appendix 2

Polypropylene Alternatives for
Medium Voltage Cable Jackets
Spring 2012 IEEE PES ICC Meeting
Group A07D – Selecting/Testing Jackets
for Underground Cables
March 27, 2012 Seattle, WA
C.L. Flenniken
1
Outline
• Medium Voltage Cable Jacketing Background
• High Thermal Rated Jackets
• Polypropylene Resin Characteristics
• Comparison of Jacketing Materials Properties
• Summary
2
Medium Voltage Cable Jacketing Background
• Prior to 1980, underground medium voltage power cables
were jacketed with PVC to reduce neutral corrosion and
improve cable life
• Early 80’s LDPE jackets were introduced
• Since the mid 80’s, Linear Low Density Polyethylene (LLDPE)
has been a primary jacketing resin for NA medium voltage
distribution cables
– Europe has focused on MDPE and low shrinkage HDPE jacketing
• In early-90’s, PP jacketing was used for EPR medium voltage
power cables for urban systems with restrictions associated
with ducted systems and growing urban population
3
Background (Fall presentation in A07D)
• Benefits of Higher Thermal Rated (HTR) Jackets
– Neutral redesign results in lower amount of copper (<<$$)
– HTR Jacket + reduced neutrals  cooler operation, lower line
loss
– Improved thermo-mechanical
• In addition, HTR Jackets provide
– Opportunity to reduce wall thicknesses of cable design
• E.g. PP jacketed EPR insulated MV cables in ducts for urban installations
4
Proposed Specification for HTR Jackets
Physical Properties
Units
Values
Tensile Strength
psi (MPa)
> 1500 (>10.3)
Elongation @ Break
%
> 150
Retained Tensile Strength
% of original
> 70%
Retained Elongation
% of original
> 70%
HEAT DISTORTION @ 131˚C
%
< 30
CARBON BLACK
%
> 2.0
UNAGED REQUIREMENTS
AGED REQUIREMENTS (121˚C for 168 hrs)
• UL 1072 Standard recognizes XLPE jackets
• ANSI / ICEA and CSA proposals in progress
5
HTR Jacket Options
• Crosslinked Polyethylene (XLPE) jackets have initially
been primary focus
– Moisture cured post extrusion
– Impacted by regional and seasonal temperature, relative humidity
fluctuations and jacket wall thickness
• Polypropylene Alternative
– Commercially used for Ethylene Propylene Rubber (EPR) power cable
jackets for > 15 years
– Good high temperature performance
– Can be optimized for low temperature performance on cable
6
Polypropylene Resin Characteristics
• Polypropylene resins (PP) deliver a broad array of
engineering design options
– High crystallinity PP homopolymers
• Provide good strength to weight ratio
• Are resistant to many corrosive chemicals
• Endure abrasive treatment
– PP copolymers
• Can offer excellent flexibility
• Improve low temperature and impact performance
7
Polypropylene Resin Characteristics …continued
(SEM of etched surface to remove rubber phase)
PP Low Rubber
• Rubber modified PP
improves flexibility and
low temperature
properties
PP High Rubber
Continuous PP phase
Etched Rubber Phase
8
Polypropylene Resin Characteristics …continued
• Level, type and dispersion
– Stiffer and stronger
– Good low temperature
performance with
improved flexibility and
impact properties
Stiffer and Stronger
9
8
Performance
of rubber component in
polypropylene copolymers
impacts
Flexibility
7
6
5
4
3
2
1
0
0
>
>>
>>>
% Rubber in PP Copolymer
9
Comparison of HTR Jacket Materials
• Resins selected
 Linear Low Density Polyethylene (LLDPE)
 Impact Modified PP-A (PP-A)
 Impact Modified PP-B (PP-B)
 Moisture Cure Cross-linked Polyethylene (XLPE)
• Both plaques and wire evaluated (relative to test)
• Typical antioxidant packages added for air oven
aging studies
10
Resin Physical Properties
LLDPE
PP-A
PP-B
XLPE
Unaged* …1500 psi tensile; 150% elongation minimums
Tensile, psi (MPa)
3870
4810
5750
3180
Elongation, %
1590
1480
1710
330
* Testing on 14 AWG Solid Cu / 30 mil wall wire, no black masterbatch
Heat Distortion, 30% maximum
100˚C
PASS
PASS
PASS
PASS
136˚C
Melts
PASS
PASS
PASS
150˚C
Melts
PASS
PASS
PASS
11
Crush on Wire (no black master batch)
12
Toughness of Impact Modified Polypropylenes
13
Tailoring Rubber Content and Structure
to Meet Performance
14
Modifications to PP Rubber Structure
to Lower Modulus
15
Coefficient of Friction
* Measured against HDPE extruded tape with no lubricant.
16
Comparison to Jacket Performance Requirements
TARGET
LLDPE
PP-A to B
XLPE
Tensile, psi
(MPa)
>1500
3870
4810 - 5750
3180
Elongation, %
>100
1590
1480 - 1710
330
Unaged*
* Testing on 14 AWG Solid Cu / 30 mil wall wire
Heat Distortion
@ 136˚C
< 30%
MELTS
PASS
PASS
17
Cable Manufacturer Benefits of Polypropylene
• Unlimited by curing process
– No pre-drying and no special extruder configuration
– Not impacted by ambient humidity
• As a thermoplastic, PP is recyclable
18
Summary
• Polypropylene has good high temperature
performance
• PP jackets have been commercially used for medium
voltage power cables for > 15 years
• Demonstrated performance in reduced wall wire constructions
with good balance of physical and abuse resistant properties
• PP can be tailored for low temperature performance
and flexibility
• Further investigation of Polypropylenes as HTR
jackets
19
THANK YOU!!
20
Disclaimer
• All information (“Information”) contained herein is provided without
compensation and is intended to be general in nature. You should
not rely on it in making any decision. LyondellBasell accepts no
responsibility for results obtained by the application of this
Information, and disclaims liability for all damages, including without
limitation, direct, indirect, incidental, consequential, special,
exemplary or punitive damages, alleged to have been caused by or
in connection with the use of this Information. LyondellBasell
disclaims all warranties, including, but not limited to, the implied
warranties of merchantability and fitness for a particular purpose,
that might arise in connection with this information.