EXPERT TIP #27: THE INS AND OUTS OF WIRING IN CATHODIC PROTECTION

The Use of Wire in Cathodic Protection
In the Cathodic Protection (CP) industry, as with many others, we use a vast assortment of electrical
devices with significant variations of operating ranges. For instance, reference electrodes operate at less
than one volt with currents measured in micro-amps. At the same time, large CP power supplies can
have system voltages exceeding 450 volts and up to 1,000 amperes of DC output. These electrical
devices all utilize wire of varying sizes and operating requirements, and the wire sizes can be small as
0.01” (10 thousandths) diameter to over 0.46” diameter.

Wire size is typically measured using the US American Wire Gauge (AWG) standards. Outside of the US,
a similar metric system is utilized. The wire gauge or size is crucial in determining the overall
performance in an electrical circuit. In the above cable size examples, 0.01” diameter wire equals #30
AWG, and 0.46” diameter equals #4/0 AWG.

There are both stranded and solid wire configurations. Stranded wire is larger in diameter than the
equivalent solid wire. Stranded wire is more flexible and better suited for bending and applications
where there may be consistent movement of the cable. In contrast, solid wire is rigid and suitable for
applications where movement and flexibility are not essential.

How Wire Gauge Affects Electrical Circuits
• Current-Carrying Capacity: One of the primary considerations when selecting a wire gauge is its
ability to carry a certain amount of electrical current without overheating. Larger diameter wires
(lower AWG numbers) have a larger cross-sectional area, which allows them to carry more electrical
current safely. Smaller diameter wires (higher AWG numbers) have a smaller cross-sectional area,
which can handle less electrical current. Using an undersized wire for a high-current application can
lead to overheating and potentially cause a fire.
• Voltage Drop: As current flows through a wire, the electrical resistance of the wire causes a voltage
drop across the wire's length. Larger diameter wires have lower electrical resistance, resulting in less
voltage drop. Voltage drop can affect the performance of electrical devices connected to the circuit,
particularly over long distances. Minimizing voltage drop is important to ensure proper operation
and avoid possible damage to the electrical devices.
• Heat Dissipation: When electrical current flows through a wire, it generates heat due to its electrical
resistance. Larger diameter wires, with less resistance, will have lower operating temperatures, thus
reducing the risk of overheating. Proper heat dissipation is essential to prevent damage to the wire's
insulation and surrounding components.
• Circuit Efficiency: An appropriately sized wire ensures the electrical circuit will operate efficiently.
Undersized wires can result in power loss, reduced efficiency, and possible damage to electrical
devices. Choosing the correct wire gauge will ensure optimal circuit performance.
• Safety: Proper wire sizing is crucial for safety. Overloaded or undersized wires can become hot
enough to melt insulation or cause a fire. Adequate wire sizing reduces the risk of overheating and
fire hazards.
• Cost and Space: Larger diameter wires are more expensive and require more installation space.
Sometimes, using a slightly larger wire than is strictly necessary can help account for future upgrades
or changes in the circuit's requirements.
• Mechanical: In the CP industry, there are many applications where the wire may only be required to
carry a relatively small amount of current, but in some applications, the wire must endure
mechanical stresses.

o An example would be the use of heavy anodes that are to be installed in a deep well anode bed.
The typical loading procedure requires that the anode be lowered into the borehole suspended by
the anode wire, which puts physical stress on the cable.
o Another example would be a test lead wire that is to be connected to a buried pipe. The
operational current may be less than a milliamp, so a #30 gauge (0.01 dia. wire) would satisfy the
electrical requirements. However, the wire would likely be damaged during the backfilling
operation of the pipeline, so a larger wire should be selected.
o Similarly, a wire that is required to be pulled through a conduit must survive the mechanical stress
regardless of the current that it will be handling.

• Over Design: Specifying a wire or cable that is larger than necessary can be a wise choice if future
electrical loads are anticipated. However, this will undoubtedly add to the system costs in several
ways, including:

 Initial cost of the cable
 Higher shipping costs
 Difficulty in installation
 The requirement of larger conduits and hardware for connections and splicing
 Larger pull boxes and/or junction boxes

Proper Cable Insulation
It is important to understand the specific requirements of wire application. Selecting the appropriate
type of wire insulation or jacket is essential for ensuring the safety, durability, and performance of
electrical systems. The choice of insulation material depends on factors such as:
• Voltage level - High-voltage applications may require insulation materials with higher dielectric
strength.
• Temperature range - Choose an insulation material that can withstand the expected temperature
conditions.
• Environmental conditions - Consider exposure to chemicals, oils, sunlight, abrasion, and other
external factors, such as submersion in soil or water.
• Flexibility and mechanical stress - Determine if the wire will be subjected to bending, twisting, or
other mechanical stress.
• Fire and flame resistance - Some applications may require flame-retardant or fire-resistant
insulation.

When selecting a wire gauge for a specific application, factors like the current load, circuit length,
voltage drop tolerance, mechanical requirements and ambient temperature should be considered.
Similar considerations should be given for the selection of cable insulation.