Technical description
3 Supporting functions
3.3 Cold load pick-up and inrush
current detection
VM50.EN004
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115
Prms
Active power rms value
Qrms
Reactive power rms value
Srms
Apparent power rms value
fy
Frequency behind circuit
breaker
fz
Frequency behind 2
nd
circuit breaker
IL1RMS
IL1 RMS for average
sampling
IL2RMS
IL2 RMS for average
sampling
IL3RMS
IL3 RMS for average
sampling
ClrCh
Clear
Remove all channels
Set
(Ch)
List of selected channels
Set = An editable parameter (password needed)
*) This is the fundamental frequency rms value of one cycle updated every
10 ms.
**) This is the fundamental frequency rms value of one cycle updated every
20 ms.
3.3.
Cold load pick-up and inrush current
detection
Cold load pick-up
A situation is regarded as cold load when all the three phase
currents have been less than a given idle value and then at
least one of the currents exceeds a given pick-up level within 80
ms. In such case the cold load detection signal is activated for a
given time. This signal is available for output matrix and
blocking matrix. Using virtual outputs of the output matrix
setting group control is possible.
Application for cold load detection
Right after closing a circuit breaker a given amount of overload
can be allowed for a given limited time to take care of
concurrent thermostat controlled loads. Cold load pick-up
function does this for example by selecting a more coarse
setting group for over-current stage(s). It is also possible to use
the cold load detection signal to block any set of protection
stages for a given time.