1. Jithin Thenasseril
Distribution Capacity Planning
March 26, 2015
ENHANCING CABLE
MODELING IN CYME

2. Introduction
 Drexel University
• Electrical Engineering
• Pre-Junior (3rd/5 years)
• Graduation: June 2017
 PECO
• Distribution Capacity Planning
• September 2014 - March 2015
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3. Challenge
 A fundamental component of the electric system is cables which are
responsible for carrying current to customers
 No cable is a perfect conductor; it has a small amount of impedance
that can cause voltage drops large enough to affect customer
experience if overlooked
 CYME has a feature that can calculate cable impedance based on
the cable’s characteristics which it then relies on to calculate voltage
drops and power losses
 Unable to use this feature for calculations because of invalid cable
characteristics in the new version of CYME
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4. Goals
 More refined calculation of power losses and voltage drops
 New cable characteristics based on PECO’s specifications
rather than a standard list from a single manufacturer
 Ability to compute impedances of cables that have
characteristics which couldn’t be modeled before
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5. CYME Cable Warnings
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Cable
warnings
Lombard_136
 Cable warnings unique to the new version of CYME
• Size of conductor must be greater than 0
• Overall diameter of cable must be greater than the current value

6. Returning to Computed Values
 Currently using user-defined positive and zero sequence impedance
values due to cable warnings
 Components of impedance: Resistance and Reactance
• Resistance (R): opposition to the flow of current
• Reactance (X): opposition to change in current or voltage
 Positive and Zero Sequence are mathematical methods created to simplify
calculations of an unbalanced power system
 Solution: Input construction and installation characteristics of cables to
reflect what PECO uses in the field so CYME can compute impedances
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User-defined impedances

7. Cable Characteristics Sources
 Cable characteristics came from a standard list:
• Conductor details: CYME conductor library
• Insulation and neutral details: Southwire product catalog
 PECO’s cables are built to PECO’s specifications from
multiple cable manufacturers
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Insulation
Concentric
neutrals
Conductor
SOUTHWIRE CABLE COMPANY
Phase Conductor Neutral Insulation
Material Size (AWG) Stranding No. of Wires Size (AWG) Thickness (mils)
CU 500 37 25 14 345
AL 750 61 24 12 345
CU 1000 61 20 10 345
CYME LIBRARY: CONDUCTOR
Material Size (AWG) Construction Type
Diameter
(inches)
R 25⁰C (ohms/mi.)
CU 500 Stranded Round 0.707 0.1196
AL 750 Stranded Round 0.998 0.1246
CU 1000 Stranded Round 1.000 0.0634

8. Evaluation of the Construction
 Current CYME Values: impedance values currently used
 New CYME Preliminary Values: impedance values calculated by
CYME after the construction details were changed
 Significant differences in Zero Sequence Resistance and Reactance
values
 The difference was due to overlooked crucial characteristics of cable
construction
• Bonding
• Lay Length
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Current CYME Values New CYME Preliminary Values
Cable Name R1 R0 X1 X0 R1 R0 X1 X0
3_1X750_AL_XLP_13KV_UC 0.15 0.50 0.17 0.12 0.13 0.42 0.17 3.80
3_1X750_AL_XLP_34KV_UC 0.15 0.50 0.20 0.15 0.13 0.42 0.19 3.75
3_1X750_CU_XLP_13KV_UC 0.11 0.32 0.17 0.10 0.08 0.37 0.18 3.79

9. Factors that Affect Resistance & Reactance
 Bonding: electrically connecting and grounding the concentric neutrals of
phase conductors
• Single-Point bond: grounding the neutrals at
one end of the cable
• Two-Point bond: grounding at both ends of the
cable
 Lay Length: longitudinal length of the neutral required to revolve around
the diameter of the cable once
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Lay Length
Two-point bonding

10. Evaluation With Corrected Bonding and Lay Length
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Current CYME Values New CYME Preliminary Values New CYME Final Values
Cable Name R1 R0 X1 X0 R1 R0 X1 X0 R1 R0 X1 X0
3_1X750_AL_XLP_13KV_UC 0.15 0.50 0.17 0.12 0.13 0.42 0.17 3.80 0.15 0.49 0.16 0.11
3_1X750_AL_XLP_34KV_UC 0.15 0.50 0.20 0.15 0.13 0.42 0.19 3.75 0.15 0.49 0.19 0.14
3_1X750_CU_XLP_13KV_UC 0.11 0.32 0.17 0.10 0.08 0.37 0.18 3.79 0.12 0.32 0.16 0.10
 Initially, a value of 0.394 inches was used for lay length and single
point bond was used
 PECO’s cables are two-point bonded and lay length is specified to
cable manufacturers as 8 times the diameter over insulation
 Change the bonding type significantly impacted R1, R0, X0, and made
a slight difference on X1
 Changing lay length significantly impacted R0 and X0

11. 11
Current CYME Values New CYME Final Values
% Difference Between Current &
New Final Values
Cable Type Cable Name R1 R0 X1 X0 R1 R0 X1 X0 R1 R0 X1 X0
PAPER & LEAD CABLE 3_1X500_P&L_13KV_UC 0.15 0.47 0.18 0.12 0.13 1.58 0.17 0.75 -13.33% 236.17% -5.56% 525.00%
FLAT STRAP CABLE 3_1X500_CU_13KV_UC 0.15 0.47 0.18 0.12 0.13 1.47 0.17 0.67 -13.33% 212.77% -5.56% 458.33%
COPPER TAPE CABLE 3_1X1000_CU_13KV_UC 0.1 0.26 0.16 0.09 0.08 1.53 0.14 0.76 -20.00% 488.46% -12.50% 744.44%
SINGLE CORE PAPER
& LEAD CABLE
3X250_CU_P&L_13KV_UC 0.26 0.66 0.17 0.42 0.14 0.32 0.11 2.51 -46.15% -51.52% -35.29% 497.62%
 Current version of CYME can’t compute impedances of cables that use
the following as neutrals:
• Lead sheath (P&L, R&L, K&L)
• Copper tape
• Flat straps
 Concentric neutrals were used for the cables listed above to calculate
Current CYME Values
 The ability to model these cables has been added to the new version
Cable Modeling Enhancements

12. Evaluating Impact
Island_Road_136 Current Island_Road_136 New
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Load Flow Box
Cable - ISLAND_ROAD_136_106854090
V base kVLL kVLN i(A)
A 119.5 13.2 7.6 75.9
B 121.0 13.2 7.7 84.9
C 121.5 13.3 7.7 60.2
Load Flow Box
Cable - ISLAND_ROAD_136_106854090
V base kVLL kVLN i(A)
A 120.3 13.3 7.6 75.9
B 120.3 13.3 7.6 84.7
C 121.2 13.3 7.7 60.0
 Only a minor impact was observed in this case because:
• Relatively short length of cable
• Cable is on a mostly balanced portion of the circuit where the large difference in Zero
Sequence Impedance has little impact

13. Future Improvements
 PECO GIS:
• Update GIS system from older format to the new format
• Improve circuit models by documenting the specific cable type and
length used in a circuit
• Standardize cable names
 3_1X750_AL_13KV_UC
 3_1X750_AL_CLPE_13KV_UC 3_1X750_AL_XLPE_13KV_UC
 3_1X750_AL_XLPE_13KV_UC
• Capture duct bank layout
 Number of ducts and spacing between ducts
 CYME:
• Option to change bonding type of all cables within CYME
• Improve modeling of a separate neutral
• Improve conductor detail
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14. Acknowledgements
Thank you!
 Manager: Suzanne Shaw
 Mentors: Nathaniel Nichols and Edmund Attuquayefio
 Special Thanks:
• Mohamed Dicko
• Larry Griess
• George Sey
• Daniel Zoladz (Distribution Equipment & Standards)
 Capacity Planning Group
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15. 15
QUESTIONS