Bulk Electric System
Facility Rating Methodology
1.0
Purpose and Scope
The purpose of this document is to summarize JEA’s rating methodology for bulk electric
system facilities of JEA’s solely and jointly-owned facilities for which JEA has
responsibility for providing ratings, in fulfillment of NERC recommendation FAC-008,
for establishing a rating methodology for Bulk Electric System Facilities. For facilities
where ownership changes in the line or terminal, JEA rates only those portions of the line
or terminal it owns. For jointly owned facilities, JEA provides ratings if JEA is the
operator as defined in contractual documents. The scope of this document includes bulk
electric system transmission facilities (transmission circuits, autotransformers and
capacitor banks that operate at voltages 100kV or higher) and generation facilities
interconnected at 100KV or higher. Other components and equipment that may limit the
ultimate ratings of these major facilities are also addressed herein, and are referred to as
auxiliary equipment and components of major facilities. Additionally, any JEA facility
rating is derived from the most limiting applicable equipment rating of the individual
equipment that comprises that facility.
In developing JEA’s facility ratings methodology, the following were considered:
• Ratings provided by manufacturer
• Design criteria, such as, manufacturer nameplate or warranty, IEEE, ANSI or other
standards
• Ambient conditions
• Operating limitations
• Other assumptions
2.0
Transmission Circuit Rating Methodology
JEA defines transmission circuits to be unique electrical circuit between the high voltage
terminations of two substations. JEA establishes the maximum rating of transmission
circuits of calculating maximum ampacity based on the allowable temperature rise of the
conductor as referenced in JEA’s “Transmission Construction Standards,” CO-1 (i.e. 200º
F for 1590 ACSR.) In cases where the transmission circuit is limited by other equipment,
the rating is limited to the most limiting equipment rating that comprises any portion of
the circuit.
2.1
Overhead Transmission Lines
The calculation methods used to determine normal and emergency ratings of JEA
bare overhead transmission conductor are based on an industry standard rating
methodology (published by Southwire Corporation). Data utilized for conductor
parameters to perform conductor calculations is taken from similar resources.
Specifically, for all JEA overhead conductor ampacity calculations, the following
local parameters are utilized to establish maximum ampacity at summer peak load
(5:00 p.m.) and winter peak load (7:00 a.m.):
Parameters
Ambient Air Temperature
Perpendicular Crosswind
Velocity
Emissivity Constant
Absorptivity Constant
Atmospheric Conditions
Solar Heat Gain
Altitude
Conductor Azimuth
Summer
90º F
2 Ft/Sec
Winter
40º F
2 Ft/Sec
0.8
0.5
Clear
5:00 PM
50 Ft
0º F
0.8
0.5
Clear
7:00 AM
50 Ft
0º F
Emergency ratings are based on the conductors’ response to a step change in
current over its assumed pre-load current (50% of normal rating) over a specified
time period (10 minutes). Operating plans shall be implemented within the time
period to reduce the load on the conductor to its normal rating.
Other ratings may be implemented as required based on detailed analysis on a
case by case basis.
2.2
Underground Transmission Lines
JEA determines underground transmission line ratings based upon cable
manufacturers recommendations and by employing professional service firms to
perform thermal modeling of underground transmission systems. These analyses
include the consideration of existing soil conditions, subterranean (or sub
aqueous) irregularities, and the presence of other underground electric
(transmission or distribution) facilities when these are sufficiently close to the
transmission facility under study.
Based on acceptable loss of life and being consistent with FRCC’s “Reliability
Process for the FRCC Bulk Electric System”, JEA has developed emergency
ratings for its underground transmission lines. These emergency ratings are 120%
of normal continuous ratings and are valid for 10 minutes. Other ratings may be
implemented as required based on detailed analysis on a case by case basis.
Operating plans shall be implemented within 10 minutes to reduce the load on the
device to its continuous rating. During these emergency periods, operation of the
device may result in reduced operating life that is acceptable to JEA. JEA
determines its own inspection and maintenance policy following these emergency
operating conditions.
3.0
Transformer Rating Methodology
3.1
Autotransformers
Autotransformers normal summer ratings are determined by the equipment
manufacturer and listed on the transformer nameplate. Typically, ratings for the
JEA system autotransformers are specified as ONAN/ONAF/ONAF. Normal
winter and emergency ratings were developed consistent with IEEE Standard
C57.91-1995 Guide for Loading Mineral Oil Immersed Transformers. The
ratings in excess of nameplate were developed and applied conservatively to
ensure less than 1% loss of life over a 24-hour period based on assumed summer
and winter load and temperature. This yields the summer and winter emergency
ratings of 130% of the normal ratings for six hours and 10 minutes.
During these emergency periods, operation of the device may result in reduced
operating life that is acceptable to JEA. JEA determines its own inspection and
maintenance policy following these emergency operating conditions.
All of JEA’s autotransformers have temperature indicating devices that generate
alarms to the JEA Control Center when temperature limits are exceeded.
Operating plans shall be implemented within the time period to reduce the load on
the autotransformer to its normal rating when the temperature alarms are indicated
at the control center.
Other ratings may be implemented as required based on detailed analysis on a
case by case basis.
3.2
Generator Step Up Transformers (GSU)
GSUs are coordinated with the maximum rated full load conditions of the
generator they are intended to operate with. These ratings are provided by the
equipment manufacturer and listed on the transformer nameplate. All
installations require that the GSU be the limiting device of the circuit in which it
is used, therefore, any associated equipment used with the GSU must handle
loadings at or above the normal levels of the GSU.
There are no ratings above nameplate for these transformers. Therefore, the
normal and emergency ratings are the same.
4.0
Capacitor Bank Rating Methodology
JEA installs shunt capacitor banks into transmission-voltage substations in order
to provide reactive power support to JEA’s generation and transmission system.
These facilities are specified in size and location by JEA’s Electric System
Planning Section. JEA installs the capacitors to deliver the reactive power
specified when the substation bus work operates at 1.0 per unit voltage.
There are no ratings above nameplate for these capacitor banks. Therefore, the
normal and emergency ratings are the same.
5.0
Transmission & Substation Auxiliary Equipment and
Components
In addition to, and as part of the rating of major transmission facilities, JEA also
coordinates ratings on miscellaneous equipment and components that may
otherwise limit the capacity of (i.e. are series connected with) JEA’s bulk power
transmission facilities. This section of this report describes how JEA determines
the adequacy of these facilities.
5.1
Circuit Breakers
Circuit breakers are coordinated with the maximum rated steady state and fault
interrupting ampacity of the circuit (or bus) that they are intended to operate with.
These required ampacities are supplied by JEA Electric System Planning
Engineers and are realized by the JEA Project Design Section Engineers at the
time of equipment selection. The actual circuit breaker design parameters are
provided by the equipment manufacturer and listed on the circuit breaker
nameplate. Summer and winter normal and emergency ratings were developed
consistent with IEEE Standard C37.010-1999 IEEE Application Guide for AC
High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis. The
ratings in excess of nameplate were developed and applied conservatively.
Summer and winter normal ratings are based on nameplate adjusted for ambient
design temperatures (90F/40F) consistent with the standard. Summer and winter
emergency ratings are based on the breakers’ response to a step change in current
over its assumed pre-load current (50% of normal rating) over a specified time
period.
Circuit breakers are often specified to provide special clearing times, synchronous
closing poles or other specifics as sated in the scope document provided by JEA
Electric System Planning. JEA Substation and Relay engineers work together to
design and select equipment to achieve these requirements.
5.2
Circuit Switchers
Circuit switchers are coordinated with the maximum capability of the circuit they
are intended to operate with. These ratings are provided by the equipment
manufacturer. The load capabilities of these devices are per industry breaker
standards per IEEE Standard C37.010-1999 IEEE Application Guide for AC
High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis. The
summer and winter normal and emergency ratings were developed consistent with
these standards.
5.3
Instrument Transformers
Instrument transformers are coordinated with the capability of the circuit or
device they are intended to operate with. These ratings are provided by the
equipment manufacturer and listed on the instrument transformer nameplate. It is
assumed that the instrument transformers that are mounted in bushings have the
same thermal heating characteristics as the circuit breaker or transformer.
Every installation requires that the instrument transformers can tolerate the circuit
conditions and in no instance will instrument transformers account for the
limitation of the circuit.
The normal and emergency ratings of instrument transformers are equal to the
normal and emergency ratings of breakers or transformers they are mounted in or
connected to.
5.4
Line Traps
Line traps are coordinated with the maximum rated steady state ampacity/voltage
of the circuit they are intended to operate with. These ratings are provided by the
equipment manufacturer and listed on the line trap nameplate.
There are no ratings above nameplate for these line traps. Therefore, the normal
and emergency ratings are the same.
5.5
Switches
Switches are coordinated with the maximum rated ampacity of the circuit they are
intended to operate with. The actual switch design parameters are provided by the
equipment manufacturer and listed on the nameplate. Summer and winter normal
and emergency ratings were developed consistent with IEEE Standard C37.371996 IEEE Loading Guide for AC High-Voltage Air Switches. The ratings in
excess of nameplate were developed and applied conservatively. Summer and
winter normal ratings are based on nameplate adjusted for ambient design
temperatures (90F/40F) consistent with the standard.
5.6
Protection, Control and SCADA Components
JEA deploys a variety of protection and control schemes (also referred to as
“relays” to assure safe and reliable operation of its bulk power transmission
facilities. These components may have the ability to limit the ability of a major
transmission facility to conduct its intended ampacity if, for instance, an overcurrent protection function were to operate a breaker at a current flow that is
below the ampacity of the respective transmission facility. JEA assures this is not
so by carefully coordinating all of its Protection, Control, and SCADA
components to assure that this do not occur. Testing of these settings and designs
is performed at the time the facilities are first placed into service.
The normal and emergency ratings of protection, control and SCADA
components are equal to the normal and emergency ratings to their connecting
instrument transformers.
5.7
Miscellaneous Components
JEA uses a wide variety of miscellaneous components in substations and on
transmission lines to assure that maximum facility ratings can be available. Some
examples of these miscellaneous facilities include, for transmission lines:
•
•
•
Connectors (dead-end compression, 4-hole pads, etc.)
Supporting Devices (Armor Grip Suspension, etc.)
Jumpers
And for substation facilities:
•
•
•
Connectors (tube to flat, expansion, etc.)
Bus work conductor (typically 4” tubing)
Jumpers (often double-conductor to preserve ratings of the circuit breaker)
In every case, these miscellaneous components are selected to assure that each
such component will not have a limiting effect on the major transmission facilities
which depend upon these components.
The normal and emergency ratings of these miscellaneous components are equal
to the normal and emergency ratings of the interconnecting breakers, switches or
transformers.
6.0
Generation Rating Methodology
JEA’s generation ratings methodology consists of unit generation real and
reactive power capabilities on a gross and net basis. JEA considers the
Emergency rating the same as the Normal rating.
6.1
Unit Generation Real Power Capabilities
The real power capability is the maximum gross and net output of the generating
unit determined based on design, test and actual operation. The ratings will be
listed as a Summer and Winter Capability.
6.1.1
Capacity Rating System
JEA documents its generator real power rating by name designation, net
and gross winter capability, net and gross summer capability, net and
gross spring/fall capability, minimum and maximum load for control
purposes.
The seasonal capability takes into account the effects of ambient
conditions, such as ambient air temperature and circulating water
temperature. The winter conditions are referenced at 24°F. The summer
conditions are referenced at 98°F.
JEA’s capability may be degraded due to operation deficiencies that effect
actual capability or environmental heat input limitations. If the
degradation is short term (less than one year); the rating will not be
changed. If the degradation is long term (greater than one year); a new
capability will be determined and the unit capability document will be
updated.
6.1.2
Unit Design Capability
Initially, the rated capability is based on the original design capability.
This design capability may change due to repowering, performance
upgrades, etc. The design capability will be based on the design heat
balances, engineering studies, manufacturer design information or other
material.
6.1.3
Real Power Unit Capability Testing
The rated capability based on design is the best estimate of unit
performance. This estimate is replaced with data generated from a
capability test as soon as practical after initial construction, repowering or
upgrade.
6.1.4
Real Power Construction, Repowering or Upgrade
After initial construction, repowering or upgrade, the capability test will
be done in accordance with the guarantee test procedure as agreed upon by
the contractor and the JEA. If this testing does not determine the
capability of the unit, additional testing will be performed to determine the
new capability.
6.1.5
Real Power Capability Test
Full load capability is often demonstrated to meet system demand. This
data is collected and compared to the published capability. Any
deficiencies will be noted and determined if they are short term or long
test degradation. Long term degradations will change the capability rating
in the unit capability document. If full load capability was not
demonstrated in the previous twelve months, a capability test shall be
performed to demonstrate capability.
6.2
Unit Generation Reactive Power Capabilities
The reactive power capability is the maximum gross and net output of the
generating unit determined based on design, test and actual operation based on
leading and lagging power factor and maximum and minimum real power output.
6.2.1
Reactive Power Rating System
JEA documents its generator reactive power rating by name designation,
Maximum Lagging Reactive Power at Maximum Real Power, Maximum
Leading Reactive Power at Maximum Real Power, Maximum Lagging
Reactive Power at Minimum Real Power and Maximum Leading Reactive
Power at Minimum Real Power. JEA rates the Summer and Winter
reactive capability the same.
JEA’s reactive capability may be degraded due to operation deficiencies
that effect actual reactive capability. If the degradation is short term (less
than one year); the rating will not be changed. If the degradation is long
term (greater than one year); a new capability will be determined and the
unit capability document will be updated.
6.2.2
Unit Reactive Power Design Capability
Initially, the rated reactive capability is based on the original design
capability consisting of generator capability curves at rated power factor.
6.2.3
Unit Reactive Testing
The rated reactive power capability, based on JEA’s Bulk Power
Operations Procedures, NERC Standards or FRCC Guidelines, may be
tested to verify rated capability. Based on the test, the rated capability will
be handled as follows:
•
•
7.0
If the transmission system cannot accept full reactive capability the
ratings will not change
If the transmission system can accept full reactive capability the
ratings will be replaced with data generated from a test as soon as
practical and the Plant Director will initiate a plan to bring the unit to
full reactive capability
Establishing and Communicating of Transmission and
Generation Facility Ratings
Based on the methodology contained in this document, transmission and
generation facilities shall be updated and published based the addition of new
facilities, existing facilities, modifications to existing facilities and re-ratings of
existing facilities.
JEA Bulk Power Operations shall forward a completed ratings report to Electric
System Planning.
JEA Bulk Power Operations shall incorporate the ratings into JEA’s operational
models and communicate to FRCC as set forth by FRCC Data Sharing and
Modeling, Coordination and Communication Requirements (ie, equipment status
report) the changes to JEA’s ratings. This ensures all operating entities are aware
of the changes.
JEA Electric System Planning shall incorporate the ratings into JEA’s planning
models and communicate to FRCC per the annual FRCC databank work the
changes to JEA’s ratings. This ensures all planning entities are aware of the
changes.
SIGNED:
GARRY BAKER
EFFECTIVE DATE:
Revision #
0
3
4
5
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Date
5/6/2002
10/6/2005
10/10/2006
6/12/2007
3/1/2008
11/1/2009
8
6/1/2011
Description
Creation
Reviewed
Reviewed
Reviewed
Reviewed
Reviewed and
Updated
Added Winter
Ratings and
Updated
Emergency
Ratings
11/1/2009
Revised By
LCR
TDW
TDW
TDW
WGB
WGB
Approval
VAB
VAB
VAB
VAB
WGB
WGB
WGB
WGB