ABB REJ 527 Technical Reference Manual page 15

ABB Substation Automation
Products and Systems
1MRS750616-MUM
Technical Reference Manual
LEAD
Io
ϕ
∆ϕ
OPERATION SECTOR
ϕ
b=-90°
∆ϕ
=80°
Fig. 4.1.3.2.-3 Operation characteristics when the basic angle ϕ
2) The operation of the directional earth-fault unit with sin(ϕ) or cos(ϕ)
characteristics is based on measuring the earth-fault current I
and further the phase angle ϕ between the voltage and current. The sinus
voltage U
0
or cosinus value for the phase angle is calculated and then multiplied by the earth-
fault current. This will give the directional earth-fault current Iϕ as a result. The
earth-fault stage starts if the following three criteria are fulfilled at the same time:
• The directional earth-fault current Iϕ exceeds the set starting level of the earth-
fault stage. The earth-fault unit has two earth-fault current stages I
• The zero-sequence voltage U
starting level, U >, serving both stages in deblocking mode.
0b
• The phase angle ϕ between the voltage and current falls within the operation
sector of the angle correction factor ϕ
When an earth-fault stage starts, a starting signal is generated and simultaneously the
display on the front panel indicates starting. If the above mentioned criteria are
fulfilled long enough to exceed the set operate time, the stage that started initiates a
tripping signal. At the same time the operation indicator on the front panel is lit. The
red operation indicator remains lit even if the protection stage resets. The direction
towards the fault spot is determined by means of the angle between the voltage and
current. The directional earth-fault characteristic sin(ϕ) corresponds to the earth-
fault protection with the basic angle -90° and cos(ϕ) to the earth-fault protection
with the basic angle 0°.
In Fig. 4.1.3.2.-4 and Fig. 4.1.3.2.-5 examples of the operation characteristics sin(ϕ)
and cos(ϕ).
LAG
Uo
Io>
exceeds the set starting level. The unit has one
0
=2...7°.
c
REJ 527
= -90°
b
and the zero-sequence
0
> and I >>.
0 0
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