5.6
SEL-387-0, -5, -6 Relay
Instruction Manual
Date Code 20170601
Metering and Monitoring
Metering Functions
Figure 5.1
SEL-387 Demand Ammeter Functions and Commands
Harmonic Metering
Function (MET H
Command)
The Harmonic Metering function, in response to the
MET H
command,
retrieves 1 full cycle of unfiltered sample data, at 64 samples per cycle, from
each of the 12 analog current inputs. Harmonic magnitudes are obtained
through use of a Fast Fourier transform method, which calculates a Discrete
Fourier transform, given by the following equation, for each harmonic from
fundamental to fifteenth.
Equation 5.2
After the 15 H
n
are calculated, they are adjusted to compensate for filter gain,
and the resulting magnitudes are listed in secondary amperes:
=>
MET H <Enter>
processing harmonic spectrum ............
XFMR 1 Date: 04/30/97 Time: 15:30:40.556
STATION A
Magnitudes of Harmonic Currents (Amps Sec)
H IAW1 IBW1 ICW1 IAW2 IBW2 ICW2 IAW3 IBW3 ICW3 IAW4 IBW4 ICW4
1 5.00 5.00 5.00 5.00 5.01 5.01 5.00 5.01 5.00 5.02 5.02 5.02
2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.01
3 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.01
4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.01 0.01 0.02
6 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
7 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.00
8 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
9 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.00
10 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
11 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
12 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
13 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
14 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
15 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
=>
The Analog Input Labels,
IAW1
, etc., will be listed as they are set in the Global
settings section of the relay.
IX
0
XD(t)
IX
.9(IX–XD(0))+XD(0)
XD(0)
t
DATCn
XD(t)=0
XD(t)
XD(t)>XDEMnP?
SET XDEMn
(Relay Word bit)
Peak Detector
X Peak Demand
(
MET P
)
Y
PXD
X Demand Current
(
MET D
)
PXD = XD(t)
Reset Peak
(
MET RP
)
Reset Demand
(
MET RD
)
(IX = IAWn, IBWn, ICWn, 3I2Wn, IRWn)
where:
N = samples per cycle = 64
n
= order of the harmonic = 1, 2, . . ., 15
h
k
= sampled data for one full cycle at system frequency
k
= summation index = 0, 1, . . ., 63
H
n
= result of the Discrete Fourier transform calculation for the
n
th harmonic
H
n
h
k
k
0
=
N 1
–
e
j
2
kn
N
-------------
•
•
=
Summary of Contents for SEL-387-0
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