Dranetz Xplorer Guia do Utilizador descarregar pdf (Página 94)

5-10

Scale Factor Setup

What is a scale

factor?

A scale factor is the ratio of the input to output for a particular current transformer (CT)

or potential transformer (PT). A scale factor is entered in PX5 and then multiplied

automatically by the measured voltage or current so the unit displays the correct values,

as referenced to the primary side, rather than the secondary side of the PT or CT.

NOTE: If voltage and current connections are made without using any of the above

named devices, the scale factor should be set to 1.

When to use

Scale factors must be entered for the following conditions:

• A Dranetz

current probe is connected to a permanently installed CT.

• The current connections are made using a Dranetz

ISO box.

• The voltage connections are made using a PT.

Non-Dranetz

equipment

Refer to the CT name plate or to the manufacturer’s literature to determine the scale

factor.

Sample

calculation

The scale factor for a single CT or PT is calculated from its step-up or step-down ratio.

Example of step-down ratio

If a current transformer has a step-down ratio of 1000A:5A, therefore:

Scale Factor = 1000/5 = 200

Example of step-up ratio

If a potential transformer has a step-up ratio of 1V:10V, therefore:

Scale Factor = 1/10 = 0.1

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Dranetz Xplorer Guia do Utilizador Página 94