1. No category

Flexible Mining Cables
Made for extremes
Mining Cables – Owen Barry – Mine Safety – 16/10/2013
From
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To
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And
Picture courtesy of NSW T&I Image Library
From
Picture courtesy of NSW T&I Image Library
To
Picture courtesy of NSW T&I Image Library
And
Picture courtesy of NSW T&I Image Library
Cable damage
 Likelihood of cable damage is elevated
– Machines are big and mobile
– Cables being dragged and pulled
– Some are continually reeled
– Other large equipment moving in close proximity
to cables
 Connection to mine earth dependent on integrity of
cable
Risk from cable damage
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Electrocution
Electric shock
Ignition of gas or dust
Fires
Burns (proximity to arc flash)
Controls to minimise risks
- from cable damage
 Cable management plans
– Training of personnel
– Placement of cables
– Cable handling equipment
 IT supply systems
– 1st fault is low energy earth fault
 Electrical protection systems
– Sensitive earth leakage
 Cables constructed to set standards
– AS/NZS 1802
– AS/NZS 1972
– AS/NZS 2802
Cable handling – O/Cut
Standards for mining cables
 AS/NZS 1802:2003 Electric cables—Reeling and
trailing—For underground coal mining
 AS/NZS 1972:2006 Electric cables—Underground
coal mines—Other than reeling and trailing
 AS/NZS 2802:2000 Electric cables—Reeling and
trailing—For mining and general use (other than
underground coal mining)
Cable design
 Earth screened
– Damage to earth before another phase
 Voltage rated for line to earth, not phase to earth
– Function of the IT supply system
 Solid construction gives impact resistance
 Sheath materials resistant to:
– Cuts, abrasions and tears
– Water ingress
– Chemicals – UV, oils and greases, acids & alkali
– Heat
Extreme cable handling
Example of poor cable handling.
Dragline cables being towed behind a dozer
AS/NZS 1802:2003
Scope
 Reeling and trailing electric cables for use in
underground coal mines.
 Cables used for alternating current supply must be
electrically symmetrical.
 Specifies construction and dimensional
requirements for specific types of cables
Cable constructions – Type 240
Cable constructions – Type 241
AS/NZS 1972:2006
Scope
 Specifies the construction of cables for use in
underground coal mines other than reeling and
trailing cables, ie
– Reticulation/feeder cables
– Machine cables
– Mine shaft winder cables
 Generally, does not apply to cables for IS circuits,
data, communication and control cables unless
specifically covered.
AS/NZS 2802:2003
Scope
 Intended for:
– surface mining,
– underground mining (other than coal mining),
and
– general use,
 Allows for two classes of multicore, elastomer
insulated and sheathed flexible reeling and trailing
cables.
 No requirement for symmetrical construction
Cable construction – Type 450
AS/NZS 2802:2003
Class 1 cables
 Insulated with a high grade ethylene propylene
rubber (XR-EP-90)
 Permits a reduced radial thickness for the
insulation compared with equivalent rated Class 2
cables
 Cable sheath is extra-heavy duty (XHD-90-CSP,
XHD-90-CPE or XHD-85-PCP)
 Designed for slow reeling or trailing applications
AS/NZS 2802:2003
Class 2 cables
 Insulated using standard R-EP-90 insulation
 Sheath material is HD-90-CSP, HD-90-CPE or HD85-PCP
 Greater insulation radial thickness required,
providing a more robust cable
 Designed for trailing and most reeling applications
Cable construction
Flexibility
 Issues affecting flexibility
– Insulation materials
– Stranding
– Length of lay
• Bunches
• Cores
– Screening technique
– Sheath thickness
– Ability of internal parts to move during flexing and
bending
Type 245
cable
Cable construction
Composite screens
 Each phase individually screened
– Semiconductive layer over insulation
• May be elastomer and or tape
• For stress relief and potential equalisation
• VR < 200 Ωm
– Copper and high tenacity yarn
• Usually woven
• May be helically wound
– Screening is also cable earth
Cable construction
Elastomer screens
 Phases individually screen
 Complete assembly collectively screened
– Must carry fault current
• VR <1 Ωm
 3 interstitial earth conductors embedded in
semiconductive elastomer
N.B. When crushed, the collective earth screen may separate
from the phase conductor
Insulation Voltage Gradient
Voltage
Phase volts
0 volts
Insulation
Semi-conductive rubber
earth screen
Distance – phase conductor to screen
Cable construction
Electrically symmetrical
 Cores arranged in geometrically symmetrical
pattern to minimise the effects of induced voltage
 Important in hazardous zones underground
– Minimises sparking between machines
– Minimises touch voltages of machines relative to
remote earth
• shuttle cars have rubber tyres
 Mandatory testing for symmetry by cable repair
facilities
Future developments
 Cable standards presently being revised
– A lot of prescriptive elements
– 1802 & 2802 will possibly be combined into
single standard
– Present tests do not adequately assess cable
performance
• No tests for bending and flexing
• No tests for semiconductive individual screen
Future developments
Performance based standard
 Cable performance outcomes to be defined
– Bending and flexing
– Tension loads
– Aging under elevated operating temperatures
 Allow for future requirements
– Fibre optics
– New insulation materials
– New manufacturing techniques
– Higher operating voltages
Performance based standard
 Performance requirements for each application of
cable to be defined:
– Draglines
– Shovels
– Feeder cables – fixed equipment
– Continuous miners
– Shuttle cars
– Monorail systems
– Shearer
Performance based standard
Tests
 Type tests to be developed
– Verify design achieves required outcomes
– Pass/fail criteria to be identified
 Routine tests to be developed
– Routine tests demonstrate that the production
run of cable is the same as the type tested unit
– Frequency of sampling
– What elements need to be checked
– Allowable tolerances from type tested unit
Repair of cables
 Presently addressed under AS/NZS 1747
– Will be revised after 1802 & 2802
 Manufacturers will need to identify how repairs will
be performed when developing new cable designs
– Repair materials
– Repair techniques
Issue: Mines will need to define element such as
stranding and length of lay for compatibility with
existing cable fleet
Thank you
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