PQ Forum 2011 proceedings http://www.leonardo-energy.org/power-quality-forum-2011-tue-eindhoven

1. Power Quality Requirements at a
Point of Connection
(project ‘KTI’)
Power Quality and Energy Saving Symposium
Presented by: Sharmistha Bhattacharyya
TU/Eindhoven, 27th January 2011
Motivation
 Increasing use of sensitive apparatus and industrial processes
 Growth of decentralized generations and their increased influences
 Economic pressure on network operator due to deregulation
 Power quality (PQ) related arguments among the involved parties at
the point of connection (POC).
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2. Themes of project ‘KTI’
Theme -1 consequences of poor
PQ?
Research on new boundary conditions for
power quality; societal importance; and
optimal PQ requirements
various consequences
at a POC?
(TU/e- EPS, Laborelec, ECN)
responsibilities of
different parties at a POC?
Characteristics and Development of new power
interactions of the electronic devices delivering
apparatus and the a good power quality (TU/e-
installations (ECN) EPE)
Theme -2 Theme -3
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Mutual responsibilities on PQ in the system
Regulators
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3. Research Approach
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Main deliverables - I
• Overview of various consequences of poor PQ
• Present PQ performance of the Dutch networks
• Flicker study: define emission limits at LV customer’s
POC, proposal for compatibility levels
• Harmonics study: analyze harmonic interactions in the
network, and propose harmonic current limits at a POC
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4. Main deliverables - II
• Voltage dip: propose limiting numbers of voltage dips in
a MV network
• Guidelines on optimal PQ criteria at a point of
connection (POC)
• Define PQ responsibilities of involved parties (namely:
the network operator, the customer and the device
manufacturer) at a POC
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Overview of PQ consequences
Source: European power
quality survey report, 2008
Network operators also suffer extra losses; and in
extreme situation device’s early aging and failure
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5. Financial impacts of poor PQ
LPQI survey (2003-2004) in EU-25 countries estimated PQ related
financial losses as 151.7 thousand million Euros
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PQ Performance in the Dutch Network
Comparison of Plt trends
Some Plt values in MV
grid exceed the limit
(0.05% cases)
(as per Dutch
Grid Code)
(as per
EN50160)
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6. Harmonics in the Dutch network
Total harmonics distortion (THDv)
Local incidents are
reported for some
specific order harmonic
voltages that exceeded
the standard limits
Voltage variations are generally found to be
within the standard limits
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Voltage dips in HV network (2008)
Residual Duration of dips (s)
voltage SEMI
(p.u) 0.01-0.02 0.02-0.1 0.1-0.5 0.5-2.5 2.5-5 graph
0.8-0.9 0.05 2.05 0.95 0.1 0.1
0.7-0.8 0.05 2.05 0.95 0 0 10s
0.6-0.7 0 0.17 0.07 0 0
0.5-0.6 0 0.17 0.07 0 0
0.4-0.5 0 0.17 0.07 0 0
0.3-0.4 0 0.125 0.08 0 0
0.2-0.3 0 0.125 0.08 0 0
0.1-0.2 0 0.125 0.08 0 0
<0.1 0 0.13 0.09 0 0
0.2s
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Total 7.8 dips per year 31-1-2011 11 of 30
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7. Main Research Contributions
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Flicker Problem in the Network
• Many complaints about flicker problem
• Lack of a global standard on flicker planning level
• Customers not aware of flicker emission at POC Three
cases are
analysed
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8. Flicker Severity in the Network
Emission limit at LV customer’s POC is estimated
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Proposed planning and compatibility limits on
flicker severity
• Compatibility level should be specified for 95%, (99%) and 100% of the time
and also for 95% and 100% locations
• In future, EN50160 standard can be extended for 100% sites and 100% times.
note: proposed limits are shown for 95% time and 95% sites
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9. Typical household model used in
harmonic simulation
Individual
spectrum
measurement
+
Combined
measurement
at POC
Harmonic fingerprint database are made for
each device and at the POC
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House models for case studies
2 PC, 1 TV, 1 Refrigerator,
• House with high load 10 CFL, 1 vacuum cleaner
(average load demand of 7.5A) (at high power stand), and
linear load (125W)
• House with average load 2 PC, 1 TV, 1
(average load demand of 5.6A) Refrigerator, 6 CFL, 1
vacuum cleaner (at low
power stand) and linear
• House with average load and solar load (125W)
inverter
(average net load demand of 3.5A)
1 PC, 1 TV, 1
Refrigerator, 2 CFL and
• House with low load linear load (125W)
(average load demand of 2.2A)
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10. Harmonics simulation
Two background pollutions: high (6%), average (3.2%)
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Harmonic current spectrums of devices
(house with average load demand)
High emission from Vacuum cleaner at low
power stand
TV
PC
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11. Lab Measurements
TV PC
THD (%) 6.6 6.6 9.4 9.4 2.5 2.5 4.5 4.5
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Harmonic simulation results
• Some orders of
harmonic voltages
exceeded EN50160
standard limits
•Harmonic currents at
household’s terminal
decay exponentially
with high orders
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12. Field survey at a household’s POC
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Observations on Harmonics Simulations
• Harmonic voltages between 9th to 25th orders are of comparable magnitude
• Harmonic currents decreases exponentially with increasing harmonic orders
• Summation component ‘alpha (α)’ for 3rd harmonic is proposed 1.2 as
sufficient diversity exists in the network
• New planning level values for ‘triple n’ harmonics are proposed
• Small installations (such as households) should fulfil maximum impedance
(or short circuit ratio) criterion
• No separate harmonic current emission limit is proposed for households
(should be as IEC/TR 61000-3-14, stage 1)
• For large LV installations, harmonic emission limits are proposed
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13. Proposed Limits on Harmonics
Harmonic voltage planning levels Current emission limits at a
for ‘triple n’ harmonics LV installation
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Example of Responsibility Sharing on
Harmonics and Flicker
Network operator should be responsible to provide a network
impedance at a customer’s POC that is smaller than maximum limit
Customer should follow the suggested limits on flicker and harmonic
current emissions at his POC
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14. Historical Average Voltage dips events
recorded in the Dutch HV Network
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Expected Number of Voltage Dips in the
Dutch MV Network
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15. Average voltage dips in the Dutch MV network
(in EN50160 format)
Residual Duration (ms)
voltage U
(in % of 10<t≤20 20<t≤100 100<t≤ 500 500<t≤ 5000
Un)
90>U≥80 0.075 1.85 0.75 1.64
80>U≥70 0.075 1.85 0.74 0.49
70>U≥60 0.025 0.26 0.18 0.31
60>U≥50 0.025 0.26 0.13 0.23
50>U≥40 0.025 0.26 0.11 0.11
40>U≥30 0 0.21 0.14 0.04
30>U≥20 0 0.21 0.13 0.04
20>U≥10 0 0.21 0.12 0.04
U<10 0 0.21 0.13 0.04
Total 0.23 5.30 2.43 2.92
Total number around 10.8 dips in a year;
out of which 2.8 dips can cause process interruptions.
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Example of Responsibility Sharing Borders
on Voltage Dips
Can not be avoided, responsible for information!
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16. Conclusions
• Flicker emission limits at LV installations are estimated
• Planning and compatibility level limits for flicker are proposed
• Proposal for modifications of harmonic voltage planning levels
for ‘triple n’ orders are proposed
• Harmonic current emission limits are suggested
• Expected number of voltage dip events in the Dutch network is
estimated
• PQ responsibilities for different parties are defined
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