The results of scientifi c research aimed at improving the State primary standard of electrical voltage unit GET 13-01, built on the basis of the Josephson quantum effect, are presented. In the process of improving GET 13-01, the following tasks were solved: the range of reproduction of constant voltage was expanded as a result of the transition from two reference points with nominal voltage values of 1 and 10 V to the range of 1·10–3–10 V; increased noise immunity of the reproducible voltage due to the introduction of a voltage measure with a hysteresis-free Josephson array; the stability of the reproduced voltage is ensured; the process of transferring a unit of voltage to both voltage measures and voltage meters is automated; the process of setting the specifi ed voltage in the time domain is provided. The improved GET 13-01 was approved with a new composition as the State Primary Standard of the unit of electrical voltage GET 13-2023. GET 13-2023 uses quantum voltage measures based on various types of Josephson arrays. The metrological characteristics of GET 13-2023 are studied in the process of comparisons of quantum measures included in its composition (with hysteresis and hysteresis-free Josephson arrays). GET 13-2023 provides reproduction of the unit of electrical voltage with a standard deviation of the measurement result of not more than 1·10–9 V, a non-excluded systematic error of not more than 1·10–9 V in the voltage range of 1·10–3–1 V and provides reproduction of a unit of electrical voltage with a standard deviation of the measurement result in the voltage range of 1–10 V not more than 10–9 multiplied by the value of the reproduced voltage, a nonexcluded systematic error of not more than 10–9 multiplied by the value of the reproduced voltage. The obtained results are relevant for ensuring the uniformity of measurements in the fi eld of constant voltage and for conducting international key comparisons.