MI 2792A PowerQ4 Plus Ang Ver 1.0 20 752 082

MI 2792A PowerQ4 Plus

Theory and internal operation

Line voltage:

Upg



1

1024

j

1024





1

(

u p j



u g j

)

2

[V], pg: 12,23,31

(2)

Phase voltage crest factor:

Cf

Up



U pPk

U p

, p: 1,2,3,N

(3)

Line voltage crest factor:

Cf

Upg



U pgPk

U pg

, pg: 12, 23, 31

(4)

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)

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 nonoverlapping.

Current values are measured according to the following equation:

Phase current:

I p



1

1024

1024



j



1

I p

2

j

[A]

,

p: 1,2,3,N

(5)

Phase current crest factor:

Ip cr



Ip

max , p: 1,2,3,N

(6)

Ip

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 A (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.

For RECORDING with aggregation time Interval: <10 sec and on-line measurements, frequency reading is obtained from 10 cycles, in order to decrease instrument response time. The frequency is ratio of 10 cycles, divided by the duration of the integer cycles.

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