MIL-HDBK-1004/10
Selection of Power Supply Type. Any source of direct current of
6.4
appropriate voltage and current can be used as a source of power for impressed
current cathodic protection systems. The selection of power supply depends
upon local conditions at the site and should be evaluated based upon life
cycle cost including maintenance and availability of ac power or fuel.
Rectifiers. Rectifiers are by far the most commonly used power
6.4.1
supply type for impressed current cathodic protection systems. They are
available in a wide variety of types and capacities specifically designed and
constructed for use in impressed current cathodic protection systems. The
most commonly used type of rectifier has an adjustable step down transformer,
rectifying units (stacks), meters, circuit breakers, lightning arresters,
current measuring shunts, and transformer adjusting points (taps), all in one
case.
Thermoelectric Generators. These power supplies convert heat
6.4.2
directly into direct current electricity. This is accomplished through a
series of thermocouples which are heated at one end by burning a fuel and
cooled at the other, usually by cooling fins. Thermoelectric generators are
highly reliable since they have few, if any, moving parts. They are available
in sizes from 5 to 500 W. They are very expensive and should only be
considered for remote locations where electrical power is not available and
fuel is available. They are used as a power supply for impressed current
cathodic protection on remote pipelines where the product in the pipeline can
be used as a fuel.
Solar. A photovoltaic solar cell converts sunlight directly into
6.4.3
direct current electricity. The cost per W is high but is decreasing as solar
cell technology is improved. Solar panels are used for cathodic protection
power supplies at remote sites where neither electrical power or fuel is
available. In order to supply current continuously, solar cells are used in a
system that supplies power to the system and recharges batteries when sunlight
is received. When sunlight is not being received, the batteries supply the
required current.
Batteries. When current requirements are low, storage batteries
6.4.4
can be used to supply power for impressed current cathodic protection systems
at remote sites. They must be periodically recharged and maintained.
Generators. Engine- or wind-driven generators can be used to
6.4.5
supply direct current power for impressed current cathodic protection systems
at sites where ac power is not available.
Rectifier Selection. The rectifier selected for a specific
6.5
impressed current cathodic protection application must be matched to both the
electrical requirements and the environmental conditions at the site.
Rectifiers are available in many electrical types and specifically designed
for use in impressed current cathodic protection systems in many environments.
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