The power supply of an impressed current system: a step-down transformer with tap settings, a silicon diode or selenium rectifying stack, meters and a shunt in a weatherproof cabinet. The negative terminal goes to the structure and the positive to the groundbed. Techs read output voltage and current on a regular schedule, which pipeline rules require, and log every tap change.
Rectifier at the valve site is putting out zero, breaker's fine, so check the stack and the AC fuses.
Reversed polarity is the cardinal sin. Confirm the negative goes to the structure before energizing, because a backwards rectifier destroys pipe faster than no CP at all.
Also heard as
- rec
- rect
- transformer-rectifier
- TR unit
Related terms
Tap
Adjustable transformer setting on a rectifier, used to raise or lower DC output in coarse and fine steps.
Shunt
Precision low-resistance resistor in a CP circuit, used to measure current from the voltage across it.
ICCP
Impressed current cathodic protection: CP powered by a rectifier pushing current through long-life anodes.
Interrupter
Timed switch fitted to a rectifier or bond that cycles CP current on and off for instant-off readings.
Groundbed
Group of impressed-current anodes buried in backfill that discharges rectifier current into the earth.