RECOGNISE THE TREND AT AN EARLY STAGE: DECISIVE ADVANTAGES THROUGH EARLY MONITORING OF INSULATION RE
Insulation monitoring devices pioneered by Bender, provide plant operators with reliable electrical safety technology which reduces the costs of maintenance, providing early trend results in monitoring the insulation resistance.
The ISOMETER® series iso685 is proven across the globe and Bender has witnessed a very positive response following the launch of the new isoHR685. This device variant can measure insulation resistances up to the 10 GΩ range in subsea applications.
Early recognition and quality assurance It is possible to counteract the sudden appearance of an insulation fault at a very early stage: The isoHR685 measures insulation resistances in a range up to 10 GΩ. The measured values are available as a trend graph in the integrated ‘isoGraph’. This graphic presentation of the insulation resistance over time enables a trend of the insulation level to be recognised at an early stage. Different time scales are available for this purpose. This makes it possible to initiate plant maintenance long before an insulation fault occurs. The ‘isoGraph’ also makes it possible to assess the quality of the electrical plant components. By way of example, it is therefore possible to understand whether the insulation level has changed when exchanging devices. From as early as the plant installation stage, records are kept regarding any change in the insulation resistance due to the connection and joining of new components.
Measurement of capacitively coupled systems
A noteworthy feature of the isoHR685 is its ability to monitor long, parallel and capacitively coupled cables. A type of synchronisation enables interference from neighbouring monitoring devices to be suppressed and filtered out. Cables over 100 km in length, and in which various unearthed power supplies (IT systems) are routed can now be monitored. It doesn’t matter whether the IT system is implemented as an AC, a DC or an AC/DC system. The AMP measuring method used can be used in all systems and it also determines the system leakage capacitance. In long cables such as those encountered in the oil and gas industry, e.g. to supply oil production facilities installed on the sea bed, energy lines, hydraulic lines and communication lines are grouped together in what is known as an umbilical cable. Since these cables are custom-made, since they have long delivery times and since they are also hugely expensive, it is of great benefit to interpret at an early stage the trend of the insulation level developing within them and to take appropriate remedial action when necessary.
Customers often have the problem that sudden and transient insulation faults occur in their installations. These faults are reported via a relay point. It is then often difficult to make decisions concerning maintenance measures if the available information only refers to this switch contact. Troubleshooting is difficult and time consuming in the absence of additional measures. On the other hand, a targeted troubleshooting process and plant analysis can be accomplished with the isoHR685 via an integrated history memory with real-time clock. Each reported insulation fault is deposited in a history memory with accurate time stamps showing when faults occur and disappear. This makes it possible to establish which consumer or which system part was switched on, switched off or switched over and at what time. Defective or faulty system parts can then be identified without switching system parts off (avoidance of failures).
State-of-the-art technology involves the use of programmable logic controllers (PLCs) controlling and monitoring plants. The Modbus TCP interface which is integrated into the isoHR685 allows straightforward communication with available PLC and control systems. All measured values can be read and displayed via this interface in the form of trend graphs. Following a security clearance, it is possible to configure all parameters of the device externally and to reset or test the device via Modbus TCP.
The device can be connected directly with an available PLC via the IOs (digital inputs and outputs) integrated in the isoHR685. Functions such as the resetting of faults, manual testing or the deactivation of insulation monitoring devices are possible via the digital inputs. Detailed fault information is available via the digital outputs. This includes information about whether the fault occurs in the intermediate circuit or, for example, whether it involves a symmetrical fault or a non-symmetrical fault.
A heterogeneous device landscape of a very wide range of manufacturers is far from unusual in plants today. All devices must be put into operation and set correctly. A commissioning wizard which is integrated into the isoHR685 guides the user or installer through the commissioning procedure without the assistance of a manual – in a similar way to devices in the consumer sector. This retrieves and sets the most important plant parameters. Following successful commissioning, the device is optimally prepared for the monitoring measurement task, it carries out a self-test and starts with continuous measurement of the insulation resistance. The settings of the device can be secured and recorded via the integrated web server and merged back into the device if necessary.
The advantages of the new isoHR685 at a glance:
• 10 GΩ measurement
• Early recognition increases operational safety and makes it easier to plan maintenance.
• Synchronisation in capacitively coupled systems
• Fault analysis with scalable history memory
• Assessment of quality of the components used
• High adaptability on systems with different properties
• Straightforward and high-performance communication interface
• Self-explanatory commissioning of a plant
• Comprehensive configuration
• Easy to use
Author: Jörg Irzinger, Product Manager, Bender GmbH & Co. KG.