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240
NVA100X-D - Manual - 02 - 2016
FUNCTION CHARACTERISTICS
enabled for transmit a selective block from/to other internal protective elements.
[1]
With single enable fl ag for fi rst or second threshold of differential protection the element can pro-
duce the output block (committed pilot wire or output relay) programmed for logic selectivity of side
H and/or side L if the
87T-BLK1
parameter is set to
ON
inside the
Set \ Profi le A(or B) \ Differential
87G-87M-87T \ Common confi guration
menu
.
Stabilization on powering and excitation of the power transformer with second and fi fth harmonic restraint
With Transformer (
Transf
) selection the second and fi fth harmonic restraint is enabled: the
ProtObj
parameter is available inside the
Set \ Base
menu.
If Motor or Generator (
GEN-MOT-LINE- BAR
) is selected the second and fi fth harmonic is auto-
matically excluded.
[2]
The second harmonic restraint of differential protection allows you to block unwanted operation at
powering of the transformer.
The fi fth harmonic restraint of differential protection allows you to block unwanted operation at dur-
ing the operation of the transformer in over-excitation state.
The relay calculates:
RMS value of the second harmonic component of differential currents:
I
d2L1
=DFT2[
I
dL1
]
I
d2L2
=DFT2[
I
dL2
]
I
d2L3
=DFT2[
I
dL3
]
where DFT2[x] is the calculated rms value of the second harmonic component of differential cur-
rents concerning the x variable obtained by Discrete Fourier Transform (DFT).
RMS value of the fi fth harmonic component of differential currents:
I
d5L1
=DFT5[
I
dL1
]
I
d5L2
=DFT5[
I
dL2
]
I
d5L3
=DFT5[
I
dL3
]
where DFT5[x] is the calculated rms value of the fi fth harmonic component of differential currents
concerning the x variable obtained by Discrete Fourier Transform (DFT).
Second harmonic component / fundamental component ratio of differential currents:
I
d2L1
/
I
dL1
I
d2L2
/
I
dL2
I
d2L3
/
I
dL3
Fifth harmonic component / fundamental component ratio of differential currents:
I
d5L1
/
I
dL1
I
d5L2
/
I
dL2
I
d5L3
/
I
dL3
If at least one ratio
I
d2L1
/
I
dL1
,
I
d2L2
/
I
dL2
,
I
d2L3
/
I
dL3
exceeds the second harmonic restraint setting
2nd-REST> the start of the second harmonic restraint in the corresponding phase goes ON (ST 2nd-
REST-L1 or ST 2nd-REST-L2 or ST 2nd-REST-L3).
If at least one ratio
I
d5L1
/
I
dL1
,
I
d5L2
/
I
dL2
,
I
d5L3
/
I
dL3
exceeds the fi fth harmonic restraint setting 5th-
REST> the start of the second harmonic restraint in the corresponding phase goes ON (ST 5th-REST-
L1 or ST 5th-REST-L2 or ST 5th-REST-L3).
An intentional reset time delay
t
HREST-RES
, common for second-fi fth harmonic restraint (with zero
adjustment the second and fi fth harmonic restraint is restored at the moment when the relationship
between the effective values of the second or fi fth harmonic and fundamental component of differ-
ential current falls below the threshold setting
2
nd-REST
> or
5
th-REST
>).
The threshold setting
2ndh-REST>
and reset time delay setting
t
HREST-RES
are available inside the
Set \ Profi le A(or B) \ Differential 87G-87M-87T \ Harmonic restraint
menu.
The start of the element can control an output relay by programming the
ST2nd-REST-K
and/or
ST5th-REST-K
parameter available inside the menu
Set \ Profi le A(or B) \ Differential 87G-87M-87T
\ Harmonic restraint
menu, similarly for LED (
ST2nd-REST-L
and/or
ST5th-REST-L
).
The start of the second harmonic restraint threshold at one phase or the fi fth harmonic restraint
threshold at the same phase determines the starting of the harmonic restraint element (ST REST-H-
L1, L2 REST-H-ST , ST H-REST-L3) for that phase.
The start of the second harmonic restraint threshold (ST 2nd-REST>) occurs at the instant of occur-
rence of the start of threshold in at least one of the L1, L2, L3 phases.
The start of the fi fth harmonic restraint threshold (ST 5th-REST>) occurs at the instant of occurrence
of the start of threshold in at least one of the L1, L2, L3 phases.
The start of the harmonics harmonic restraint is produced from start of the second or fi fth harmonic
restraint threshold (ST 2nd-REST>or ST 5th-REST>).
Nota 1 The exhaustive treatment of the internal selective block (Block 4) function may be found in the “Internal selective block” paragraph inside
CONTROL AND MONITORING
section.
Note 2 Regardless of the value set all parameters in the
Set \ Profi le A(or B) \ Differential 87G-87M-87T \ Harmonic restraint menu
are not signifi cant
A)
B)
C)
D)