A nice success in electrical distribution and automation
Schneider Eelctric is part of an aimportant project concerning the city of Agde in France. Agde has renovated and extended its wastewater plant. The first objective was to have the plant comply with European quality directives regarding effluent discharge, which will be put into application starting in 2005. The second objective was to make sure that the plant could meet major load variations, with the population increasing from 25,000 in winter to 250,000 in summer.
OTV France was entrusted with its design and construction, selecting Schneider Electric to supply the electrical distribution and automation equipment.
The existing plant, with a capacity of 140,000 equivalent inhabitants, has several sections. The oldest ones, T1 and T2, treat water using a simple biological process, while T3 and T4 use a physical-chemical process. With the construction of the T5 section in 2002, the plant's capacity went up to 178,000 equivalent inhabitants, and T1 and T2 were stopped at the same time.
> A three-phase treatment process
The T5 treatment chain consists of three main phases: preliminary treatment, physical-chemical treatment and finally, biofiltration treatment. The processes developed by OTV are used respectively during these phases.
> The Schneider Electric solution
Three Premium PLCs combined with a supervision function are used to control the treatment process
Electrical distribution for the plant is handled by a 20 kV supply substation. The substation is equipped with Merlin Gerin brand SM6 protection cubicles, two step-down transformers (20 kV/410 V) and Prisma general LV distribution switchboards (TGBT) to supply power to the automation cabinets.
The different treatment phases of the T5 section are controlled by an automated system consisting of three Telemecanique Premium PLCs communicating with each other and controlled by a PC Vue supervision unit via an Ethernet network.
The PLCs manage more than 1,000 all-or-nothing I/Os and around one-hundred analog I/Os. They process information transmitted by sensors set up on the plant (flow, temperature, level, bit, position of valves…) and control the various actuators (solenoid valves, pumps, air superchargers, motors...). The motors are primarily controlled via 45 Telemecanique brand Altivar 58 and 68 11 to 90 kW variable-speed drives.
The speed drives are connected to each other and communicate with the PLCs via a Fipio field bus.
The PLCs control the regulation loops for the various treatment processes and the cleaning of filters. All information is made available to the supervision system, which enables plant control and monitoring by way of animated views: preliminary treatment, physical-chemical treatment, biofiltration, sludge water removal, automated system architecture, management of status reports, defects and alarms…
The plant's water operations have been satisfactory since mid-2002.The vacation period, with its ten-fold load increase was perfectly absorbed by the wastewater treatment plant. In addition, the plant's 12 filters offers great flexibility and adaptability to load variations.
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