Explanations of the measured values
Measured value
• A measured value (in the UMG508) is a effective value which is formed over a period (measuring window) of 200ms.
• A measuring window is 10 periods in the 50Hz network and 12 periods in the 60Hz network.
• A measuring window has a start time and an end time.
• The resolution between the start time and end time is approximately 2ns.
• The accuracy of the start time and end time depends on the accuracy of the internal clock.
(Typically +- 1 minute/month)
• In order to improve the accuracy of the internal clock, it is recommended that the clock in the device is compared
with a time service and reset.
n Mean time / seconds
0 5
1 10
2 15
3 30
4 60
5 300
6 480
7 600
8 900
Mean value of measured value
• For each measured value, a sliding mean value is calculated over the selected averaging time.
• The mean value is calculated every 200ms.
• You can take the possible averaging times from the table.
Max. value of measured value
• The max. value of the measured value is the largest measured value which has occurred since the last deletion.
Min. value of measured value
• The min. value of the measured value is the lowest measured value which has occurred since the last deletion.
Max. value of mean value
• The max. value of the mean value is the largest mean value which has occurred since the last deletion.
Nominal current, voltage, frequency
• The limit values for events and transients are set by the nominal value in percentage.
Nominal current I
rated
• The Irated is the nominal current of the transformers and is required for calculation of the K-factor.
Peak value negative
• Highest negative sampling value from the last 200ms measuring window..
Peak value positive
• Highest positive sampling value from the last 200ms measuring window.
Crest factor
• The crest factor describes the relation between the peak value and effective value of a periodic quantity. It serves as
a characteristic value for general description of the curve form of a periodic quantity. The distortion factor is another
example of a quantity for characterization of the difference from the pure sinusoidal form.
• Example
A sinusoidal change voltage with an effective value of 230 V has a peak value of approx. 325 V.
The crest factor is then 325 V / 230 V =1.414 .
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