Current Measurement (Magnitude Of Supply Current); Frequency Measurement - METREL MI 2792 PowerQ4 Plus Instruction Manual

MI 2792 PowerQ4 Plus
Line voltage:
Phase voltage crest factor:
Line voltage crest factor:
The instrument has internally 3 voltage measurement ranges. Middle voltage (MV) and
high voltage (HV) systems can be measured on lowest voltage range with assistance of
voltage transformers. Its voltage factor should be entered into Voltage ratio: 1:1 variable
in CONNECTION SETUP menu.

5.1.3 Current measurement (magnitude of supply current)

Standard compliance: Class S (Section A.6.3)
All current measurements represent RMS values of the 1024 samples of current
magnitude over a 10-cycle time interval. Each 10-cycle interval is contiguous and non-
overlapping.
Current values are measured according to the following equation:
Phase current:
Phase current crest factor:
The instrument has internally two current ranges: 10% and 100% range of nominal
transducer current. Additionally Smart current clamps models offer few measuring
ranges and automatic detection.

5.1.4 Frequency measurement

Standard compliance: IEC 61000-4-30 Class S (Section 5.1)
During RECORDING with aggregation time Interval: ≥10 sec frequency reading is
obtained every 10 s. As power frequency may not be exactly 50 Hz within the 10 s time
clock interval, the number of cycles may not be an integer number. The fundamental
frequency output is the ratio of the number of integral cycles counted during the 10 s
time clock interval, divided by the cumulative duration of the integer cycles. Harmonics
and interharmonics are attenuated with 2-pole low pass filter in order to minimize the
effects of multiple zero crossings.
The measurement time intervals are non-overlapping. Individual cycles that overlap the
10 s time clock are discarded. Each 10 s interval begin on an absolute 10 s time clock,
with uncertainty as specified in section 6.2.17.
1024
1


(
Upg u
1024 p
j

1
j

Cf
Up
U

pgPk
Cf
Upg
U
pg
1024
1


I
p
1024

j

Ip
cr
Theory and internal operation
 2
) [V], pg: 12,23,31
u
g
j
U
pPk , p: 1,2,3,N
U
p
, pg: 12, 23, 31
,
2
[A] p: 1,2,3,N
I
p
j
1
Ip
max , p: 1,2,3,N
Ip
102
(2)
(3)
(4)
(5)
(6)