(50Sef); Wattmetric Protection - Siemens 7SR12 Argus Manual

7SR11 & 7SR12 Commissioning and Maintenance Guide
definition reduce towards zero. It is therefore necessary to increase the residual current or to temporarily disable
the Wattmetric function to allow the directional boundary to be tested.
If the 67SEF Compensated Network setting is set to Enabled, the directional boundaries will be extended to
MTA+87º and MTA-87º.
MTA
Lag (point C)
Pick-up Drop-off Pick-up Drop-off
MTA-85
.............
...........
SEF
2.9.2 Definite Time Overcurrent
If DTL setting is small, gradually increase current until element operates.
If DTL is large apply 0.9x setting, check for no operation, apply 1.1x setting, check operation
Apply 2x setting current if possible and record operating time
P.U. Ph. Dir
D.O.
&
TIMING
I
4
TESTS
Check correct indication, trip output, alarm contacts, waveform record.
Note that these elements can be set to directional.
If VTS action is set to BLOCK, this option should be tested. Apply balanced voltage and current. Reduce a-phase
voltage to cause a VTS condition. Increase a-phase current and check that the element does not operate.
If VTS action is set to Non-Directional, this option should be tested. Apply balanced voltage and current. Reduce
a-phase voltage to cause a VTS condition. Increase a-phase current and check that the element operates at its
normal setting. Reverse the voltage phase direction whilst checking that the element does not reset.
2.9.3

Wattmetric Protection

The Wattmetric Earth Fault protection requires that the SEF current setting is exceeded, the residual
power setting is exceeded and the directional element operated, simultaneously.
During testing of the 67SEF Wattmetric power setting it is essential that the current setting is also
exceeded. This can usually be achieved by applying current which is above setting to the SEF input
whilst applying single phase voltage, in anti-phase with the current, to any 1 phase to neutral voltage
input. In this way, the wattmetric power is equal to the product of the applied current and applied
voltage and can be adjusted by adjustment of the voltage magnitude.
Wattmetric Power
Setting
©2017 Siemens Protection Devices Limited
Forward
Lead (point A)
MTA+85
.........
...

(50SEF)

Char. Is TM
(NI EI VI LTI, (A)
DTL)
Current Dir
Applied
Io
Lead(point B)
Drop-
Pick-up Pick-up
off
MTA-85 MTA-85
............ ............
Operate Current
P.U. D.O. Tol
(Amps) (Amps)
Operate Voltage
Vo
Reverse
Lag (point D)
Drop-off
Operate Time
2 x Is 5 x Is Tol
(sec) (sec)
Calculated Po
Io x Vo
Chapter 6 Page 34 of 72