Application - ABB RET670 Applications Manual

1MRK504116-UUS C
3.7.3.1
3.7.3.2
Application manual

Application

In many applications, when fault current is limited to a defined value by the object
impedance, an instantaneous ground-fault protection can provide fast and selective
tripping.
The Instantaneous residual overcurrent EFPIOC (50N), which can operate in 15 ms (50
Hz nominal system frequency) for faults characterized by very high currents, is
included in the IED.
Setting guidelines
The parameters for the Instantaneous residual overcurrent protection EFPIOC (50N)
are set via the local HMI or PCM600.
Some guidelines for the choice of setting parameter for EFPIOC (50N) is given.
The setting of the function is limited to the operate residual current to the protection
(Pickup).
The basic requirement is to assure selectivity, that is EFPIOC (50N) shall not be
allowed to operate for faults at other objects than the protected object (line).
For a normal line in a meshed system single phase-to-ground faults and phase-to-phase-
to-ground faults shall be calculated as shown in figure
currents (3I ) to the protection are calculated. For a fault at the remote line end this
0
fault current is I . In this calculation the operational state with high source impedance
fB
Z and low source impedance Z
A
fault current is I . In this calculation the operational state with low source impedance
fA
Z and high source impedance Z
A
A
Z
~
A
IED
ANSI09000022 V1 EN
Figure 188: Through fault current from A to B: I
188
should be used. For the fault at the home busbar this
B
should be used.
B
I
fB
B
Z Z
L
Fault
fB
Section 3
IED application
and figure 189. The residual
~
B
ANSI09000022-1-en.vsd
419