Areva MiCOM P441, Техническое руководство

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Relay Description P44x/EN HW/E33
MiCOM P441/P442 & P444 Page 17/44
4. DISTANCE ALGORITHMS
The operation is based on the combined use of two types of algorithms:
•
"Deltas" algorithms using the superimposed current and voltage values that are
characteristic of a fault. These are used for phase selection and directional
determination. The fault distance calculation is performed by the "impedance
measurement algorithms ” using Gauss-Seidel.
•
"Conventional" algorithms using the impedance values measured while the fault
occurs. These are also used for phase selection and directional determination.
The
fault distance calculation is performed by the "impedance measurement
algorithms." Using Gauss-Seidel.
The "Deltas" algorithms have priority over the "Conventional" algorithms if they have been
started first. The latter are actuated only if "Deltas" algorithms have not been able to clear
the fault within two cycles of its detection.
4.1 Distance and Resistance Measurement
MiCOM P44x distance protection is a full scheme distance relay. To measure the distance
and apparent resistance of a fault, the following equation is solved on the loop with a fault:
(n).Z
L
Relay
P3030ENa
R
F
Z
SL
I
L
Local
Source
(1-n).Z
L
Z
SR
I
R
I
F
=
I + I
'
Remote
Source
V
L
= (Z
L
x
I
x D)+ R
F
x
I
F
= ((r +jx) x
I
x D) +R
F
x
I
F
where
V
L
V
L
= local terminal relay voltage
r = line resistance (ohm/mile)
x =
=
=
=
line reactance (ohm/mile)
current measured by the relay on the faulty phase
current flowing into the fault from local terminal
= current flowing into the fault from remote terminal
= fault location (permile or km from relay to the fault)
current flowing in the fault (
I
+
I
') I
F
I
I
'
R
F
Assumed Fault Currents:
For Phase to Ground Faults (ex., A-N),
For Phase to Phase Faults (ex., A-B),
I
F
= 3
I
0
I
A
for 40ms, then after 40 ms
I
F
=
I
AB
Relay
V
R
D
= fault resistance
= apparent fault resistance at relay; R x (1 +
I
'/
I
)
R
FIGURE 5 - DISTANCE AND FAULT RESISTANCE ESTIMATION
The impedance measurements are used by High Speed and Conventional Algorithms.