On-Load Tap Changer Tester|XHYZ1668 Precision Transition Resistance & Waveform Analysis for YN, Y, and Delta Transformer Diagnostics Product Overview The XHYZ1668 On-Load Tap Changer (OLTC) Tester is a high-precision diagnostic instrument designed for comprehensive evaluation of transformer on-load tap changers—the only moving component in the transformer circuit connection. Per the requirements of the Power Equipment Commissioning and Preventive Test Regulations, this