1. ESWW4 5-9 Nov 2007 GETG Splinter Meting Pipe to soil voltages1 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

2. ESWW4 5-9 Nov 2007 GETG Splinter Meting Pipe to soil voltages2 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.

3. ESWW4 5-9 Nov 2007 GETG Splinter Meting Pipe to soil voltages3 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.

4. ESWW4 5-9 Nov 2007 GETG Splinter Meting Pipe to soil voltages4 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

5. ESWW4 5-9 Nov 2007 GETG Splinter Meting Pipe to soil voltages5 Geomagnetically induced pipe-to-soil voltages - problems 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?

6. ESWW4 5-9 Nov 2007 GETG Splinter Meting Pipe to soil voltages6 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