(SSD’s) Solid State Decoupler

The Solid State Decoupler (SSD) functions as a DC voltage level clamping device in buried pipeline and storage tank systems.

It can, at the same time, mitigate AC voltage. This feature allows up to 15A AC induced current to pass and prevents the flow of DC current while the DC voltage remains below the predetermined design blocking threshold. When the DC voltage exceeds the threshold, the device instantly switches on forming a near short circuit across the circuit and limits the DC voltage of the device under Cathodic Protection. Immediately, the voltage falls as the surge event passes and decays to below the threshold level, the SSD switches off and reverts to its blocking mode (“Off State”).

These types of devices do not fully comply with NFP 70 guidelines when they are in conduction mode. Both cathodic protection applied DC and Induced AC present on the operating circuit (Insulated / coated Structure) is short circuited (to Ground). Once “on”, current flowing through the device can maintain these devices in the conducting state even when the voltage fault threshold has fallen below the level set. Their application can result in surging of cathodic protection power supplies.

Typical current discharge limits are 1,2kA, 2kA, 3,7kA, and 5kA. Greater discharge limits are available but are by special request.

Solid State Decoupler (SSD) devices are typically factory set to standard thresholds ranging from +2V to –2V through –20V.