Insulation fault location in coupled systems

The larger the unearthed system (IT system) to be monitored, the more difficult it is to locate possible insulation faults. With the aid of automatic insulation fault location systems, precisely this challenge can be addressed while the system is in operation. As a result, system availability is considerably increased while downtimes are minimized. Additional electrical components are required for insulation fault location systems.

The iso685-D-P version of the iso685 series can be used for systems with insulation fault location. A built-in locating current generator creates a limited locating current to earth when an insulation fault occurs. This locating current can be variably adjusted. With insulation fault locators from the ISOSCAN® series, this locating current can be assigned to a defective load using a measuring current transformer. The iso685-D-P communicates with the EDS440 and EDS441 insulation fault locators via an RS-485 sensor bus or top-hat rail bus. All settings for the EDS44x devices can be operated and configured via the iso685-D-P web server. It is possible to configure the parameters for each channel separately or all channels at the same time. 

The iso685-D-P insulation monitoring device can also be used in applications with coupled systems. Thanks to the EDSsync function, all iso685-D-P devices in a group and consequently also all EDS devices connected to it participate in the insulation fault location. This function is independent of whether the insulation monitoring in the coupled systems is performed via ISOnet or by the disabling of a digital input.

Insulation fault location in coupled systems

If the iso685-D-P device is disabled by a digital input, permanent insulation monitoring is carried out on both sides. One of the two insulation monitoring devices will only be disabled if both systems are coupled. This ensures a short insulation resistance measuring time and rapid insulation fault location in the event of a fault without a time delay.

Ring systems are regularly used aboard ships. To ensure short measuring times and rapid insulation fault location here too, disabling via a digital input is often selected. These systems have a special characteristic: the ISOloop function can be activated to ensure insulation monitoring and insulation fault location even if all coupling switches are closed. If all coupling switches are closed, one io685-D-P always remains active if the ISOloop function is activated. There is no need for an elaborate control system via a PLC. The insulation monitoring devices must simply be connected via Ethernet and have their parameters configured. This ensures that even insulation faults in loads that are only switched on briefly can be detected.

Insulation monitoring in ring systems

New measuring methods also make it possible to locate high-impedance faults with high system leakage capacitances and low locating currents. The faulty channels are indicated on the display of the iso685-D-P and can be replaced by plain text messages. For example, in the event of an insulation fault on a motor, the message “Insulation fault compressor 1” could be displayed. This allows fault location without having to study a wiring diagram, further facilitating insulation fault location.