【PM8000】Over V unbalance alarm

[Miyai]

Hello,

Could you please advice about the formula for calculating V unbalance.
The displayed V unbal when the voltage drops does not match the calculation.
I think my calculation formula is wrong, but I don't know where to correct it.

For example:
Vln a = 110V
Vln b = 110 V
Vln c = 101 V
Vln avg = 110 + 110 + 101 / 3 = 321 / 3 = 107 V
Vln B (110) has the largest deviation from Vln avg (107)
ABS ((Vln B – Vln avg) / Vln avg) x 100% = ABS ((110 – 107) / 107) x100% = 2.8%
However, the V unbal displayed by the PM8000 is 5.6%.

If the voltage increases, the displayed value and the calculated value will match.
Vln a = 110V
Vln b = 110 V
Vln c = 119 V
Vln avg = 110 + 110 + 119 / 3 = 339 / 3 = 113 V
Vln B (119) has the largest deviation from Vln avg (113)
ABS ((Vln B – Vln avg) / Vln avg) x 100% = ABS ((119 – 113) / 113) x100% = 5.3%
The V unbal displayed by the PM8000 is 5.3% ⇒OK.

Regards,

[DanL · Accepted solution]

In the default framework, the input of Setpoint #22 labelled "Over V unbal" is linked to the Power Meter Module output "V unbal".

For this output, you got the equation correct, but the execution of your example wrong.

Vln a = 110V
Vln b = 110 V
Vln c = 101 V
Vln avg = 110 + 110 + 101 / 3 = 321 / 3 = 107 V
Vln C (101) has the largest deviation from Vln avg (107)
ABS ((Vln C – Vln avg) / Vln avg) x 100% = ABS ((101 – 107) / 107) x100% = 5.6%
This matches the V unbal displayed by the PM8000 = 5.6%

[Miyai]

Hello @DanL 

I understand.

Thank you for your advice.

Regards,

Miyai