Power quality-requirements-point-connection
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Transcript of Power quality-requirements-point-connection
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
EES 1 of 30
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).
2
EES 2 of 30 31-1-2011
Themes of project ‘KTI’
Characteristics and
interactions of the
apparatus and the
installations (ECN)
Development of new power
electronic devices delivering
a good power quality (TU/e-
EPE)
Research on new boundary conditions for
power quality; societal importance; and
various consequences
(TU/e- EPS, Laborelec, ECN)
Theme -1
Theme -2 Theme -3
consequences of poor PQ?
optimal PQ requirements
at a POC?
responsibilities of different parties at a POC?
EES 3 of 30 31-1-2011
Mutual responsibilities on PQ in the system
Regulators
3
EES 4 of 30 31-1-2011
Research Approach
EES 5 of 30 31-1-2011 5 of 7
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
4
EES 6 of 30 31-1-2011 6 of 7
• 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
Main deliverables - II
EES 7 of 30 31-1-2011
Overview of PQ consequences
Network operators also suffer extra losses; and in
extreme situation device’s early aging and failure
Source: European power
quality survey report, 2008
5
EES 8 of 30 31-1-2011
Financial impacts of poor PQ
LPQI survey (2003-2004) in EU-25 countries estimated PQ related
financial losses as 151.7 thousand million Euros
EES 9 of 30 31-1-2011
Some Plt values in MV
grid exceed the limit
(0.05% cases)
Comparison of Plt trends
PQ Performance in the Dutch Network
(as per
EN50160)
(as per Dutch
Grid Code)
6
EES 10 of 30 31-1-2011
Harmonics in the Dutch network
Total harmonics distortion (THDv)
Voltage variations are generally found to be
within the standard limits
Local incidents are
reported for some
specific order harmonic
voltages that exceeded
the standard limits
EES 11 of 30 31-1-2011
Voltage dips in HV network (2008)
Residual
voltage
(p.u)
Duration of dips (s)
0.01-0.02 0.02-0.1 0.1-0.5 0.5-2.5 2.5-5
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
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
10s
0.2s
SEMI
graph
Total 7.8 dips per year
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EES 12 of 30 31-1-2011
Main Research Contributions
EES 13 of 30 31-1-2011
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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EES 14 of 30 31-1-2011
Flicker Severity in the Network
Emission limit at LV customer’s POC is estimated
EES 15 of 30 31-1-2011
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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EES 16 of 30 31-1-2011
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
EES 17 of 30 31-1-2011
House models for case studies
• House with high load
(average load demand of 7.5A)
• House with average load
(average load demand of 5.6A)
• House with average load and solar inverter
(average net load demand of 3.5A)
• House with low load
(average load demand of 2.2A)
2 PC, 1 TV, 1
Refrigerator, 6 CFL, 1
vacuum cleaner (at low
power stand) and linear
load (125W)
2 PC, 1 TV, 1 Refrigerator,
10 CFL, 1 vacuum cleaner
(at high power stand), and
linear load (125W)
1 PC, 1 TV, 1
Refrigerator, 2 CFL and
linear load (125W)
10
EES 18 of 30 31-1-2011
Harmonics simulation
Two background pollutions: high (6%), average (3.2%)
EES 19 of 30 31-1-2011
Harmonic current spectrums of devices
(house with average load demand)
High emission from Vacuum cleaner at low
power stand
CFL PC
TV
11
EES 20 of 30 31-1-2011
Lab Measurements
TV PC
THD (%) 6.6 6.6 9.4 9.4 2.5 2.5 4.5 4.5
EES 21 of 30 31-1-2011
Harmonic simulation results
• Some orders of
harmonic voltages
exceeded EN50160
standard limits
•Harmonic currents at
household’s terminal
decay exponentially
with high orders
12
EES 22 of 30 31-1-2011
Field survey at a household’s POC
EES 23 of 30 31-1-2011
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
13
EES 24 of 30 31-1-2011
Proposed Limits on Harmonics
Current emission limits at a
LV installation
Harmonic voltage planning levels
for ‘triple n’ harmonics
EES 25 of 30 31-1-2011
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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EES 26 of 30 31-1-2011
Historical Average Voltage dips events
recorded in the Dutch HV Network
EES 27 of 30 31-1-2011
Expected Number of Voltage Dips in the
Dutch MV Network
15
EES 28 of 30 31-1-2011
Average voltage dips in the Dutch MV network
(in EN50160 format)
Residual
voltage U
(in % of
Un)
Duration (ms)
10<t≤20 20<t≤100 100<t≤ 500 500<t≤ 5000
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.
EES 29 of 30 31-1-2011
Example of Responsibility Sharing Borders
on Voltage Dips
Can not be avoided, responsible for information!
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EES 30 of 30 31-1-2011
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