Underground System Design TADP 547 - Gonzaga …web02.gonzaga.edu/orgl/tadp547final/547w2p1v1/artic/547w2p1v1.pdf · Underground System Design TADP 547 Cable Types Presentation 2.1

Underground System Design

TADP 547

Cable Types

Presentation 2.1

Instructor: George R. Matto

Underground Cable Selection

Underground Cable Types

• Conductor Design

• Paper Insulation

• EPR Rubber Insulation

Conductor Design

Purpose of Conductors

Provides a low resistance path for the flow of current such that:

– cable temperature ratings are not exceeded

– voltage regulation is within acceptable limits

Conductor - Effectiveness

Conductivity Comparison

Copper 100%

Aluminum 61%

Steel 16.6%

Tin 15%

Lead 8%

Silver 108%

Conductor Terminology

Conductor Class – Solid, or Stranded (Class B, C, H

etc.)

Conductor Size – American Wire Gauge and

Conductivity (AWG, MCM, kcmil)

Conductor Shape – Round, Sector, Segmental

Conductor Strand Count – Class B

1 + 6 = 7

1 + 6 + 12 = 19

1x, 7x, 19x, 37x, 61x, 91x, 127x, etc…

1

Classes of Conductor Strand

Example: (500 MCM - kcmil) conductor size

Class B – 37 wires

Class C – 61 wires

Class H – 427 wires

Note: Copper content remains the same

Ref EHB

Circular Mil - Area Definition

American Wire Gauge (AWG)

Unit of AREA in thousands of circular mils:

1 circular mil = diameter of wire in mils squared (D2)

(Note: no π in formula)

Hence, AWG: MCM, Kcmil

Conductor Size Designation

For 500 MCM (class B – 37 x 0.1162‖)

Diameter of = 0.1162‖ or 116.2 mils area of

1X = (116.2)2 = 13,502 circular mils

13,502 x 37 = ~500,000 circular mils

500,000 circular mils = 500 MCM (or kcmil)

Example Calculation - 500 MCM Conductor

Conductor Size and CMA

Conductor Size Circular Mil Area

#1 83,690

1/0 105,600

4/0 211,600

250 mcm 250,000

500 mcm 500,000

EHB Excerpt, P. 1, Table 1.1

On more than one occasion, guy strands

have been used as conductors due to their

physical and electrical properties.

In spite of its resistivity, galvanized steel has

been used due to extreme ice and wind

loads combined… and not just in Alaska

Did you know?

Strand Count Progression as Conductor Size

Range Increases - but all Class B Strand

7 wire 19 wire 37 wire 61 wire

24 AWG

to #2#1 to 4/0 250 to 500 600 to 1100

Class B Conductor Stranding Types

Strand Type Comparison (diameter in mils)

Stranding Shapes

Concentric Round - Irregular Surface

Compact Round - Smallest Diameter

Compact Sector - Smallest 3/C Cable

Segmental - Large Conductors, Low Skin Effect

Strand Type Comparisons (dia. in mils)

Kcmil Concentric Compressed Compact

4/0, 19X 528 512 475

350, 37X 681 661 616

500, 37X 813 789 736

750, 61X 998 968 908

Compressed strand is 3% smaller than Concentric

Compact strand is 8 - 10% smaller than Concentric

Wire Drawing Die

Multiple (4) Wire Drawing Dies

Drawn Strand Ready to be Loaded onto ―Strander‖

Copper and Aluminum have the same conductivity?

But how or, when?

At 70 degrees KelvinDid you know…

Conductor Summary…Strand Count and Conductor Shape

• As cable size increases so does strand count and

strand size

• As Class of conductor progresses (B, C, H) strand

count goes up and strand diameter changes as

needed

• Round conductor — usual shape

• Sector – 3/C paper insulated ―Pie‖ shape

• Segmental – 1/C constructed of 4 sections

• For given size the metal content is constant

Types of Underground Cable

• Conductor Design

• Paper Insulation

• EPR Rubber Insulation

Types of Underground Cable

• PILC – Paper Insulated Lead Cable

• LPFF – Low/Med. Pressure Fluid or Gas Filled

• HPFF & HPGF – High Pressure Fluid or Gas Filled

• HPLPP – High Pressure Laminated Paper Poly-

propylene

• Solid Dielectric, EPR – Ethylene Propylene Rubber

Paper Insulated Lead Cables

Solid Paper

Cable - PILC

Solid Paper Insulated Cable (1 kV – 46 kV)

Paper Insulated Lead Covered (PILC) Cable

Conductor & Stranding – Cu, Al / Strand Class

Insulating -- Layer Identification

Lead Sheath – Function & Protection

Jacket – Purpose & Types

Applications – Past and Present

Single and 3 Conductor -- Selection

Paper Insulated – Lead Sheath

Cable - jackets optional

Single Conductor – 1 kV to 46 kV

3 Conductor (Belted) – 1 kV to 15 kV

3 Conductor - Sector Type H

(Shielded) – 1 kV to 46 kV

Single Conductor PILC

A – Compact Copper or Aluminum

B – Carbon conducting paper tape

C – Insulating Kraft Paper Tape

D – Carbon Black Paper Tape

E – Copper Baring Lead Sheath

F – Overall Protective Jacket

A

B

CD

E

F

Note: Jacket Options: Low Smoke,

PVC, Reinforced Coverings

1/Conductor Non-Shielded PILC

A – Copper, compact Sector pre-twisted

conductor.

B – Strand Screen, Carbon Black Paper

Tapes

C – Insulation- Impregnated Helically

Applied Paper Tapes

D – Insulation Screen – Carbon Black

Paper Tape

E – Intercalated Copper Shield Tape

F – Fillers- Impregnated Paper Tape

G – Copper Binder Tape

H – Sheath- Copper Bearing Lead

J – Jacket –PE

3#

ABCDEFG

H

J

3/Conductor PILC Type H

Types of Underground Cable

PILC – Paper Insulated Lead Cable

LPFF – Low/Med. Pressure Fluid or Gas Filled

HPFF & HPGF – High Pressure Fluid or Gas Filled

HPLPP – Hi Pressure Laminated Paper Polypropylene

Solid Dielectric, EPR – Ethylene Propylene Rubber

Types of Underground Cable

―Streamers‖ in Insulation vs. Pressure

Low & Medium Pressure Fluid Filled Cable:

LPFF & MPFF

3/Conductor Compact Sector Strand

Low & Medium Pressure Fluid & Gas Filled

Design, Application

and Operation

Medium Pressure Fluid Filled

Steel Spiral Core

Copper Conductor

Carbon Paper Tape

Kraft Paper Tape

Carbon & Metalized

Paper Tapes

Lead Sheath

PE Jacket

LPFF and MPFF – Possible Applications

• Submarine cables - across harbors, rivers, sounds,

inlets and bays

• Overhead to underground transmission to urban

substations

• Substations to specific large loads- skyscrapers or

factories

• Large urban area transmission ring

Types of Underground Cable

PILC – Paper Insulated Lead Cable

LPFF – Low/Medium Pressure Fluid or Gas Filled

HPFF & HPGF – High Pressure Fluid or Gas Filled

HPLPP – Hi Pressure Laminated Paper Polypropylene

Solid Dielectric, EPR – Ethylene Propylene Rubber

Pipe Cable Cable

Compact Segmental

Conductors

High Pressure Fluid/Gas FilledHPFF & HPGF

Source: EEI Report 06-88-22, Transmission Cable Operation -- 1987,‖ May 1988

Substation

Four-bottle Gas Cabinet - Auto/Remote Control

Nitrogen Gas System Valves Manifold and Controller

HPFF and HPGF Possible Applications

• Directional bore across harbors, rivers, and inlets

with long lengths of three single conductors

installed simultaneously.

• Connect overhead transmission lines to urban sub-

stations.

• Substations to specific large loads – skyscrapers

or factories

• Large urban area transmission ring or multiple

rings at various voltages

• Power plant step-up transformer to switchyard

• And more …….

Types of Underground Cable

PILC – Paper Insulated Lead Cable

LPFF – Low/Med. Pressure Fluid or Gas Filled

HPFF & HPGF – High Pressure Fluid or Gas Filled

HPLPP – Hi Pressure Laminated Paper Polypropylene

Solid Dielectric, EPR – Ethylene Propylene Rubber

HPLPP - High Pressure Laminated Paper Polypropylene

HPLPP - High Pressure Laminated Paper Polypropylene

Paper vs. LPP (Laminated Paper/ Polypropylene) at 345 kV

Paper Insulation

727 MVA

2500 kcmil – copper

0.905“ Paper

3.85” Diameter

12.45 lbs/ft

10” Steel Pipe

2600 Gal. Oil / 1000’

47.0 kw/mi

Joints 105”L X 5.65” Dia

Laminated Paper/

Polypropylene

725 MVA

2000 kcmil – copper

0.569“ Paper

2.98” Diameter

8.3 lbs/ft

8” Steel Pipe

1700 Gal. Oil / 1000’

12.4 kw/mi

Joints 41”L X 4.2” Dia.

Note: Original EPRI Data may have changed only slightly

Existing pipe cable

can be upgraded -

to larger conductor

or higher voltage

and

digging up the street

is not required.

Pipe Cable ―Plugs Into‖ SF6 Sub Station

115 kV SF6 Substation

Pipe Cable to SF6 Substation

115 kV Bus Access Ports

Typical MV or HV Termination Structure

Comparison of magnetic field from overhead conductor and single under-ground conductor in duct.

Compare to next graph representing pipe cable.

Source:

1994 IEEE/PES, T&D Conference, Training Session

Chicago, Il

Source:

1994 IEEE/PES, T&D Conference, Training Session

Chicago, Il

Magnetic Field Comparison

Subtle feature of all pipe cables

that does not add to cost - the

magnetic field of 1 - 2 milligauss

is almost 50 times lower than

singles in duct and overhead

lines.

The field magnitude is so

different that two graphs with

different scales are required to

show results.

Paper Cable Summary

• Since their inception, paper cables have been

extremely reliable.

• HV Systems have evolved from Low Pressure to

High Pressure Pipe Type Cable.

• Significant advances have been made in HPFF

and HPGF cable systems.

• Latest improvement was to combine paper and

polypropylene into an insulation laminate.

• Significant economies are realized in the use of

HPLPP.