7EN02-0423-02

Monitoring power system insulation

The device monitors the ungrounded power system insulation in resistance in accordance with the following timing diagram which represents the default settings:

0 An insulation decrease is detected on the system. The insulation resistance drops below the preventive insulation alarm threshold. The preventive insulation alarm relay switches and the preventive insulation alarm indicator light lights up.
1 An insulation fault is detected on the system.
2 Once T (insulation alarm delay) has elapsed, the device switches to the insulation alarm state. The insulation alarm relay switches and the insulation alarm indicator LED turns ON.
3 Press the button to acknowledge the insulation alarm. Both the insulation alarm relay and the preventive insulation alarm relay revert back to their initial state. Depending on the setup of the I/Os, the preventive insulation alarm relay and the insulation alarm relay may or may not revert back to their initial states. The timing diagram represents the case when the I/Os are set up to acknowledge the relays. See Relay Mode for more information on relay modes. See Relay Acknowledgement for more information on relay acknowledgement.
4 The insulation fault is corrected. The alarm LED turns off. The device reverts to normal status.
NOTE: If you don't acknowledge the insulation alarm state, and the insulation rises again above the insulation alarm threshold, then the insulation fault is recorded as transient.

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