The rapid growth of wind and PV generation is increasing the utilisation of existing grid infrastructure and intensifying the need for operational solutions that enable higher integration without immediate grid reinforcement. Energy control automatic (ECA) systems raise the available transfer capacity by releasing grid reserves normally withheld for contingency situations to be used already in normal operation, while maintaining secure system operation. In contingency situations the system is designed to trip generation within milliseconds. Under operating conditions with high feed-in, such actions may alter power flows, reactive power balance, and voltage profiles in a dynamic manner. Since high inverter-based generation is often associated with reduced system strength, transient voltage stability is examined by extensive grid studies before such schemes are built and operated. This paper presents an RMS simulation study of a wind-dominated 110 kV German distribution grid incorporating an ECA system. The triggering instant, the contingency, an incorrect activation and the dispatch of an embedded High-Voltage-Direct-Current (HVDC) link are varied. In addition an overvoltage-driven cascade among plants without high-voltage ride-through capability is assessed. The results show, for the investigated scenarios, a transient overshoot to about 1.1 p.u. after fault clearing, while the curative disconnection adds about 0.01 p.u. for less than 40 ms. This voltage spike can be suppressed by varying the triggering time of the ECA. Potential cascades remain unlikely in the scenarios investigated. ECA operation therefore introduces no significantly increased transient stability risk beyond steady-state voltage considerations in the grid region. These findings support the secure use of ECA as an operational measure for the grid operator,