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DMC3S - Manual - 08 - 2021
It follows that for both the above criteria, the protection measures:
• For phase L1, the phase shift α
1
of current phasor I
L1
relative to phasor U
23
, negative with current
delayed relative to the voltage (α
1
= ∠ I
L1
- ∠ U
23
, where ∠ is the argument operator).
• For phase L2, the phase shift α
2
of current phasor I
L2
relative to phasor U
31
, negative with current
delayed relative to the voltage (α
2
= ∠ I
L2
- ∠ U
31
).
If the current I
L2
is not available, it is reconstructed vectorially.
• For phase L3, the phase shift α
3
of current phasor I
L3
relative to phasor U
12
, negative with current
delayed relative to the voltage (α
3
= ∠ I
L3
- ∠ U
12
).
The operating mode can be selected in the menu Set \ Protections \ Maximum directional current
- 67 \ Common configurations, by setting Mode67; the available values are I (modulus mode) and
I*cos (projection mode). For each of the four thresholds (I
PD>
, I
PD>>
,
I
PD>>>
, I
PD>>>>
) the charac-
teristic angle can be regulated (in the range 0…359° common to the three phases) relative to the
polarising parameter (θ>, θ>>, θ>>>, θ>>>>), conventionally assumed to be positive in the clockwise
direction.
The regulation of the characteristic angle identifies the angular position of the characteristic half-ax-
is, which represents the bisector of the angular trip sector with an angular amplitude of 180°.
A regulation of the characteristic angle in the range 0°...90° or 270°...359° corresponds to protection
“towards line”, while regulation in the range 91°...269° corresponds to protection “towards bar”.
The parameters are available in the menu relating to the four thresholds, separately for the definite
and inverse time functions (where available).
Two separate protection trip logics are available:
• One of three - 1/3, in which it is sufficient that one of the three phases violate the set threshold.
• Two of three - 2/3, in which at least two of the three phases must violate the set threshold.
The trip logic can be selected in the menu Set \ Protections \ Maximum directional current - 67 \
Common configurations, by setting Logic67; the available values are 1/3 (at least one current)
and 2/3 (at least two currents).
When modulus mode detection and one of three - 1/3 trip logic are selected, the start (START) of any
threshold of protection 67 occurs when the following two conditions are both satisfied:
A) In at least one phase, the fundamental component of the current (I
L1
, I
L2
, I
L3
) violates the set
threshold (I
PD>
, I
PD>>
,
I
PD>>>
, I
PD>>>>
).
B) The current phasor for the phase in point A) is in the angular sector with semi-am-
plitude 90° and bisector the characteristic half-axis of the threshold in point A)
(ThetaP>, ThetaP>>, ThetaP>>>, ThetaP>>>>), i.e. the condition -90° ≤ (ThetaP-α
x
) ≤ +90° is satis-
fied, in which x is the index of the phase/s in point A) (x = 1, 2 or 3) and ThetaP is the regulation of
the characteristic angle of the threshold in point A (ThetaP>, ThetaP>>, ThetaP>>>, ThetaP>>>>).
When the threshold starts, so does its timer.
If for the entire operating time of the threshold (t
PD>
, t
PD>>
,
t
PD>>>
, t
PD>>>>
) the conditions in points A)
and B) persist, when the time expires the threshold trips (TRIP), otherwise it resets.
When modulus mode detection and two of three - 2/3 trip logic are selected, the start (START) of any
threshold of protection 67 occurs when the following two conditions are both satisfied:
C) In at least one pair of phases the fundamental component of the current (I
L1
e I
L2
, I
L2
e I
L3
, I
L3
e I
L1
)
violates the threshold (I
PD>
, I
PD>>
,
I
PD>>>
, I
PD>>>>
).
D) The current phasors for the pair of phases in point C) are both in the angular sec-
tor with semi-amplitude 90° and bisector the characteristic sector for the thresh-
old in point C) (ThetaP>, ThetaP>>, ThetaP>>>, ThetaP>>>>), i.e. the condition -90°
≤ (ThetaP-α
x
) ≤ +90° is satisfied, where x is the index of the pair of phases in point 1
(I
L1
and I
L2
, I
L2
and I
L3
, I
L3
and I
L1
) and ThetaP is the regulation of the characteristic angle of the
threshold in point C (ThetaP>, ThetaP>>, ThetaP>>>, ThetaP>>>>).
When the threshold starts, so does its timer.
If for the entire operating time of the threshold (t
PD>
, t
PD>>
,
t
PD>>>
, t
PD>>>>
) the conditions in points C)
and D) persist, when the time expires the threshold trips (TRIP), otherwise it resets.
When projection mode detection and one of three - 1/3, trip logic are selected, the start (START) of
any threshold of protection 67 occurs when one of the following two conditions is satisfied:
• the projection of the current phasor for at least one phase along the characteristic axis I
Lx-
cos(ThetaP>-α
x
), I
Lx
cos(ThetaP>>-α
x
), I
Lx
cos(ThetaP>>>-α
x
), I
Lx
cos(ThetaP>>-α
x
) (x=1, 2, 3) is
positive and violates the threshold (I
PD>
, I
PD>>
,
I
PD>>>
, I
PD>>>>
).
• in at least one phase, the fundamental component of the current (I
L1
, I
L2
, I
L3
) violates the set thresh-
old (I
PD>
, I
PD>>
,
I
PD>>>
, I
PD>>>>
).
When the threshold starts, so does its timer.
If for the entire operating time of the threshold (t
PD>
, t
PD>>
,
t
PD>>>
, t
PD>>>>
) the above condition per-
sists, when the time expires the threshold trips (TRIP), otherwise it resets.
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