Protective Elements
Temporarily Restraining (by
CT
saturation monitoring)
Beside the harmonic temporary restraining triggers, the protective device offers another trigger function - the
Transients Monitor (Gradient Monitor). This monitor supervises the current transformer saturation. This monitor will
be triggered by the behavior of the phase currents (their slopes, normalized derivative).
The normalized derivative is defined as:
m
=
1
ω∗
I
peak
⋅
di
dt
,
where
I
peak
is the peak value within a half cycle and
ω
is the system frequency.
For a purely sinusoidal waveform, the normalized derivative should be equal to 1. Under CT saturation, m will be
greater than 1. The setting CT Satur Sensitvn should be set properly to identify effectively CT saturation but not to
generate a nuisance trigger.
When the CT saturation monitor is active, it will trigger the temporary restraining if m exceeds an internal threshold.
The temporary restraining, whenever effective, will essentially add a constant
d
(
H , m
)
to the fundamental
restraining. Graphically, the static tripping curve is temporarily raised by
d
(
H , m
)
which the sensitivity of the
differential protection function is reduced temporarily.
The internal threshold can be modified by means of the CT Saturation Sensitivn. The CT saturation monitor will
behave more sensitively the lower the setting value is set.
Temporary Dynamic Rise of the Static Tripping Characteristic.
626
MCDLV4
DOK-HB-MCDLV4-2E
IdH
Id[Is1]
Id[Is0]
Id[Is1]´
Id[Is0]´
Id[Is2]
Id[Is2]´
d[m]
Id min´
Id min
d
[H,m]
Is1= 2
x
Ib
Is2= 10
x
Ib
Is/Ib
Trip Range
Operating Range
Id/Ib
Summary of Contents for HighPROtec MCDLV4
Page 3: ...Order Code Order Code 3 MCDLV4 DOK HB MCDLV4 2E...
Page 47: ...Installation and Connection 47 MCDLV4 DOK HB MCDLV4 2E...
Page 164: ...Input Output and LED Settings 164 MCDLV4 DOK HB MCDLV4 2E...
Page 433: ...Parameters 433 MCDLV4 DOK HB MCDLV4 2E...
Page 457: ...Device Parameters 457 MCDLV4 DOK HB MCDLV4 2E...
Page 473: ...Blockings 473 MCDLV4 DOK HB MCDLV4 2E...
Page 988: ...Protective Elements 988 MCDLV4 DOK HB MCDLV4 2E P P Q P Q P Q Q Q P S S...
Page 989: ...Protective Elements 989 MCDLV4 DOK HB MCDLV4 2E Pr Q P Q P Qr...
Page 1023: ...Protective Elements 1023 MCDLV4 DOK HB MCDLV4 2E...
