IG-267-EN versión 01; 07/04/2017
37
General Instructions
ekor.rpa
Protection functions
4.7. Second harmonic blocking unit
The ekor.rpa-100 systems are fitted with the second
harmonic blocking unit.
This function blocks the overcurrent units whenever the
transformer energisation conditions are met:
• High fundamental current value.
• High second harmonic current value.
4.7.1. Functionality
The second harmonic blocking unit has 5 modules, one
for each current (I
A
, I
B
, I
C
, I
N
and I
NS
). Each of these modules
generates a blocking signal associated to the overcurrent
unit whenever the following conditions are met
simultaneously:
• The ratio between the second harmonic and the
corresponding current fundamental must be higher
than the setting “2nd harmonic threshold ratio”.
• The fundamental value of the corresponding current
must be higher than the setting “Min. phase/neutral/
senst. neutral current”.
Moreover, the following condition must be met in the three
phase current modules (I
A
, I
B
and I
C
):
• The fundamental value of the corresponding current
must be lower than the setting “Max phase current”.
Any of the following conditions must come about to disable
the block:
• The ratio between the second harmonic and the
corresponding current fundamental must be lower than
the setting “Second harmonic threshold”.
• The fundamental value of the corresponding current
must be lower than the setting “Min. phase/neutral/
senst. neutral current”.
• The time during which it remains blocked must be lower
than the setting “Max. blocking time”.
• The fundamental value of the corresponding current
must be higher than the setting “Max phase current”
(modules for I
A
, I
B
and I
C
only).
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