- 400 Aon each of the two incomers, with automatic transfer
- 8process motors: five direct-on-line and three with drives
- 50 kAshort-time withstand current for 1 s
- 5SIVACON S8 sections over a 4,200 mm front
Power for the boiler auxiliaries
For the auxiliary boilers of the Ostrołęka combined cycle plant (Poland), Cerney commissioned MIESA to build the motor control centre that feeds, protects and switches their motors: feedwater pumps, discharge pumps and burner fans. MIESA’s scope was the switchboard; the power plant, the boilers, the control system and commissioning in Poland were outside it.
The MCC is a five-section Siemens SIVACON S8 assembly (600 + 600 + 1,000 + 1,000 + 1,000 mm), 2,000 mm high plus a 100 mm plinth and 600 mm deep, front-access only for installation against a wall. It operates at 400 V AC and 50 Hz, with phases, neutral and protective conductor, has IP41 protection and a short-time withstand current (Icw) of 50 kA for 1 s. The rating plate refers to IEC 61439-1 and IEC 61439-2 and indicates class A arc protection.
Two incomers with automatic transfer
Two withdrawable, motorised, four-pole 400 A Siemens 3WA circuit breakers feed the MCC from two sources. A Siemens SENTRON ATC6300 controller monitors both lines and manages the automatic changeover between them, with mechanical and electrical interlocking so that the breakers can never close at the same time.
Each breaker has an ETU600 electronic trip unit —overload, short-time and instantaneous short-circuit, neutral and earth-fault protection— and signals open, closed and tripped; the controller also reports transfer failures.
Direct-on-line starters and SINAMICS G120 drives
Direct-on-line
- Three 11 kW feedwater pumps
- Two 3 kW discharge pumps
- Two spare starters fitted, 11 and 3 kW
With drives
- Three 55 kW burner fans
- Siemens SINAMICS G120: PM240-2 and CU240E-2 PN
- Drives on fixed mounting plates, fed from withdrawable units
- Operator panel on the door
The switchboard also includes two 230 V AC, 63 A feeders —one to a control panel and one spare—, a spare 400 V outgoing feeder for 55 kW and free space for future extensions. The eight process motors total 204 kW rated power.
The outgoing feeders are withdrawable units with service, test and disconnected positions, position indication and 40-pin control connectors. On the front they carry controls, run, stop and trip lamps, lamp test and starter test, which makes maintenance and checking of each feeder easier.
Signals to the control system and communications
Each direct-on-line starter is hard-wired to the plant control system for start and stop commands, running, stopped, ready and overload states, and motor current as 4–20 mA through Circutor transducers. The drives receive commands and a 4–20 mA setpoint in the same way and return their states, readiness and fault. All feeders include the interface with the external emergency stop.
For metering and monitoring, the MCC has a Siemens SENTRON PAC3220 power meter with three 400/5 A current transformers, COM190 modules in the incoming breakers with PROFINET IO and Modbus TCP interfaces, and a SCALANCE XB008G industrial switch that brings the Ethernet links of the breakers and the meter together into one external connection.
Workshop testing and dossier
Before shipment, the MCC passed routine verification to IEC 61439-1 in the MIESA workshop: mechanical and electrical checks, wiring, protection, controls, indication and communications, with dielectric strength and insulation resistance tests.
The dossier includes as-built electrical and dimensional drawings, the certificate of conformity, installation, operation and maintenance manuals and component manuals, the verification protocol with its test reports, and transport and storage instructions. The switchboard was packed and delivered to Cerney’s premises in Zaragoza in October 2023.
More SIVACON projects
MIESA has built SIVACON S8 and S4 switchboards for industry, energy and water in five countries.
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