14-8
IM 760201-01E
Power Accuracy
Item
Specifications
Accuracy (at 6 months)
Conditions
Same as the conditions for the voltage and current accuracies.
Frequency
Accuracy
±(reading error + measurement range error)
DC
0.1% of r 0.1% of range
0.5 Hz ≤ f < 45 Hz
0.3% of r 0.2% of range
45 Hz ≤ f ≤ 66 kHz
0.1% of r 0.1% of range
66 Hz < f ≤ 1 kHz
0.2% of r 0.2% of range
1 kHz < f ≤ 10 kHz
{0.1 + 0.067 × (f – 1)}% of r 0.3% of range
10 kHz < f ≤ 100 kHz
{5.1 + 0.18 × (f – 50)}% of r 0.3% of range
* The unit of f in the reading-error equations is kHz.
• For the external current sensor range, add (50
µ
V / external current sensor range rating) ×
100% to the DC power accuracy.
• For the directly applied current input range, add (500
µ
A / external current sensor range rating)
× 100% of range to the DC power accuracy.
• Influence of temperature changes after zero-level compensation or range change.
DC voltage accuracy: add 0.02% of range/°C. DC current accuracy for direct input: add 500
µ
A/°C. DC voltage accuracy for external sensor input: add 50
µ
V/°C. DC power accuracy: add
the product of the voltage influence and the current influence.
• Influence of self-generated heat caused by voltage input
Add 0.0000001 × U
2
% of reading to the power accuracies. Add 0.0000001 × U
2
% of r
0.0000001 × U
2
of range to the DC current and voltage accuracies. U is the voltage reading (V).
Even if the voltage input decreases, the influence from self-generated heat continues until the
temperature of the input resistor inside the WT500 decreases.
• Influence of self-generated heat caused by current input
Add 0.00013 × I
2
% of reading to the power accuracies. Add 0.00013 × I
2
% of r 0.0004
× I% of reading to the DC current and voltage accuracies. I is the current reading (A).
Even if the current input decreases, the influence from self-generated heat continues until the
temperature of the shunt resistor inside the WT500 decreases.
• Accuracy changes caused by data update interval
When the data update interval is 100 ms, add 0.05% of reading to all accuracy figures.
• Guaranteed accuracy ranges for frequency, voltage, and current
All accuracy figures for 0.1 to 10 Hz are reference values.
The power accuracy figures for 30 kHz to 100 kHz when the voltage exceeds 750 V are
reference values.
The power accuracy figures for DC, 10 Hz to 45 Hz, and 400 Hz to 200 kHz when the current
exceeds 20 A are reference values.
Effective input range
0 to ±110% of the measurement range for DC power. For AC, current and voltage are 1 to ±110% of
the measurement range and power is up to ± 110%.
*
However, the synchronization source signal level must meet the frequency measurement input
signal level (see section 14.6 for details).
* 100% for the maximum voltage range.
Lower limit of measurement
frequency
Same as the lower limits for the voltage and current measurement frequencies.
Power factor influence
(not including when
λ
= 1)
• When
λ
= 0
Apparent power reading × 0.2% in the range of 45 to 66 Hz.
For other frequency ranges, see below. However, be aware that these figures are reference
values.
Apparent power reading × (0.2 + 0.2 × f (kHz))%
• When 0 <
λ
< 1
(Power reading) × [(power reading error %) + (power range error %) × (power range/indicated
apparent power value) + {tan
f
× (influence when
λ
= 0%)}]
where
f
is the phase angle between the voltage and current.
14.5 Accuracy
