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LAAKSONEN Hannu – Finland – RIF Session 3 – Paper 0431

PROTECTION SYSTEM FOR FUTURE LV MICROGRIDS. In the future, traditional fuse based over-current protection of LV networks will not be applicable for LV microgrids with island operation capability Because high fault currents are not present during island operation

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LAAKSONEN Hannu – Finland – RIF Session 3 – Paper 0431

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  1. PROTECTION SYSTEM FOR FUTURE LV MICROGRIDS • In the future, traditional fuse based over-current protection of LV networks will not be applicable for LV microgrids with island operation capability • Because high fault currents are not present during island operation • Therefore, new protection approach is needed • In this paper novel adaptive protection system for LV microgrids is proposed LAAKSONEN Hannu – Finland – RIF Session 3 – Paper 0431

  2. PROTECTION SYSTEM FOR FUTURE LV MICROGRIDS • Adaptivity means that protection system takes into account • The operation state of the LV microgrid and • The number, type and fault current feeding capability of DG units • Fast and selective operation is achieved by utilization of high-speed communication LAAKSONEN Hannu – Finland – RIF Session 3 – Paper 0431

  3. PROTECTION SYSTEM FOR FUTURE LV MICROGRIDS • In the development of the new protection scheme for LV microgrids many things must be considered such as • The number of protection zones in LV microgrid • Which defines the needed amount of protective devices (PDs) • Speed requirements for the microgrid protection in different operation states and configurations • Two main reasons for the speed requirements are stability and customer sensitivity • The protection principles for parallel and island operation of the microgrid LAAKSONEN Hannu – Finland – RIF Session 3 – Paper 0431

  4. PROTECTION SYSTEM FOR FUTURE LV MICROGRIDS • In this figure the LV microgrid protection zones and types of protective devices (PD 1-4) chosen for the new LV microgrid protection system are presented • The needed protection devices (PD 1-4) are • PD 1: Protection in connection point of LV microgrid • PD 2: LV feeder protection • PD 3: Customer protection • PD 4: DER unit protection LAAKSONEN Hannu – Finland – RIF Session 3 – Paper 0431

  5. PROTECTION SYSTEM FOR FUTURE LV MICROGRIDS • In the proposed LV microgrid protection system for example the PD 2s of LV feeders are able to adapt to the current configuration and operation state • Change of settings and pick up limits of PD 2s could be done by Microgrid Management System (MMS) when microgrid configuration changes • Fast real-time communication is needed for microgrid protection purposes between PDs and also between MMS and DER units during microgrid island operation LAAKSONEN Hannu – Finland – RIF Session 3 – Paper 0431

  6. PROTECTION SYSTEM FOR FUTURE LV MICROGRIDS • Based on extensive simulation studies with PSCAD, also the pick-up limits and operation curves for PDs are defined in the paper • In this figure for example the operation curves for PD 1 and PD 4 are presented LAAKSONEN Hannu – Finland – RIF Session 3 – Paper 0431

  7. PROTECTION SYSTEM FOR FUTURE LV MICROGRIDS • Operation curves of PDs LAAKSONEN Hannu – Finland – RIF Session 3 – Paper 0431

  8. PROTECTION SYSTEM FOR FUTURE LV MICROGRIDS • The idea was that the operation curves of different PDs could be the same during normal and island operation as far as possible • However, during island operation the operation curve and principle of PD 2 needed to be changed to be adaptive and multicriteria based LAAKSONEN Hannu – Finland – RIF Session 3 – Paper 0431

  9. PROTECTION SYSTEM FOR FUTURE LV MICROGRIDS • Also few additions to the proposed protection system were defined in the paper to take into account for example: • Protection of long LV feeders with section CBs, • Connection of large DG units (e.g. > 50 kVA) to LV microgrid and • Directly connected SGs should be connected either 1) directly or 2) with own LV feeder to the MV/LV distribution substation • Protection issues related to possible ring operation of LV feeders LAAKSONEN Hannu – Finland – RIF Session 3 – Paper 0431

  10. CONCLUSIONS • In this paper novel protection system for LV microgrid, including the operation curves for PDs, during normal and island operation has been presented • Realization of LV microgrids as integrated part of future Smart Grids needs new grid codes where the protection requirements and settings for LV microgrids are clearly determined • The proposed new LV microgrid protection system also revealed the need for fast, accurate, low-cost, and programmable PDs with high-speed communication capability in future smart LV networks LAAKSONEN Hannu – Finland – RIF Session 3 – Paper 0431

  11. Thank you for your attention LAAKSONEN Hannu – Finland – RIF Session 3 – Paper 0431

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