Functions
2.8 Earth Fault Protection in Earthed Systems (optional)
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
235
The parameters
3116
,
3126
,
3136
and
3157
are used to define which stage is to be blocked during the single-
pole dead time. If the corresponding stage is to be blocked, the setting
YES
remains unchanged. If not, set
No
(non-dir.)
.
Note
Stages of the earth fault protection, which are not to be blocked during the single-pole dead time, will not be
blocked even if the earth fault protection itself gives a single-pole trip command. Pickup and trip command of
the earth fault protection can thus only drop out if the earth current caused by the load current lies below the
threshold value of such a stage.
The earth fault protection can also be blocked by the differential protection. The parameter
3175
EF BLK
Dif.PU
can be used to activate (setting value
YES
) or deactivate (setting value
NO
) this blocking. For the du-
ration of blocking the earth-fault protection trip the message 1335
„EF TRIP BLOCK“
is reported as ON.
Trip
When setting the power system data (Section 2.1.2.1), it was specified whether single-pole tripping is set for
all stages of the earth fault protection together or separately.
When setting
238
EarthFltO/C 1p
to
stages together
, parameter
3109
Trip 1pole E/F
becomes
visible; the parameters for phase-selective settings are hidden.
Address
3109
Trip 1pole E/F
specifies that the earth fault protection trips single-pole, provided that the
faulted phase can be determined with certainty. This address is only valid for devices that have the option to
trip single-pole. If you are using single-pole automatic reclosure, the setting
YES
(default setting) remains valid.
Otherwise set
NO
.
When setting
stages separat.
, the parameters for the phase-selective setting are visible (
3117
Trip 1p
3I0>>>
,
3127
Trip 1p 3I0>>
,
3137
Trip 1p 3I0>
and
3158
Trip 1p 3I0p
) parameter
3109
Trip
1pole E/F
is hidden.
The parameters
3117
,
3127
,
3137
and
3158
can be used to determine which stage is to trip 1-pole, provided
that the faulted phase can be determined with certainty. If the corresponding stage is to trip 1-pole, the setting
YES
remains unchanged; if not, set
NO
.
Definite time stages
First of all, the mode for each stage is set: address
3110
Op. mode 3I0>>>
, address
3120
Op. mode 3I0>>
and address
3130
Op. mode 3I0>
. Each stage can be set to operate
Forward
(usually towards line),
Reverse
(usually towards busbar) or
Non-Directional
(in both directions). If a single stage is not required,
set its mode to
Inactive
.
The definite time stages
3I0>>>
(address
3111
),
3I0>>
(address
3121
) and
3I0>
(address
3131
) can be
used for a three-stage definite time overcurrent protection. They can also be combined with the inverse time
stage
3I0p PICKUP
(address
3141
, see below). The pick up thresholds should in general be selected such
that the most sensitive stage picks up with the smallest expected earth fault current.
The 3
I
0
>> and 3
I
0
>>> stages are best suited for fast tripping stages (instantaneous), as these stages use an
abridged filter with shorter response time. Whereas, the stages 3
I
0
> and 3
I
0P
are best suited for very sensitive
earth fault detection due to their effective method of suppressing harmonics.
If no inverse time stage, but rather a fourth definite time stage is required, the „inverse time“ stage can be im-
plemented as a definite time stage. This must already be taken regard of during the configuration of the pro-
tection functions (refer to Section 2.1.1.3, address
131
Earth Fault O/C
=
Definite Time
). For this
stage, the address
3141
3I0p PICKUP
then determines the current pickup threshold and address
3147
Add.T-DELAY
the definite time delay.
