•
Measurement of the fundamental comp.:
This measurement method processes the sampled current values and numerically filters out the funda-
mental component.
•
Measurement of the parameter value RMS value:
This measurement method determines the current amplitude from the sampled values according to the
definition equation of the RMS value. Harmonics are included in the analysis.
Pickup Mode
The Pickup mode parameter defines whether the protection stage picks up if all 3 measuring elements
detect the undercurrent condition (3 out of 3) or if only 1 measuring element has to detect the undercur-
rent condition (1 out of 3).
Blocking the Stage
When blocked, the picked-up protection stage will drop out. Blocking the stage is possible externally or inter-
nally via the binary input signal
>Block stage
.
Activation and Blocking of the Stage Depending On the Circuit-Breaker Condition
With the parameter Activation, you define if the Undercurrent protection stage is always active or only
active if the circuit breaker is indicating closed.
If the parameter Activation is set to with CB closed and the local circuit breaker is not closed, the func-
tion Undercurrent protection is blocked and no pickup is generated.
The circuit-breaker position is detected as closed if one of the following conditions is met:
•
The binary inputs are connected to the auxiliary contacts of the circuit breaker. The circuit-breaker switch
position is detected as closed via the related binary inputs of the Position indication. This is also true
under the condition that no phase current is flowing.
•
The current-flow criterion indicates that the circuit breaker is closed. This is also true under the condition
that the auxiliary contacts indicate the circuit breaker as open.
Application and Setting Notes
Parameter: Activation
•
Default setting (_:13051:103) Activation = with CB closed
Parameter Value
Description
with CB closed
The Undercurrent protection is active only when the circuit-breaker posi-
tion is detected as closed.
A precondition is, that the Position indication is routed to binary inputs to
obtain the CB position information via the CB auxiliary contacts. If this is not
the case, the function will always be inactive.
always active
The Undercurrent protection stage is always active independent of the
position of the circuit breaker.
Parameter: Method of measurement
•
Recommended setting value (_:13051:8) Method of measurement = fundamental comp.
With the Method of measurement parameter, you define whether the stage uses the fundamental
comp. (standard method) or the calculated RMS value.
Parameter Value
Description
fundamental comp.
Select this method of measurement if harmonics or transient current peaks
are to be suppressed.
Siemens recommends using this method as the standard method.
6.16.4
Protection and Automation Functions
6.16 Undercurrent Protection
630 SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
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