Transcript Comments to the study on the pipe-to

Comments to the study on the
pipe-to-soil voltages induced in
the Czech oil pipelines
(Issues behind science)
Pavel Hejda
Institute of Geophysics of the ASCR, Prague, Czech Republic
ESWW4 5-9 Nov 2007
GETG Splinter Meting
Pipe to soil voltages
1
Oil pipelines in the Czech Republic
Owner of the Czech pipelines is the
company MERO ČR a.s.
The monitoring of cathodic protection
is provided by service company
1.korozni, spol. s r.o.
MERO ČR operates two pipeline
systems: Družba built in sixties
and seventies and IKL (Ingolstadt –
Kralupy) built in the beginning of
nineties.
ESWW4 5-9 Nov 2007
GETG Splinter Meting
Pipe to soil voltages
2
Data
We have obtained data registered at (remote control) stations for monitoring of cathodic
protection (distant from cathodic protection stations)
• 63 stations distributed over the entire network
• sampling rate: 30 seconds or 1 minute
• time interval: autumn 2004 – spring 2005
However, technicians of the company were stingy about technical details. They were also afraid
of leaking of information.
ESWW4 5-9 Nov 2007
GETG Splinter Meting
Pipe to soil voltages
3
Preliminary results: Correlation between pipe-to-soil voltages and
geoelectric field computed from geomagnetic observatory data November 6 to 11, 2004
As the induced pipe-to-soil voltage depends not only on the magnitude of the electric field but
also on its direction, we computed a direction which gives the highest correlation.
The size of the arrows is proportional to the correlation coefficient (maximum is 0.88) and the
angle shows the best fit direction.
Electrified railways – DC supplied and AC supplied
ESWW4 5-9 Nov 2007
GETG Splinter Meting
Pipe to soil voltages
4
Geomagnetically induced pipe-to-soil voltages - problems
15-00V_Bites
0
300
-0.4
200
-0.8
100
-1.2
0
-1.6
-100
I32Vrbice
100
-1.8
0
-2
-100
-200
-2
-2.4
7-Nov-04
7-Nov-04
-300
8-Nov-04
-200
8-Nov-04
9-Nov-04
14-04Orechov
9-Nov-04
-0.6
200
PtoS voltage (V)
-0.8
I28Katerina
100
-1
0
-1.2
-100
-1.4
-200
-1.6
1
300
0
200
-1
100
-2
0
-3
-100
-4
7-Nov-04
-200
8-Nov-04
ESWW4 5-9 Nov 2007
GETG Splinter Meting
9-Nov-04
Computed E (mV/km)
PtoS voltage (V)
-1.8
7-Nov-04
-300
8-Nov-04
9-Nov-04
The best-fit directions confirm the prevailing influence of
component of electric field parallel to the pipe-line, but only in
Druzba pipeline!
Changes in orientation: do they corresponds to the standing
waves in transmission line?
The effect of cathodic protection?
Pipe to soil voltages
5
Computed E (mV/km)
-2.2
Computed E (mV/km)
PtoS voltage (V)
-1.6
Computed E (mV/km)
200
PtoS voltage (V)
-1.4
Can we get more?
Boteler (1991) has shown that the telluric voltage induced in the pipeline can
be calculated using distributed source transmission line (DSTL) theory.
However:
• the pipelines are divided into segments (10 – 20 km) by ferro-concrete shafts
• there is always a bundle of pipelines (oil, gas, ..)
• the long-distance pipelines are crossed by many local (gas) pipelines
ESWW4 5-9 Nov 2007
GETG Splinter Meting
Pipe to soil voltages
6