Chapter 5 Measurement Description
Accura 2300/2350 User Guide
Page 204
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Unbalance(NEMA MG1)
Line-to-neutral Voltage Unbalance
It represents the degree of voltage that deviates most from the average voltage of the three-phase voltage.
The phase voltage unbalance index is 0 even when the phase voltages are equal in magnitude and the phases
are unbalanced.
𝑃ℎ𝑎𝑠𝑒 𝑉𝑜𝑙𝑡𝑎𝑔𝑒 𝑈𝑛𝑏𝑎𝑙𝑎𝑛𝑐𝑒 =
𝑀𝑎𝑥(𝛥𝑉𝑝ℎ)
𝑉𝑝ℎ, 𝑎𝑣𝑔
× 100 [%]
Vph,avg
: Average of line-to-neutral voltages of 3-phase.
Max(
Δ
Vph)
: Difference voltage most deviating from the average of line-to-neutral voltages.
Line-to-line Voltage Unbalance
It indicates the degree of line-to-line voltage that deviates most from the average voltage of the three-phase
line-to-line voltage. If the magnitude of the phase voltage is the same and the phase is unbalanced, the phase
voltage unbalance index is zero, but the line-to-line voltage unbalance index is not zero.
𝐿𝑖𝑛𝑒 − 𝑡𝑜 − 𝑙𝑖𝑛𝑒 𝑉𝑜𝑙𝑡𝑎𝑔𝑒 𝑈𝑛𝑏𝑎𝑙𝑎𝑛𝑐𝑒 =
𝑀𝑎𝑥(𝛥𝑉𝐿𝐿)
𝑉𝐿𝐿, 𝑎𝑣𝑔
× 100 [%]
VLL,avg
: Average of line-to-line voltages of 3-phase.
Max(
Δ
VLL)
: Difference voltage most deviating from the average of line-to-line voltages.
Current Unbalance
It represents the degree of current that deviates most from the average current of the three-phase currents. The
current unbalance index is zero even if the magnitude of the current is the same and the phase is unbalanced.
𝐶𝑢𝑟𝑟𝑒𝑛𝑡 𝑈𝑛𝑏𝑎𝑙𝑎𝑛𝑐𝑒 =
𝑀𝑎𝑥(𝛥𝐼𝑝ℎ)
𝐼𝑝ℎ, 𝑎𝑣𝑔
× 100 [%]
Iph,avg
: Average current of three-phase currents.
Max(
Δ
Iph)
: Difference current most deviating from average current of three-phase currents.
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