When a higher rating factor is needed, the designer should consider a relay class transformer. A relay class transformer will guarantee the transformer will not saturate at 20 times the rated current and be within +/- 10% accuracy. This allows a meter to detect larger fluctuations in the primary current.

The relay class transformers are classified as follows:
20 • (Rated Secondary Current) • (Burden) = Relay Class Rating

20 • (5 amps) • (1.0 Ohm Burden) = C100

MCT has developed many different types of relay class transformers in the past for a variety applications.