Transcript Protection System for Future LV Microgrids

Frankfurt (Germany), 6-9 June 2011
PROTECTION SYSTEM FOR FUTURE LV
MICROGRIDS

In the future, traditional fuse based overcurrent protection of LV networks will not
be applicable for LV microgrids with island
operation capability
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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
Frankfurt (Germany), 6-9 June 2011
PROTECTION SYSTEM FOR FUTURE LV
MICROGRIDS
 Adaptivity means that protection system
takes into account
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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
Frankfurt (Germany), 6-9 June 2011
PROTECTION SYSTEM FOR FUTURE LV
MICROGRIDS

1)
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

2)
Speed requirements for the microgrid protection
in different operation states andconfigurations

3)
Which defines the needed amount of protective devices (PDs)
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
Frankfurt (Germany), 6-9 June 2011
PROTECTION SYSTEM FOR FUTURE LV
MICROGRIDS
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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
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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
Frankfurt (Germany), 6-9 June 2011
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

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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
Frankfurt (Germany), 6-9 June 2011
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
Frankfurt (Germany), 6-9 June 2011
PROTECTION SYSTEM FOR FUTURE LV
MICROGRIDS

Operation curves of PDs
LAAKSONEN Hannu – Finland – RIF Session 3 – Paper 0431
Frankfurt (Germany), 6-9 June 2011
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
Frankfurt (Germany), 6-9 June 2011
PROTECTION SYSTEM FOR FUTURE LV
MICROGRIDS

1)
2)
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

3)
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
Frankfurt (Germany), 6-9 June 2011
CONCLUSIONS
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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
Frankfurt (Germany), 6-9 June 2011
Thank you for your attention
LAAKSONEN Hannu – Finland – RIF Session 3 – Paper 0431