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29
29.1
29.1.1
29.1.2
29.1.3
Sudden change in residual current
protection (SCRC)
Sudden change in residual current
protection (SCRC)
Prepare the terminal for verification of settings as outlined in
this chapter.
Measuring the operate limit of set values
Sudden change in residual current
The sudden change in residual current protection algorithm measures the difference in amplitude
of the residual current between two consecutive periods, and compares this difference to a set
value.
Dependability test
Procedure
1.
Inject a three-phase balanced current, close to the rated secondary
current, and add a small residual current.
2.
Measure the residual current, with an external device.
3.
Activate the SCRC_CR binary input.
4.
Make a rapid small positive step-change of the residual current.
5.
Check if the SCRC_START (or SCRC_TRIP) signal appears.
6.
Compare the measured change in residual current with the set value
DIN>.
7.
Repeat item 4-6, with successively increased step-size, until thRe-
peat item 1-7, with a lower/higher balanced current in item 1.Repeat
item 1-7, with a lower/higher balanced current in item 1.
8.
Repeat item 1-8, with a larger residual current in item 1.
9.
Repeat item 1-9, with a negative step-change in item 4.
Time delay test
Procedure
1.
Inject a three-phase balanced current, close to the rated secondary
current, and add a residual current.
2.
Prepare measurement of the time between the sudden change in re-
sidual current and the appearance of the SCRC_START
(SCRC_TRIP) signal.
3.
Activate the SCRC_CR binary input.
4.
Make a rapid step-change of the residual current, significantly larger
than the set value DIN>.
Chapter 13
Verifying settings by secondary
section 2 "Preparing for test"
injection
in
153
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