ABB REL650 Technical Manual page 160

Section 6
Impedance protection
154
TRUE
TRUE
TRUE
startIN
IEC16000022 V1 EN-US
Figure 75: No Preference mode
Preference modes
In the preference modes (for example, '1231c'), the internal under-voltage phase
selection status is filtered with the selected preference scheme to achieve the
desired phase preference. Only the preferred phase-to-earth loop of the distance
protection is released to operate. In addition to the voltage phase selection, a
residual current start is required.
A logic is also included to handle the special case where only one start (startL1-3)
is present.
The internal under-voltage phase selection always issues a release in at least two
phases, but the inputs RELL1-3N can be activated with some time apart. If no
measures are taken, the phase activated first will pass through the preference
scheme and release the distance protection. Since it could a be non-preferred phase,
a time delay of 40 ms is provided to release if only one phase is detected, in order
to wait for the second phase to be activated. If no second phase is detected within
40 ms, the single phase is released without preference.
Additionaly, there are some cases where no release would be issued:
• All three phases are involved in the fault and a cyclic scheme is selected
• No faulty phase can be detected due to an insufficient voltage drop
In both cases, no release signals come from the phase preference scheme. For these
cases, an additional logic is provided that releases all phases if there is no output
from the preference scheme after 40 ms from the activation of the residual current
start.
Hence, if there is a residual current start, it is guaranteed that the distance
protection is released in at least one phase. This is valid for all phase preference
schemes.
1MRK 506 382-UEN A
zrelL1
AND
zrelL2
AND
zrelL3
AND
IEC16000022-1-en.vsdx
GUID-BE61A451-E389-4136-8C0B-2C04888EEACE v1
Line distance protection REL650 2.2 IEC
Technical manual