| MONITOR | 1/2018 18 INNOVAT I VE PRODUCTS Insulat ion moni toring device ISOMETER® isoHV1685D-425 The induction furnace has established itself along- side the electric arc furnace as an alternative smelting device in the global growth business of electrically powered steel-making. It offers benefits in terms of the process and of environmental technology that make it an interesting and cost-effective proposition for use in large as well as small steelworks. Other reasons that make it suitable for successful use in large steelworks include the fact that its power supply is based on high-performance converters, as well as the neutral and basic refractory lining. Large amounts of electrical power are needed to operate induction furnaces. They source this power through special frequency converters (e.g. inverters), or directly from the mains power grid. This yields vari- ous potential sources of fault that can adversely affect or even shut down production and processing opera- tions. To ensure that the technology of today remains dependable in the future, Bender has developed solutions specifically for this application to ensure failure safety and protection. In the challenging environment presented by the monitoring of induction furnaces, the device variant isoHV1685D-425 has proven itself to be very capable indeed. In a similar way to other furnace applications, the special requirement of induction furnaces, that operate at a very low level of insulation coupled with a high nominal voltage value, is to find a reliable way of detecting and reporting any drop below a critical insulation resistance threshold. A particular customer benefit for plant designers deriving from the choice of the isoHV1685D-425 for insulation monitoring is the extended degree of scope it affords for optimising process parameters. For exam- ple, a significantly higher level can be permitted for the conductivity of VE water (demineralised water) without jeopardising the insulation monitoring function. Device variant isoHV1685D-425 satisfies the stringent requirements for the insulation monitoring of induction furnaces up to AC 2000 V/DC 3000 V. isoHV1685D-425 Optimised Monitoring of Induction Furnaces in the Medium-Voltage Sector