Embed Size (px)
Citation preview
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.
