What is Class 5 timing accuracy as described in the Sepam Operation manual?
Issue
User needs clarification of what Sepam class 5 timing accuracy is as a percentage
Product Line
Sepam series 20, 40, and 80
Environment
Accuracy specifications
Resolution
Class 5 accuracy is defined in the IEC 60255-151 standard. Class 5 accuracy is ±5%.
This 5% has factors to be considered referring to different parts of the IDMT curve. These factors are defined in part 5.2(Accuracy related to the operate time) table 1 IEC60255-151(2009). This table is provided below.
This table gives the factors for different ranges (Gs= threshold). To determine the real accuracy, multiply the assigned error of 5% by the limiting error from the above table. The assigned error is based on the accuracy class 5 for the Sepam relay. The real accuracy values for each of these ranges is below:
- For current between 2 to 5, real accuracy would be 2.5*5% = 12.5%
- For current between 5 to 10, real accuracy would be 1.5*5% = 7.5%
- For current higher than 10*Gs or 10 times threshold, real accuracy would be 1*5% = 5%