References

Dragutin Vojković, M.Sc.E.E. 1.      Frequency converters and soft starters for asynchronous motors

  • more than 25 frequency converters in conveyer and ventilator drives
  • 7 soft starters in pump drives (2×45 kW, 4×75 kW, 1×110 kW)
  • 1 soft starter in mill drive (1×75 kW)
  • 5 frequency converters in crane drives in the VARAŽDIN HEPP and DUBRAVA HEPP
  • 6 frequency converters in pump drives in the VARAŽDIN HPP (6×75 kW)

2.         Baker oven controller

  • burner control and fan speed control depending on the measured temperature inside the oven (for STROJOTERM d.o.o. Lepajci)

3.         Reactive power compensation equipment

  • about 40 new units in industrial plants drives with asynchronous motors with rated power from 2, 5 kW to 220 kW
  • 5 units for asynchronous generators in the HEPP-s VARAŽDIN, ČAKOVEC and DUBRAVA
  • several repairs of equipment due to the problems caused by high current harmonics (TERMIKA d.o.o. Novi Marof etc.)
  • expertises of high harmonics distorsion and its influence on the equipment (Laundry-rooms in Plat and in the TURISTHOTEL in Zadar)

4.         Water level controllers

  • about 20 systems for water level control in metal, plastic or concrete tanks – using pumps or solenoid valves on inlet or outlet pipes; too high or too low water levels signalization

5.         Temperature controllers

  • digital (ON-OFF) water temperature control systems using pneumatically operated valves or solenoid valves, and
  • analog water temperature control systems using mixing 3-ways pneumatically operated valves.
  • Totally 26 digital and 2 analog control systems were delivered to the KRALJEVICA SHIPYARD in 2005. and.2006.

6.         Electric heaters voltage controllers

  • three types of voltage regulators for electrical heating tools in a shoe industry have been developed and delivered (IVANČICA d.d. Ivanec)

7.         Cooling water flow controllers

  • 2 controllers in the circuits for lubrication of plastic shaft joints of the units in the DUBRAVA HEPP (in order to avoid problems caused by wearing out of joints)

8.         Humidity controllers in the pool of wooden chips

  • four-channel device for the regulation of humidity in the concrete pool with wooden chips inside the factory for a mechanical-biological waste treatment plant in Varaždin (including the delivery of moisture gauges and solenoid valves) has been developed, delivered and put into operation (ordering party: AGINONET d.o.o. Varaždin)

9.         Automatic control equipment

  • automatic device for the hydraulic drive control on the machine for winding a linen from a bale to another one was designed (TMT d.o.o. Čakovec)

10.       Optical measuring link OML-30

  • development and testing of an optical measuring link (with analog circuits) designed for a measuring in high voltage power plants in order to avoid interference of strong electromagnetic fields on the measuring accuracy (collaboration with the firms: ENERGY INSTITUTE Zagreb and COX d.o.o. Ljubljana) – tested in the HEPP DUBROVNIK and in the high voltage laboratory in the ENERGY INSTITUTE)

11.       Transformer oil control system for filling of tanks

  • conceptual project of the local and remote control system for pumps and valves in order to avoid overfilling
  • delivering of control equipment, pneumatically controlled valves and control solenoid valves (KONČAR – POWER TRANSFORMERS Zagreb, 2010. and 2011.)

12.       Supervising

  • building of a system for remote monitoring and management of the Međimurje region water supply, Čakovec
  • reconstruction of the 0.4 kV electrical distribution system in the high voltage substation no. 2 (TS-2) at the factory INAS-TAS d.o.o. in Zagreb
  • reconstruction of the 10 kV electrical distribution system in the high voltage substation no. 2 (TS-2) in order to enable closing of the 10 kV ring at the factory INAS-TAS d.o.o. in Zagreb
  • building of a system for the remote monitoring and control of the Ivanec region water supply (in several stages)

13.       Quality assurance

  • building of the PAG high voltage power plant 110/20(10) kV (for ENERGY INSTITUTE Zagreb)
  • validation of documentation for three power transformers produced in foreign factories

14.       Study works for the ENERGY INSTITUTE

  • Contribution to the study “Analysis of the failures, planned stoppages and repair works on the units in the HEPP-s VARAŽDIN, ČAKOVEC and DUBRAVA regarding required working regime and maintenance problems”
  • Part of the project documentation “Conceptual design for the revitalization of the control and monitoring systems and the telecommunications system in the GOJAK HEPP”
  • Part of the report “Analysis and comparison of national and international standards in the field of power lines conductors – preparation for drafting of new Croatian standards”
  • Part of the study “ Determination of the main technical parameters of units in NOVO VIRJE HEPP, book 4.2.. Possibilities of working of the units of NOVO VIRJE HEPP and units of the HEPP-s on the Drava river on the isolated network”

15.       Energy inspections

  • I am a co-author of the electrical energetics part of the study “Energy inspection of the Sugar Factory Ormož d.o.o., Ormož, Slovenia (1998.), made for the purpose of the Phare Program for Slovenia. Another co-authors were experts with:
    • The STENG ARMATURE d.o.o. Pesnica pri Mariboru,
    • The University of Maribor – The Faculty of Chemistry and Chemical Technology and
    • The Sugar Factory Ormož
  • I am a co-author of the electrical energetics part of the study “Energy inspection of the DROGA d.d. PC GOSAD in Središče ob Dravi, Slovenia, made for the purpose of the Phare Program for Slovenia Another co-authors were experts with:
    • The STENG ARMATURE d.o.o. Pesnica pri Mariboru,
    • The University of Maribor – The Faculty of Chemistry and Chemical Technology

16.       LUDBREG small scale HEPP For the purposes of the investor CONCEPTUS ELECTRICA d.o.o. from Varaždin, I made:

  • The Conceptual Project of the Revitalization of the LUDBREG smal scale HEPP (ELIT d.o.o. Čakovec, October 2011.) and
  • The Conceptual Project of the Building up a New LUDBREG smal scale HEPP (ELIT d.o.o. Čakovec, April 2012.) and
  • Analyzed the condition of buildings and electromechanical equipment of the existing derivative small scale hydroelectric power plant (construction started in 1904th, several reconstructions, working on the isolated network supplying the mill drives) and available data on the produced energy amounts.
  • Analyzed the data on the Bednja river flow rates during the period 2000th ÷ 2010th and estimated the possibility of producing electricity for several different assumed values of the Bednja river biological minimum flow rates (because the actual request on the amount is still not known).
  • Reviewed and outlined the scope of works and supply of equipment necessary for the revitalization / building up of the small scale hydro power generation in order to supply the public grid.

17.       Photovoltaic Power Plants (PVPP)

     Main projects for the PVPP-s

  • SEKETIN in Seketin                                                             (March 2012.)
  • TTB in Turčin                                                                        (August 2012.)
  • FLORA VTC in Virovitica                                                       (October 2012.)
  • AKORD in Županja                                                                (January 2013.)
  • CONSORS in Donje Ladanje                                                 (April 2013.)
  • MIPCRO in Ivanec                                                                 (May 2013.)
  • SREDNJA STRUKOVNA ŠKOLA VINKOVCI                       (May 2013.)
  • DOM SLAKOVEC in Slakovec                                               (May 2015)

(Ordered by WORK-ING d.o.o. from Varaždin)  

      Supervising of building up of the PVPP-s SE

  • CONSORS in Donje Ladanje        (2013.)
  • MIPCRO in Ivanec                               (2013.

        Investigation of the PVPP-s working on the grid      (2014.)

  • GUMIIMPEX-GRP in Trnovec Bartolovečki
  • GUMIIMPEX-GRP VARAŽDIN 1 in Varaždin
  • GUMIIMPEX-GRP VARAŽDIN 2 in Varaždin
  • CONSORS in Donje Ladanje
  • MIPCRO in Ivanec
  • several PVPP-s with lover nominal powers

        New software development (2014.)

We have developed the software which enables us to:

  • get daily values of the active and reactive energy amounts in both directions,
  • get daily diagrams for an active and reactive powers in both directions as well as a power factor depending on the time,
  • optimise a nominal reactive power of the compensation unit (reactor or capacitor) in order to avoid paying for too high reactive energy amounts generated into the grid or consumed from the grid.

Input data are the records of the active and reactive power amounts made, by the local distributing company, every 15 minutes for all four quadrants.  

Solving of the problem when the PVPP generates a reactive energy into the grid (2014.)

  • GUMIIMPEX-GRP in Trnovec Bartolovečki
  • GUMIIMPEX-GRP VARAŽDIN 1 in Varaždin
  • GUMIIMPEX-GRP VARAŽDIN 2 in Varaždin