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146
Sudden voltage change function (SVC)
SVC-BLOCK
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SVC-VTSU
t
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du
dt
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The output signal SVC-START and the start signal ZnRW-START from the impedance
function should be configured to an AND-gate for the release of the trip signal to the
line circuit-breaker. An example of the tripping logic for the impedance protection and
the functions SVC and SCC (Sudden Change Current function) is shown in figure 65.
Z n R W -
S T A R T
S V C -
S T A R T
S C C - S T A R T
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The parameters for the sudden voltage change function are set via the local HMI or PST
(Parameter Setting Tool). Refer to the Technical reference manual for setting parame-
ters and path in local HMI.
The setting of the operate value for the step voltage measuring element du/dt must be
greater than the highest expected voltage drop due to load change on the protected line.
An additional margin of at least 10% in addition to the declared inaccuracy of the volt-
age transformers and the measuring element should be allowed for in the setting.
&
t
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e n 0 2 0 0 0 5 1 2 . v s d
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SVC-START
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