Wöhrle system solution based on ABB UPS for wastewater business

Stadtentwässerung Stuttgart (SES) is the responsible public body for collecting and treating wastewater in the Stuttgart area, Germany. With 370 employees and covering an area that includes 700,000 inhabitants, as well as Stuttgart airport, there are always plenty of projects and investments of SES with a total of 30 to 40 million Euros per year.

SES plans, runs and maintains rainwater runoff and wastewater infrastructure for the region. Part of SES’s responsibility is procuring equipment to run the electrical side of the company. The installed electrical plant is significant: apart from the collection of large electrical pumps and other equipment distributed around the network, there is also a substantial amount of electrical equipment at four large wastewater treatment plants (the one at Mühlhausen is the largest in the state of Baden-Württemberg) and a central sludge incineration plant.

Any wastewater business has to function 24/7 to ensure that all wastewater is properly processed. Clearly, for this to happen a high-quality power supply has to be available at all times. This is why SES has invested in a system solution from Wöhrle Stromversorgungssysteme GmbH based on ABB uninterruptible power supply (UPS) equipment.

The customer required two fully separate and independent UPS systems: for three-phase 400 V and for 24 VDC. The special challenge lay therein that all the UPS electronics had to be housed in the same cabinet as the associated batteries. In addition, the cabinet had to withstand the rugged environment in which it would find itself.

After reviewing the various bids tendered, SES decided on the System Solution from Wöhrle Stromversorgungssysteme GmbH, which is a business partner of ABB for many years, and the flexible UPS units from ABB. The delivery comprised an UPScale RI 22 (RI = rack independent) three-phase UPS, with two 10 kW UPS modules, plus a special power supply, of type DPN 402880/19-2, designed by Wöhrle to cover the 24 V side of things.

Wöhrle’s solution based on ABB UPS technology in a glass-fronted, air-conditioned Rittal cabinet.
The Wöhrle supply was realized in 19“ format with a 400 V input and 28 V, 80 A output. Two 12 V, 28 Ah battery units provided energy reserve for the 24 V UPS.

The solution was delivered in a glass-fronted, air-conditioned Rittal cabinet. The contract includes an annual maintenance agreement.

The customer has benefitted from sourcing the UPS concept, as well as design, build and service, from a single partner. Also, because the 24 V DC UPS was made from existing Wöhrle components and both UPS elements were installed in one cabinet, significant cost savings could be made and passed on to the customer.

The architecture of the ABB UPS system has inherent advantages: The UPScale RI 22 UPS comprises a sub-frame, to be installed into a 19” frame, with individual power modules. These modules can be hot-swapped, i.e. they can be removed and inserted, for maintenance without powering down the system. Both modules share the load and the size of the system is designed such that if one module should fail, the remaining module would not be overloaded by all consumers at maximum consumption. This makes servicing easy, gives very high availability. The size of the system can be designed to ensure that all the modules operate at maximum efficiency and that supporting full load in case of maintenance is guaranteed. ABB UPS units achieve efficiency of 96 percent, an industry best. In times of rising energy prices, high efficiency has a high value not to mention the benefit to the environment of reduced CO2 emissions.

Moreover, the initial equipment purchase is made easier in financial terms. Over all, the solution fulfills all the requirements, has a very low cost of ownership and a short return of investment.