In order to select the proper indoor type voltage transformer for an application we need to define customer requirements based on the primary circuit and the metering and protection chains; i.e. define customer requirements in terms of voltage transformer specifications, key specifications can be summarized as follows:

• Rated primary voltage(s) or insulation level Ur/Ud/Ui in kV.
• Rated secondary voltage(s).
• Rated frequency (e.g. 50 or 60Hz).
• Earthing system (isolated or not).
• Desired accuracy class in measurement chain (e.g. class 1, 0.5 …etc).
• Desired rated burden (in VA) for measurement chain (e.g. 25VA).
• Desired accuracy class in protection chain (e.g. class 3P, 6P …etc).
• Desired rated burden (in VA) for protection chain (e.g. 25VA).
• Special requirements such as out-of-standard temperature/environment/altitude; connections; terminal covers; etc

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Released for:Schneider Electric South Africa