ABB Relion REG670, Technical Manual, Page: 353 / 1298

Phase-phase short circuit:
1 2 1 2 1 2 1 2
= - = -
refL L L L dirL L L L
U U U I I I
EQUATION1449 V1 EN
(Equation 57)
2 3 2 3 2 3 2 3
= - = -
refL L L L dirL L L L
U U U I I I
EQUATION1450 V1 EN
(Equation 58)
3 1 3 1 3 1 3 1
= - = -
refL L L L dirL L L L
U U U I I I
EQUATION1451 V1 EN
(Equation 59)
Phase-earth short circuit:
1 1 1 1
= =
refL L dirL L
U U I I
EQUATION1452 V1 EN
(Equation 60)
2 2 2 2
= =
refL L dirL L
U U I I
EQUATION1453 V1 EN
(Equation 61)
3 3 3 3
= =
refL L dirL L
U U I I
EQUATION1454 V1 EN
(Equation 62)
The polarizing voltage is available as long as the positive-sequence voltage exceeds
4% of the set base voltage
UBase . So the directional element can use it for all
unsymmetrical faults including close-in faults.
For close-in three-phase faults, the U1
L1M
memory voltage, based on the same
positive sequence voltage, ensures correct directional discrimination.
The memory voltage is used for 100 ms or until the positive sequence voltage is
restored.
After 100 ms, the following occurs:
• If the current is still above the set value of the minimum operating current
(between 10 and 30% of the set terminal rated current
IBase ), the condition seals
in.
•
If the fault has caused tripping, the trip endures.
• If the fault was detected in the reverse direction, the measuring element in
the reverse direction remains in operation.
• If the current decreases below the minimum operating value, the memory resets
until the positive sequence voltage exceeds 10% of its rated value.
The directional setting is given as a characteristic angle AngleRCA for the function and
an angle window AngleROA .
1MRK502052-UEN B
Section 8
Current protection
347
Technical manual