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The paper is a contribution to work on the problem of synthetic testing under short-line fault conditions. Traditional 'current-injection' circuits for terminal faults have already been extended to the case of the short-line fault by various authors. The circuit which is proposed in the paper accurately reproduces an actual short-line fault occurring in a network under most general conditions. The test circuit is described, and a survey is given on a complete series of tests carried out at CESI Laboratories, with the object of comparing synthetic and direct methods of testing. Test results have shown that the synthetic circuit adopted complies with the requirements for equivalence to the corresponding direct circuit. A confirmation of the results is given both by statistical analysis and by current-zero measurements, which allow a better insight into the interaction between test breaker and test circuit.List of principal symbols e.m.f. of the generator of direct circuit voltage across the tested breaker in the direct circuit or in the synthetic circuit arc voltage of the breaker under tests P current through the tested breaker in the direct circuit or in the synthetic circuit supply-side voltage; i.e. voltage across C d in the direct circuit or voltage across C z in the synthetic circuit charging voltage of the main capacitor bank (V h ~ V d ) charging voltage of the rate capacitance C z (V o equals the voltage drop on the line) e.m.f. of the generator of the high-current circuit in the synthetic scheme injected current failure probability of the circuit breaker mean value and standard deviation, respectively, of the dv probabilistic distribution -= f(p) at dv X dṽ j-= rate of rise of transient recovery voltage (r.r.r.v.) variable load, or parameter. In the statistical series of tests the r.r.r.v. was chosen as the variable load U p = normal standardised variable