Checking The Earth Current Differential Protection - Siemens Siprotec 7UM62 Manual

3 Installation and Commissioning
Table 3-25 Displayed Phase Angle Dependent on the Protected Object (Three-Phase)
→
Protect. Object
Generator/Motor
↓ Phase Angle
ϕL1S2
ϕL2S2
ϕL3S2
1
) Values are valid for measurement if the higher voltage side is defined as side 1; when measuring from the lower voltage side, 360°
minus the stated angle is valid
Differential and
Restraint Currents
3.4.4

Checking the Earth Current Differential Protection

Preparation
368
The polarity of the current connections and the parameterized polarity are taken into
consideration when the angles are displayed. Thus, if all three angles differ by 180°
from the theoretical value, the polarity of one complete transformer set is wrong. This
can be corrected by checking and changing the corresponding plant parameters:
Address 0201 STRPNT->OBJ S1 for the primary winding,
Address 0210 STRPNT->OBJ S2 for the secondary winding,
0 1
180° 180° 150° 120°
60°
60° 30°
300°
300° 270° 240° 210° 180° 150° 120°
Before the tests with symmetrical currents are terminated, the differential and restraint
currents are checked. Even though the tests which have been carried out so far should
have revealed most of the possible connection errors, matching errors or wrong vector
group allocations cannot be ruled out.
Switch to the operational measured values to read out the calculated values. When
assessing the currents, note that the differential and restraint values are referred to
the rated current of the protected object. This fact should be kept in mind when
comparing them to the test currents.
If considerable differential currents occur, recheck the following parameters:
For transformer protection (as per Section 2.12.2.2): addresses 0241, 0249 and
0202 (matching of winding 1), 0243, 0249 and 0211 (matching and vector group
of winding 2);
For generator or motor protection (as per Section 2.12.2.2): addresses 0251 and
0252 (matching of machine ratings);
The symmetrical current tests are now completed. Disconnect the protected object
(shut down generator) and earth it, remove the test equipment.
Switch the differential protection to being operative (address 2001: DIFF. PROT. =
ON); it works now as a short-circuit protection for all subsequent tests.
The primary test checks the correct integration of the 7UM62 into the system, espe-
cially the CT connection. Before commencing any primary tests, make sure that the
configured object is actually the one you want to protect. To do so, verify the settings
used in the configuration of the protection function, in Power System Data 1 and in the
protection function itself.
Set the earth current differential protection (address 2101 REF PROT.) to Block re-
lay, or interrupt the trip command lines.
Transformer with Vector Group Numeral
2 3 4 5
90° 60° 30°
0° 330° 300° 270° 240° 210° 180° 150° 120°
1
)
6 7 8 9
0° 330° 300° 270° 240° 210°
90° 60° 30°
7UM62 Manual
C53000-G1176-C149-3
10 11
90°
0° 330°