Traditional junction termination extension (JTE) designs required precise control of dopant profiles in the JTE layer in order to achieve total depletion at the desired blocking voltage. To extend the HE range of impurity concentration for obtaining high breakdown values we have optimised and developed a new termination called "guards rings assisted HE structure" which has proved to show a high efficiency on breakdown capabilities. The new structure has been implemented on 1.7kV range 4H-SiC pn diodes. Reverse measurements have shown that a near ideal breakdown (approaching 95% of the ideal plane junction breakdown voltage) can be reached on diodes with the proposed termination and have confirmed the great reliability of this developed termination as compared to the classical JTE, double HE and guard rings.