Bipolar current inputs are passive inputs, meaning, that they are supplied by the pulse giver. This means that
they are isolated elements. Bipolar current pulses are direct current pulses that change polarity with each
pulse. Each 0V-Line cross-over will define a pulse. This can also be accomplished using a constant (not in
pulse form) direct current. The polarity must be changed, thus providing the necessary 0V-Line cross-over,
for each meter pulse.
24-Volt current is usually used, but may also vary from between 19V and 60V. The input current drawn by
our electronic bipolar current inputs is less than 2mA (with 24V).
Since each meter pulse implies an input-polarity change IED modules internally produce a complete 90ms type
pulse for each valence change. This must be taken into account in coordination with the maximum pulse
frequency (< 7Hz). IED modules that produce 20ms type pulses are also available. They can be used with a
pulse frequency of up to 30Hz.
Since bipolar current transmission is not easily interfered with, they are highly recommended for use with
long transmission distances. Depending on the particular circumstances (other inductive sources in the
vicinity, very long transmission distances, etc.), shielded cable or cable with larger cross section might still
be recommended, if this is possible.