Schweitzer Engineering Laboratories SEL-751 - Table 7.23 HSG Command; Figure 7.27 HSG Command Response

7.38
SEL-751 Relay Instruction Manual Date Code 20170927
Communications
Communications Protocols
HSG Command
When the SEL-751 is ordered with the Arc Sense technology (AST) option for
the high-impedance fault (HIF) detection, the relay provides high-impedance
fault histogram data with the HSG (histogram) command. The HSG
command displays 100 long-term and 100 short-term histogram counter
values of the Phases A, B, and C current odd-harmonic content (ISM) plus the
learned limits for the histograms.
Figure 7.27 shows the HSG command response.
The purpose of the Statistics function is to learn the effects of feeder normal
loads on the detection quantity ISM. The function keeps two histogram
counters, each has 100 units.
HIF odd-harmonic decision function generates HIF alarms if the difference
between two histograms is statistically substantial (determined by using their
means and standard deviations). When the difference between the two
histograms is not substantial, the long-term histogram is updated through an
Table 7.23 HSG Command
Command Description Access Level
HSG Displays high-impedance fault (HIF) histo-
gram data.
1
NOTE:
LT HIS A, LT HIS B,
LT HIS C
Long-term histogram counter values of the Phases A, B, and C
current odd-harmonic content (ISM).
ST HIS A, ST HIS B,
ST HIS C
Short-term histogram counter values of the Phases A, B, and C
current odd-harmonic content (ISM).
HISLIMA,
HISLIMB, HISLIMC
Learned histogram thresholds for Phases A, B, and C.
Mean Mean values of short- and long-term histograms for Phases A,
B, and C.
Std Standard deviations for the short- and long-term standard devia-
tions for the short- and long-term histograms for Phases A, B,
and C.
NFA, NFB, NFC Pickup thresholds of decision timers for Phases A, B, and C.
=>>HSG <Enter>
SEL-751 Date: 04/11/2011 Time: 16:07:15.933
FEEDER RELAY Time Source: Internal
Counter# LT HIS A ST HIS A LT HIS B ST HIS B LT HIS C ST HIS C
1 0 0 0 0 0 0
2 0 0 0 0 0 0
3 0 0 0 0 0 0
•••••••
•••••••
•••••••
98 0 0 0 0 0 0
99 0 0 0 0 0 0
100 0 0 0 0 0 0
Mean 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
std. 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
HISLIMA HISLIMB HISLIMC NFA NFB NFC
0.0000 0.0000 0.0000 99999.0000 99999.0000 99999.0000
=>>
Figure 7.27 HSG Command Response