Siemens 7SJ82 - Functional Test Differential Protection for Capacitor Banks; Secondary Tests

Functional Test Differential Protection for Capacitor Banks
Secondary Tests
Secondary tests can never replace the primary tests described in the following chapter 11.17.2 Primary Tests,
because they cannot include connection faults.
Secondary tests are used to check the following:
•
Checking the setting values
•
Proper reaction of the protection function
•
Engineering (for example, routing the respective logic signals, display images with measured values,
logics in CFC, and much more)
If you want to perform secondary tests, observe the following instructions.
i
i
NOTE
For tests with secondary test equipment, ensure that no other measurands are connected and the trip
commands to the circuit breakers are interrupted, otherwise, the circuit breakers could be activated.
Perform the tests with the current setting values for the device. If these values are not (yet) present, check
with the default values.
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i
NOTE
The measuring accuracy to be attained depends on the electrical data of the test sources. The accuracies
stated in the Technical Data can be expected only if the reference conditions stipulated in VDE 0435/
part 303 and IEC 60255 are ensured and precision instruments are used. The stated tolerances refer to the
default data for the protected objects. If the rated current of the protected object in relation to the rated
current of the current transformer deviates considerably from the rated current of the device, you must
assume higher response tolerances.
For differential protection, you can check each side separately. This corresponds to the simulation of a fault
supplied from one side. If a side has several measuring points, the measuring inputs not included in the test
carry no current. The pickup value is tested by increasing the test current slowly.
i
i
NOTE
Tests of currents via quadruple device-rated current (or a maximum of 20 A) lead to an overload of the
input circuits and may be performed only briefly. You can find more information in chapter 12.28 Differen-
tial Protection for Capacitor Banks. Interrupt testing to allow cool-down!
The set pickup values refer to symmetrical 3-phase current in the case of 3-phase protected objects.
If you are testing parameters set during operation, you must ensure that the setting value for the differential
protection refers to the rated current of the protected object.
If you wish to check the characteristic curve, Siemens recommends using the standard testing programs of
digital test equipment. For the manual checking of points on the characteristic curve, feed in a through-
flowing current which corresponds to a current value on the stabilization axis. Then change the phase angle
of the test current on one side, so that the necessary differential current is achieved. Check a value with a
tolerance of 5 % above and below the point on the characteristic curve which is to be tested.
For capacitor banks, the actual pickup values for 2-phase testing also depend on the vector group of the
capacitor bank.
To obtain the actual pickup value, multiply the setting value by a vector-group factor k
SG
according to the
following formula:
11.17
11.17.1
Functional Tests
11.17 Functional Test Differential Protection for Capacitor Banks
1402 SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017