GE P444 User Manual

P
44x/EN AP/Hb6
Application Notes
(AP) 5
-42 MiCOM P40 Agile
P442, P444
right hand and left hand resistive reach constraints of each zone are displaced by +RPh and
-RPh either side of the characteristic impedance of the line, respectively. RPh is generally
set on a per zone basis, using R1Ph, R2Ph, RpPh and RqPh. Note that zones 3 and 4 share
the resistive reach R3Ph-R4Ph.
When the relay is set in primary impedance terms, RPh must be set to cover the maximum
expected phase-to-phase fault resistance. In general, RPh must be set greater than the
maximum fault arc resistance for a phase-phase fault, e.g. calculated as follows:
R
a
= (28710 x L) / I
f
1.4
RPh ≥ R
a
Where:
I
f
= Minimum expected phase-phase fault current (A);
L = Maximum phase conductor spacing (m);
R
a
= Arc resistance, calculated from the van Warrington formula (Ω).
Typical figures for R
a
are given in Table 2 below, for different values of minimum expected
phase fault current.
Conductor
spacing (m)
Typical system
voltage (kV)
I
f
= 1kA I
f
= 5kA I
f
= 10kA
2 33
3.6 Ω 0.4 Ω 0.2 Ω
5 110
9.1 Ω 1.0 Ω 0.4 Ω
8 220
14.5 Ω 1.5 Ω 0.6 Ω
Table 2: Typical arc resistances calculated using the Van Warrington formula
The maximum phase fault resistive reach must be limited to avoid load encroachment trips.
Therefore, R3Ph and other phase fault resistive reach settings must be set to avoid the
heaviest allowable loading on the feeder. An example is shown in Figure 20 below, where
the worst case loading has been determined as point “Z”, calculated from:
Impedance magnitude, Z = kV
2
/ MVA
Leading phase angle, ∠Z = cos
–1
(PF)
Where:
kV = Rated line voltage (kV);
MVA = Maximum loading, taking the short term overloading during out ages of
parallel circuits into account (MVA);
PF = Worst case lagging power factor.

GE P444 Specifications

General

Brand	GE
Model	P444
Category	Protection Device
Language	English