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5 Theory and internal operation
78
Total power factor (vector):
St
Pt
PFtot
=
.
(16)
Figure 5.2: Vector representation of total power calculus
5.1.7 Energy
Standard compliance:
IEC 61557-12 (Annex A)
Energy counters are linked to RECORDER functionality. Energy counters measure
energy only when RECORDER is active. After power off/on procedure and before start
of recording, all counters are cleared.
Instrument use 4-quadrant measurement technique which use two active energy
counters (eP
+
, eP
-
) and two reactive (eQ
+
, eQ
-
), as shown on bellow.
Figure 5.3: Energy counters and quadrant relationship
Instrument has 3 different counters sets:
1. Total counters
TotEN
are intended for measuring energy over a complete
recording. When recorder starts it sums the energy to existent state of the
counters.
2. Last integration period
LastIP
counter measures energy during recording over
last interval. It is calculated at end of each interval.
3. Current integration period
CurrIP
counter measures energy during recording over
current time interval.