With a total of 25,000 inhabitants, Esch on the Alzette is the second largest city in Luxemburg. Power supply for the industries and private households is guaranteed by the Esch City Works. Power distribution with the aid of transformers and switch gear is nothing new. If, however, one takes a look at the control system and the measuring transducers required to convert analog standard signals, one immediately recognizes the modern standards. Here, as in other sectors, cost-saving and the latest technical developments were the decisive factor for investment.

It therefore comes as no surprise that the city of Esch has opted for technological progress and, with the aid of products from PHOENIX CONTACT, is profiting from new control and safety aspects in power supply.

The station in the Brill area of Esch houses a medium voltage switchgear and distribution system. The 20 kV three-wire system with ungrounded star point is converted to two 400 V earthed star-point networks in this station via two 630 kVA dry-type transformers, and then distributed along busbar systems. Twelve 1200/5 type current transducers convert the primary current to a secondary standard current of 5 A. Six transducers convert the outgoing transformer currents to both the busbar systems. The power is then distributed to 16 decentralized distributor boxes for household supply. Since only spot check monitoring of the current is necessary at this point, the other six current transducers can moni! tor two of the 16 outputs. Twelve loop-powered current measuring transducers reduce the secondary 5 A transducer signals to analog standard signals of 0..20 mA. With the aid of an Interbus module, serial transmission of the signals is effected to the control room approx. 800m away. Monitoring and control software ensures reliable power supply.

Many more loop-powered current measuring transducers are used in the medium voltage switchgear and distribution system in Ehlerange (Ehleringen). Using three 15 or 25 MVA transformers a 65 kV voltage level is transformed down to 20 kV. As opposed to the Brill station, the transformers are outdoors, where further transformations to the 400 V level take place. 30 current transducers and MCR current measuring transducers record the measured currents for further signal processing. A total of approx. 130 loop-powered current measuring transducers are in use in the Esch city works.

The favorable price and advanced technology convinced Claude Bock, the network manager in charge, together with his technical assistant, Jean-Paul Adler, to plan further projects in 1999 with the analog converters.