Alarm Level Operation - ABB Relion 650 Series Applications Manual

1MRK 504 124-UEN B
Basic data:
Transformer rated current on HV winding:
Current transformer ratio:
CT Class:
Cable loop resistance:
Max fault current:
Calculation:
>
UR
EQUATION1219 V1 EN-US
Select a setting of
The current transformer saturation voltage at 5% error can roughly be calculated from the
rated values.
E P 5
EQUATION1220 V1 EN-US
that is, greater than 2 ·
Check from the table of selected resistances the required series stabilizing resistor value to
use. As this application it is required to be so sensitive so select
which gives a current of 20 mA.
To calculate the sensitivity at operating voltage, refer to equation
gives around 10% minimum operating current.
300
=
IP
EQUATION1221 V1 EN-US
The magnetizing current is taken from the magnetizing curve for the current transformer
cores which should be available. The value at
resistor current the top value of voltage 20 · √2 is used and the top current used. Then the RMS
current is calculated by dividing with√2. Use the maximum value from the curve.
6.3.4.4

Alarm level operation

The 1Ph High impedance differential protection HZPDIF function has a separate alarm level,
which can be used to give alarm for problems with an involved current transformer circuit. The
setting level is normally selected to be around 10% of the operating voltage
As seen in the setting examples above the sensitivity of HZPDIF function is normally high,
which means that the function will in many cases operate also for short circuits or open
current transformer secondary circuits. However the stabilizing resistor can be selected to
achieve sensitivity higher than normal load current and/or separate criteria can be added to
Transformer protection RET650
Application manual
250
( )
× × + =
15 0.66 0.8
300
U>Trip =20 V.
( )
> + × =
10 0.66 20 213.2
U>Trip
(
× ° + ° + ×
20 0 5 0 4 20 60
1
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250 A
300/1 A (Note: Must be the same at all locations)
10 VA 5P20
2
<50 m 2.5mm (one way) gives 2 · 0.4 ohm at 75° C
The maximum through fault current is limited by
the transformer reactance, use 15 · rated current of
the transformer
18.25 V
V
)
- ° £
approx .25.5
U>Trip is taken. For the voltage dependent
(Equation 41)
(Equation 42)
SeriesResistor = 1000 ohm
43 which is acceptable as it
A
U>Trip .
Section 6
Differential protection
(Equation 43)
M16850-196 v3
105