▎ 摘　　要

This paper describes the measurements of the ac quantum Hall effect (QHE) in epitaxial graphene in a set of six different devices. In typical graphene devices, capacitive losses cause a negative frequency dependence of the quantum Hall resistance, in contrast to the positive frequency dependence observed in GaAs devices. In one sample, very low ac dissipation was measured along with a quantum Hall resistance decreasing by less than one part in 10(7) between 0 and 10 kHz, which demonstrates the potential of the QHE in graphene samples to be used as a primary standard of impedance.