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Facility Rating Methodology

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Facility Ratings Methodology

FAC-008-3 Compliance Document

Establishment Date: December 19, 2016

Effective Date: July 14th, 2017

Approved by:

Job Title Name

Manager, Network & IRP Transmission Planning

Sachin Verma

Version:1 0.5

1 The Facility Ratings Methodology (FRM) was established on December 19, 2016, and is subject to change based on new information and input collected during NV Energy Facility Ratings data collection.


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Contents

Scope ............................................................................................................................................................................. 4

Overview ................................................................................................................................................................... 4

Hierarchy of Reference Sources for Manufacturer/Nameplate Ratings ................................................................... 4

Determination of Most Limiting Facility .................................................................................................................... 4

Jointly-Owned Facility Ratings................................................................................................................................... 5

Procedures for Ring and Breaker-and-a-Half Bus Configurations ............................................................................. 5

Procedures for Non-standard Bus Configurations .................................................................................................... 5

Methodology ................................................................................................................................................................. 6

Transmission Line Conductor - [TRANSMISSION PLANNING].................................................................................... 6

Underground Cable Ratings .................................................................................................................................. 8

Transformers – [TRANSMISSION PLANNING] .......................................................................................................... 10

Shunt Compensation Devices [SUBSTATION DESIGN] ............................................................................................ 12

Series Compensation Devices [SUBSTATION DESIGN] ............................................................................................ 13

Circuit Breakers/Circuit Switchers [SUBSTATION DESIGN]...................................................................................... 14

Bus [SUBSTATION DESIGN] ...................................................................................................................................... 15

Jumpers [SUBSTATION DESIGN] .............................................................................................................................. 17

Disconnect Switches [SUBSTATION DESIGN] .......................................................................................................... 18

Line Switches [TRANSMISSION ENGINEERING] ....................................................................................................... 19

Current Transformers (CTs) [SUBSTATION DESIGN & SYSTEM PROTECTION] ........................................................ 20

Control Cables and Wiring [SUBSTATION DESIGN] ................................................................................................. 21

Protective Relay Devices [SYSTEM PROTECTION] ................................................................................................... 22

Wave Traps [SUBSTATION DESIGN] ........................................................................................................................ 24

Facility Rating Communication ................................................................................................................................... 25

Reliability Coordinator Communication .................................................................................................................. 25

Neighboring Entities ................................................................................................................................................ 25

Communication of Thermal Rating Incursions ........................................................................................................ 25

Change Control Process .............................................................................................................................................. 26

Facility Ratings Methodology .................................................................................................................................. 26

Facility Ratings Data/Spreadsheet .......................................................................................................................... 26

Facility Ratings Updates – SharePoint Workflow .................................................................................................... 30

Example Workflow .............................................................................................................................................. 31

Version History ............................................................................................................................................................ 33

Appendix A - Analysis of Weather Assumptions .......................................................................................................... 34

Appendix B - Standard Conductor Ratings................................................................................................................... 37

Appendix C – NV Energy MOT Conductor Ratings ....................................................................................................... 41


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Appendix D – Aluminum Conductor Bus Ratings (Classes AA and A) .......................................................................... 42

Appendix E - Standard Bus Ratings .............................................................................................................................. 44

Appendix F – Control Cable Ratings ............................................................................................................................. 45

Appendix G – NVE Jointly-owned Facility Rating Data Request .................................................................................. 46


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Scope Overview This document provides NV Energy’s methodology for developing and communicating Facility Ratings of its solely

and jointly-owned Facilities. This document defines the basis for the calculation of normal and emergency ratings

of NV Energy Bulk Electric System (BES) Facilities, to comply with the requirements of NERC Reliability Standard FAC-

008-3.

NV Energy’s Transmission Planning department has primary responsibility for developing and maintaining the Facility

Ratings and methodology, beyond the Generator Step-up (GSU) Transformer high-side bushings2. Facility Ratings

collection is a collaborative effort between multiple NV Energy departments: Substation Construction and

Maintenance, Substation Design, System Protection, Transmission Civil Engineering and Construction, and

Transmission Planning. The NV Energy Generation department maintains primary responsibility for developing

Facility Ratings for Generation Facilities and equipment up to the high-side bushings of the GSU3.

NV Energy’s transmission system is designed such that the high-side bushings of the GSU are the point of

interconnection between the Generator Owner and the Transmission Owner. Given that there are no Facilities

between the generation Facilities and the point of interconnection with the Transmission Owner, NV Energy, by

definition does not own or operate Facilities addressed under Requirement 2. Procedural documents and Element

data association with Generation Facilities are owned and maintained by the NV Energy Generation department.

Hierarchy of Reference Sources for Manufacturer/Nameplate Ratings Several reference sources will be used to establish equipment ratings based on manufacturer or nameplate ratings. The following list establishes a hierarchy of reference sources used when establishing equipment nameplate or manufacturer ratings. 1) Manufacturer data or correspondence 2) Nameplate drawing or image 3) Engineering single line diagram 4) Other engineering drawings (plan view, section views, bill of materials, etc.) 5) Purchase Orders The highest ranked resource known at the time the rating is established will be used in establishing the equipment

rating.

Determination of Most Limiting Facility The NERC defined term, Facility, is “a set of electrical equipment that operates as a single Bulk Electric System

Element.” In addition, the NERC defined term, Element, is “any electrical device with terminals that may be

connected to other electrical devices such as a generator, transformer, circuit breaker, bus section, or transmission

line. An Element may be comprised of one or more components.”

Elements in series, which make up a Facility (line section, substation transformer circuit, shunt reactive device), will

be reviewed to determine which Element(s) have the most limiting rating. NV Energy’s Facility Rating shall respect

the most limiting applicable Equipment Rating of the individual equipment that comprises that Facility4.

2 FAC-008-3 R6 3 FAC-008-3 R1 4 FAC-008-3 R3.3


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If information is received suggesting that a more limiting Element exists on a Facility, NV Energy will take steps to

verify the information, which may include field inspections. Once review and field verification, (if applicable) is

complete, NV Energy will take steps to mitigate any differences identified for either the Facility normal rating or

Facility emergency rating.

Jointly-Owned Facility Ratings In cases where a BES Facility is shared with an external entity (such as a line terminal being owned by one party

and the line conductor by another party), NV Energy takes into account rating data provided by the owner(s) of the

segment(s) of the Facility and applies the most limiting rating as the rating of the Facility. The communication

process for requesting these ratings can be found in the Establishment and Communication of Facility Ratings

section of this Methodology.

In cases where a Facility is jointly owned (such as two owners each owning an undivided 50% ownership interest in

a Facility), the operator of the Facility determines the Facility rating and shares this rating information with the

other joint owners.

Procedures for Ring and Breaker-and-a-Half Bus Configurations In the event that a line section or bulk power transformer terminates on a substation configured as a ring bus or a

breaker-and-half, the facility rating for long-range planning models will be determined assuming a closed ring bus

or closed breaker-and-a-half. The most limiting facility rating of the entire ring bus or the most limiting facility

rating of the breaker positions adjacent to the line section or bulk power transformer in a breaker-and-a-half

scheme are considered in determining the rating of the line section or bulk power transformer. In order to account

for the flow split when entering a closed ring or closed breaker-and-a-half, a multiplier is used to adjust the ratings

of the ring bus or breaker-and-a-half facilities. The multiplier assumes a split of 50%-50%, meaning that 50% of the

line section flow or bulk transformer flow is assumed to be transferred onto one leg of the ring bus or breaker-and-

a-half. This results in the ring bus or breaker-and-a-half limit (including breakers, switches, and jumpers) being

adjusted by 200% to account for the flow split of a closed ring or a closed breaker-and-a-half.

Procedures for Non-standard Bus Configurations In the event that a bulk power transformer terminates on a substation not configured in a ring bus or a breaker-

and-half, the facility rating for long-range planning models will still be determined assuming a configuration with

all breakers closed. In order to account for the flow split when entering, the non-standard configuration, a

summation of the connected breaker ratings (Breaker A + Breaker B….+ Breaker N = Facility Rating) multiplied by a

safety factor of .75, is used to adjust the ratings of transformer facilities.


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Methodology5 Transmission Line Conductor - [TRANSMISSION PLANNING]

Background

NV Energy’s original “Legacy” ratings for Northern Transmission Lines were based on values in the Westinghouse

Transmission & Distribution Reference books.

For the Northern system, lines will keep their “Legacy” ratings until Maximum Operating Temperatures (MOTs) are

known (pending completion of LiDAR analysis). Once MOTs are known, the ratings will be re-calculated based on

the IEEE 738 assumptions in this report.

Most of the lines in Southern Nevada have LiDAR verified MOT information available. In absence of LiDAR MOT or

verified DOT information, it is assumed that the line meets clearance requirements, and can operate up to the

maximum conductor temperature. The ratings for these lines are determined based on RateKit IEEE738

calculations using standard weather assumptions for that region, and the conductor’s MOT.

In the Northern System, NV Energy previously had the underground cable manufacturer perform the design based

on information provided to them. The manufacturer then provided NV Energy a rating for the complete line design

as it was to be constructed in the field.

Lead lines connected from the high-side bushing of the GSU, are designed not to be limiting Elements for the

operation of the GSU or the Transmission Line Facility.

Procedure

NV Energy uses the following procedure to determine ratings on overhead conductors.

LiDAR MOT?

Confirmed DOT?

Is there a Westinghouse Rating available for the conductor?

Run Ratekit with Conductor MOT

No

NoNo

Westinghouse Ratings

Yes

Is this line on an exception list in NVE’s FAC-008-3 Policy?

No

Yes

Run RateKit with the Exception Weather Parameters in the Policy.

Run Ratekit with the Standard North or South rating parameters.

No Yes

Yes

North or South?

North

Run Ratekit with Conductor MOT

South

NOTE: If the LiDAR Clearance MOD or DOT is above the Conductor

MOT, the lower is used.

Figure 1: Conductor Rating Procedure

5 FAC-008-3 R3


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Switches are included in the line facility rating if they meet the below flow-chart criteria.

Is the switch connected to any bus-work?

Yes

Include in Line Listing

No

Addressed in FAC-008-3 Ratings Spreadsheet

Figure 2: Procedure to Determine Switch Inclusion in Line Ratings

Normal & Emergency Current Ratings

The ratings calculated by RateKit using the weather assumptions (Appendix A) result in the “Continuous Current

Rating” of the conductor. NV Energy uses an emergency rating for conductor equal to the normal rating.

Within the NV Energy system, there are instances where dynamic ratings are used for transmission lines.

Protection of these locations are done through thermal-loading protective relaying schemes. Dynamic ratings of

transmission lines are not a common practice in NV Energy. The following lines are identified with dynamic ratings:

Line #118: Eagle – Oreana 120kV Line

Line #173: Mira Loma – Airport 120kV Line

Standard Weather Assumptions

Below are the standard weather assumptions for use in RateKit IEEE738 conductor rating calculations. Under

certain conditions, NV Energy may monitor ambient temperature and dynamically rate lines for operational

purposes.

Figure 3: RateKit Parameters

North South Laughlin

Air Temperature (°C) 40 (104F) 44.4 (112F) 48.9 (120F)

Wind Speed (Ft/Sec) 2 2 2

Wind Angle relative to conductor 90 90 90

Elevation (Ft) 5500 2000 800

Latitude (Deg N) 39 36 35

Date (Month/Day) 4-Jul 4-Jul 4-Jul

Solar Time (Hr) 17 17 17

Coefficient of Emissivity 0.7 0.7 0.7

Coefficient of Solar Absorptivity 0.8 0.8 0.8

Conductor Orientation (North=0) 0 0 0

Atmosphere

Conductor Type

Diameter (In)

Conductor Resistance (ohms/mi) @ 25°C

Conductor Resistance (ohms/mi) @ 75°C

MOT (°C)

Actual

Actual (or DOT)

IEEE 738 Steady State Thermal Rating Calculation Parameters

Clear


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Westinghouse & RateKit Engineering Reference

Appendix C is a list of all conductor types that NV Energy owns on 55kV or above facilities. For each conductor, the

Westinghouse Legacy Rating is included (if available). Additionally, the conductor code-name used for RateKit is

included, and RateKit ampacity ratings are calculated using the standard weather assumptions plus the conductor’s

MOT.

Laughlin Weather Assumptions (Exception)

The Laughlin Area subjects NV Energy’s lines to different conditions than those present in Vegas. For Laughlin, the

same assumptions are used as in Vegas, except for the following alterations:

Ambient Temperature: 48.9°C

Altitude: 800 feet

Latitude: 35°

This exception applies to the following list of lines:

Laughlin - Mohave 500kV #1

Laughlin - Mohave 500kV #2

Laughlin - Southpoint 69kV

Laughlin - River Road 69kV

Laughlin - Big Bend 69kV

River Road - Kidwell 69kV

Southpoint – Big Bend 69kV

Kidwell – Searchlight 69kV

Underground Cable Ratings For NV Energy, the normal rating will be ampacity that produces a conductor temperature of 90⁰C. A four hour

emergency rating may be applied if needed to meet contingencies; the emergency rating shall be equal to the

ampacity that will produce a conductor temperature of 105⁰C.

NV Energy designs and constructs the underground cable system duct-bank around physical space constraints such

as highways, parallel transmission lines sewer and water lines, or other subsurface utilities. The rating may be

calculated using a program called Cymcap or may be based on outside consultant’s engineering study, or cable

manufacturer provided data.

Initial design takes into account the ampacity requirement, and what short circuit ratings are necessary

from the underground cable system.

If necessary, parallel cables may be placed in the same duct bank.

CYMCAP is then used to rate the ampacity of the cable using:

o Cable system design and/or “As Built” conditions.

o Cable information from manufacturer.

o Concrete thermal data.

o PVC pipe thermal data.

o NV Energy utilizes thermal conductivity of the soil for ampacity calculations. If unavailable,

typical data may be utilized.

o The software considers crossover points for underground mutual heating.

o 90⁰C/105 ⁰C Normal/Emergency is the maximum operating temperature assumed for

underground cable.


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If necessary, outside consultants may be engaged to conduct an ampacity study for a specific cable

installation. This study may use CYMCAP software, or other software that may be proprietary to the

consultant.

Assumptions

Conductor Rating Methodology Summary Table

FAC-008 R3.1 Methodology Used 1) Industry Standard 2) Equipment Manufacturers

FAC-008 R3.2.1 Standard Used ANSI/IEEE Standard 738 Method of Calculation

FAC-008 R3.2.2 Manufacturers Ratings Westinghouse Ratings (See Appendix B)

FAC-008 R3.2.4 Ambient Conditions See ‘Standard Weather Assumptions’ above

FAC-008 R3.2.4 Operating Limitations N/A


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Transformers – [TRANSMISSION PLANNING]

Procedure

NV Energy will use the manufacturer’s transformer nameplate rating to determine normal and emergency current

ratings.

Normal Ratings

For each winding on a transformer, NV Energy uses the maximum nameplate MVA rating as the Normal rating for

that particular winding, unless a detailed engineering study has shown that the transformer needs to be de-rated

below this value.

Emergency Ratings

In general, NV Energy utilizes the following priority list for selecting transformer ratings:

1. Manufacturer provided 2-hour thermal MVA ratings.

2. 2-hour thermal ratings based on a detailed engineering study, as detailed in the following section:

Emergency Load Rating Methodology.

3. In the absence of other information, NV Energy will use a default 2-hour rating equal to 120% of the

maximum nameplate value.

In situations where known operational response time is shorter than 2-hours (for example 30-minutes) such

ratings may be used with comments indicating the timeframe in the Facility Ratings spreadsheet.

The default emergency 2-hour rating of 120% is based on ANSI C57.92-1981, Tables 3(m)(n)(p). The emergency

rating assumes 70% initial load or lower (see Figure below).

Legacy Transformer Emergency Ratings


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Application of Transformer Facility Ratings (For System Modeling Purposes)

A Target Operational Nominal kV Base (for example 525kV) is provided in the Facility Ratings Spreadsheet.

Two categories of ratings are considered for each winding when applying Transformer Facility Ratings to models:

Transformer Rating o Transformers in NV Energy’s system will be rated in terms of MVA (as opposed to Amps).

Connected Equipment Rating o All connected amp-limited equipment will be identified with a rating in Amps. o The minimum Amp rating is the total rating of the Connected Equipment. o The Amp rating, on the Operational kV Base, provides an MVA rating for the Connected

Equipment. The minimum MVA rating of these two is the total Facility Rating for a Transformer Winding.

Emergency Load Rating Methodology

For detailed engineering studies on transformer ratings, the loading capability will be calculated utilizing the EPRI

PTLOAD (Version 6.1) computer program which models/simulates the electrical and thermal properties of the

transformer. The calculations are based on a 113 degree maximum 24 hour ambient temperature provided by

weather service hourly data and typical 24 hour load cycle profiles provided by Transmission and Distribution

Planning and System Operations with all existing cooling fans or pumps in continuous operation.

For each calculation, the maximum allowable values of winding temperature (hot spot), top oil temperature, and

Acceptable Loss of (transformer) Life of insulation were specified. Specific test parameters associated with each

transformer were used, including heat run (temperature rise data), load and no load losses, core and coil weight,

gallons of oil, etc.

Emergency rating limitations are based upon a 2 hour period: Hot Spot and Top Oil temperature limitations of

140C and 110C respectively in addition to other limiting parameters described below. Acceptable Loss of Life of

0.04% is considered along with a typical 24 hour load cycle preload.

Assumptions

Transformer Rating Methodology Summary Table

FAC-008 R3.1 Methodology Used Manufacturer’s nameplate and Engineering Analysis

FAC-008 R3.2.1 Standard Used IEEE C57.91 – 2011 IEEE C57.92 - 1981

FAC-008 R3.2.2 Manufacturers Ratings Nameplate rating

FAC-008 R3.2.4 Ambient Conditions 65 Degree C Rise



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Shunt Compensation Devices [SUBSTATION DESIGN]

Background

NV Energy has Shunt Reactors and Shunt Capacitors within its system.

Procedure

The normal rating shall be the continuous rating provided by the equipment manufacturer or obtained from

manufacturer specifications such as the top nameplate rating of the capacitor, reactor, or that of the most limiting

device (e.g., a disconnect switch) in the series circuit for series compensation or in the shunt circuit for shunt

compensation.


Normal and Emergency current ratings are equivalent.

Assumptions

Shunt Devices Rating Methodology Summary Table

FAC-008 R3.1 Methodology Used Manufacturer’s Nameplate Rating

FAC-008 R3.2.1 Standard Used N/A

FAC-008 R3.2.2 Manufacturers Ratings Manufacturer’s Nameplate Rating

FAC-008 R3.2.4 Ambient Conditions N/A



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Series Compensation Devices [SUBSTATION DESIGN]

Background

NV Energy only has Series Capacitors within its system. NV Energy does not have Series Reactors within its system.

Procedure

The normal rating shall be the continuous rating provided by the equipment manufacturer or obtained from

manufacturer specifications such as the top nameplate rating of the capacitor, reactor, or that of the most limiting

device (e.g., a disconnect switch) in the series circuit for series compensation or in the shunt circuit for shunt

compensation.



Assumptions

Series Capacitor Rating Methodology Summary Table

FAC-008 R3.1 Methodology Used Manufacturer’s Nameplate Rating


FAC-008 R3.2.2 Manufacturers Ratings Manufacturer’s Nameplate Rating




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Circuit Breakers/Circuit Switchers [SUBSTATION DESIGN]

Background

In some locations in Northern Nevada and Southern Nevada, Power Circuit Breakers have breaker bypass switches

installed. These switches are designed for providing a current path during maintenance of the circuit breaker.

Operationally, NV Energy will only use breaker bypass switches in as-needed emergencies. Bypass switches are

rated at the same current as the connected circuit breaker, unless otherwise noted in the Facilities Rating

spreadsheet.

Procedure

Nameplate Ratings are used for circuit breakers and circuit switchers, unless the manufacturer provides specific calculations. These are based on the current ANSI, NEMA, and IEEE Standards. Circuit breakers in the SPPC system are rated at 40° C ambient temperature as per the latest version of IEEE C37.04. Circuit breakers in the NEVP system are designed to have a continuous current rating at 50° C ambient temperature.


Normal and Emergency ratings are equivalent to nameplate unless the manufacturer provides specific normal and

emergency ratings.

Assumptions

Circuit Breaker Rating Methodology Summary Table

FAC-008 R3.1 Methodology Used Manufacturer’s nameplate rating

FAC-008 R3.2.1 Standard Used IEEE C37.04

FAC-008 R3.2.2 Manufacturers Ratings Manufacturer’s nameplate rating

FAC-008 R3.2.4 Ambient Conditions 40° C for SPPC; 50°C for NEVP



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Bus [SUBSTATION DESIGN]

Background

Presently for Transmission Line conductors, for SPPC, lines will keep their “Legacy” ratings until Maximum

Operating Temperatures (MOTs) are known (pending completion of LiDAR analysis). Once MOTs are known, the

ratings will be re-calculated based on the IEEE 738 assumptions in this report.

Most of the lines in NEVP have LiDAR verified MOT information available.

In order to maintain consistency with similar conductor types used for lines, substation bus conductor ratings will

be the same as transmission line conductors.

Procedure

Bus Conductor

Bus conductor located in SPPC substations will use the Westinghouse ratings located in Appendix B as an initial

rating.

Bus Conductor located in NEVP substation will use ratings based on Conductor MOT’s, calculated from IEEE 738

calculations and weather assumptions for the South. These values are shown in Appendix C.

Bus Conductor used in NEVP substations that do not have a Conductor MOT listed in Appendix C, will use ratings

from Standard Handbook for Electrical Engineers (13th Ed.), D. Fink &H.W. Beaty Eds., McGraw-Hill, Aluminum

Conductor – Physical Characteristics, Classes AA and A, Table 4-22, (Appendix D)

Aluminum Bus

Bus Ratings for both NEVP and SPPC shall be based on Table 13-27 from Aluminum Electrical Conductor Handbook

(3rd Ed.), L. Kirkpatrick. The current ratings selected should use the values for Schedule 40 pipe for Aluminum

6063-T6 Temper located in Appendix E6.

GIS Bus

Bus Ratings for both NEVP and SPPC shall be based on Manufacturer’s Specifications.


NV Energy uses an emergency rating for all bus types equal to the normal rating.

6 http://www.aflglobal.com/productionfiles/resources/catalogs/afl-substation-bus-conductors

http://www.aflglobal.com/productionfiles/resources/catalogs/afl-substation-bus-conductors


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Assumptions

Bus Conductor

Weather assumptions used for IEEE738 Transmission Line Conductor calculations are the same assumptions used

for Bus Conductors.

For bus conductors used in NEVP substations that do not have a Conductor MOT listed in Appendix C, The

following conditions will be assumed: 40°C Rise over 40°C Ambient with 2.0 ft/sec crosswind, 0.5 emissivity factor,

without sun.

Jumper Rating Methodology Summary Table

FAC-008 R3.1 Methodology Used 1) Equipment Manufacturers 2) Industry Standard



FAC-008 R3.2.4 Ambient Conditions See Transmission Line Conductors Ambient Conditions

FAC-008 R3.2.4 Operating Limitations Not Applicable

Aluminum Bus

Per NV Energy’s Substation Material Standard SB-6, Aluminum Bus shall be designed to meet standard ASTM

B241/B241M using a material of Seamless Aluminum 6063-T6 temper, produced from hollow extrusion ingrot and

extruded by use of the die and mandrel method. Weather assumptions match the assumptions used by AFL

Global: 30 degree C rise over 40 degree C ambient, horizontally mounted conductors, with spacing sufficient to

eliminate proximity effects, 2 ft./sec crosswind, nominal oxidized surface (e=0.50).

Bus Rating Methodology Summary Table

FAC-008 R3.1 Methodology Used Manufacturers Rating

FAC-008 R3.2.1 Standard Used Not Applicable

FAC-008 R3.2.2 Manufacturers Ratings Manufacturer’s Specifications provided by AFL Global

FAC-008 R3.2.4 Ambient Conditions 30 degree C rise over 40 degree C ambient, horizontally mounted conductors, with spacing sufficient to eliminate proximity effects, 2 ft./sec crosswind, nominal oxidized surface (e=0.50).



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Jumpers [SUBSTATION DESIGN]

Background

Currently at SPPC, Transmission Line conductors, will keep their “Legacy” ratings until Maximum Operating

Temperatures (MOTs) are known (pending completion of LiDAR analysis). Once MOTs are identified, the conductor

ratings will be re-calculated based on the IEEE 738 assumptions in this report.

The majority of the lines owned by NEVP have LiDAR-verified MOT information available.

In order to maintain consistency with similar conductor used for lines, substation jumper ratings will be identified

as the same as transmission line conductors.

Procedure

As an initial rating, jumpers located in SPPC substations will use the Westinghouse ratings located in Appendix B.

Jumpers located in NEVP substations, will use ratings based off of Conductor MOT’s, calculated from IEEE 738

calculations and weather assumptions for the South. These values are shown in Appendix C.

Jumpers used in NEVP substations that do not have a Conductor MOT listed in Appendix C, will use ratings from

Standard Handbook for Electrical Engineers (13th Ed.), D. Fink &H.W. Beaty Eds., McGraw-Hill, Aluminum

Conductor – Physical Characteristics, Classes AA and A, Table 4-22, , Pg. 4-59


NV Energy uses an emergency rating for jumpers equal to the normal rating.

Assumptions

Weather assumptions used for IEEE738 Transmission Line Conductors calculations are the same assumptions used

for jumpers.

Jumper Rating Methodology Summary Table

FAC-008 R3.1 Methodology Used 1) Equipment Manufacturers 2) Industry Standard



FAC-008 R3.2.4 Ambient Conditions See Transmission Line Conductors Ambient Conditions



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Disconnect Switches [SUBSTATION DESIGN]

Procedure

For switches manufactured under the ANSI standards, the normal rating shall be the rating provided by the

manufacturer or obtained from the manufacturer specifications such as the nameplate rating of the switch.

The ANSI temperature rise is based on the allowable temperature rise in ANSI C37.37 for the specific switch

contact material utilized in the switch (e.g., copper/copper alloy or aluminum).

In some instances, if no manufacturer’s drawing(s) or nameplate information was available, an assumed rating of

600 amps for the disconnect switch was used for these instances. This assumption is based on the known

information for existing disconnect switch ratings offered by NVE vendors, and manufacturers.



Assumptions

Substation Disconnect Switch Rating Methodology Summary Table

FAC-008 R3.1 Methodology Used Equipment manufacturer

FAC-008 R3.2.1 Standard Used ANSI IEEE C37.37

FAC-008 R3.2.2 Manufacturers Ratings Nameplate rating

FAC-008 R3.2.4 Ambient Conditions 40°C



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Line Switches [TRANSMISSION ENGINEERING]

Background

NV Energy has transmission line switches in operation from several manufactures with widely varying

manufacturer dates, configuration types, voltage classes and current ratings. In general, NV Energy has required

the switch manufacturers to provide switches that been rated by applicable ANSI and IEEE standards. Therefore,

NV Energy uses the current rating provided on the final drawings or nameplate.

Procedure

For switches manufactured under the ANSI standards, the normal rating shall be the rating provided by the

manufacturer or obtained from the manufacturer specifications such as the nameplate rating of the switch.

For the Northern System, if no nameplate is available then the switches should be assumed to be rated for 600

amps, which is the lowest rating that is available in a line switch.


Normal and Emergency ratings are equivalent.

Assumptions

Transmission Line Switch Rating Methodology Summary Table

FAC-008 R3.1 Methodology Used Ratings provided by equipment manufacturers through drawings or nameplates. NV Energy requires to manufacturers to determine rating based on several ANSI/IEEE standards.

FAC-008 R3.2.1 Standard Used ANSI C29.8, ANSI C29.9, IEEE C37.30, ANSI C37.32, IEEE C37.37

FAC-008 R3.2.2 Manufacturers Ratings Manufacturer’s Information

FAC-008 R3.2.3 Ambient Conditions -40°C to 50°C based on current specification.

FAC-008 R3.2.4 Operating Limitations N/A.


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Current Transformers (CTs) [SUBSTATION DESIGN & SYSTEM PROTECTION]

Background

The standard nominal rating of all CTs in the NVE system is 5 A secondary. The primary CT rating is part of the

major equipment specifications of which the CTs are a part. For example, a 2000 A rated circuit breaker would

typically include 2000:5 multi-ratio bushing CTs, unless specified otherwise. Multi-ratio CTs use standard tap

ratios, as listed in IEEE C57.13-2016, Table 11 (or its successor).

Continuous overload thermal rating factors will be applied to tapped windings per manufacturer’s data and

recommendations. The thermal rating factor (TRF) allows multiplication of secondary current rating by the

specified value (1.0, 1.33, 1.5, 2.0, 3.0, or 4.0).

Procedure

For calculation of CT ratings, if the thermal rating factor is available, NVE will use this value. If a CT rating factor is

unknown, NVE will assume a TRF = 1.0.

For CTs, with tapped windings not set on the highest available tap, a continuous overload rating will be calculated

based on the methodology created by PJM Interconnection, and documented within PJM article VI.C “Circuit

Breakers” and PJM article VI.F “Current Transformers”.

Itap = Adjusted rated continuous current of specific current transformer tap under consideration

Ir = Rated continuous current (current transformer nameplate rating)

Itapr = Rated continuous current of specific current transformer tap under consideration

RF = Continuous thermal current rating factor

n = 2; NV Energy will always use the more conservative value of “2” (Circuit Breaker “n” equals 1.8) for rating CTs

Auxiliary CT’s

For those instance where auxiliary CT’s are used, the auxiliary CT will always be rated at TRF = 1.0


Normal and Emergency ratings are equivalent.

Assumptions

Current Transformer Rating Methodology Summary Table

FAC-008 R3.1 Methodology Used PJM Method, see above Engineering Analysis


FAC-008 R3.2.2 Manufacturers Ratings Manufacturer’s Specifications

FAC-008 R3.2.4 Ambient Conditions See Standard Weather Assumptions under T-Line Conductor



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Control Cables and Wiring [SUBSTATION DESIGN]

Background

NV Energy substation design recommended practices specify installation of 12 AWG through 8 AWG for control

leads and current transformer secondary leads.

Procedure

The smallest CT cable from the CT through the CT circuit will be used as the limiting rating for the CT cable. In

instances where the CT cable is unknown, 12AWG will be assumed.

Ratings of the cable type can be determined by the NEC Table 310.15(B)(16) Allowable Ampacities of Insulated

Conductors… (Appendix F).

In instances where there is an auxiliary CT in a CT circuit, if the auxiliary CT ratio decreased the current then the

cable rating will be determined by multiplying the cable rating by the primary CT ratio. If the auxiliary CT ratio

increases the current, then the rating of the cable should be adjusted by multiplying the cable rating by the

auxiliary CT ratio and the primary CT ratio.



Assumptions

CT Cable Rating Methodology Summary Table

FAC-008 R3.1 Methodology Used Industry Standard

FAC-008 R3.2.1 Standard Used NEC Table 310.15(b)(16) Allowable Ampacities of Insulated Conductors

FAC-008 R3.2.2 Manufacturers Ratings N/A




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Protective Relay Devices [SYSTEM PROTECTION]

Background

NV Energy System Protection maintains a philosophy for new protective relay installations, or revisions to existing

protective relaying packages, to use Schweitzer Engineering Laboratories (SEL) microprocessor relays. The model of

the SEL relay selected is based on the specific application requirements.

Previous protective relaying philosophy, required installation of various relay equipment types and manufacturers,

based on precedence, education, and technology available. Regardless of philosophy, Substation relays and

protection control equipment match or exceed the 5A secondary current transformer Ratings used by NV Energy.

Procedure

NV Energy uses the manufacturer’s standard equipment ratings for relays that require AC current to operate.

Additionally, NV Energy System Protection personnel will determine the specific relay AC current ratings by

referencing the manufacturer’s instruction manuals, or by using a conservative assumption of 10 A. For instances

where currents from multiple CT’s are summed together and then go to a relay (such as for a high impedance

differential relay), the current seen by the relay during load conditions would nominally be zero. As such, the

ratings for these relays should not be considered.

In instances where there is an auxiliary CT in a CT circuit, if the auxiliary CT ratio decreased the current then the

relay rating will be determined by multiplying the relay rating by the primary CT ratio. If the auxiliary CT ratio

increases the current, then the rating of the relay should be adjusted by multiplying the relay rating by the

auxiliary CT ratio and the primary CT ratio.

For facilities subject to NERC Standard PRC-023, Criteria 1 may be used to ensure adequate margin between the

facility rating and the relay trip setting. For facilities subject to NERC Standard PRC-023 which are using a different

Criteria or facilities not subject to NERC Standard PRC-023, best efforts are made to set the trip points above the

facility ratings. In instances where this is not possible, the relay trip setting will be the new limiting factor.


Normal and emergency ratings are the same.

Example Data Entry

To simplify the data entry process, the following process has been implemented:

Engineers first enter:

o Lowest Tapped CT Ratio

o Lowest Relay Rating

o Blank entry for “Relay CT Ratio”

By default, the spreadsheet will make the conservative assumption that the “Relay CT Ratio” is the Lowest

Tapped CT. If this causes a system limitation on the facility, the following investigation must be

performed:

o For each CT connected, multiply the CT Ratio (as found at actual tap) by the Relay Rating.

o Select the lowest multiplied value, and enter the “Relay CT Ratio” and “Relay Rating” based on

this final, lowest rated value.

Below is an example for properly entering the Relay Rating.


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Assumptions

Protective Relay Rating Methodology Summary Table

Equipment Thermal Rating Relay Settings

FAC-008 R3.1 Methodology Used Manufacturer Ratings NA

FAC-008 R3.2.1 Standard Used NV Energy purchase specifications NA

FAC-008 R3.2.2 Manufacturers Ratings Manufacturer Specifications NA

FAC-008 R3.2.4 Ambient Conditions NA NA

FAC-008 R3.2.4 Operating Limitations NA PRC-023, when applicable


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Wave Traps [SUBSTATION DESIGN]

Background

Transmission line wave traps are designed to meet ANSI and IEEE Standards, as well as other international

standards. Terminals are supplied to meet the applicable IEEE standards.

Wave trap Ratings assume a 40° C rise over a 24-hour mean ambient temperature as per the latest version of

IEEE/ANSI Standards.

Procedure

For wave traps manufactured under the ANSI standards, the normal rating shall be the rating provided by the

manufacturer or obtained from the manufacturer specifications such as the nameplate rating of the wave trap.

In some instances, if no manufacturer’s drawing(s) or nameplate information was available, an assumed rating of

800 amps for the wave trap was used for these instances. This assumption is based on the known information for

existing wave traps and the similarities to the known wave traps with ratings and the wave traps without ratings.



Assumptions

Wave Trap Rating Methodology Summary Table

FAC-008 R3.1 Methodology Used Manufacturer’s Rating

FAC-008 R3.2.1 Standard Used Not Applicable

FAC-008 R3.2.2 Manufacturers Ratings Manufacturer’s Ratings

FAC-008 R3.2.4 Ambient Conditions 40° C rise over a 24-hour



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Facility Rating Communication NV Energy Transmission Owner (and each Generator Owner subject to Requirement R2) shall provide requested

information as specified below (for its solely and jointly owned Facilities that are existing Facilities, new Facilities,

modifications to existing Facilities and re-ratings of existing Facilities) to our Reliability Coordinator, and neighboring

Planning Coordinator(s), Transmission Planner(s), Transmission Owner(s) and Transmission Operator(s).

Reliability Coordinator Communication NV Energy’s communication of Facility Ratings to the Reliability Coordinator (PeakRC) consists of coordination of

System Operating Limits (SOLs) per FAC-014, and then communication to PeakRC, our internal Transmission,

Distribution, and Network Operations groups.

The following process is to occur after revisions to Facility Ratings:

Collected Facility Ratings will be used to establish NV Energy SOLs based upon NVE’s SOL methodology

NVE will ensure that NVE established SOLs are consistent with PeakRC’s SOL methodology7

Update NVE SOLs documentation accordingly

Communicate any newly established SOL’s to PeakRC8

Communication to NVE Operations personnel of any newly established SOL’s

Updated NVE EMS to account for newly established SOL’s

Neighboring Entities NV Energy has multiple Facilities that are jointly-owned with a neighboring entity. These Facilities may also have

different ownership percentages associated with Elements that make up the Facility. Regardless of ownership

percentage, NV Energy will provide Facility Rating data upon request of the neighboring entity9.

NV Energy will also have the obligation to submit Facility Rating requests to an Entity that shares ownership of a

Facility. The NVE Transmission Planning department will be the conduit for NV Energy to request Facility Ratings

from jointly-owned Facilities. Transmission Planning will maintain a NV Energy Interconnection spreadsheet that

will contain the locations of the jointly-owned Facilities, as well as the communication information of the

personnel at the Entity that will receive the data request. Transmission Planning will submit (through electronic

mail) a request (see Appendix G), to the identified point of contact (POC) of the Entity, for ratings of the Entity-

owned Element(s) that make up the shared Facility.

Communication of Thermal Rating Incursions NV Energy will provide the information described in R8.1 within 30 calendar days (or a later date if specified by the

requester), for any requested Facility with a Thermal Rating that limits the use of Facilities under the requester’s

authority by causing any of the following:

1) An Interconnection Reliability Operating Limit

2) A limitation of Total Transfer Capability

3) An impediment to generator deliverability

4) An impediment to service to a major load center

7 FAC-011-2, FAC-014-2 8 FAC-014-2 R5.2 9 FAC-008-3 R8.1


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In addition to providing the Thermal Rating that limits the use of Facilities under the requestor’s authority by causing

any of the limitations described in 1-4 above, NV Energy will provide the identity of the next most limiting equipment

(R8.2.1) and the thermal rating (R8.2.2) of the Facility.

Change Control Process

Facility Ratings Methodology

Documentation Location

The Facility Ratings Methodology will be located on the Transmission Planning department’s SharePoint site,

within the Facility Ratings library.

Users will be granted access permissions based on need (read/write requirements), by the owner of the SharePoint

site, Manager of Network & IRP Transmission Planning and/or delegated Transmission Planning Engineer.

Review Process

This document will be reviewed by the NV Energy Transmission Planning department every 12 calendar months.

Revisions to the document can occur during the review process, or through communication of methodology

changes for Element rating data collection by Element owners. All revisions to this document will require approval

by the Manager, Network & IRP Transmission Planning.

Document Revision Notification

Upon completion of revisions to the Facility Ratings Methodology, notification of the revisions will be required to

be delivered to management personnel of the following Facility Ratings stakeholders:

Compliance & Standards

Substation Design

Substations & Technical Operations

Transmission & Distribution Operations

Transmission Planning

Transmission Civil Engineering & Construction

Facility Ratings Data/Spreadsheet

Documentation Location

The Facility Ratings spreadsheet will be located on the Transmission Planning department’s SharePoint site, within

the Facility Ratings library.

Users will be granted access permissions based on need (read/write requirements), by the owner of the SharePoint

site, Manager of Network & IRP Transmission Planning and/or delegated Transmission Planning Engineer.

Review Process

This spreadsheet will be reviewed annually as part of the Technical Assessment, conducted by the Senior

Compliance Engineer in Compliance & Standards. Findings from the review will be delivered to the Manager,

Network & IRP Transmission Planning, and a corrective action plan and timeline will be requested for any findings

that require revisions to the spreadsheet.

Additionally, it is the responsibility of the Element owners to review this spreadsheet at their own discretion.

Ongoing review by the Element owners will ensure the spreadsheet will contain correct Facility Rating data.


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Revision Notification Process

Revisions to the Facility Ratings spreadsheet will be required in the following scenarios:

Installation of a new Facility

Modifications to an existing Facility

Modifications in the Element owners methodology for establishing Rating

Modifications to an existing jointly-owned Facility

To ensure that all Element ratings are accounted for during the aforementioned scenarios, it will require the

diligent effort of all Element owners to maintain consistent communication with Transmission Planning on the

occurrence of these scenarios.

Installation of a New Facility

The process for data collection for new predicted installations of Elements will begin and close with Transmission Planning. Transmission Planning will be the single point of data entry for Facility Ratings for new installations. Transmission Planning personnel will update the Facility Ratings spreadsheet, upon receipt of a completed Facility Ratings installation form (referred to as the “Form”). Upon completion of revisions, identified NV Energy Facility Ratings stakeholders will be notified of the changes. The Form will live throughout the lifetime of a project, and all document-required data will be completed by project stakeholders (if necessary) at the close of the project. Data entry and management roles and responsibilities are as follows:

1. Initial data entry would be completed by Transmission Planning, on what the existing Facility Ratings are for projected connections, and what the Facility must be rated for

2. The Project Manager’s responsibility is to verify that stakeholders have provided Element data to Transmission Planning by the close of a capital project.

3. Data should be communicated to Transmission Planning through a completed Form(s), or other mutually agreed upon format, by close of pre-energization meeting(s) by the Project Manager or Facility Rating stakeholder.

4. Project Managers also have the responsibility of notifying EIM and/or Transmission Technology Engineers of projected Facility ratings. Information is required for updates to NVE EMS network model, and quarterly CAISO model updates.

5. It is the responsibility of the Facility Rating stakeholders to verify that data provided is correct within the Form(s), or other mutually agreed upon format, to the Project Manager and/or Transmission Planning.

6. Substation Design will then fill in the Form with their ratings, as determined by procured material for the project. This will include the majority of elements within the Form.

7. System Protection will provide tapped CT Ratio, Relay Thermal Rating, and Loadability to the Form 8. Transmission Engineering will provide transmission line parameters to the Form. Line parameter data will be

used for MOT calculations completed by Transmission Planning, prior to data entry in the Facility Ratings spreadsheet.

9. Substation Construction & Maintenance will provide the final verification of the data on the Form. Substation Construction will verify that installed equipment matches the equipment identified within the Form. Any incorrect information will be identified, and revised on the document by Substation Construction & Maintenance personnel.

10. If Transmission Planning identifies any issues with the data in the Form, they will provide corrective action requests to identified stakeholder personnel

Modifications to an Existing Facility

The assumption is that instances of “modifications” to existing Facilities would occur due to an unpredictable

occurrence (i.e. identified while doing maintenance, an outage, or other emergencies). For all modifications to


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Facilities conducted through planned and managed scheduled projects, please refer to the processes in the

Installation of a New Facility.

The key to capturing necessary data through an unpredictable occurrence is to document the occurrence and necessary processes required for the installation. The identified responsible parties for data collection are Substation Construction & Maintenance, System Protection, and Transmission Lines, as their equipment and field personnel would be more than likely affected by unpredictable events and immediate Element installation. Field personnel from these departments would be required to document the ratings (and other identifying data) of the equipment that is being installed. This ratings information should be entered directly into the Form, or through another mutually agreeable format.

For unplanned equipment installation, Substation Construction & Maintenance and System Protection personnel will replace the equipment with similar equipment; however, in the event that similar equipment is unavailable, it is the responsibility of field personnel to document the installation of unlike equipment for delivery to Transmission Planning for entry into the Facility Ratings spreadsheet. For unplanned maintenance of transmission lines, personal will repair the equipment with the same size conductor however, in the event that a similar conductor is unavailable and another conductor must be used in the replacement/repair, it is the responsibility of field personnel to provide the new conductor information to Transmission Engineering. Transmission Engineering will use this information to update the NV Energy PLS-CADD model (if available), and then Transmission Engineering will deliver the Element ratings to Transmission Planning. To track and process Facility Rating updates, Facility Rating stakeholders will submit their rating changes, and justification, through the Transmission Planning SharePoint site. Stakeholders will upload documentation of necessary Facility Rating changes to the Facility Ratings Update library. Manager of IRP Transmission Planning will delegate (through SharePoint work task) Transmission Planning Engineering personnel to review the rating change and justification prior to updating the Facility Ratings spreadsheet and model. Upon completion of review, the Engineer has completed his SharePoint work task, and upon closing the item out, a subsequent work task will be delivered to the Manager of Network Engineering & EIM Market Operations for review. Manager of Network Engineering & EIM Market Operations will delegate (through the same SharePoint work task) Network Engineering personnel to review the rating change and justification prior to requesting updates to the NVE EMS model.

Modifications to Element Ratings Methodology

All modifications to an Element Ratings Methodology must follow the procedures listed above in the Review

Process section of the Facility Ratings Methodology.

Any modifications to Element Ratings Methodologies that effect the rating values of the Element itself (based upon

changes in calculations, analysis, etc.), will require the associated Element owner to provide updated ratings to the

Facility Ratings spreadsheet. The notification system within SharePoint will provide other Element owners

awareness of the revisions to the spreadsheet, as well as the revisions to the Facility Ratings Methodology. In

addition, all revisions to the spreadsheet, and Methodology, must be completed with a detailed description of the

revisions with in the versioning history of the spreadsheet and Word document.

Modifications of a Jointly-Owned Facility by the Non-NVE Owner

These modifications will be initiated based upon communication from the external party that shares ownership

with NV Energy of a Facility. NV Energy will provide third-party communication of NV Energy Facility Ratings

modifications through the Transmission Planning department; however, it cannot be assumed that all Facility

modifications will be communicated from third-parties through Transmission Planning. It will be the responsibility

of all Element owners to provide communication to the Manager of Network & IRP Transmission Planning of third-

party Facility modifications that would require adjustments to currently maintained Facility Ratings.


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Upon notification of third-party Facility modifications, Transmission Planning will be the point of contact for NV

Energy for retrieving all necessary Element ratings data to update the NV Energy Facility Ratings spreadsheet.

Additional Element Owner Responsibilities

It is the responsibility of all Element owners to provide appropriate training and education on the change control

processes listed in the Methodology.


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Facility Ratings Updates – SharePoint Workflow A “Facility Ratings Updates” SharePoint library is being maintained to:

1. Store detailed documentation for every Facility Rating Update

2. Provide document versioning (e.g. for spreadsheets that get regular updates and impact ratings)

3. Give managers flexibility in tracking assignments

4. Improve transparency for compliance purposes

When a document is uploaded to the “Facility Ratings Updates” library, a SharePoint Workflow will automatically

initiate an “Approval” process on the uploaded document.

1. A task is created and an email is sent to a manager in Transmission Planning to review the item.

(A manager may complete the task, or re-assign the task)

Transmission Planning must do the following, then mark the item as “Approved”:

a. Implement the rating in the Master.SAV PSLF case, and create a “Change Log” to include in the

Master Case Corrections folder.

b. Modify the Facility Ratings spreadsheet to reflect the update.

2. Once TP marks the item as “Approved”, the task is assigned to Operations, and an email is sent to a

manager in Operations.

Operations must do the following, then mark the item as “Approved”:

a. Review & implement changes to operational SOLs (if necessary)

b. Review & implement the rating in their alarm settings (if necessary)


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Example Workflow

Figure 4: Facility Rating Update Submittal Process (Users submitting ratings changes are done at this point)

Figure 5: Automatic Email Received by Manager


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Figure 6: Task Review & Approval Process

Figure 7: Compliance Monitoring of Updates (Clicking the “In Progress” button will show full detail of task timeline)


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Version History Version

No. Issue Date Name Description or reason for revision

0.0 12/19/2016 Salsbury Initial version

0.1 12/21/2016 Salsbury Multiple revisions

0.2 12/29/2016 Salsbury Revision to Change Control Process to incorporate Sub Construction &

Maint., Major Projects

0.3 1/27/2017 Salsbury Revised to include dynamic line ratings; Updated Change Control

Process; Rating appropriation for ring and breaker-and-a-half scheme

0.4 6/20/2017 Ben Multiple revisions

0.5 7/14/2017 Ben Underground Cable methodology revisions


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Appendix A - Analysis of Weather Assumptions The IEEE 738 standard discusses how to rate Transmission Lines, and it includes thermal models to determine an

Amp rating based on Maximum Operating Temperature (MOT) and weather assumptions. The RateKit software

package is used to perform these calculations based on the below parameters.

Air Temperature

Ratings should use 40C (104F) ambient air temperature conditions for Northern Nevada based on the temperature

data below. This is a conservative value, since the temperature is below 40C for 99.99% of the recorded values. For

Southern Nevada, ratings would use 44.4C (112F). The historical temperature in Las Vegas was below this value for

99.94% of the recorded values.

Figure 8: Ambient Air Temperature

Wind Speed

In reference to CIGRE TB299, IEEE 738 says the following:

“In the absence of data from field rating studies, the use of certain worst-case weather conditions including

a 2 ft./s (0.61 m/s) perpendicular wind speed and an air temperature near the seasonal maximum should be

used.”10

10 IEEE Std 738-2012, Page 30


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Due to the sparse nature of NV Energy’s transmission system and the variety of weather conditions to which our

lines may be subject, ratings should use a 2 ft./s perpendicular Effective Wind Speed11 assumption per IEEE 738.

Emissivity & Absorptivity

Emissivity (ε) and absorptivity (α) are addressed in IEEE 738 and CIGRE TB299.

“For sag-limited lines, the JTF recommends that base ratings be calculated for an effective wind speed of 0.6

m/s, an ambient temperature close to the maximum annual value along the line route and a solar radiation

of 1000 W/m2. When combined with an assumed conductor absorptivity of no less than 0.8 (Conductor

emissivity should be chosen to be 0.1 less than absorptivity), this combination can be considered safe for

thermal rating calculations without field measurements.”12

Based on the above references, ratings should use: α = 0.8 ε = 0.7

Elevation

NV Energy uses the average elevation of Nevada for Northern Nevada rating calculations, which is 5500 ft. per a

book entitled “The Average Elevation of the United States” by Henry Gannett, Department of the Interior – US

Geological Survey.

For Southern Nevada, the elevation of Las Vegas is used (2,000 ft.).

Latitude

Carson City (Nevada’s Capital) is located at approximately 39° Latitude in Northern Nevada. This is used as the

reference Latitude for the rest of Northern Nevada’s transmission system.

For Southern Nevada, the latitude of Las Vegas is used (36°).

Date & Solar Time

NV Energy uses July 4th @ 1700 as its Date & Solar Time assumption.

MOT13

A line’s Maximum Operating Temperature is determined on a case-by-case basis, and is either limited either by line

clearance or by the temperature at which the conductor begins to anneal (whichever is lowest).

Clearance

Where LiDAR data is available, the MOT is calculated based on NEC14 & NESC15 clearance limitations.

11 Per CIGRE TB299, August 2006, Page 10: “Most transmission lines consist of multiple line sections, each line section being terminated by strain structures. Wind speed and direction (and thus conductor temperature) may vary along each line section but the sags depend on the average conductor temperature in the line section. The effective wind speed is that perpendicular wind speed which yields the same average conductor temperature along the line section as the actual variable wind. 12 CIGRE TB299 2006, Page 14-15 13 Maximum Operating Temperature (MOT): Means the maximum temperature at which an aerial conductor may continuously operate with the conductor clearance meeting or exceeding the minimum National Electrical Safety Code (NESC) clearance requirements applicable at the time of construction, and the maximum temperature at which an aerial conductor may continuously operate that will not cause permanent damage to the conductor, whichever is more limiting. 14 National Electrical Code 15 National Electrical Safety Code


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Conductor Annealing

On lines with abundant clearance, the next most limiting factor is the temperature at which there would be loss of

life due to annealing of the conductor as follows:

AA 95C

ACSR 100C

ACCC 180C

ACSS 200C


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Appendix B - Standard Conductor Ratings The table below includes Westinghouse conductor ratings, Manufacturer Ratings,

ACSR Conductor Data from “Westinghouse – Electrical Transmission & Distribution Reference Book”


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Copperweld Conductor Data from “Westinghouse – Electrical Transmission & Distribution Reference Book”


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Copper Conductor Data from “Westinghouse – Electrical Transmission & Distribution Reference Book”


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Aluminum Conductor Data from “Westinghouse – Electrical Transmission & Distribution Reference Book”


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Appendix C – NV Energy MOT Conductor Ratings

Conductor Rating Reference (Westinghouse Ratings and RateKit IEEE738 Ratings with Standard Weather Assumptions + Conductor MOT)

Unique ID Size TypeConductor

MOT (°C)

Conductor

MOT (°F)

RateKit IEEE738

Wire Name

Legacy Wire

Ratings

(Westinghouse)

North

IEEE738

Calc

South

IEEE738

Calc

Laughlin

IEEE738

Calc

Manufacturer

Ratings

2011 NEC

Table 310.15(B)(16)

4 / 0 CU I-Beam 4 / 0 CU IB 75 167Copper Twisted I-Beam

Use: CU4/0AWG-7520 371 358 329 - -

2A Copperweld 2A Copperweld 125 2572A Copperweld

Use: CU2AWG-7240 287 289 284 - -

721 ACAR 721 ACAR 95 203CURTIS

Use: ORCHID

776

(For ORCHID)777 771 741 - -

1272 ACSS 1272 ACSS 200 392 BITTERN/ACSS - 2173 2198 2188 - -

1272 ACSS, Old 1272 ACSS 200 392 PHEASANT/ACSS - 2149 2173 2164 - -

954 ACSS 954 ACSS 200 392 CARDINAL/ACSS - 1772 1792 1785 - -

1949 ACCC 1949 ACCC 180 356 LAPWING/ACCC/TW - 2599 2626 2610 - -

1026 ACCC 1026 ACCC 180 356 DRAKE/ACCC/TW - 1713 1732 1722 - -

431 ACCC 431 ACCC 180 356 LINNET/ACCC/TW - 968 979 973 - -

4 / 0 CU 4 / 0 CU 75 167 CU4/0AWG-7 480 371 358 329 - -

2 / 0 CU 2 / 0 CU 75 167 CU2/0AWG-7 360 279 269 247 - -

1 / 0 CU 1 / 0 CU 75 167 CU1/0AWG-7 310 241 233 214 - -

#4 CU #4 CU 75 167 CU4AWG-7 180 136 131 121 - -

#2 CU #2 CU 75 167 CU2AWG-7 230 181 175 161 - -

#1 CU #1 CU 75 167 CU1AWG-7 270 209 202 186 - -

250 CU 250 CU 75 167 CU250-37 540 413 398 365 - -

350 CU 350 CU 75 167 CU350-37 670 508 490 449 - -

2156 ACSR 2156 ACSR 100 212 BLUEBIRD - 1776 1768 1708 - -

1590 ACSR 1590 ACSR 100 212 LAPWING 1380 1474 1468 1418 - -

1272 ACSR 1272 ACSR 100 212 BITTERN 1200 1283 1277 1234 - -

954 ACSR, North 954 ACSR 100 212 RAIL 1010 1072 1067 1032 - -

954 ACSR, South 954 ACSR 100 212 CARDINAL 1010 1084 1080 1043 - -

795 ACSR 795 ACSR 100 212 TERN 900 955 951 919 - -

795 ACSR, Old 795 ACSR 100 212 DRAKE 900 973 969 936 - -

636 ACSR 636 ACSR 100 212 GROSBEAK 780 843 839 812 - -

556.5 ACSR 556.5 ACSR 100 212 DOVE 730 773 770 744 - -

477 ACSR 477 ACSR 100 212 HAWK 670 700 696 673 - -

397.5 ACSR 397.5 ACSR 100 212 IBIS 590 622 619 599 - -

397.5 ACSR, Old 397.5 ACSR 100 212 LARK 600 631 628 607 - -

336.4 ACSR 336.4 ACSR 100 212 LINNET 530 559 556 538 - -

4 / 0 ACSR 4 / 0 ACSR 100 212 PENGUIN 340 371 369 357 - -

3 / 0 ACSR 3 / 0 ACSR 100 212 PIGEON 300 322 320 310 - -

2 / 0 ACSR 2 / 0 ACSR 100 212 QUAIL 270 284 282 273 - -

1 / 0 ACSR 1 / 0 ACSR 100 212 RAVEN 230 249 248 240 - -

#2 ACSR #2 ACSR 100 212 SPARROW 180 188 187 181 - -

4 / 0 AAC 4 / 0 AAC 95 203 OXLIP 380 383 380 366 - -

2 / 0 AAC 2 / 0 AAC 95 203 ASTER 282 286 283 273 - -

1 / 0 AAC 1 / 0 AAC 95 203 POPPY 242 246 244 235 - -

#2 AAC #2 AAC 95 203 IRIS 180 184 182 175 - -

2500 AAC 2500 AAC 95 203 LUPINE - 1772 1758 1689 - -

2250 AAC 2250 AAC 95 203SAGEBRUSH

Use: BLUEBIRD- 1681 1668 1602 - -

2000 AAC 2000 AAC 95 203 COWSLIP - 1569 1557 1496 - -

1590 AAC 1590 AAC 95 203 COREOPSIS 1380 1371 1361 1307 - -

1272 AAC 1272 AAC 95 203 NARCISSUS 1210 1197 1188 1142 - -

954 AAC, North 954 AAC 95 203 GOLDENROD 1000 1005 998 959 - -

954 AAC, South 954 AAC 95 203 MAGNOLIA 1000 999 992 953 - -

795 AAC 795 AAC 95 203 ARBUTUS 897 895 889 854 - -

636 AAC 636 AAC 95 203 ORCHID 776 777 771 741 - -

556.5 AAC 556.5 AAC 95 203 DAHLIA 710 712 706 679 - -

477 AAC 477 AAC 95 203 COSMOS 646 646 641 616 - -

397.5 AAC 397.5 AAC 95 203 CANNA 575 574 570 548 - -

336.4 AAC 336.4 AAC 95 203 TULIP 514 518 513 494 - -

NV Energy Conductor RatingsRating (Amps)


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Appendix D – Aluminum Conductor Bus Ratings (Classes AA and A)


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Appendix E - Standard Bus Ratings The table below shows manufacturer ratings provided by AFL Global. Current ratings used should be for 6063-T6,

Schedule 40 Pipe.


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Appendix F – Control Cable Ratings


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Appendix G – NVE Jointly-owned Facility Rating Data Request The following text contains language designed to be a template for requesting Element ratings from multiple Entities.

TO: [Enter Interconnection Entity Contact Name]

DATE:

RE: Request to provide Element Ratings for [Enter Interconnection Name]

Per FAC-008-3, NV Energy needs to identify all Elements ratings associated with the requested Facilities below, at

the location listed above. This will allow NV Energy to identify the most limiting element of our jointly-owned

Facility. Additionally, if you require any Element information from NV Energy, please request as needed.

For Transmission Lines – Provide ratings for associated circuit breakers, switches, wavetraps (if applicable), relays

and current transformer ratings that are in conjunction with the circuit breakers as well as any shunt or series

compensation devices associated with the transmission line.

For Transformers – Provide ratings for associated circuit breakers, switches, relays and current transformers in

conjunction with those circuit breakers or the transformer. Also provide transformer normal and emergency

rating.

Please respond to this request within 30 calendar days. If you are unable to provide NV Energy with the

aforementioned information in the timeline requested, please feel free to contact us with a more agreeable

timeframe for submitting the data

Contact Sachin Verma with NV Energy for any questions regarding this request.

Sachin Verma

Manager, Network & IRP Transmission Planning

775-834-4878, [email protected]

mailto:[email protected]

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