Buried or permanent reference electrodes are often installed close to pipelines and other
buried or submerged structures with the idea that they will provide more accurate or more
representative potential data, at that specific location, than a reference electrode on the ground
surface.
Such potential data may be used to determine the local cathodic protection level, potential
shifts, the presence or absence of interference or for control of automatic output rectifiers.
But what if proximity of pipeline and buried reference electrode is not a guarantee of accurate
potential data at that point? If the buried reference electrode is installed adjacent to a pipeline
with a high quality coating, what will it read?
Coating defects, away from the buried reference electrode location, can have a major impact
on the measured potential. Compound this with the presence of foreign voltage gradients (at
pipeline crossings), and it will be shown that the potential recorded using the permanent
reference electrode may be far removed from reality.
Key Words: permanent reference electrode, buried reference electrode, cathodic protection,
coating defects, holidays, close interval potential survey (CIS), pipeline crossings, interference,
voltage gradients, -0.85V criterion, 100mV criterion.