Load Tap Changing (LTC) Transformers are widely used in a Power Distribution System to regulate the voltage level within standard operational limit. In a SCADA connected network, the performance of LTC transformers can be improved by utilizing a closed loop monitoring and control mechanism. The widely used SCADA communication protocols, including Modbus and DNP3, have been proven vulnerable under cyber attack. In this paper, we conduct a vulnerability analysis of LTC transformers under malicious modification of measurement data. Here, we define two different attack strategies, (i)attack targeting energy system efficiency, and (ii) attack targeting energy system stability. With theoretical background and simulation results, we demonstrate that the attack strategies can significantly affect the power distribution system operations in terms of energy efficiency and stability. The experiments are performed considering IEEE benchmark 123 node test distribution system.