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Technical catalog for Susol & Metasol ACB
Technical catalog for Susol & Metasol ACB
D
Voltage / Current RMS Value for P, S Type
i(k): Instantaneous value of current waveform (Sampling Value) Assume that current RMS is calculated with 32
sampling in a cycle.
Ih : Harmonics element (I1:fundamental, I2:2 harmonics...)
Choosing 32 samplings per a cycle to transform analogue frequency of current to digital signals will allow to
measure as much as 15 harmonics. Therefore, after 15 harmonics can not be taken into consideration for
measurement.
V phasor : phasor value size
Assume that current RMS is calculated with 32 Samplings in a cycle.
T: time taken for 1 cycle
ecos, esin : Sine, Cos Map for fundamental frequency
Irms =
1
32
i(k)
2
I
2
h
=
31
k=0
15
h=1
1. RMS Values
Measurements that is required for every over current relay of P and S type are based on RMS values.
1) Low voltage system enclose much of harmonics elements due to non-linear loads at the feeder level.
2) Harmonics current overheats loads and equipments from its thermal element.
3) Hence, low voltage relay based on thermal element should include harmonics.
4) RMS values include every harmonics elements
5) Hence, over current/ fault current relay of P and S type react to harmonics.
2. Phasor Value - Fundamental Frequency Element Size
P and S type’s voltage relay (under voltage, over voltage) operate by using phasor value.
1) Voltage is relatively low on harmonics comparing with current.
2) Voltage Relay is using fundamental frequency excluding effects from harmonics.
3) P and S type’s OUR and OVR operate based on fundamental frequency excluding effects from harmonics
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