Complex sentence: For many power transformer applications, a supply interruption during a tap change is unacceptable, and the transformer is often fitted with a more expensive and complex on-load tap-changing (OLTC, sometimes LTC) mechanism.
Split into simpler sentences: For many power transformer applications, a supply interruption during a tap change is unacceptable. In these types of applications, the transformer is often fitted with a more expensive and complex on-load tap-changing (OLTC, sometimes referred to as an LTC) mechanism.