About three-phase unbalance standard

[YKC]

Hello everyone,

Recently, my manager asked me to collect the standard about three-phase unbalance include voltage and current.
I already read some standards, like 1)IEEE std.1159, 2)IEC 61000-2-2, 3)EN 51600, 4)ANSI C84.1, 5)NEMA MG-1.
However, most of them only mentioned about the limit of voltage unbalance (like "not reach over 3%.").

Following are my questions:
Q1: Does any standard mention about the current unbalance?
Q2: I would like to know how to decide the limit values in each area or country? E.g. IEEE std.1159 set the limit value = 5%, but ANSI C84.1 set the limit value = 3%. Could someone please tell me the reason why they choose 5% / 3% as their standard.

Thank you, and please have a nice day
YKC

 

[Hector04]

To understand current imbalance it is best through transformations. In the graph we see the transformations of Fortescue, Clark and Park. I also show you a transformation that I developed with a colleague, which led us to enact the conservation of the electric angle in the face of current imbalances.

 

[YKC]

Hi everyone,

It's been a while, and I got a question while reading the standard.
Could anyone tell me the difference between "public low-voltage supply system" and "low-voltage supply system"?
I asked "Dr. Chatgpt" and he/she told me that their voltage levels are the same, so I am not sure what's the difference.

The refer standards are IEC 61000-3-11 and IEC 61000-3-13, these two standard are also similar, but forcing on difference issues, could anyone please also tell me the difference between these two standards.

Thanks a lot, and please enjoy your day!

 

[Gr8blu]

Not sure, but ... my guess would be that a "public" system would supply more than one user and (generally) be EXTERNAL to an industrial facility. The "non-public" system might be INTERNAL to a facility, such as dedicated emergency standby generation - which by its nature has no way to provide power to the "public" grid.

If the facility is intended to operate on either mode of supply (i.e. external utility or internal generation) then the voltages have to be the same (or very close to it). If a portion of the facility ONLY works on the internal generation, then the voltage can be anything at all that works for the attached equipment.

In reality, the equipment connected to a distribution bus (and the protection devices used) are intended for operation at specific voltage levels - which tends to force even the "oddball" internal distribution voltages to match up with the utility standard(s).

Converting energy to motion for more than half a century

 

[waross]

Another WAG.
A public system would be a system operating at the utility supplied low voltage.
This may not include plants with primary supply who step down to their own internal low voltages.
$80 volt supplies with some 120/240 Volt internal systems would still be a public low voltage system.
Just a Wild A--- Guess.

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Ohm's law
Not just a good idea;
It's the LAW!