Siemens 7SJ82 Manual page 364

Protection and Automation Functions
6.4 Voltage-Dependent Overcurrent Protection, Phases
Parameter: Method of measurement
•
Recommended setting value (_:11491:8) 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
fundamental comp.
RMS value
Parameter: Threshold
•
Default setting (_:11491:3) Threshold = 1.500 A
The recommended setting value of 1.500 A is suitable for most applications.
Set the Threshold and Type of character. curve parameters for the specific application.
The setting depends on the maximum occurring operating current. Pickup by overload must be excluded since
overcurrent protection operates with short tripping times as short-circuit protection and not as overload
protection.
Set the Threshold parameter for lines to approx.10 %, for transformers and motors to approx. 20 % above
the maximum expected load.
Note that a safety margin is set between pickup value and threshold value. The stage only picks up at approx.
10 % above the Threshold.
Parameter Type of character. curve
•
Default setting (_:11491:101) Type of character. curve = IEC normal inverse
The device offers all the usual inverse-time characteristic curves according to IEC and ANSI. Select the Type
of character. curve required for your specific application.
Parameter: Reset
•
Default setting (_:11491:102) Reset = disk emulation
The Reset parameter allows you to define whether the stage decreases according to the dropout character-
istic curve (behavior of a disk emulation = rotor disc) or instantaneously.
Parameter Value
disk emulation
instantaneous
Parameter: Time dial
•
Default setting (_:11491:103) Time dial = 1
You can use the Time dial parameter to displace the characteristic curve in the time direction.
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Description
Select this method of measurement if harmonics or transient current peaks
are to be suppressed.
Siemens recommends using this method as the standard method.
Select this method of measurement if you want the stage to take harmonics
into account (for example, at capacitor banks). Consider that aperiodic DC
components present in the secondary circuit are measured and can cause
an overfunction.
For this method of measurement, do not set the threshold value of the
stage to less than 0.1 I
rated,sec
point are added up in the current interface of a function group, the setting
value should not be set lower than 0.1 I
added currents.
Description
Select this setting if the device is coordinated with electromechanical
devices or other devices which perform a dropout after a disk emulation.
Select this setting if the dropout does not have to be performed after a disk
emulation and an instantaneous dropout is desired instead.
. If currents from more than one measuring
multiplied by the number of
rated,sec
SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017