Siemens 7SR51 - 50;51 Phase Overcurrent

Element BI Inhibits
49
50/51 Phase Overcurrent
Some other current protection functions may overlap with these functions during testing, it may be useful to
disable some functions to avoid ambiguity. It should be particularly noted that if the function is enabled, the
51C Cold Load settings may modify the normal 50-n and 51-n settings if the CB is open during testing.
Voltage inputs may not be required for this function if the Phase Overcurrent functions are not directional
but it may be advantageous to apply balanced 3 phase nominal rated voltage to the VT inputs during testing
to avoid inadvertent operation of other functions. Particular care should be taken when testing overcurrent
functions that the thermal rating of the current inputs is not exceeded.
Instantaneous Overcurrent – Phase (50)
If DTL setting is small, gradually increase current until element operates.
If DTL is large apply 0.9 times setting, check for no operation, apply 1.1 times setting, check operation.
Apply 2 times setting current if possible and record operating time.
Phase Dir. I
set
(Amps) DTL (sec) P.U.
Current
Amps
Tolerence Op. Time 2 ⋅
I
set
Tolerance
CT1(I
A
)
CT2(I
B
)
CT3(I
C
)
Check correct indication, trip output, alarm contacts, waveform record.
Time Delayed Overcurrent – Phase (51)
It will be advantageous to map the function being tested to temporarily drive the relevant pickup output in the
Pickup Config sub-menu in the Output Config menu as this will allow the Pickup LED to operate for
the function.
Gradually increase current until Pickup LED operates.
Apply 2 times setting current and record operating time.
Apply 5 times setting current and record operating time.
Compare to calculated values for operating times.
Gradually reduce current until the element drops off and record the level.
Table 9-4
P.U. D.O. & Timing Tests
Phase Dir Char.
Curve
I
set
(Amps)
Tm Operate Current Operate Time
P.U.
(Amps)
D.O.
(Amps)
Tol 2 ⋅ I
set
(sec)
5 ⋅ I
set
(sec)
Tol
CT1(I
A
)
CT2(I
B
)
CT3(I
C
)
Calculated timing values in seconds for Tm = 1.0
Curve
2 ⋅ I
set
5 ⋅ I
set
IEC-NI 10.03 4.28
IEC-VI 13.5 3.38
IEC-EI 26.67 3.33
9.9.11
Functional Tests
9.9 Protection Functional Tests
474 Reyrolle 7SR5, Overcurrent Protection Device, Device Manual
C53000-G7040-C014-1, Edition 11.2019