Siemens 6MD85, Manual

Page: 725 / 1256

Parameter Value Description
yes
When the transformer inrush-current detection detects an inrush
current that would lead to an operate of the stage, the start of the
operate delay and operate of the stage are blocked.
Select this setting if the device is used on transformers and the
threshold value of the stage is set below the maximum inrush current
of the transformer. This applies to the overcurrent-protection stage,
which is used as a backup stage with grading time for faults on the
undervoltage side of the transformer.
Parameter:
Min. time of the curve
•
Default setting
(_:4891:114) Min. time of the curve
=
0.00 s
This parameter is only available in the advanced stage.
With the parameter
Min. time of the curve
, you define a minimum operate delay time. The operate
delay time of inverse-time characteristic curve never falls below the minimum operate delay time. If the
setting is left on its default value of 0 s, this parameter has no effect on the inverse-time characteristic curve.
This parameter is only required for time coordination in recloser schemes. For all other applications, Siemens
recommends keeping the default setting of 0 s.
i
i
NOTE
If the set value is smaller than the smallest possible time delay of the inverse-time characteristic curve, the
parameter has no influence on the delay time.
Parameter:
Additional time delay
•
Default setting
(_:4891:115) Additional time delay
=
0.00 s
With the parameter
Additional time delay
, you define a definite-time delay in addition to the inverse-
time delay.
If the setting is left on its default value of 0 s, this parameter has no effect on the inverse-time characteristic
curve.
This parameter is only required for time coordination in recloser schemes. For all other applications, Siemens
recommend keeping the default setting of 0 s.
Parameter:
Threshold
•
Default setting
(_:4891:3) Threshold
=
1.20 A
The setting depends on the minimal occurring ground-fault current. This must be detected.
Consider 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
(_:4891:130) 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:
Time dial
•
Default setting
(_:4891:101) Time dial
=
1
You can use the
Time dial
parameter to displace the characteristic curve in the time direction.
The setting value for the
Time dial
parameter is derived from the time-grading chart that has been
prepared for the electrical power system.
Protection and Automation Functions
7.7 Directional Overcurrent Protection, Ground
SIPROTEC 5, High-Voltage Bay Controller, Manual 725
C53000-G5040-C015-9, Edition 11.2017