Alstom MiCOM P846, Technical Manual

Page: 83 / 298

Operation P846/EN OP/D
MiCOM P846
(OP) 5-5
OP
1.3 Principles of operation
The DLO algorithm is made up of five major building blocks as shown on figure 2:
Line voltages
Breaker currents
Reactor currents
Anti - alias
filtering
Kalman
Filter
Pre -
processor
Fuzzy -
logic
Engine
logic
&
Vp (
fn
)
V(
dc
)
)
In ( )
Vn (
fn
) R rules
Sampling
N Fuzzy
variables
32 points/
cycle
Ip (
fn
fn
I(
dc
)
Output
P4055ENa
Figure 2: DLO processing logic
1.3.1
ith 400 Hz anti-aliasing filters and
of 32 samples per cycle (at 60 Hz
r 40 samples per cycle (at 50 Hz
er second). The data captured has a resolution
x channels for current inputs and three channels
.
(t), I
b
(t) and I
c
(t) are
ransform.
For a given three-ph Clarke components
Data acquisition
The front end of the system is a data acquisition module, w
16 channels of sample and hold capture, running at a rate
nominal, this corresponds to 1920 samples per second) o
nominal, this corresponds to 2000 samples p
of 16 bits, four channels as voltage inputs, si
being dedicated as voltage rail checks
From there, phase voltages V
a
(t), V
b
(t) and V
c
(t) and currents I
a
V
α
(t), V
β
(t) and I
α
(t), I
β
(t) with the Clarke t
ase signal set {f
a
(t), f
b
(t), f
c
(t)}, the corresponding
as follows:
converted into orthogonal components
{f
α
(t), f
β
(t), f
0
(t)}, are computed
From the resulting orthogonal components is synthesized the instantaneous space-phasor
f
s
(t) = f
α
(t) + j f
β
(t)
which contains all the required information about the positive and
negative sequences of the fundamental and all the harmonic and inter-harmonic frequencies
present in the original signal set {f
a
(t), f
b
(t), f
c
(t)}.
It can therefore be used as an input for the next stage, the Kalman filter.