With the fluctuation of renewable energies, the gas composition in the gas network may change dramatically as the hydrogen injection fluctuates. The gas interchangeability may be adversely affected. To investigate the dynamics of the ability to defend the fluctuating hydrogen injection, this chapter proposes a gas interchangeability resilience evaluation method for hydrogen-blended integrated electricity and gas systems (H-IEGS). First, gas interchangeability resilience is defined by proposing several novel metrics. Then, A two-stage gas interchangeability management scheme is proposed to accommodate the hydrogen injections. The steady-state optimal electricity and hydrogen-gas energy flow technique is performed first to obtain the desired operating state of the H-IEGS. Then, dynamic gas composition tracking is implemented to calculate the real-time travel of hydrogen contents in the gas network and evaluate the time-varying gas interchangeability metrics. Moreover, to improve the computation efficiency, a self-adaptive linearization technique is proposed and embedded in the solution process of discretised partial derivative equations. Finally, an IEEE 24 bus RTS and the Belgian natural gas system are used to validate the proposed method [17].