Technical aspects affecting the use of insulation fault location systems 4. How does an insulation fault location system work? An insulation fault location system comprises an insulation fault test device and an insulation fault evaluator connected to one or more measuring current transformers. The A-ISOMETER® of the IRDH575 series features a built-in insulation fault test device. Functional sequence: • Insulation fault location is started by activating theA-ISOMETER® insulation fault test device.• The insulation fault test device briefly connects the liveconductors to earth. • Electronic current limiting, this connection and the insulation fault create a closed circuit, in which a test current I
T idetermi-ned by the system voltage flows. The test current is limited to a maximum value.• The test current pulse flows from the insulation fault testdevice via the live conductors, the insulation fault R
Figure 4.1: Operating principle of insulation fault location f and the earth wire (PE conductor) and back to the insulation fault test device.• The test current signal is detected by all measuring current transformers on the circuit and evaluated by EDS insulation fault evaluators. • The fault location can be identified using the assignmentbetween measuring current transformers and circuit.
Figure 4.2: Characteristic of test current I T EDS system Figure 4.3: Test current pulse cycle on the EDS system Annex 1.9.2 174 Main catalogue part 1 – 08.2007/Insulation monitoring