Protective Function Configuration
Siemens Energy & Automation, Inc. 23
5.6 Phase Time Overcurrent (51)
The Phase Time Overcurrent function uses a selected time
overcurrent characteristic curve to determine the trip time for
the applied phase currents. The defined characteristic curves
are valid over a range of multiple of pickup values. The func-
tion also includes the ability to select a customer defined
curve. This function is always enabled. Refer to Appendix A
for detailed trip curve information.
The Curve parameter (1702) allows the selection of the pre-
programmed characteristic curve used by this function. The
ISGS relay comes with nine standard and one custom over-
current characteristic curves that can be adjusted with the
Time Dial parameter. The custom curve is a user-definable
protective curve that integrates with instantaneous reset. The
lower limit of the custom curve is 1.10. The maximum time to
trip is the time at 1.10.
The range of the pickup value (1703) depends on the sec-
ondary phase CT rating (1 A or 5 A) and the value is in sec-
ondary amperes. The function begins timing when any
individual phase current exceeds the pickup current setting.
Note: The pickup point is 1.06 of the pickup set-
ting. Refer also to paragraph on Pickup in
Section 5.1.
The Time Dial parameter (1705) used for the selected curve
allows the time-to-trip of the curve to be raised or lowered
The dial can be adjusted from 0.1 to 9.9 in steps of 0.1.
The Filter parameter (1706) sets the sensing method used by
the function in its pickup calculations. The rms filter uses fun-
damental current plus harmonics, while the fundamental filter
ignores harmonics.
A1700 Phase Time Overvurrent (51)
Address Parameter Option
1702 Curve Inverse
Short Inverse
Long Inverse
Moderately Inverse
Custom
Very Inverse
Extremely Inverse
Definite Inverse
Slightly Inverse
I
2
T Without Limit
1703 Pickup 5 A CTs: 0.5-20 A or
1 A CTs: 0.1-4 A
(0.1 A steps)
1705 Time Dial 0.1-9.9 (0.1 steps)
1706 Filter rms or fundamental
1709 Reset Instantaneous or Disk Emulation
1710 Freeze Wfm1 on Pickup, on Trip, or None
1711 Freeze Wfm2 on Pickup, on Trip, or None
1712 Blocked by None, 50HS, 50HSN, or
50HS & 50 HSN
The Reset parameter (1709) offers instantaneous or disk
emulation settings. Selecting Instantaneous causes the relay
to clear the timer when the current drops below the pickup
threshold. Selecting Disk Emulation causes the relay to simu-
late the integrating disk characteristics of electromechanical
relays, where the delay time decays over time. With disk
emulation, a relay that continuously picks up and drops out
will eventually trip. Set this parameter to Instantaneous when
using a custom curve.
Each of the two waveform capture buffers (1710 and 1711)
can be independently programmed to freeze snapshots on
pickup or trip.
The function is able to actuate any binary output contact on
pickup, and any trip or binary output contact on trip.
5.7 Neutral Time Overcurrent (51N)
The Neutral Time Overcurrent function uses a selected time
overcurrent characteristic curve to determine the trip time for
the applied current at the fourth current input. The defined
characteristic curves are valid over a range of multiple of
pickup values. The function also includes a customer defined
curve. Refer to Appendix A for detailed trip curve informa-
tion.
The Neutral or Ground Time Overcurrent function can be
enabled and disabled (1801).
The Curve parameter (1702) allows the selection of the pre-
programmed characteristic curve used by this function. The
ISGS relay comes with nine standard and one custom over-
current characteristic curves that can be adjusted with the
Time Dial parameter. The custom curve is a user-definable
A1800 Neutral Time Overcurrent (51N)
Address Parameter Option
1801 Function Enabled or Disabled
1802 Curve Inverse
Short Inverse
Long Inverse
Moderately Inverse
Custom
Very Inverse
Extremely Inverse
Definite Inverse
Slightly Inverse
I
2
T Without Limit
1803 Pickup 5 A CTs: 0.5-20 A or
1 A CTs: 0.1-4 A
(0.1 A steps)
1805 Time Dial 0.1-9.9 (0.1 steps)
1806 Filter rms or fundamental
1809 Reset Instantaneous or Disk Emulation
1810 Freeze Wfm1 on Pickup, on Trip, or None
1811 Freeze Wfm2 on Pickup, on Trip, or None
1812 Blocked by None, 50HS, 50HSN, or
50HS & 50 HSN
5
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