Siemens 7SR224 Technical Manual page 241

to increase/decrease the angle until the instrument reads 'Rev'. Record the angle (Reverse lead PU).
Reduce the current angle until the 'Rev' extinguishes (Reverse lead DO). and the 'Fwd' subsequently returns
(Forward lead PU), recording the angles. Repeat the above tests, starting from the Characteristic Angle, but
reducing the current phase angle to record the directional boundaries in the opposite (lag) direction. The
recorded angle should be the angle at which the phase current leads the phase-phase polarising voltage.
This measurement is greatly simplified if the polarising reference voltage is set to 0deg and the current
phase angle is measured with respect to this reference.
Alternatively, the instrument can be checked at the 4 points marked a,b,c & d on Figure 2-1 only.
Lag (point C)
Pick-up
MTA MTA-85
Phase A
Phase B
Phase C
Figure 2-1 Directional Phase Fault Boundary System Angles
5. With the instrument reading 'Fwd' or 'Rev', reduce the voltage until the element resets. Record the minimum
phase-phase operate voltage.
Minimum Voltage Setting
©2010 Siemens Protection Devices Limited
Forward
Lead (point A)
Drop-off Pick-up Drop-off
MTA+85
7SR224 Argus Commissioning & Maintenance Guide
Reverse
Lead(point B)
Pick-up Drop-off
MTA-85
Measured
Lag (point D)
Pick-up Drop-off
MTA-85
Chapter 6 Page 15 of 73