Siemens Reyrolle 7SR45 Argus Device Manual page 64

Functions
3.7 Time-Delayed Measured Earth Fault Protection (51G)
Gn 51G-n Follower DTL
Default setting: 0.00 s
This setting allows an additional time to be added to that achieved by the selected characteristic curve. It is
applied as a DTL time after the operate state from the curve is achieved. With this setting, the whole curve is
shifted linearly on the time axis by this additional definite time.
This is traditionally used with recloser systems only and otherwise is recommended to be left at the default
setting of 0s.
Gn 51G-n Reset
Default setting: 0.00 s
The reset parameter is used to define whether the element pickup resets to 0 instantaneously when the
current falls below the setting or a reset curve characteristic or fixed DTL is applied. This operation is signifi-
cant during intermittent faults where an induction disc device would be partially rotated when the fault
current is re-applied.
Parameter Value
IEC/ANSI Decay
00 s
01 s – 60 s
51G-n Inrush Action
Default Setting: Off
High levels of inrush currents into reactive components such as transformers when they are switched can
result in operation of overcurrent elements. The Inrush current can be detected by a high percentage of
second harmonic current content by the 81HBL2 element. This parameter can be configured to inhibit the
earth fault element automatically by configuration of this setting.
Parameter Value
Off
Inhibit
Settings Example
The 51G-n characteristic element provides a number of time/current operate characteristics. The element can
be defined as either an Inverse Definite Minimum Time Lag (IDMTL) or Definite Time Lag (DTL) characteristic.
If an IDMTL characteristic is required, then IEC and ANSI/IEEE curves are supported. IDMTL characteristics are
defined as inverse because their tripping times are inversely proportional to the fault current being measured.
This makes them particularly suitable to grading studies where it is important that only the relay(s) closest to
the fault operate. Differentiation can be achieved with minimised operating times. For more details, refer to
5.3 Time-Delayed Overcurrent (51/51G/51N)
64
Description
This selection applies a resetting curve to the element pickup to provide
emulation of an induction disc device. The standard IEC curve is applied if
the operating Char is an IEC Characteristic and the ANSI reset curve is
applied for an ANSI operating Char. Select this setting if the device is coor-
dinated with electromechanical devices or other devices which perform a
disc emulation reset.
Use this setting for instantaneous reset of the element. When the current
falls below the setting, the pickup resets completely instantaneously and
subsequent increase in current above the setting will restart the operation
delay from 0.
The percentage operated state is retained when the current falls below the
setting for a period of the set delay. Subsequent increase in current to
above the setting within the set delay allows operation to resume from the
partially operated state instead of 0.
Description
The earth fault element is not affected by operation of the 81HBL2 element.
The earth fault element is inhibited by operation of the 81HBL2 element
and automatically released when the 81HBL2 element resets.
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Reyrolle, 7SR45, Device Manual
C53000-G7040-C101-2, Edition 09.2020