7SR45 Description of Operation
© 2017 Siemens Protection Devices Limited Chapter 1 Page 21 of 34
Table 3-5 Instantaneous Measured Earth Fault Protection (50G-n)
Parameters Description Default Value Min Max Step Change
50G-n
Element
50G-n Block Disabled - - -
50G-n Setting Current Set point 1xIn 0.2xIn 20xIn 0.01
50G-n Delay Delay time 0 0 s 600 s 0.01
3.6 Time Delayed Measured Earth Fault Protection (51G)
One instantaneous time delayed measured earth fault element is provided in the 7SR45 self powered overcurrent
and earth fault relay.
51G-1
51G-n Setting sets the pick-up current level.
A number of shaped characteristics are provided. An inverse definite minimum time (IDMT) characteristic is
selected from IEC and ANSI using 51G-n Char. A time multiplier is applied to the characteristic curves using the
51G-n Time Mult setting. Alternatively, a definite time lag (DTL) can be chosen using 51G-n Char.
When DTL is selected the time multiplier is not applied and the 51G-n Delay (DTL) setting is used instead.
The 51G-n Reset setting can apply a definite time delayed reset, or when the operation is configured as an IEC
or ANSI if the reset is selected as IEC/ANSI (DECAY), reset the associated reset curve will be used. The reset
mode is significant where the characteristic has reset before issuing a trip output.
A minimum operate time for the characteristic can be set using 51G-n MinOperate setting.
A fixed additional operate time can be added to the characteristic using 51G-n Follower setting.
Operation of the time delayed measured earth fault elements can be inhibited by assigning binary inputs.
Inhibit 51G-n A binary input.
Figure 3-6 Logic Diagram: Measured Time Delayed Earth Fault Element
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