Siemens 6MD85, Manual

Page: 618 / 1256

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
(_:691:115) Additional time delay
=
0.00 s
With the
Additional time delay
parameter, 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
time.
This parameter is only required for time coordination in recloser schemes. For all other applications, Siemens
recommends keeping the default setting of 0 s.
Parameter:
Threshold
•
Default setting
(_:691:3) Threshold
=
1.500 A
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
.
EXAMPLE
Overcurrent-protection stage: 110-kV overhead line, 150 mm 2 cross-section
Maximum transmittable power
P
max
= 120 MVA
Correspondingly
I
max
= 630 A
Current transformer = 600 A/5 A
Settings in primary and secondary values result in the setting values:
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Parameter:
I0 elimination
•
Default setting
(_:661:120) I0 elimination
=
no
This parameter is not visible in the basic stage.
Protection and Automation Functions
7.4 Overcurrent Protection, Phases
618 SIPROTEC 5, High-Voltage Bay Controller, Manual
C53000-G5040-C015-9, Edition 11.2017