DC Decouplers and Spark Gaps

These units are perfect to protect your assets from HVAC or HVDC lines or Lightening surges. This is an product of M.C. Miller and ADEE. CGL is distributors in Thailand, both companies. M.C. Miller SSDs&PCRs are made in USA and ADEE PCRs are made in France.
DC Decouplers and Spark Gaps
Polarization Cell Replacement (PCR)

PCR is a solid state decoupler devices which conduct once a predetermined voltage has been attained. Once conducting, they maintain the predetermined volt drop across the device. The voltage clamping devices will “soft turn on” as the threshold approaches and have a partial turn on, bleeding more and more current off of the pipeline as the voltage threshold is approached. Once at predetermined threshold, the voltage will be clamped while the conduction will be at maximum.These types of devices can have AC mitigation circuits in parallel to decouple AC steady state interference from overhead powerlines on the pipe to cater for AC voltage below the cathodic protection DC fault threshold level. Once “on”, current flowing through the device will not keep the device conducting if the voltage falls below the predetermined threshold.

Solid State Decoupler (SSD)
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. The SSD can be applied as follows.
  • corrosion be AC bonded but isolated in the DC mode.
  • Isolate electrical DC equipment in Cathodic Protection systems.
  • AC coupling to earth where DC blocking/isolation is required.
  • Over voltage conditions emanating from induced AC surges,
  • Protection of insulating joints on pipelines.
  • Mitigation of AC induced voltages.
  • Decoupling in gradient control (earth/grounding) mats from pipelines
  • spark gaps
    A spark gap consists of an arrangement of two conducting electrodes separated by a gap usually filled with a gas such as air, designed to allow an electric spark to pass between the conductors. When the potential difference between the conductors exceeds the breakdown voltage of the gas within the gap, a spark forms, ionizing the gas and drastically reducing its electrical resistance. An electric current then flows until the path of ionized gas is broken or the current reduces below a minimum value called the “holding current”. This usually happens when the voltage drops, but in some cases occurs when the heated gas rises, stretching out and then breaking the filament of ionized gas. Usually, the action of ionizing the gas is violent and disruptive, often leading to sound (ranging from a snap for a spark plug to thunder for a lightning discharge), light and heat. A spark gap e can be applied as follows :
  • For indirect connection / earthing of functionally isolated parts of installations under lightning conditions
  • For lightning equipotential bonding according to IEC 62305 in hazardous areas (zone 2)
  • Corrosion-resistant zinc die-cast enclosure with plastic cover and flexible cable connection
  • For bridging insulating joints, insulating flanges etc. in cathodically protected pipe sections
  • Extremely heavy-duty device

    spark gap consists of an arrangement of two conducting electrodes separated by a gap usually filled with a gas such as air, designed to allow an electric spark to pass between the conductors.

    In AC mitigation applications, the De-Coupler should provide a continuous conduction path to ground for the AC while preserving the applied Cathodic ProtectionDC and provide over voltage protection when AC & DC rise above a specified predetermined level.

    There are a few differences to note, primarily in the fault current range of products offered. The PCR offers 4 fault current ratings: 3.7KA, 5KA, 10KA and 15KA. The SSD range also offers 4 fault current rating options, lower scale. The SSD line offers: 1.2KA, 2KA, 3.7KA and 5KA.

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