
Leaders in Pipelin
e Survey Systems
C
C
C
-
-
-
S
S
S
C
C
C
A
A
A
N
N
N
2
2
2
0
0
0
1
1
1
0
0
0
SYSTEM MANUAL Version 6.03i
79
16. FAQ / NOTES
16.1. TR Stations – The need to disconnect
Do I have to disconnect the TR station?
There are several answers to this question:
a) If you want to connect the generator across the TR station (i.e. use the TR station
to apply the signal to the pipeline) then YES you MUST disconnect the TR station.
Failure to do so can cause significant damage to the Generator.
b) If you wish to apply the signal to the pipeline using a CP test post, then no, you
may not have to, but it is wise not to connect the generator within 1500-3000ft of a
TR station.
If you use a CP test post to apply the signal to the pipeline and do not disconnect the TR
station, then as you survey towards the TR station the signal on the pipeline may die away
to zero; the current from the generator is being lost through the TR station to the ground
bed. If this happens you have several choices:
(i)
Survey up to the TR station then move the generator to the other side of the TR
station and connect to another CP test post and survey back to the TR station in
the other direction, as shown below. In this instance it will not be possible to
overlap surveys as the entire signal will leave the pipeline at the TR station.
(ii)
Turn off the TR station but do not disconnect it. Depending on the type of TR
station, the signal from the generator may pass by without being lost to the ground
bed, allowing you to survey across the TR station as if it were not there.
(iii)
If the TR station is turned off but the signal is still lost through it, then you will have
to use either the method as stated in (
i
) or the TR station will have to be
disconnected.
16.2. Generator Connection Problems
Connecting the Signal Generator and injecting a good signal consists of two parts: 1)
connecting to the Pipeline and, 2) connecting to a suitable earth. Each of these is as
important as each other, as the level of the injected signal will depend on the loop
impedance. Each part is discussed separately, below:
TR
CP
CP
Survey 1
Survey 2