approves NERC revisions to BES definition for radial facilities, local networks

FERC on March 20 approved NERC’s proposed revisions to its definition of the bulk electric system (BES) (Docket No. RD14-2).

“Today’s order approves NERC’s proposal to refine the exclusions for radial facilities and local networks,” the commission said in a statement. “Additionally, today’s order approves revisions clarifying that all forms of generation, including variable generation resources, are included in the bulk electric system and that certain generator interconnection facilities also are included in the bulk electric system.”

NERC on Dec. 13, 2013, proposed revisions (Phase 2) to the definition of the BES to address previous FERC directives, specifically in Orders 773 and 773-A, and to respond to industry concerns raised during the initial development of the revisions to the definition (Phase 1).

The primary revisions NERC proposed were to certain inclusions and exclusions, namely to inclusion I4 (dispersed power producing resources) and exclusions E1 (radial systems), E3 (local networks) and E4 (reactive power devices).

NERC also proposed minor clarifying changes to inclusion I1 (transformers), inclusion I2 (generating resources), and inclusion I5 (static or dynamic reactive power devices). The entity did not propose any changes to the core definition, inclusion I3 (blackstart resources) or exclusion E2 (behind the meter generation).

NERC asked that FERC approve the revisions by March 31 so that they could go into effect on July 1.

In other actions taken on reliability standards, FERC in the order:

Approved five standards requiring generator owners, and in some cases, transmission owners, to provide verified data for certain power system planning and operational studies, to improve the accuracy of the studies and enhance the coordination of protection system settings.

Proposed to approve a new standard on Generator Relay Loadability designed to prevent generators from tripping offline prematurely or unnecessarily during a system disturbance, and NERC’s proposed revisions to an existing standard on Transmission Relay Loadability.

Granted clarification in part and denied rehearing of Order No. 791, which approved version 5 of the Critical Infrastructure Protection standards.

Proposed revisions in NERC’s Dec. 13, 2013 filing

Inclusion I4 (Dispersed Power Producing Resources):

  • Collector systems, from the point where the generation aggregates to 75 MVA to a common point of connection at a voltage of 100 kV or above, are proposed to be included in the BES.

“We approve NERC’s revision to inclusion I4 to include collector systems from the point where the gross nameplate capacity aggregates to greater than 75 MVA to a common point of connection at a voltage of 100 kV or above,” FERC said. “We also approve NERC’s clarification to inclusion I4 that all forms of generation resources, including variable generation resources, are included in the bulk electric system. … We agree with NERC that, given the increasing presence of wind, solar, and other non-traditional forms of generation, continuing the inclusion of individual variable generation units within the scope of the definition is appropriate to ensure that, where necessary to support reliability, these units may be subject to Reliability Standards.”

Exclusion E1 (Radial Systems):

  • A threshold of 50 kV is proposed as the operating voltage below which loops between radial systems will not preclude the application of Exclusion E1;
  • In accordance with Order Nos. 773 and 773-A, Exclusion E1 is proposed to be modified so that it does not apply to tie-lines, i.e., generator interconnection facilities, for BES generators.

“We find that NERC’s modification to exclusion E1, to add a 50 kV threshold for excluding certain radial loops, is reasonable,” FERC said in the order approving the revisions. “We find that NERC’s technical justification based on the scenarios and configurations utilized in its analysis supports the selection of a 50 kV threshold and represents the vast majority of configurations that will be encountered in the industry.”

Exclusion E3 (Local Networks):


  • In accordance with Order Nos. 773 and 773-A, the 100 kV minimum operating voltage for Exclusion E3 is proposed for removal;
  • In accordance with Order Nos. 773 and 773-A, Exclusion E3 is proposed to be modified so that it does not apply to tie-lines, i.e., generator interconnection facilities, for BES generators;
  • A revision is proposed to Exclusion E3 to include any part of a permanent Flowgate.


Exclusion E4 (Reactive Power Devices):

  • A revision is proposed to Exclusion E4 to remove ownership implications consistent with the component-based nature of the BES Definition.

Development of BES definition

In 2010, FERC directed NERC in Order 743 to change the definition of the BES to include any facilities necessary for operating the interconnected transmission network. In the same order, FERC determined that one of the best ways to eliminate inconsistences across regions with respect to which elements are included in the definition of the BES was to set a bright-line threshold to include all facilities operated at and above 100-kV, with the exception of radial lines.

The commission gave NERC the opportunity to propose an alternative to FERC’s approach; NERC in 2012 proposed provisions to include and exclude facilities from the “core” definition of the BES, or inclusions and exclusions, which FERC approved in Order 773, issued in December 2012. In Order 773, FERC directed NERC to modify the local network exclusion (E3) to remove the 100-kV minimum operating voltage to allow systems that include one or more looped configurations connected below 100-kV to be eligible for the local network exclusion.

In Order 773-A, which largely affirmed its findings in Order 773, FERC directed NERC to implement certain exclusions and modify other exclusions to ensure that generator interconnection facilities at or above 100-kV connected to bulk electric system generators identified in inclusion I2 are not excluded from the bulk electric system. Order 773-A was issued in April 2013.

About Rosy Lum 525 Articles
Rosy Lum, Analyst for TransmissionHub, has been covering the U.S. energy industry since 2007. She began her career in energy journalism at SNL Financial, for which she established a New York news desk. She covered topics ranging from energy finance and renewable policies and incentives, to master limited partnerships and ETFs. Thereafter, she honed her energy and utility focus at the Financial Times' dealReporter, where she covered and broke oil and gas and utility mergers and acquisitions.