Setting Guidelines - ABB REL650 Applications Manual

Section 7
Current protection
7.1.3
7.1.3.1
170
operate very quickly for faults very close to the generation (and relay) point, for which
very high fault currents are characteristic.
The instantaneous phase overcurrent protection 3-phase output PHPIOC (50) can operate
in 10 ms for faults characterized by very high currents.

Setting guidelines

The parameters for instantaneous phase overcurrent protection 3-phase output PHPIOC
(50) are set via the local HMI or PCM600.
This protection function must operate only in a selective way. So check all system and
transient conditions that could cause its unwanted operation.
Only detailed network studies can determine the operating conditions under which the
highest possible fault current is expected on the line. In most cases, this current appears
during three-phase fault conditions. But also examine single-phase-to-ground and two-
phase-to-ground conditions.
Also study transients that could cause a high increase of the line current for short times. A
typical example is a transmission line with a power transformer at the remote end, which
can cause high inrush current when connected to the network and can thus also cause the
operation of the built-in, instantaneous, overcurrent protection.
GlobalBaseSel: Selects the global base value group used by the function to define (IBase),
(VBase) and (SBase).
Pickup: Set operate current in % of IBase.
Meshed network without parallel line
The following fault calculations have to be done for three-phase, single-phase-to-ground
and two-phase-to-ground faults. With reference to figure 78, apply a fault in B and then
calculate the current through-fault phase current I
the minimum source impedance values for Z
for Z in order to get the maximum through fault current from A to B.
B
. The calculation should be done using
fB
and the maximum source impedance values
A
1MRK 506 334-UUS A
Application manual