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# Term for normalized percent error?

## Term for normalized percent error?

(OP)
Is there a term for percent error type calculations when using the full scale value as the denominator instead of the actual value? Using percent error results in very high values when the actual quantities are small.

For example on a line rated at 500 MW with an error of 10 MW, what would I call the calculation that results in 2% for both of these cases:
assuming a calculated flow of 10 MW and an actual flow of 20 MW
% error = 50% =abs(10 MW-20 MW)/20 MW
% ????? = 2% =abs(10 MW-20 MW)/500 MW

assuming a calculated flow of 490 MW and an actual flow of 500 MW
% error = 2% =abs(10 MW-20 MW)/20 MW
% ????? = 2% =abs(490 MW-500 MW)/500 MW

### RE: Term for normalized percent error?

If you are talking about instrument measurement accuracy, they are rated by percent of full scale. The reason you do not use instruments to measure values that are one percent of full scale is that the percent error in actual reading will be huge.

### RE: Term for normalized percent error?

(OP)
Getting into the weeds a bit, I am looking to flag components of a large power grid simulation if the calculated power flows are significantly different than measured power flows. The full scale measurements for various components range a couple of orders of magnitude from about 1 MW for a small generator to over 5000 MW for large transmission path.

### RE: Term for normalized percent error?

#### Quote (Bacon)

what would I call the calculation that always gives 2%
I would call it (politely) an incorrect calculation

### RE: Term for normalized percent error?

Consider:

The speeding ticket 80 km/h in a posted 40 km/h Zone.

Ferraro Enzo ZXX owner "Top speed of my car is 395 km/h. (80-40)/395 is barely more than 10% over the limit."

Tata Nano owner "Top speed of my car is 110 km/h. (80-40)/110 36% over the limit! Man I was really flying!"

Who pays the higher fine?

Bonus question: Who pays the higher fine as a percentage of their income?

### RE: Term for normalized percent error?

I was told that in Italy, it's not how fast you drive, but who you manage to pass along the way.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

### RE: Term for normalized percent error?

(OP)
Although percent error is useful for many things, I cannot use it in this case because sometimes the actual flows are zero when the simulated flows are non zero, leading to a divide by zero error.

Mint,
Does my edited post make more sense? I agree that a calculation that always had the same result would be wrong.

Your bonus question is quite on the point. It uses the percent Full Scale of the owners income rather than using percent error.

### RE: Term for normalized percent error?

In Austria, the fine you in accordance with your ability to pay.

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