IEEE Insulated Conductors Committee
Spring 2011, St. Petersburg, FL
Spring 2011 St Petersburg FL
Subcommittee B, Cable Accessories
Presentation by: Thomas C Champion
Presentation by: Thomas C. Champion
History of IEEE 592
y First Edition, 1977
IEEE Standard for Exposed Semiconductive Shields on Premolded High Voltage Cable Joints and Separable Insulated Connectors
y N. Piccione, Chair; 10 Working Group Members
y 1st Revision, 1990
IEEE Standard for Exposed Semiconductive
p
Shields on High g
Voltage Cable Joints and Separable Insulated Connectors
y G. P. Rampley, Chair; 16 Working Group Members
y Dropped “Premolded”
y 2ndd Revision, 2007
IEEE Standard for Exposed Semiconducting Shields on High Voltage Cable Joints and Separable Connectors
y Michael W. Malia, Chair; 16 Working Group Members
Michael W Malia Chair; 16 Working Group Members
y Dropped “Insulated” from Separable Connector
Purpose of Semiconductive Shield
y Protect the insulation
y Provide voltage stress relief
y Maintain the accessory surface at or near ground potential under normal operating conditions
y Initiate fault‐current arcing if the accessory should fail
I i i f l
i if h h ld f il
“This standard sets forth tests and requirements to “Thi
t d d t f th t t d i
t t demonstrate that the shield will perform these duties.”
What’s Included?
y Maximum Shield Resistance
y Assure that the accessory provides stress relief
y Assure shield surface is maintained at or near ground g
protential
y Shield Fault Initiation Test
y Assure initiation of fault current arcs to ground that will cause overcurrent protective devices to operate
d
Limitations:
y Full circuit voltage is applied during the test
y Doesn’t attempt to simulate all service conditions nor field assemblyy
Performance Requirements
Shield Resistance
y Measured from cable entrance to furthest extremity
y ≤ 5000 ohms
h
Fault Current Initiation
y Capable of initiating two consecutive fault current arcs to ground y 10kA, 10 cycles minimum
y Initiation within 3 seconds of voltage application
Number of Samples
y Minimum of 2 samples per test
Mi i
f l Shield Resistance Test
y Use voltmeter‐ammeter method, either ac or dc power supply allowed
Current Connections:
y Separable Connector—cable entrance to furthest shield extremity, circumferential connections
hi ld t
it i
f
ti l ti
y Joint – cable entrance to physical center of the shield, circumferential connections
y Apply current of 1.0 mA
Apply current of 1 0 mA ± 0.2 mA, measure voltage
0 2 mA measure voltage
Shield Resistance Test
y Measure shield resistance under two sets of conditions
Specimen Aging Condition
y Unaged specimen
y Specimen aged in air oven for 504 hours at 121 ± 5 °C Specimen Temperature Condition
y Test specimen at 20 ± 5 °C y Test specimen at 90 ± 5 °C Fault Current Initiation Test
y Assemble per manufacturer’s instructions
y Exception: metallic cable shield extended over the accessory shield
hi ld
y Fault rod of erosion resistant metal (copper tungsten)
3/8 inch diameter, threaded into accessory connector,
3/8‐inch diameter
threaded into accessory connector
flush with outer shield surface of accessory
y Mount accessories in typical field position
yp
p
y Elbow – vertical, rod close to shield extremity
y Joint – horizontal, rod at center of connector
Fault Current Initiation Test
g
pp
p
y Voltage source applied between specimen neutral ground and cable conductor
y Applied voltage
Separable Connector
Joint
Test
Voltage Rating
Phase‐to‐Ground*
Voltage Rating
Phase‐to‐Ground^
Applied Voltage Phase‐to‐Ground
(kV rms), Fig. 1
(kV rms), Fig. 2
(kV rms)
8.3
8.7
7.0
15.2
14.4
11.7
21.1
19.4
12.2
* For separable connector voltage ratings, see IEEE 386
^ F j i l
^ For joint voltage ratings, see IEEE 404
i
IEEE Lower test voltage may be used provided fault is initiated and sustained for minimum required cycles.
Fault Current Initiation Test
y Available short circuit current of 10kA
y
y
y
y
y
(Note: No specification on tolerance, IEEE 4 assumed)
Two applications of fault current
Minimum current flow duration of 10 cycles
Fault initiation must occur within 3 seconds
Initiate second fault current application in the “ h t t “shortest practical time”
ti l ti ”
Do not disturb samples between fault applications
Fault Current Initiation Test
y Separable Connector
y Joint
Error in Drawing
Fault Rod is in wrong position!
Place Rod at GREATEST
Distance from NEAREST
Ground
1990 and 2007 Versions
Original 1977 Version
Why the current interest?
y Field installation practices have changed
y The IEEE 592 standard was written many years ago when semiconductive shields were exposed and not covered
y Most cables are now jacketed, which means that bl
k d h h
h
jackets are now applied over joints and portions of terminations
y The effect of a jacket on the performance of semiconductive shielding systems has never been evaluated, although most installations now use ,
g
jacketed constructions Why the current interest?
y Coverings may affect the distribution of the ionized plasma generated during a fault
y This could impact the ability of the shielding system to Thi ld i
h bili f h hi ldi conduct and maintain the fault for sufficient time to clear
y Different types of coverings may give different response
p
How might a jacketed joint respond differently during a fault?
differently during a fault?
y Cold shrink coverings
y Flexible ‐
Fle ible expands on one side, pulled in and seals on the e pands on one side pulled in and seals on the other
IONIZED GASES MAY NOT
REACH AREA OF NEUTRAL
WIRES
RE-JACKETING
MATERIAL, COLD
COLD-SHRINK
SHRINK
JACKET MATERIAL
STRETCHES IN RESPONSE
TO FAULT ENERGY RELEASE
How might a jacketed joint respond differently during a fault?
differently during a fault?
y Heat shrink coverings
y Less flexible, more rigid, allows plasma to encompass L fl ibl i id ll
l
t component or may burn through at the failure site
RE-JACKETING
MATERIAL, HEAT-SHRINK
IONIZED GASES MAY NOT
REACH AREA OF NEUTRAL
WIRES
JACKET MATERIAL MAY BURN
THROUGH AND RELEASE
PLASMA TO THE OUTSIDE
ENVIRONMENT
How might a jacketed joint respond differently during a fault?
differently during a fault?
y Hand‐taped coverings
y Tapes spread apart, channeling plasma away from shield
RE-JACKETING
MATERIAL, HAND-TAPED
COVERING
IONIZED GASES MAY NOT
REACH AREA OF NEUTRAL
WIRES
JACKET MATERIAL MAY
SPREAD APART AND
RELEASE PLASMA TO THE
OUTSIDE ENVIRONMENT
Test Configuration for Separable Connectors
RE-JACKETING MATERIAL,
HEAT-SHRINK, COLD-SHRINK,
OR HAND-TAPED
Exposed Semi-conductive
Shield
Jacket
J
k tM
Material
t i l Installed
I t ll d Over
O
Semi-conductive Shield
Test Configuration for Joints
Exposed
p
Semi-conductive
Shield
Jacket Material Installed Over
Semi-conductive Shield
RE-JACKETING MATERIAL,
HEAT-SHRINK , COLD-SHRINK,
OR HAND-TAPED
Test Configuration for Joints
y Two possible issues with joint testing configuration
y How far above (or below) the joint body should the neutral wires be placed? Should other configurations be considered, such as spreading wires around the joint?
y Is the orientation top to bottom optimal? Should the fault rod be on the top side and the neutrals on the b
bottom? (Hot gases wouldn’t rise up into the neutral)
? (H ld ’ i i h l)
ACCESSORY
SHIELD
ACCESSORY
INSULATION
FAULTING ROD
?
CABLE NEUTRAL
ACCESSORY GROUNDING
CONNECTION
COMPRESSION
CONNECTOR
TO SYSTEM
NEUTRAL GROUND
What’s Needed or Missing?
No mention of what should go in the test report
y Time between fault applications is “shortest practical time.” Why not record this time in the test report?
i
” Wh d hi i i h y Resistance values are recorded when samples are within a given temperature range Why not report the within a given temperature range. Why not report the actual temperature at the time of test?
y Minimum current flow duration of 10 cycles during fault‐current test. Record the actual number of cycles.
What’s Needed or Missing?
y Developmental Tests for use in developing new D l
l T
f i d l i materials?
y Why wait to test on full scale products?
y Why not test on sample sheets of material?
y Platens
y How could this test be performed?
y Do the test values scale?
Where Do We Go From Here?
y IEEE 592‐201?
IEEE Standard for Exposed Semiconductive Shields on High Voltage Cable Joints and Separable Insulated High‐Voltage Cable Joints and Separable Insulated Connectors
y IEEE 592‐201?
IEEE Standard Fault Duty Requirements for y q
Semiconductive Shielding of High‐Voltage Electrical Components
D
hi A l
O h El
i l
Does this Apply to Other Electrical Equipment?
Polymer Insulated Vacuum Recloser
y Painted semiconductive
P i d i
d i
shield over vacuum bottle casting
y Shield fails to carry sufficient fault current
y Circuit protective devices did not operate
y Multiple failures
An Example—Vacuum Recloser
y Dielectric puncture occurring at embedded metallic screen
y Current transfers to painted shield
y Shield impedance limits fault current
y Polymer insulation chars along path to nearest metallic ground
lli d
Consequences of Failure to Clear Fault
y Severe electrical noise
y Flicker
y Molten and flaming y
y
y
y
components dropping to ground
d
Pole fire
Ground fire
Damage to equipment beyond initial failure
Service interruption
Consequences of Failure to Clear Fault
y Safety hazard to personnel
y Damage may not be externally visible
y Voltage present within a normally grounded area
Problems and Solutions
Problem
y Change in scope would broaden coverage of standard to areas outside the jurisdiction of ICC
id h j i di i f ICC
Solution
y Joint Working Group with T&D
J i W ki G
i h T&D
Are There Other Examples?
y
Other Problems and Solutions?
y