Impacts of Short Circuit Currents

1
Impacts of Short Circuit Currents
strips
Kabelbündelungen
Clamps
Attenuation of short-circuit-currentalong the
cableNAKBA 240 mm2
Impacts of short-circuit-current at cable-clamps
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Relaxation Oszillations
Resonanz at system frequency during switch-on of
transformers or during earth faults Cause
Interacting of inductances of VT with the system
capacities against earth Consequences
overcurrents and overvoltages
Only in isolated or resonant-earthed systems
Damping in open delta-winding
3
Partial discharge
electrical rust
audible above 200 pC visible above 1000 pC
4
Water-Trees
During the production of PE- medium-voltage
cables between 1970 and 1980 there had been a lot
of outages caused by insulating collapses. The
collapses were caused by contaminations of
isolation, associated with the humidity in the
electrical field between wire and shielding. The
humidity caused increases of structure changes in
the PE- isolation They look like little trees,
therefore these changes are calledwater-trees. D
uring power-on time the trees grew and caused an
electrical breakdown. The problems are nowadays
solved by new raw materials and an extremly clean
production. The danger of formation of
water-trees ist still present, if assembly is
incorrect so that humidity can break into a PE-
or XLPE- high- or mediumvoltage-cable.
outer guiding bed
defect
insulating
inner guiding bed
wire
Water- trees in PE- isolation
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Pattern of defects continous earthfault
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Pattern of defects intermittenly earthfault
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Pattern of defects short circuit (3-phases,
with earth connection)
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Effects of failures (highvoltage)
porcellain weight ca 10 kg range of flight ca.
15 m
Fußpunkte
Flashover at surge voltage protector by a thistle
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Effects of failures (transformers)
Voltage transformer
Interturn fault in HV-winding of a
400-kVA-transformer
10
Effects of failures (transformer)
Not properly tightend transformer-cable
Interturn fault inLV-winding of a
630-kVA-transformer Damages of HV-winding and
core Bursted tank started ca. 1 h after power-up
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Effects of failures (transformer)
Failure at an off-circuit-tap-changer of a
8-MVA-generator-transformer 6 / 20 kV YOM.1961
Heavy accumulation of oil-coal
Actuate tap changer during maintenance!
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Effects of failures (cable)
Damaged XLPE-cable by excavator
Damage od paper-insulated cable by cutter saw
Lightning stroke in a illumination-cable
Earthfault at XLPE-cable (incorrect installation)
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Effects of failures (cable)
Iron-bar of a road curb lin in a paper-insulatet
cable
Wooden bar for afence... (LV)
Roots at atelecomunication cable
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Effects of failures (overhead transmission lines)
Grid constallation
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Effects of failures (overhead transmission lines)
Manipulation a steel tower Blackout for
350.000 people up to 6 h
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Effects of failures (overhead transmission lines)
Provisionary solution after outage
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Effects of failures (overhead transmission lines)
breakdown
Messages in system control center at first
minute 2436
power-up by generators (wind generators,distric
t heating generators) und motorloads
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Effects of failures (overhead transmission lines)
Power up of busbar
L1
L3
Peak stress
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Effects of failures (overhead transmission lines)
Power up of busbar (load)
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Effects of failures (switchgear)
Fuse-switch disconnector 400 A IK ca. 15 kA, t
1,5 sec.
Before
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Effects of failures (switchgear)
Material defect in mechanical breaker mechanism
Switch disconnector (bus section) 2500 A IK ca.
30 kA, t 1,3 sec.
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Effects of failures (switchgear)
Cable disconnector Contacts not proper
closed Result complete breakdown of transformer
substation
Fuse-switch disconnector HH-fuse destroyed by
Switching overvoltage
integrated substation with hard material
insulation Not recognized PD
23
Effects of failures (switchgear)
Water inrushin substation by water main burst
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Effects of failures (switchgear)
Water inrush in integrated substation Swichtgear
SF6 insulated operating without problems
During
summer breakdown most likely !
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Effects of failures (LV)
Knocked over cable distribution cabinett Cabinet
is still energized ! Danger for pedestrians
! Only partial blackout.
After disconnecting Carefully putting-up of
cabinet Cover exposed electrical parts
! Replace the cabinet as soon as possible.
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Effects of failures (LV)
Burnt-down LV-distribution Cause ??
LV-circuitbreaker Contact attenuation by cold
flow of Al-Wire
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Effects of failures(LV)
Short-circuit by incorrect installation
(disregarding of Five-saftey-rules)
Short circuit by careless insertation of a
NH-fuse
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Internal Arc Test 1. Compressionphase
PEHLA-Prüfung, 24-kV-Anlage 12 kA, 1 sec
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Internal Arc Test 2. Expansionphase
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Internal Arc Test 3. Emmissionsphase
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Internal Arc Test 4. Thermophase
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After test
Kriterien 1 - 6 erfüllt
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Pressure curve in chamber (passer-by protection)
Closed test room
With de-smoker fan (0,2 m2)
34
Estimation of pressure
Stability of walls Lime sand bricks, 24er 30
mbar Gas concrete, 24er 15 mbar Ready-mix
concrete 50 mbar Ready-mix concrete (cubicle
construction) 160 mbar Jon-mixed concrete B25
70 mbar Poroton 36 mbar
Ceiling height 2,38 m
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Druckabschätzung II
Stability of walls Lime sand bricks, 24er 30
mbar Gas concrete, 24er 15 mbar Ready-mix
concrete 50 mbar Ready-mix concrete (cubicle
construction) 160 mbar Jon-mixed concrete B25
70 mbar Poroton 36 mbar
Ceiling height 2,38 m
36
Estimation of pressure
Stability of walls Lime sand bricks, 24er 30
mbar Gas concrete, 24er 15 mbar Ready-mix
concrete 50 mbar Ready-mix concrete (cubicle
construction) 160 mbar Jon-mixed concrete B25
70 mbar Poroton 36 mbar
switchgear Husemann GF1
Ceiling height 2,50 m
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Constructional solutions passive
Decrease of temperature ? decrease of pressure by
great surfaces
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Constructional solutions
Results of an internal-arc test with
arcing-absorber test setup -
feeder
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Constructional solutions
Results of an internal-arc test with
arcing-absorber
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Constructional solutionsaktive
Störlichtbogenbegrenzer (Fa. Driescher), aktive
Erdung
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Beispiele für Störlichtbogenprüfungen
Störlichtbogenprüfung Kompaktstation Zugänglichkei
tsgrad A 16 kA, 1 sec
Störlichtbogenprüfung Kompaktstation Zugänglichkei
tsgrad B 14 kA, 1 sec
Störlichtbogenprüfung Kompaktstation Zugänglichkei
tsgrad A 20 kA, 1 sec, PB4,5 bar nicht bestanden
Störlichtbogenprüfung luftisolierte
Schaltanlage 20 kA, 1 sec Erdungsschalter nach 68
ms
Störlichtbogenprüfung luftisolierte
Schaltanlage 16 kA, 1 sec