ABB RELION REX640 Technical Manual page 554

Section 4
Protection functions
548
value. Tilt angle should be 10 degrees especially if the residual current
is measured with Holmgreen (sum) connection of phase current CTs.
Blocking logic
There are three operation modes in the blocking functionality. The operation modes
are controlled by the BLOCK input and the global setting Configuration/System/
Blocking mode which selects the blocking mode. The BLOCK input can be controlled
by a binary input, a horizontal communication input or an internal signal of the
protection relay's program. The influence of the BLOCK signal activation is
preselected with the global setting Blocking mode.
The Blocking mode setting has three blocking methods. In the "Freeze timers" mode,
the operate timer is frozen to the prevailing value. In the "Block all" mode, the whole
function is blocked and the timers are reset. In the "Block OPERATE output" mode,
the function operates normally but the OPERATE output is not activated.
If the BLOCK input of MFADPSDE is used in the configuration, then
"Block all" mode is recommended.
Recommended uses of the BLOCK input of MFADPSDE are:
1. Connecting the start signal of non-directional earth fault protection (EFxPTOC),
set to operate in case of a cross-country fault, to BLOCK input of MFADPSDE to
reset phasor accumulation during a cross-country fault. MFADPSDE can then
adapt to a fault direction change more rapidly if a single-phase earth fault persists
in the system after the other faulty feeder has been tripped (the cross-country fault
has been transformed into a single-phase earth fault).
2. Connecting the 'Auto-Reclose in progress' output (INPRO) from DARREC to
BLOCK input of MFADPSDE to allow faster reset of MFADPSDE during high-
speed auto-reclosing cycle HSAR when setting Reset delay time equals or is
higher than the dead time of high-speed auto-reclosing cycle HSAR.
3. In case of a network with distributed coils but no centralized arc suppression coil
at the primary substation (unearthed network), it is recommended to add an
additional logic to protection configuration, which blocks MFADPSDE if the
frequency of measured Uo and Io becomes lower than nominal. Such condition
is valid in network when earth fault becomes disconnected and a phenomenon
called 'post-fault oscillation' is initiated.
4. If the parallel resistor of the coil has long connection delay, it is recommended to
add an additional logic to protection configuration to enable the release of
MFADPSDE at the time of the parallel resistor switching.
The logic to release MFADPSDE at time of resistor (re)connection is illustrated in
Figure 299.
1MRS759142 C
REX640
Technical Manual