recent developments in mv cable materials

Dow.com

Dow Electrical & Telecommunications

Brent Richardson

May 2015

Recent Developments in MV Cable

Materials

Midwest Energy Association

16th Annual Electric Operations Technical

& Leadership Summit

The Cable Value Chain

Feed-stocks Compound Cable

Manufacturers Utilities Consumers

Regulators

2

DOW CONFIDENTIAL - Do not share without permission

Base Resin

®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow

Packaging Bin

Hopper Car

Resin/Additive Feeder

Uniclean Package

Reactor

Mixing Equipment

Insulation Manufacturing Process

3


Insulation Compound Cleanliness Specifications

4

Cleanliness is critical:

• Contaminants reduce breakdown strength

• Contaminants act as electrical stress enhancers

Extra Clean (EC) insulation is recommended for MV applications with a

specifications of no more than 2 contaminants between 127 and 254

mm, and zero contaminants greater than 254 mm (per 1.6 kg basis)*

Super Clean (SC) insulation is recommended for HV/EHV up to 230 kV

applications with a specification of zero contaminants greater than 100

mm (per kg basis)

EHV insulation is recommended for EHV above 230 kV with a

specification of zero contaminants greater than 70 mm (per kg basis)

* European EC specs allow 3 contaminants between 100 and 200 mm and zero contaminants greater than 200mm


Insulation Compound Cleanliness Camera Tape Contamination Test System

5

Clean Room (Class 10,000)

T-Die

Labeler

Clean Box

(Class 1000)

Take-up Roll

Tape

Camera

Box

Extruder

Detector


Insulation Manufacturing Product Packaging

6

EC for MV

packaged into railcars

SC for HV

packaged into

boxes


Insulation Types for Medium Voltage Cables

7

The Insulated Conductors Engineering Association

(ICEA) recognizes four types of material for the

purpose of providing insulation for MV cables

•Cross Linked Polyethylene (XLPE)

•Tree Retardant Cross Linked Polyethylene (TR-XLPE)

•Ethylene Propylene Rubber (EPR)

•Ethylene Alkene Copolymer (EAM)

®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow 8

Chronology of TR-XLPE Insulation

1983 – Market Introduction by Union Carbide First commercial TR-XLPE insulation with demonstrated long

life performance-HFDA-4202

1998 – Processing Improvements Provided Maintained the excellent electrical performance of the A4202

with improved properties for more robust cable manufacturing-

HFDB-4202

2001-Competitive Materials Introduced Borealis enters the NA market with LE-4212

2010 – Longer Life Materials Introduced Advancements to enhance longer life, ease of installation

and further manufacturing robustness to ensure quality

and consistency-HFDC-4202

8


TR-XLPE Insulation Components

9

Polyethylene

Tree Retardant

Antioxidant package

Cure System


Chronology of EPR Insulation

1955 – Polymer Technology Developed Carl Ziegler developed a novel catalyst for polymerization of ethylene to

polyethelyne-copolymerizing ethylene with propylene yields a new

elastomer, EPM

Early 1960’s– EPM Compound Production Begun

1962- Cable Applications Begun

Late 1960’s- Compounded EPDM introduced for

Crosslinking Attributes

1970’s-Broad Molecular Weight Distribution improves

processing

1990’s-Development of Mettalocene Catalyst Technology

10


EPR Insulation Components (typical formulation)

11

Elastomer

Kaolin clay

Antioxidant package

Vinyl Silane

Heat Stabilizer

Red Lead

Wax

Low Density Polyethylene

Dicumyl Peroxide


TR-XLPE & EPR Insulation materials

TR-XLPE

• Unfilled

• Pure, simple polymer

• Extra clean, natural

• Dry cure

• True-triple extrusion

• Clean interfaces

• Higher aged electrical strength

• Deformation resistant

• Tougher

EPR

• Highly filled material

• Complex mixtures

• Cannot see contaminants

• Steam cure

• Mostly 2+1 extrusion

• More interfacial stress risers

• Lower aged electrical strength

• Deformation resistant

• Softer / more flexible

Generic Material Properties

12


924

844

724

860

564

500

924

476

372

948

860

452

764

560

467

780

476

404

0

100

200

300

400

500

600

700

800

900

1000

New 90° C 45° C

No

min

al A

C B

rea

kd

ow

n S

tren

gth

(V

/mil

)

Cable Design Aging Test NEETRAC Project Number 97-409

AC Breakdown Results Averages, 345 Mil Wall

New and Aged 4 Years @ 90 & 45 Deg. C, 69 kV

TR-XLPE 1

TR-XLPE 2

TR-XLPE 3

TR-XLPE 4

EPR 1

EPR 2

Note: The insulation shield used on EPR1was found to be incompatible with the insulation at the elevated conductor temperature of 90 Deg. C

NEETRAC 35 KV Test Results

This graph is a compilation of data from various figures included in NEETRAC Baseline Project Report 97-409. It was prepared and provided under Clause 6 of the terms and

conditions outlined in the NEETRAC Publication Policy on the use of Baseline Project Results/Data. In keeping with that policy, the graph was reviewed and approved by

NEETRAC and only Dow Chemical products can be identified outside the NEETRAC Membership.

It is also important to note that ac breakdown was one of several tests used to evaluate the performance of complete cable designs in this accelerated aging test program.

While comparing average ac breakdown strength values provides some insight into cable performance differences (or similarities), a statistical analysis/review of all measured

performance values and characteristics is required to provide a complete indication of performance.


EAM Background

The medium voltage filled insulation market has been dominated by

Ethylene Propylene Rubber (EPR) based “leaded” insulations for the

last forty (40) years

The solution for increasing cable performance, dealing with

environmental concerns, and addressing changing market dynamics

requires modifications to the insulation system’s base polymer and

stabilization package

Over the last ten (10) years the performance of metallocene

catalyzed Ethylene-Alkene Copolymers (EAM’s) have improved

significantly; in concert with stabilizer package development, lead-

free EAM insulation meeting utility MV performance requirements

has been created


Definition of Insulation Materials per ANSI/ICEA

ANSI/ICEA S-94-649 and S-97-682 allow alternate EAM insulating materials meeting

the same physical and electrical requirements of XLPE, TRXLPE, and EPR

EAM materials are first identified in a footnote under Table 4-1 in ANSI/ICEA S-94-649

and S-97-682 and are further explained in Appendix I and Appendix H respectively.

EAM materials have been listed since 1996


Definition of Insulation Materials per ANSI/ICEA


Why Elastomers are Used in MV Cable Applications

Elastomers are polymers that exhibit high extension and flexibility

when placed under low mechanical stress

Low crystallinity of elastomers permit excellent flexibility that

enables ease of cable installation

Low crystallinity of elastomers require higher filler incorporation that

in turn permits cross linked compounds to exhibit high heat and oil

resistance


LF Filled EAM Insulation for Cable Applications

18

Continuing technological developments in polymer catalyst technology

make available more diverse polymers suitable for medium voltage cable

applications

General Cable developed LF Filled EAM with a Dow elastomer which uses

the traditional ethylene backbone of an EPR formulation, but with a longer

side chain

The increasing side chain lengths in EAM compounds improves flexibility

and the resulting electrical performance is improved without lead Ease of installation: Improved flexibility and trainability; Less spring-back

Environmental sustainability is gained and recyclability is improved

LF Filled EAM retains the inherent benefits of EPR insulations with

improved thermal stability


Why Lead-Free?

With safety as a top concern, the industry has focused on removing

hazardous materials from cable products

RoHS, California Prop. 65, REACH all restrict lead use; EPA

currently says that the lead content in MV EPR insulation is below

threshold limit, but what will be the future limits?

> 250,000 lb of red lead oxide used in MV EPR insulation production

by one manufacturer per year; Each year as the volume of

traditional EPR consumption keeps growing the amount of red lead

oxide grows

≈ 43 lb of red lead oxide per circuit mile of 4/0 Al 220 mils wall EPR-

insulated MV cable


LF Filled EAM Insulation Cable Testing

Lead-Free EAM is more flexible than Leaded EPR; 33% reduction in flex modulus when compared to semicrystalline

Leaded EPR.

Flexibility Testing

Lead-Free EAM

Leaded EPR


Comparison of Insulation Materials

The chart below compares key attributes of MV cables for each of the

three major insulation types

TR-XLPE EPR EAM

Greater flexibility for ease of installation C B A

Environmental Sustainability A C A

Recyclability B C B

Suitability for constrained space C B A

105/140 C insulation rating A A A

Dielectric losses (dissipation factor) A C B

Highest Retained Breakdown Strength (AWTT) A C B

Insulation by TypeCable Attribute


Features & Benefits of EAM Insulated Cables

Lead-Free Filled EAM compounds offer improved installation

performance and an environmentally conscious alternative for

demanding MV Utility insulation applications

Lead-free Filled EAM has demonstrated thermal, wet & dry electrical

stability

Improved flexibility; Improved trainability and less spring-back o Easier handling during installations

o Appealing for the installation crew; Better ergonomics; Less fatigue after handling

Better wet electrical aging performance vs. a Leaded EPR as

demonstrated by AWTT and ACLT testing

Meets or exceeds ANSI/ICEA S-94-649 & S-97-682 and AEIC CS8

A “Green” Sustainable Solution o Eliminates the last hazardous material from MV cable designs

o Low and stable dissipation factor (lower losses) at elevated temperatures

o Green solution may aid in rate case approvals


Summary

Today’s MV insulations have positive and negative

attributes and should be evaluated based on the utility

need

Continued research and development of materials and

manufacturing methods has produced longer lasting

cables for the industry

Update your cable specification and consider the

purchase of cables that best meet your specific

application


Brent Richardson

[email protected]

704-721-0288

24

mailto:[email protected]

recent developments in mv cable materials

Documents