Understanding Cathodic Protection Test Stations
The Purpose of a CP Test Station
The main purpose of a cathodic protection (CP) test station is to provide an access point to terminate cables from a buried structure (pipeline) to take electrical measurements or readings on that structure.
Because it is impractical to excavate the structure every time a measurement must be taken, a test station is used to provided electrical access to the structure, via connecting cables, to obtain needed CP data.
In its most basic form, a test station is simply an enclosure (above or at grade) with cable connecting points that allow cables from a buried structure, such as a pipeline, to be terminated. This electrical access to the structure allows technicians to perform necessary CP tests. In addition to structure access, a test station can also allow a technician to monitor other CP components such as an anode, a stationary reference electrode, or a CP coupon.
In some cases, more than one structure may be monitored from a single test station, which will require more cables and cable terminations. Alternatively, multiple cable connections can be affixed to the same structure, in this case, a pipeline, to determine if a buried pipeline isolator is functional. The test station design will still include an enclosure with cable connecting points even with added complexity.
Capabilities and Advancements
While a test station has a relatively simple job, cathodic protection designers have altered the basic design to include other internal testing components to include current measurement shunts, on/off switches, bond jumpers and more. The basic enclosure and cable terminations are still core components even in the more advanced test stations.
The History
The first test station enclosures were invented in the mid-1900s and made from metallic alloys. These enclosures were designed for aboveground service and included a non-metallic panel for cable terminations. Concrete "valve boxes" were also used for at-grade test stations employing a non-metallic panel board with cable terminations. Later, metallic test station bodies were designed for at-grade use.
In the later 1900s, plastic compounds evolved, and non-metallic test stations entered the CP market. These aboveground test stations were made from polycarbonate, a very durable plastic compound still used today. Later, the same polycarbonate materials were used for buried or at-grade versions.
The Value
Test stations are very important to the CP industry, allowing technicians to monitor pipelines or other critical buried metallic structures. While they have evolved and can include sophisticated electronics to monitor buried structures remotely, CP testing stations' basic use and testing principles have changed very little.