Time Delayed Measured Earth Fault Protection (51G); Figure 3.3-3 Logic Diagram: Measured Time Delayed Earth Fault Element (51G); Applications Guide - Siemens 7SR224 Technical Manual

3.3.3 Time Delayed Measured Earth Fault Protection (51G)

Four elements are provided e.g. giving the option of using two elements set to forward and two to reverse.
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 curves 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
full list of operating curves is given in section 2 – 'Settings, Configuration and Instruments Guide'. Operating curve
characteristics are illustrated in section 3 – 'Performance Specification'.
The 51G-n Reset setting can apply a definite time delayed reset, or when configured as an ANSI characteristic
an ANSI (DECAYING) reset. If ANSI (DECAYING) reset is selected for an IEC characteristic, the reset will be
instantaneous. The reset mode is significant where the characteristic has reset before issuing a trip output – see

'Applications Guide'.

A minimum operate time for the characteristic can be set using 51G-n Min. Operate Time setting.
A fixed additional operate time can be added to the characteristic using 51G-n Follower DTL setting.
For the directional elements the direction of operation can be set using 51G-n Dir. Control setting. Directional
logic is provided independently for each 51G-n element.
Operation of the time delayed measured earth fault elements can be inhibited from:
Inhibit 51G-n
79 E/F Inst Trips: 51G-n
51G-n Inrush Action: Inhibit
51G-n VTSAction: Inhibit

Figure 3.3-3 Logic Diagram: Measured Time Delayed Earth Fault Element (51G)

©2010 Siemens Protection Devices Limited
A binary or virtual input, or function key
When 'delayed' trips only are allowed in the autoreclose sequence
(79 E/F Prot'n Trip n = Delayed).
Operation of the inrush current detector function.
Operation of the VT Supervision function.
7SR224 Argus Description of Operation
Chapter 1 Page 25 of 70