On-Load Tap Changers (OLTC) generate transients in power transformer voltage regulation, these transients are analyzed to determine the OLTC condition, and find malfunctions in order to prevent system failures. OLTC conditional analysis is so relevant, because 40% of power transformers failures in the world come from failures in this device. This paper take data from a distribution transformer and a OLTC under maintenance, for transient simulations of a changing Taps, and compare them with some laboratory experiments taking transient measuring signals.