What is the CCR-to-series-circuit interface?
The point where the CCR output meets the primary cable loop — terminals, isolation and cable termination, matched and made safe.
The CCR-to-series-circuit interface is the point where the CCR output meets the primary cable loop. It consists of the OUT and RTN output terminals, normally an isolating arrangement so the circuit can be disconnected from the CCR, and the termination of the primary cable.
At this point the CCR hands a constant current to the loop, so the two must be matched: the CCR rating has to suit the circuit load, and the cable and terminations have to be insulated for the highest voltage the CCR can produce. The terminals carry hazardous voltage when energised, and a live loop must never be opened because the CCR will drive the voltage up across the break. See circuit load, series circuit voltage and circuit termination.
- Isolate. De-energise and isolate the CCR before any work.
- Terminate. Fit the terminations to the ends of the primary cable.
- Connect. Join the cable to the CCR OUT and RTN terminals.
- Check isolation. Confirm the isolating arrangement works and is clearly labelled.
- Check ratings. Confirm the CCR suits the circuit load and the cable suits its voltage.
- Test. Prove continuity and insulation before energising.
Frequently Asked Questions
Q1What is the CCR-to-series-circuit interface?
The point where the CCR hands its constant current to the primary cable loop. It is made up of the CCR output terminals, normally an isolating arrangement, and the termination of the primary cable.
Q2What does the interface consist of?
The OUT and RTN output terminals of the CCR, an isolating switch or similar means of disconnecting the circuit from the CCR, and the cable termination that connects the primary cable to them.
Q3What has to be matched at the interface?
The CCR rating must suit the circuit load in current, power and voltage, and the cable and its terminations must be insulated for the maximum output voltage the CCR can produce.
Q4Why must a live loop never be opened?
The CCR keeps trying to hold its set current, so a break in a live loop makes the voltage across the break rise sharply. This is dangerous to anyone working on it. The CCR is isolated first, and the site procedure is followed.
Q5Is the CCR output connected to earth?
No. The loop is normally insulated from earth, and the current returns through the cable. The CCR frame is earthed for safety, but an unintended connection between the loop and earth is an earth fault. See series circuit current path.
Q6How is the interface checked before the CCR is energised?
With the circuit isolated, the loop is tested for continuity and insulation, and the terminations are inspected, so that the path is complete and well insulated from the CCR outwards.
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