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Impacts of Inductive and Conductive Interference due to High-Voltage Lines on
Coating Holidays of Isolated Metallic Pipelines
René Braunstein
Frankfurt (Germany), 6-9 June 2011
René Braunstein– AT – S2 PQ&EMC – 0013
Introduction
A.C. voltage interference Capacitive Interference Inductive Interference Conductive Interference
Frankfurt (Germany), 6-9 June 2011
René Braunstein– AT – S2 PQ&EMC – 0013
Coating Holidays?
Small defects of isolating pipeline coating
Coating Holidays + Inductive and/or conductive Interference Material removal
Frankfurt (Germany), 6-9 June 2011
René Braunstein– AT – S2 PQ&EMC – 0013
A.C. corrosion likelihood CEN/TS 15280 - Comité Européen de
NormalisationNormal operation – long-term influencea.c. voltage should not exceed: RMS a.c. current density (J ~) :
10 V für RE > 25 Ωm; J ~ < 30 A/m2: no/low likelihood 4 V für RE < 25 Ω J ~ 30 A/m2 - 100 A/m2 : medium likelihoodat any time J ~ > 100 A/m2 : very high likelihood
Frankfurt (Germany), 6-9 June 2011
René Braunstein– AT – S2 PQ&EMC – 0013
Modelling Coating Holidays (1)
1 … R leakage in the soil2 … R pore3 … R polarisation4 … Coating5 … Steeld … pore diametert … depth of the pore (coating thickness)
Source: CEN/TS 15280: Evaluation of a.c. corrosion likelihood of buried pipelines- Application to cathodically protected pipelines. CEN, March 2006, modified.
Frankfurt (Germany), 6-9 June 2011
René Braunstein– AT – S2 PQ&EMC – 0013
Modelling Coating Holidays (2)
Simplified as a circularplate earthing system
Source: CEN/TS 15280: Evaluation of a.c. corrosion likelihood of buried pipelines- Application to cathodically protected pipelines. CEN, March 2006, modified.
E
ch
2 rr (1 arctan )
4 d 2 H
ρE … Specific soil resistivity in Ωmd … Coating holiday diameterH … Distance between earth‘s surface and Coating Holiday
Frankfurt (Germany), 6-9 June 2011
René Braunstein– AT – S2 PQ&EMC – 0013
Dependency on specific soil resistivity ρE
101
102
103
101
102
103
104
105
106
Specific soil resistivity in m
r ch in
d= 1 mm
d= 5 cm
Frankfurt (Germany), 6-9 June 2011
René Braunstein– AT – S2 PQ&EMC – 0013
Currents over Coating Holidays
101
102
103
10-6
10-4
10-2
100
Specific soil resistivity in m
I ch in
A/m
2
Ui=1V
101
102
103
10-6
10-4
10-2
100
Specific soil resistivity in m
I ch in
A/m
2
Ui=4V
101
102
103
10-5
100
Specific soil resistivity in m
I ch in
A/m
2
Ui=10V
101
102
103
10-5
100
Specific soil resistivity in m
I ch in
A/m
2
Ui=20V
d= 1 mm
d= 5 cm
Frankfurt (Germany), 6-9 June 2011
René Braunstein– AT – S2 PQ&EMC – 0013
Current Densities at Coating Holidays
101
102
103
100
102
104
Specific soil resistivity in m
J ch in
A/m
2
Ui=1V
101
102
103
100
102
104
Specific soil resistivity in m
J ch in
A/m
2
Ui=4V
101
102
103
100
102
104
Specific soil resistivity in m
J ch in
A/m
2
Ui=10V
101
102
103
102
104
Specific soil resistivity in m
J ch in
A/m
2
Ui=20V
d= 1 mm
d= 5 cm
Frankfurt (Germany), 6-9 June 2011
René Braunstein– AT – S2 PQ&EMC – 0013
Conductive Interference (1)
conductive influenced pipeline areauninfluenced pipeline area
lLrL
CQ /2
Icch
rch
2rp
2rp
2rp
2rp
rLlL
cp/2
cp/2
cp/2
induced voltage Ui
Pi – equivalent circuit of influenced pipeline segments
Frankfurt (Germany), 6-9 June 2011
René Braunstein– AT – S2 PQ&EMC – 0013
Conductive Interference (2)
0 1 2 3 4 5 6 7 8 9 100
5
10
15
20
25
Pipeline-km
Inte
rfer
ence
Vol
tage
in %
of
U pg
d=10mmcoating holidaysd=20 mmd=50mm
Frankfurt (Germany), 6-9 June 2011
Summary
Coating Holidays can bee seen as very high impedant earthing systems
A.C. corrosion likelihood decreases with raising ρE
The cumulated impact of inductive and conductive interference is relevant for A.C. corrosion
The shown values can be seen as practicable reference values
René Braunstein– AT – S2 PQ&EMC – 0013
