'(& )( )'& &) ( &!& ")& &$(( $# Ć %&( $# #)" &&#$
6 - 52
Siemens AG ⋅ May 1998
4. The test is repeated with different constant curĆ
rents I
1
. (correct shape of the characteristic is givĆ
en in Fig 6.4).
Remark:
The stabilizing current of the ZPS-BSZ1 shown
under DA 7400/ZE does not consider the special
treatment according to chapter 4.4.
k = 0.8
Diff-current
DI
Diff-current
limit
a = arctan (0.8)
Stabilizing current S I I I
6.5.3 Checking the differential current limit for
differential current supervision
6.5.3.1 Test set-up
(as in chapter 6.5.2.1)
Time measurement can be done directly with modern
test sets.
6.5.3.2 Bus-section specific protection
The check zone must have a higher setting than the
bus-section specific protection, so that the differenĆ
tial current supervision of the check zone picks up
after that of the bus-section specific protection.
Example
:
The supervision for the bus-section specific protecĆ
tion with diff-current limit I > DIFsup:BZ
(DA 6305/ZE) = 0.2 I/I
no
is to be checked. The time
T-DIFF-SUP (DA 6304/ZE) is to be set to 2.0 s.
The setting for the check zone Iāā>āāDIFsupā:CZ (DA
6306/ZE) could then be set to 0.8 I/I
no
.
Settings
:
D In order for the diff-current supervision to block
the protection, it must be operative, i.e. the paĆ
rameter DIFF SUPERV (DA 6303/ZE) must be set
to "active".
D The differential current limit (DA 6305/ZE) and the
blocking time for the diff-current supervision (DA
6304/ZE) are set as required.
D The overcurrent limits "I>TRIP" for the respecĆ
tive bays (blocks 65) must be parameterized to 0.
Test steps
:
Parameter DA 6307/ZE set to "blocking"
1. Bays 1 and 2 are connected to separate busbars.
2. Current I
1
in bay 1 is gradually increased until difĆ
ferential current supervision is indicated. The curĆ
rent is recorded and must correspond to the set
pick-up limit (DA 6305/ZE).
3. A current of 4 x I
N
is injected in feeder 2. With
correct protection operation, the portable test set
is disconnected from feeder 2.
Test steps 2. and 3. should prove that the diff-curĆ
rent supervision is bus-section specific.
Parameter DA 6307/ZE set to "alarm"
4. Bays 1 and 2 must be connected to the same bus
section. The current I
1
in bay 1 is increased graĆ
dually until the alarm appears. Then a current 4 x
I
N
is switched on. With correct functioning, a trip
command is given.
5. In order to measure the time delay for diff-current
blocking, a current of 2 x the set diff-current limit
I > DIFsup: BZ (DA 6305/ZE) is injected by portaĆ
ble test set into feeder 1. Test set is disconnected
by the diff-current supervision signal. The measuĆ
red time corresponds to the set time T-SUPERV
(DA 6304/ZE).
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