| 摘要 |
<p>Method for testing fault current protection circuits in permanently earthed systems by producing by means of two mutually opposed Zener diodes a constant AC voltage whose magnitude is equal to the given maximum contact voltage which it is permissible to apply to the fault current protection circuits. This AC voltage, corresponding to the RMS value of a sinusoidal voltage, is applied to the resistance of the protective circuit, causing a fault current which, depending on the value of the earth contact resistance, will trip the fault current breaker if the current exceeds the fault current breaker tripping current. In order to limit the energy developed in the circuit a timer element is included which automatically breaks the test voltage as soon as the test has been completed. A safety device against wrong connection is also included. </p> |
