Schweitzer Engineering SEL-387-0 - Figure 5.1 SEL-387 Demand Ammeter Functions and Commands

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 Hn 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)
tDATCn
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
hk = 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
nth harmonic
H
n
h
k
k0=
N1–

e
j
2kn
N
-------------•
• =