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COOPERATION OF
DISSIPATED ENERGY
SOURCES WITH POWER
SYSTEM
Michał Zeńczak
Faculty of Electrical Engineering
West Pomeranian University of Technology, Szczecin
(former Szczecin University of Technology)
ul. Sikorskiego 37
70-313 Szczecin
Many incompatible classifications of
distributed generation (DG) are used.
For example:
• small DG (5 kW < P < 5 MW),
• medium DG (5 MW < P < 50 MW),
• big DG (50 MW < P < 150 MW).
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CONNECTION • Electric power companies have their
own
rules
about
technical
requirements
OF DG TO
for the units connected to power system,
POWER
SYSTEM • The question is essential if the DG is
adopted to isolated operation
(islanding).
• DC or AC?
• Cable line or overhead line.
• The choice of method of working of
neutral points.
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CONNECTION
OF DG TO
POWER
SYSTEM
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DG AND LEVEL • New sources of electrical energy in
power system change the reactive power
OF VOLTAGE
flows and value of voltage in nodes,
• Often the levels of voltages would be too
high, if the regulation of voltage were
not be done,
• The important limit is allowable range of
operation of generator, which should not
be exceeded,
• Possibility of effects of generator on the
level of voltage depends on its location
in power system and their parameters.
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DG AND LEVEL For cable lines for the power 200 kW the LV
OF VOLTAGE is sufficient.
For the power at 5 MW the MV is sufficient.
For 515 MW the MV or HV are sufficient.
Over 15 MW the HV is necessary.
Still's formula makes it possible to
calculate approximately the proper value of
voltage level for overhead line:
l
U  5.5
 0.01P
1.609
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PD
DG AND
CURRENTCARRYING
CAPACITY
~
PF
P’AB
A
C
B
P”AB
PB
When
then
When
then
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PC
P"AB  PG  PB  PC  PABcc
DG AND • DG have rather not high power,
therefore the changes of short-circuits
SHORTconditions are not high.
CIRCUIT
CONDITIONS • DG appears very often on the areas,
where the distribution network is not
developed, the short-circuits capacities
of elements selected for low shortcircuits currents.
• The highest value of power of WPF Sn
should fulfill the relationship:
S  20S n
"
K
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DG AND • Principles of protection of big DG units
are the same like units in common
POWER
electric power station.
SYSTEM
PROTECTION • In case of medium and small DG there
are special requirements for the
protection of the connection of DG to
power system, apart from the
autonomous protection of DG units.
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DG AND
POWER
SYSTEM
PROTECTION
PROTECTION OF DG AND POWER SYSTEM
HAVE THE FOLLOWING FUNCTIONS:
• disconnection of generator from power
system, when the parallel cooperation
with grid is impossible,
• protection of power system against
disturbances in DG units,
• protection of DG units against
disturbances in power system.
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DG AND
POWER
SYSTEM
PROTECTION
Influence of DG on existing protections in
Power System:
• Changes in current flows, changes of
resultant impedances cause the necessity
of analyzing setting of protection
equipment.
• Correction of setting values in distance
protection.
• Frequency protection of DG and automatic
load shedding in PCC.
• Cooperation of Autoreclosing with distance
protection.
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DG AND • Local (static) stability is determined by
the immunity from little disturbances in
STABILITY
power system.
• Global (dynamic) stability is determined
by the immunity from big disturbances
comparable with nominal power of
units (for example short-circuit).
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DG AND
STABILITY
Behavior of DG units during short-circuits
RFT - Ride Fault Through.
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OTHER
PROBLEMS
• Harmonics,
• Flicker,
• Electric and magnetic fields of 50 Hz
related to dissipated generation and
their effect on natural environment,
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Dissipated Generation (DG) creates many
technicals problems in Power System
Team for grid analysis and unconventional
power stations deals with these problems:
Ryszard Pałka, Prof. D.Sc. Ph.D. Eng.
Michał Zeńczak, D.Sc. Ph.D. Eng.
Olgierd Małyszko, Ph.D. Eng.
Sebastian Szkolny, Ph.D. Eng.
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RESEARCH
PROPOSAL
• The research proposal is related to the
above mentioned problems
• The study should be done for the micro,
small, medium and big DG units
connected to the isolated power system
(islanding) or to real power system
• The problems may be very interesting
for connection of power systems of two
countries
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Thank You
for Your
Attention
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