MA-041
–
DGA 900 Plus - Installation & Commissioning Manual - Rev 1.1
4-Mar-22
Page 89 of 99
If the C1% measurement is above 5% after these checks, please contact GE customer
support team.
10.4.4
C.4
Tan
δ
(Power Factor) Measurement
To verify that the wiring is correct and that initial alarms levels are appropriate for the
system with instantaneous Tan
δ
measurements:
▪
Select
BMT > Configuration
as shown in Figure 10-24 to verify
the ‘
Exponential
Moving Average Configuration
’. Ensure that:
−
‘
Daily Moving Average Enable
’ is
Off
−
‘
Moving Average Factor Phase Angle
’
is
100
(factory default is 10000)
Figure 10-24: Exponential Moving Average Configuration
▪
Select
BMT > Live Measurement
as shown in Figure 10-25 to verify
the ‘Measured
Phase Angle’. Ensure that:
−
the measured angles are within 2
degrees of the expected angles. If the phase
angles are measuring more than 2
degrees, contact GE Technical Support for
further guidance. If applicable, check the same on secondary bushings.
−
the imbalance (polar plot amplitude) for tan
δ
is less than 120%. If the tan
δ
is
more than 120%, the alarm limit should be adjusted. The alarm is recommended
to be set at 50% above the highest measurement. If applicable, check the same on
secondary bushings.
Figure 10-25: Measured Phase Angle
To change the
Polar Plot PF
% alarms:
▪
Select
Alarm > Bushing Alarm Configuration > Primary Polar Plot PF%
as shown
in Figure 10-26 to adjust the alarm as required for both Primary and Secondary
sources, High-High and High limits.