In the protection of transformers, harmonic restraint is used to guard against

• A. Switching over voltages
• B. Magnetizing inrush current
• C. Unbalanced protection
• D. Lightning

Answer: (B)

Initial inrush of magnetizing currents have high component of even and odd harmonics.
2nd - 63%
3rd -26.8%
4th- 5.1%
5th- 4.1%
6th- 3.7
7th-2.4