Directional Or Non-Directional Earth-Fault Current Unit - ABB REJ 527 Product Manual

4
Directional or Non-Directional Earth-Fault
Relay
Directional or non-directional
earth-fault current unit
The high-set and the low-set stage the direc-
tional earth-fault current unit can be config-
ured to be either directional or non-direc-
tional. The directional earth-fault stages can
be given either a basic angle or a sin(ϕ) or a
cos(ϕ) characteristic.
The start and the tripping of the directional
earth-fault stages with the basic angle charac-
teristic are based on measuring the earth-fault
current, I , the zero-sequence voltage, U
0
and the phase angle, ϕ, between the voltage
and the current. An earth-fault stage will start
when the following three criteria are fulfilled
at the same time:
• The earth-fault current, I
start value of the low- or high-set earth-
fault stage.
• The zero-sequence voltage, U
the set start value of U
0b
same for both stages in the deblocking
mode.
• The phase angle, ϕ, between the voltage
and current falls within the operation sec-
tor ϕ ±∆ϕ.
b
The basic angle of the network is -90° for iso-
lated neutral networks and 0° for resonant
earthed networks, earthed with an arc sup-
pression coil (Petersen coil) with or without a
parallel resistor. The operation sector is
selectable and can be either
∆ϕ = ±80° or ±88°. Both operation sectors
can be extended.
When an earth-fault stage starts, a start signal
will be generated and a start indication shown
on the HMI. If the above mentioned criteria
remain fulfilled until the set operate time
elapses, the stage will deliver a trip signal and
a trip indication will be shown on the HMI.
The trip indication will remain active
although the protection stage is reset. The
direction of the fault spot is determined by
means of the angle between the voltage and
the current. Basic angle ϕ
b
-90° and 0°. When basic angle ϕ
negative quadrant of the operation sector can
be extended with ϕ
. Extended operation sec-
a
tor ϕ
can be set between 0 and 90°.
a
The start and the tripping of the directional
earth-fault stages with the sin(ϕ) or the cos(ϕ)
characteristic are based on measuring the
earth-fault current, I , the zero-sequence volt-
0
, and the phase angle, ϕ, between the
age, U
0
voltage and the current. The sinus or cosinus
value of the phase angle is calculated and
multiplied by the earth-fault current to get the
directional earth-fault current, I
fault stage will start when the following three
criteria are fulfilled at the same time:
• The directional earth-fault current, Iϕ,
exceeds the set start value of the low- or
high-set earth-fault stage.
• The zero-sequence voltage, U
the set start value of U
,
0
same for both stages in the deblocking
mode.
• The phase angle, ϕ, between the voltage
and the current falls within the operation
sector, corrected with ϕ
, exceeds the set
0
When an earth-fault stage starts, a start signal
will be generated and a start indication shown
on the HMI. If the above mentioned criteria
remain fulfilled until the set operate time
, exceeds
0
elapses, the stage will deliver a trip signal and
>, which is the
a trip indication will be shown on the HMI.
The trip indication will remain active
although the protection stage is reset. The
direction of the fault spot is determined by
means of the angle between the voltage and
the current. Directional earth-fault character-
istic sin(ϕ) corresponds to the earth-fault pro-
tection with the basic angle -90° and cos(ϕ)
to the earth-fault protection with the basic
angle 0°.
The operation directions, forward or reverse,
of the directional earth-fault stages can be
selected independently of each other. The
directional stages may also be separately con-
figured to be non-directional.
The low-set stage I
protection against intermittent earth-faults,
which may occur in insulated cables used in
compensated networks.
When the earth-fault current exceeds the set
start value of low-set stage I
unit will start to deliver a start signal after a
~70 ms' start time. When the set operate time
can be set between
at definite-time characteristic or the calcu-
is 0-°, the
b
lated operate time at inverse definite mini-
mum time (IDTM) characteristic elapses, the
earth-fault unit will deliver a trip signal.
When the earth-fault current exceeds the set
start value of high-set stage I
fault unit will start to deliver a start signal
after a ~60 ms' start time. When the set oper-
ate time elapses, the earth-fault unit will
deliver a trip signal.
REJ 527
1MRS751132-MBG
. An earth-
ϕ
, exceeds
0
>, which is the
0b
.
c
> can also be used for
0
>, the earth-fault
0
>>, the earth-
0