Siemens 7SJ82 - Functional Test of Transient Ground-Fault Protection

Functional Test of Transient Ground-Fault Protection
General
This function requires the correct polarity of the ground current IN and the neutral-point displacement voltage
VN respectively the zero-sequence voltage V0. For the direction test of these quantities, refer to chapter
11.3 Direction Test of Ground Quantities for Directional Ground-Fault Functions.
The function is based on the evaluation of the transient in the zero-sequence system after the ground-fault
ignition.
For issuing the signal
(_:13021:302) Ground fault , the following 2 conditions must be met:
•
There is a transient in the ground quantities.
•
The fundamental compoment of the zero-sequence voltage V0 exceeds the threshold (_:13021:103)
V0> threshold value.
The following 2 methods are available for testing of the signal
(_:13021:302) Ground fault :
•
Replaying real transient ground-fault recordings to the device
•
Using secondary test equipment which allows to simulate transients ground faults
However, the setting of parameter (_:13021:103) V0> threshold value cannot be tested precisely
with the mentioned 2 methods, since this test requires a static V0. An easy way to test the setting is described
in the following.
Secondary Test
This test must be carried out by injecting static secondary quantities. The test equipment needs to be config-
ured in a way that it generates zero-sequence current 3I0 and zero-sequence voltage V0, which are injected to
the SIPROTEC 5 device. By carrying out a shot, for example, a status change from zero-sequence values of 0 A
and 0 V to the values not equal to zero, a transient is generated. The signal (_:13021:302) Ground
fault is issued as long as the static zero-sequence voltage of the 2nd state is greater than the set threshold.
As amplitude for the secondary 3I0, 100 mA is a suitable value. In this test, the directional result contained in
the signal
(_:13021:302) Ground fault is not defined and relevant, since the task is to test the setting
of parameter (_:13021:103) V0> threshold value only.
For testing the threshold, shots must be carried out with a static V0 slightly below the threshold and slightly
above the threshold, for example, to 98 % and 102 % of the threshold value or to a threshold value of -0.2 V
and +0.2 V (the greater absolute deviation of the threshold value must be selected) .
Consider that the V0 threshold is defined according to the definition of the symmetrical components. A full
neutral-point displacement voltage VN of 100 V causes V0 = 57.7 V.
Example
•
(_:13021:103) V0> threshold value = 15 V
•
3 shots from 0 to V0 = 14.7 V and 3I0 = 100 mA
No signal
(_:13021:302) Ground fault is issued.
•
3 shots from 0 to V0 = 15.3 V and 3I0 = 100 mA
Signal (_:13021:302) Ground fault is issued
If the test result is not as expected, check the injected static V0 voltage via the operational measurement of
the device which contains the zero-sequence components.
11.8
Functional Tests
11.8 Functional Test of Transient Ground-Fault Protection
1386 SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017