Directional Criteria - ABB REL650 Technical Manual

Section 6
Impedance protection
6.1.7.4
96
zero sequence current is relatively high due to a source with low Z0/Z1 ratio. In
these situations zone measurement will be released both for the related phase-to-
earth loops and the phase-to-phase loop simultaneously. On the other hand,
simultaneous faults closer to the remote bus will gradually take on the properties of
a phase-to-phase-earth fault and the function will eventually use phase-to-phase
zone measurements also here.
In cases where the fault current infeed is more or less completely of zero sequence
nature (all phase currents in phase), the measurement will be performed in the
phase-to-earth loops only for a phase-to-phase-earth fault.
Should it be desirable to use phase-to-earth (and only phase-to-earth) zone
measurement for phase-to-phase-earth faults, there is a setting INReleasePE that
can be lowered from its excessive default value to the level above which phase-to-
earth measurement should be activated.

Directional criteria

Several criteria are employed when making the directional decision. The basis is
provided by comparing a positive sequence based polarizing voltage with phase
currents. For extra security, especially in making a very fast decision, this method
is complemented with an equivalent comparison where, instead of the phase
current, the change in phase current is used. Moreover, a basic negative sequence
directional evaluation is taken into account as a reliable reference during high load
condition. Finally, a zero sequence directional evaluation is used whenever there is
more or less exclusive zero sequence in-feed.
The directional sectors that represent forward direction, one per measuring loop,
are defined by the following equations.
U
PolL 1
− ° < 15 arg < 120
I
L 1
IECEQUATION15059 V1 EN-US
U
PolL L 1 2
15 arg 120
− ° < <
I
L L 1 2
IECEQUATION15060 V1 EN-US
Where:
U is the polarizing voltage for phase L1.
PolL1
I is the phase current in phase L1.
L1
U is the polarizing voltage difference between phase L1 and L2 (L2 lagging L1).
PolL1L2
I is the current difference between phase L1 and L2 (L2 lagging L1).
L1L2
The corresponding reverse directional sectors range from 165 to -60 degrees.
°
°
1MRK 506 382-UEN A
GUID-24431EEC-5037-41CD-BC4A-7AC196F158F3 v5
Line distance protection REL650 2.2 IEC
Technical manual
(Equation 1)
(Equation 2)