Measuring The Operating Time Of The Circuit Breaker - Siemens siprotec 7SA6 User Manual

Bus-
bar
Transformer
Figure 8-27 Polarity check of I

8.3.11 Measuring the operating time of the circuit breaker

Only for
Synchronism
Check
7SA6 Manual
C53000-G1176-C133-1
Test source
, example with earth current from a power transformer star-point
4
After switching the test source on and off again, the direction indication must be
checked: In the fault messages (refer also to Sub-section 7.1.1.3) at least the following
alarms must be present "() 3LFNXS" and "() IRUZDUG". If the directional pick-up
alarm is missing, a connection error of the earth current connection I
wrong direction is indicated, the earth current connection I
The connection must be rectified after the test source has been switched off. The
measurement must then be repeated.
If the pick-up alarm is missing altogether, this may be due to the fact that the test
current is too small.
Attention! If parameters were changed for this test, they must be returned to their
original state after completion of the test!
If the device is equipped with the function for synchronism and voltage check and it is
applied, it is necessary — under asynchronous system conditions — that the
operating time of the circuit breaker is measured and set correctly when closing. If the
synchronism check function is not used or only for closing under synchronous system
conditions, this subsection is irrelevant.
For measuring the operating time a setup as shown in figure 8-28 is recommended.
The timer is set to 1 s and a graduation of 1 ms.
The circuit breaker is closed manually. At the same time the timer is started. After
closing the poles of the circuit breaker, the voltage U
stopped. The time displayed by the timer is the real circuit breaker closing time.
If the timer is not stopped due to an unfavourable closing moment, the attempt will be
repeated.
It is particularly favourable to calculate the mean from several (3 to 5) successful
switching attempts.
Installation and Commissioning
I
L1
I
L2
I
L3
I '
L1
I '
L3
I '
L3
I '
4
I
4
Line
4
appears and the timer is
Line
A
B
C
6$
is present. If the
4
has a swapped polarity.
8-57