With renewable energy generators integrated into power system, the fault current characteristics are greatly influenced. There exist adaptability issues when traditional protections are used in such system. Focusing on power-frequency based distance protection configured on the transmission line emanating from Inverter Interfaced Renewable Energy Generators (IIREGs), the fault current of the IIREG is calculated under typical fault ride through controls and its amplitude and angular characteristics and effect factors are analyzed. Then the operation performances of impedance relay with both AG element and BC element are discussed under both symmetrical and asymmetrical faults. Results show that despite of the AG element or the BC element, the impedance relay of the IIREG side refuses to operate easily under all kinds of fault types, while that of the system side can operate more reliably. Simulations on RTDS verify the conclusions. This work is supported by National Key Research and Development Program of China (No. 2016YFB0900503), National Natural Science Foundation of China (No. 51407067), and Fundamental Research Funds for Central Universities (No. 2016ZZD01).