BES Definition (approved by FERC 3-20-14)

Project 2010-17 Definition of Bulk Electric System (Phase 2)

Bulk Electric System (BES): Unless modified by the lists shown below, all Transmission Elements
operated at 100 kV or higher and Real Power and Reactive Power resources connected at 100 kV or
higher. This does not include facilities used in the local distribution of electric energy.
Inclusions:
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I1 - Transformers with the primary terminal and at least one secondary terminal operated at 100
kV or higher unless excluded by application of Exclusion E1 or E3.
I2 – Generating resource(s) including the generator terminals through the high-side of the stepup transformer(s) connected at a voltage of 100 kV or above with:
a) Gross individual nameplate rating greater than 20 MVA. Or,
b) Gross plant/facility aggregate nameplate rating greater than 75 MVA.
I3 - Blackstart Resources identified in the Transmission Operator’s restoration plan.
I4 - Dispersed power producing resources that aggregate to a total capacity greater than 75
MVA (gross nameplate rating), and that are connected through a system designed primarily for
delivering such capacity to a common point of connection at a voltage of 100 kV or above.
Thus, the facilities designated as BES are:  
a) The individual resources, and
b) The system designed primarily for delivering capacity from the point where those
resources aggregate to greater than 75 MVA to a common point of connection at a
voltage of 100 kV or above.  
I5 –Static or dynamic devices (excluding generators) dedicated to supplying or absorbing
Reactive Power that are connected at 100 kV or higher, or through a dedicated transformer with
a high-side voltage of 100 kV or higher, or through a transformer that is designated in Inclusion
I1 unless excluded by application of Exclusion E4.  

Exclusions:


E1 - Radial systems: A group of contiguous transmission Elements that emanates from a single
point of connection of 100 kV or higher and:
a) Only serves Load. Or,
b) Only includes generation resources, not identified in Inclusions I2, I3, or I4, with
an aggregate capacity less than or equal to 75 MVA (gross nameplate rating).
Or,
c) Where the radial system serves Load and includes generation resources, not
identified in Inclusions I2, I3 or I4, with an aggregate capacity of non-retail
generation less than or equal to 75 MVA (gross nameplate rating).
Note 1 – A normally open switching device between radial systems, as depicted on
prints or one-line diagrams for example, does not affect this exclusion.
Note 2 – The presence of a contiguous loop, operated at a voltage level of 50 kV or
less, between configurations being considered as radial systems, does not affect this
exclusion.
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Project 2010-17 Definition of Bulk Electric System (Phase 2)

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E2 - A generating unit or multiple generating units on the customer’s side of the retail meter
that serve all or part of the retail Load with electric energy if: (i) the net capacity provided to the
BES does not exceed 75 MVA, and (ii) standby, back-up, and maintenance power services are
provided to the generating unit or multiple generating units or to the retail Load by a Balancing
Authority, or provided pursuant to a binding obligation with a Generator Owner or Generator
Operator, or under terms approved by the applicable regulatory authority.

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E3 - Local networks (LN): A group of contiguous transmission Elements operated at less than
300 kV that distribute power to Load rather than transfer bulk power across the interconnected
system. LN’s emanate from multiple points of connection at 100 kV or higher to improve the
level of service to retail customers and not to accommodate bulk power transfer across the
interconnected system. The LN is characterized by all of the following:
a) Limits on connected generation: The LN and its underlying Elements do not
include generation resources identified in Inclusions I2, I3, or I4 and do not have
an aggregate capacity of non-retail generation greater than 75 MVA (gross
nameplate rating);
b) Real Power flows only into the LN and the LN does not transfer energy
originating outside the LN for delivery through the LN; and
c) Not part of a Flowgate or transfer path: The LN does not contain any part of a
permanent Flowgate in the Eastern Interconnection, a major transfer path within
the Western Interconnection, or a comparable monitored Facility in the ERCOT
or Quebec Interconnections, and is not a monitored Facility included in an
Interconnection Reliability Operating Limit (IROL). 

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E4 – Reactive Power devices installed for the sole benefit of a retail customer(s).

Note - Elements may be included or excluded on a case-by-case basis through the Rules of Procedure
exception process.
Effective Dates
This definition shall become effective on the first day of the second calendar quarter after applicable
regulatory approval. In those jurisdictions where no regulatory approval is required, the definition shall
become effective on the first day of the second calendar quarter after Board of Trustees adoption or as
otherwise made effective pursuant to the laws of applicable governmental authorities.

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Project 2010-17 Definition of Bulk Electric System (Phase 2)

Version History

Phase

Date

Action

Change
Tracking

1

1/25/12

Respond to FERC Order No. 743 to

clarify the definition of the Bulk Electric
System

2

11/21/13

Adopted by NERC Board of Trustees

Phase 2
clarifications to
the original
revisions.
Respond to
directives in
FERC Orders 773
and 773-A. 

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