Spark Gap in Cathodic Protection Systems

A spark gap, also known as a cathodic spark gap, is a safety device used in cathodic protection (CP) systems.

Here’s how a spark gap functions in a CP system:

  • Isolation: One of the crucial aspects of CP systems is maintaining electrical isolation between the protected structure and other surrounding metals. This isolation prevents unwanted current from interfering with the CP system’s effectiveness.
  • Surge Protection: While isolation is necessary, there might be instances where a temporary connection to ground becomes essential. This could be due to lightning strikes or other transient voltage surges. A spark gap offers a controlled path for these surges to safely discharge to the ground.
  • Safety Mechanism: The spark gap acts as a safety valve. In normal operation, the gap in the device remains open, preventing any current flow between the CP system and the ground. However, if a surge in voltage occurs, the gap breaks down, allowing the surge current to pass through to the ground and safeguarding the CP system from damage.

Spark gaps are typically installed alongside isolation joints in CP systems. Isolation joints electrically isolate the protected structure from the rest of the piping network.

Here are some additional points to consider regarding spark gaps:

  • Types: Spark gaps come in various types, including regular and explosion-proof versions for hazardous environments.
  • Selection Criteria: The selection of a suitable spark gap depends on factors like the voltage rating and expected surge current in the CP system.

If you’d like to delve deeper into the technical details of spark gaps or cathodic protection systems in general, I can’t provide specific resources due to my limitations on providing links. However, I can recommend searching for terms like “cathodic protection spar k gap” or “cathodic protection system components”.


A cathodic spark gap typically consists of the following components:

  • Electrodes: Two metal electrodes, usually made of stainless steel, housed in an insulating enclosure.
  • Electrode gap: The distance between the electrodes is precisely set and plays a crucial role in determining the spark gap’s breakdown voltage.
  • Insulating enclosure: The enclosure protects the electrodes from the external environment and prevents gas leaks or moisture ingress.
  • Fill gas: The enclosure can be filled with gases such as air, nitrogen, or SF6. The type of gas affects the breakdown voltage and overall performance of the spark gap.


Under normal conditions, the voltage applied to the CP system is lower than the breakdown voltage of the spark gap. In this state, the electrode gap acts as an insulator, preventing the flow of electric current between them.

However, if a transient or surge voltage, such as lightning, is applied to the CP system, the voltage may exceed the spark gap’s breakdown voltage. In this scenario, the electrode gap breaks down, creating a path for the surge current to discharge to earth.

This action helps protect other components of the CP system from damage caused by overvoltage.

Additional Notes:

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