| 摘要 |
A transient voltage surge suppressor (10) is used in a single or poly-phase power distribution network (P). The surge suppressor connects in parallel between each phase (A, B, C) and neutral (N), each phase and electrical ground (G), and between neutral and ground. An improvement comprises an electrical circuit (30) for monitoring the loss of surge protection due to the occurrence of a current surge or voltage transient in a neutral-to-ground path (32). An MOV-type semiconductor (VR1) is connected in the ground-to-neutral path. The semiconductor is normally non-conducting, but switches into conduction when its voltage threshold is exceeded by a surge current or voltage transient. An excessive surge or transient causes the semiconductor to fail. Respective fuses (F1A, F2B) are connected in series with the semiconductor. These fuses clear (blow) upon a semiconductor failure to create an open circuit neutral-to-ground path. An indicator lamp (20) provides an indication of loss of surge protection due to an excessive surge or transient. A semiconductor switch (42) controls lamp operation. The switch normally maintains the lamp in an ON state, but the switch is responsive to the fuses clearing to switch the lamp OFF. This is indicative of a loss of surge protection on the neutral-to-ground mode. An isolation element (44) is connected in the neutral-to-ground path and responds to clearing of the fuses to switch the semiconductor switch from ON to OFF.
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