Hioki PQ3100 User Manual

Appx.23
Method for Calculating Active Power Accuracy
Appx. 8 Method for Calculating Active Power
Accuracy
The accuracy of active power calculations can be calculated as follows, taking into account the
phase accuracy:
Example measurement conditions
Wiring: 3-phase/4-wire (3P4W)
Current sensor: Model CT7136
Current range: 50 A (power range: 150 kW)
“14.8 Range Conguration and Combination Accuracy” (p. 188)
Measured values: Active power of 30 kW, power factor lag 0.8
Accuracy
Current sensor combined accuracy (Model CT7136 sensor, 50 A range): ±0.5% rdg.±0.22% f.s.
Internal circuit voltage of the instrument - current phase difference: ±0.2865° (Effect of power factor:
1.0% rdg. or less)
Phase accuracy of the CT7136: ±0.5°
“14.2 Input Specications/Output Specications/Measurement Specications” (p. 155)
“14.8 Range Conguration and Combination Accuracy” (p. 188)
Phase accuracy shown in “Specications” of the CT7136 Instruction Manual
Power factor accuracy based on phase accuracy
Phase accuracy (in combination with current sensor) = Instrument internal circuit phase accuracy
(±0.2865°)
+ CT7136 phase accuracy
(±0.5°) = ±0.7865°
Phase difference
θ
= cos
−1
(power factor)
= cos
−1
0.8= 36.87°
Power factor error range based on phase accuracy
= cos(36.87°±0.7865°) = 0.7916 to 0.8082
Power factor accuracy based on phase accuracy (minimum)
=
0.7915 0.8
100%
0.8
−
×
= −1.05%
use the worst value as the power factor accuracy.
Power factor accuracy based on phase accuracy (maximum)
=
0.8083 0.8
100%
0.8
−
×
= +1.025%
The value, whichever is
worse, is specied to be
the phase accuracy.
Power factor accuracy based on phase accuracy: ±1.05% rdg.
Active power accuracy
Active power accuracy = current sensor combined accuracy + power factor accuracy based on
phase accuracy
= ±0.5% rdg. ±0.22% f.s. ±1.05% rdg.
= ±1.55% rdg.±0.22% f.s.
Accuracy relative to measured values = active power
30 kW × ± 1.55% rdg. + 150 kW
range
× 0.22% f.s.
= ±0.795 kW
= ±0.795 kW/30 kW = ±2.65% rdg.
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Appx. Ind.

Hioki PQ3100 Specifications

General

Brand	Hioki
Model	PQ3100
Category	Measuring Instruments
Language	English