Instrumentation, measurement and control of bio process parameters ( Temperat...
Hormonics impact and_mitigation
1. Harmonics Impact and
Mitigation
R.Panneer Selvam, B.E.,M.I.E,
Former Superintending Engineer
Tamil Nadu Electricity Board
Mob- +91 9444389547
Mail id : panneer.rps@gmail.com
15. Harmonic Generation
Harmonics are mainly produced by
non-linear loads which draw
current of a different wave form
from the supply voltage
(see fig. )
The spectrum of the harmonics
depends on the nature of the load.
Harmonic voltages occur across
network impedances resulting
distorted voltages which can
disturb the operation of other
users connected to the same supply
Degradation of network voltage caused by a non-linear load.
16. Main sources of harmonics
Industrial loads
Power electronic equipment:
drives, rectifiers (diode or
thyristor), inverters or switching
power supplies;
Loads using electric arcs:
arc furnaces, welding machines,
lighting (discharge lamps,
fluorescent tubes).
Starting motors using electronic
starters and
power transformers energisation
also generates (temporary)
harmonics.
Domestic loads with
power inverters or
switching power supplies
such as television,
microwave ovens, induction
hotplates, computers,
printers,photocopiers,
dimer switches,
electrodomestic
equipments, fluorescent
lamps.
17. Harmonic levels
The sources usually generate
odd harmonic components
(see fig. in next slide ).
Power transformer
energisation, polarised
loads (half-wave rectifiers)
and arc furnaces generate
even harmonics in addition
to odd harmonics
components.
Inter harmonics are sinusoid
components with frequencies
which are not integer ultiples of
the fundamental component
(they are located between
harmonics).
They are due to periodic or
random variations in the power
drawn by various devices such as
arc furnaces, welding machines
and frequency inverters (drives,
cycloconverters).
20. Harmonic Impact on Electrical Network
Higher usage of of “Energy Efficient” power Electronics
loads ( Nonlinear loads) pollute Electrical networks with
harmonics
In extreme cases excessive harmonic may lead to
failure of equipment
The usage of PF correction Capacitors further
complicates the situation
Capacitors don’t generate harmonics but may result in
“Resonance”, when interact the presence of harmonics
with the existing network.
21. EFFECT OF HARMONICSIN ELCTRICAL NETWORK
Harmonics have varied effect on the equipment
and devices. The classified as
Instantaneous Effect , and
Long Term Effect
22. INSTANTANEOUS EFFECT
Series / Parallel Resonance may happen
Vibration and noise in Transformers, Reactors and Induction
Motors
Mal functioning sensitive electronics devices (PLC Circuits,
Measuring and Lab Equipments )
Increase of zero sequence component – Hot neutral
Interference in communication and control circuit ( Telephone,
control and Monitoring circuit ) Total energy requirement to
perform desired function increases.
23. MEDIUM TERM EFFECTS
Failure of rotating machines
Harmonic rotating field cause pulsating mechanical torque
resulting in vibration and increased mechanical failure.
Reduction in capacitor Life
Draws high current and results in reduction in life.
Premature failure in equipments such as
Transformers , cables etc.
Harmonics causes additional iron loses and and copper
losses ( due to Skin effect)
Leads to increase in operating Temp
Cause premature failure
24.
25.
26. COST RELATED TO HARMONIC POLLUTION IN ELECTRICAL
NETWORK
Direct Cost
Indirect Cost
28. INDIRECT COST
Maintenance Cost
Because of the problems listed above, maintenance activity increases
Due to heating , the insulation of motors degrades, warranting rewinding
and results in increased maintenance cost
Down-time cost
Failure of equipment increases the down time and results in production cost
Losses will be more on continuous process industry like petrochemical
paper and cement industries.
Equipment Replacement cost
High level of harmonics may result in failure of equipment in electrical
network ( Eg. PF correction capacitors, sensitive PLC cards, electronic
devises etc.
Result in replacement cost
29. INDIRECT COST ( Contd.)
Equipment de-rating Cost
When harmonics are present in the network equipments
connected should have immunity level to harmonics
Or, the equipment shall be de-rated.
According to IEC 61000-2-4 electrical networks are classified
as
Class – 1 - upto 5% THD
Class – 2 - upto 8% THD
Class – 3 - upto 10% THD
Equipments to be designed to class 3 network will be costlier
than for class 1 network
30. INDIRECT COST ( Contd.)
Safety cost
Safety criteria is extremely important in modern buildings whether
commercial or residential
Triplen harmonics are odd multiples of third harmonics
Common in Single phase SMPS driven loads like computer, television
and other office equipments
They are abundant in IT parks and modern buildings
The magnitude of neutral current may exceed the line current.
Conventionally designed neutral current may get over-loaded, causing
fire hazard.
This can cause neutral open, and result in dangerous over voltage
across single phase equipments
Resulting in equipment failure
Pose a serious risk to life of operating personnal
31. Safety cost
Safety criteria is extremely important in modern buildings whether
commercial or residential
Triplen harmonics are odd multiples of third harmonics
Common in Single phase SMPS driven loads like computer, television
and other office equipments
They are abundant in IT parks and modern buildings
The magnitude of neutral current may exceed the line current.
Conventionally designed neutral current may get over-loaded, causing
fire hazard.
This can cause neutral open, and result in dangerous over voltage
across single phase equipments
Resulting in equipment failure
Pose a serious risk to life of operating personnal
32.
33.
34.
35.
36.
37.
38. HARMONIC MITIGATION SOLUTION
There are several methods of harmonic mitigation
Harmonic mitigation shall provide following
benefits
Reduce harmonic level to a desired level
Provide required Capacitive KVAR to improve PF
Prevent series or parallel resonance
40. PASSIVE HARMONIC FILTER
A series combination of reactor (L) and capacitor ( C )
Impedance based filter
Filtering capability depends on relative impedance w.r.t network
impedance
The Reactor blocks the harmonic current flow to the capacitor
They are further classified as detuned or tuned based on proximity of its
self tuned frequency
Self resonance frequency related to tuning factor
Tuning Factor p % =( XL / XC ) * 100
Tuning Frequency fr (HZ) = fs / (p/100) , where fs is
fundamental frequency.
41. DETUNED FILTER
If the tuning frequency of the filter is lower than 90%of the lowest harmonic
frequency with considerable amplitude, it is called the “Detuned filter”
Eg. 7% tuning factor corresponds to the resonant frequency of 189 Hz ( fs =
50HZ)
Is a detuned filter for 5th harmonics ( 250 HZ )
It acts as capacitor for frequencies lower than its tuning frequency
As an inductor for higher frequencies
Series / parallel resonance at frequencies higher than tuned
frequency is eliminated as the filter behaves like an inductor.
As it behaves like a capacitor for frequencies below tuning
frequencies, care shall be taken to ensure that no significant
harmonic component present below tuning frequency
42. TUNED FILTER
If the resonant frequency of the filter is within 10% of the harmonics
to be filtered
Called as tuned filter
Carry more current as they offer low impedance path
More expensive
Used only in Special cases- where detailed system study was
carried out
Efficiency changes when network is modified.
Several tuned filters are to be used in parallel, if more than one
harmonic frequency to be filtered.
43. APPLICATION CONSTRAINTS FOR IMPEDANCE BASED
(PASSIVE) FILTERS
Sensitive to changes in the network
Cannot handle wide spectrum of harmonic distortion
Sensitive to System frequency changes
Location limitations especially in vicinity of AC / DC drives
Likely to permanently fail in case of sustained harmonic
over load.
Prier Knowledge of harmonic spectrum is required
44. ACTIVE HARMONIC FILTER
• New generation of
harmonic filters
• Very high Speed IGBT
ensuring response time of a
few milliseconds
• Capable of generating wide
spectrum of harmonic
currents to inject into the
network to cancel the
harmonic current drawn
from the source by
nonlinear loads
• Additionally they can
generate both capacitive
and inductive reactive
power in a step-less
manner improving the PF of
the load.
45. HYBRID FILTERS
A combination of detuned
and Active filter
Active filters are used to
handle the dynamically
varying harmonic
component and
Detuned filters handle more
predictable narrow band in
addition to providing
capacitive reactive power
compensation at
fundamental frequency
46.
47.
48. Impact of Harmonics
The consequences of harmonics are linked
to the increase in peak values (dielectric breakdown),rms values (excessive
overheating) and
to the frequency spectrum (vibration and mechanical stress) of voltages and
currents.
The effects always have an economic impact resulting from the additional
costs linked to:
degradation in the energy efficiency of the installation (energy loss),
oversizing of equipment,
loss of productivity (accelerated ageing of equipment, unwanted tripping).
Malfunctions are probable with a harmonic distortion factor of greater than 8 %
of the voltage.
Between 5 and 8 %, malfunctions are possible.
Thermal control devices. Indeed, when protective devices of this
type calculate the rms value of the current from the peak value,
there is a risk of error and unwanted operation even during
normal operation with no overload.
49. Impact of Harmonics
Disturbances induced by low current systems (remote control,
telecommunications, hi-fi systems, computer screens, television
sets).
Abnormal vibrations and acoustic noise (LV switchboards,
motors, transformers).
Destruction of capacitors by thermal overload If the actual
frequency of the upstream capacitor-network system is similar to
a harmonic order, this causes resonance and amplification of the
corresponding harmonic.
Loss of accuracy of measurement instruments
A class 2 induction energy meter will produce in current and voltage,
a 0.3 % additional error in the presence of 5 % of harmonic 5.
50. Impact of Harmonics
Long term effects
Current overload produces excessive overheating and leads to
premature ageing of equipment:
Overheating of sources: transformers, alternators (through increased
joule and iron losses).
Mechanical stress (pulse torque in asynchronous machines).
Overheating of equipment: phase and neutral conductors through
increased joule and dielectric losses.
Capacitors are especially sensitive to harmonics as their impedance
decreases in proportion to the harmonic order.
Destruction of equipment (capacitors, circuit breakers,etc.)
51. Impact of Triplen Harmonics
Overload and excessive overheating of the neutral conductor may result
from the presence of third harmonic (and multiples of 3) currents in the
phase conductors which add in the neutral.
The TNC neutral earthing system uses the same conductor for neutral and
protection purposes.
This conductor interconnects the installation earth, including the metal
structures of the building.
Third harmonic (and multiples of 3) currents will flow through these
circuits and produce variations in potential with the following results:
corrosion of metal parts,
overcurrent in the telecommunication links between the exposed-conductive-
part of two devices (for example, printer and computer),
electromagnetic radiation causing screen disturbance (computers, laboratory
apparatus).
59. CASE STUDY – 5
Jindal Steel & Power Ltd.
DRI-II, Raigarh (MP)
4 Nos.150 Amp AF3 at KILN – 8
Existing Set - up at DRI - II Plant
The major loads in DRI :
DC Thyristor Drives
UPS’s
AC Drives
60. The existing power Distribution in DRI
- No. of KILNs - 4 Nos.
- No. of Power Supply Transformer – 4 Nos.
- Transformer rating – 1.7MVA
- Load Distribution- One Trafo for per KILN.
- Spare Transformer – 1 No.
- Transformer efficiency (@ PF-1, assumed) – 98%
61. Problems Faced by user
- Cable Over heating
- Transformer over heating
- Frequent failure of electronic PCB’s
for unknown reasons
- Frequent tripping of breakers
resulting into interruption in process
62. Performance Results of AF3
Sr.
No
.
Test
Condition
Phase R Y B
1
With One AF3
Connected
Load Current (Amp) 558 A 612 A 560 A
Current T.H.D. % 27.60% 29.40% 28.50%
Power Factor 0.63
2
With Two AF3
Connected
Load Current (Amp) 540 A 590 A 540 A
Current T.H.D. % 7% 10% 10%
Power Factor 0.72
3
With Three
AF3
Connected
Load Current (Amp) 480 A 487 A 482 A
Current T.H.D. % 8% 7.90% 6.90%
Power Factor 0.8
4
With Four AF3
Connected
Load Current (Amp) 340 A 350A 344 A
Current T.H.D. % 7.80% 8% 6%
Power Factor 0.92
63. Customer Delivered Value
Direct
1) Savings in KVA
2) Savings in Transformer losses (KW)
Indirect
3) With AF3 two distribution transformers freed for future expansion
4) Cable temperature reduced
5) Stopped frequent & spurious tripping of MCCBs
6) Spurious blowing of fuses in distribution controlled
7) Due to improvement in power quality, the electronic control systems and
logics are well protected
8) KVA demand is made free for additional usage
64. Summary of AF3 Test Results
• Input currents reduced from 680 A to 350 A per phase.
• Input PF is improved from 0.57 to 0.92
• Input current distortion reduced from 57% to 7-8%
• Input KVA reduced from 489 to 252 KVA
• KVA Released - 237KVA (direct reduction)
• Existing transformer of 1.7 MVA
was supporting 0.97 MW load earlier
Now, it can support 1.56 MW load,
if Harmonics & PF are controlled.
65. • Input currents reduced from 680 A to 350 A per phase.
• Input PF is improved from 0.57 to 0.92
• Input current distortion reduced from 57% to 7-8%
• Input KVA reduced from 489 to 252 KVA
• KVA Released - 237KVA (direct reduction)
• Existing transformer of 1.7 MVA
was supporting 0.97 MW load earlier
Now, it can support 1.56 MW load,
if Harmonics & PF are controlled.
67. Problems Experienced
- Frequent failure of Electronic Boards in Servers
and Work Station areas
- Slow down of Network for reason unknown
- Tripping of Generator
- Distribution Transformer getting overheated
Site Condition
Installed Power = 640 KVA
Generator Capacity = 300 KVA
68. Load Current and THDv (measured in UPS panel)
Phases Load Current
without AF3
Load Current
with AF3
R 237 A 182 A
Y 208 A 168 A
B 187 A 150 A
Phases VTHD
without AF3
VTHD
with AF3
R 7.8% 2.6%
Y 8.3% 2.5%
B 7.6% 2.5%
69. THDi (measured in UPS panel)
Phases iTHD
without AF3
iTHD
with AF3
R 62% 12.7%
Y 62.8% 14.5%
B 64.8% 16.5%
70. Results
●
Substantial KVA demand reductions up to 32.16 KVA
●
Issues related with the noise, EMI and RFI in the facility was
eliminated
●
Failure of Electronic Boards in the Server stopped completely
●
Generator and EB Transformer heating issues resolved
●
Generator capacity requirement reduced to half
71. Critical Problems Solved
●
Inoxpa India Limited, Pune – D G Hunting Problem and
Maintenance Cost reduction ( AHF + TVSS + Detuned
reactors + Earthing System Improvement )
●
Savings in the Diesel Consumption, Load running on
Single DG Set and DG Hunting stopped.
●
80 % Electronic Component Failure reduction – reported
by the Customer.
72. Critical Problems Solved
●
Suprabha Industries Limited Lucknou.
●
Load – Seam Welding, Co2 and Spot Welding
●
Product – Fuel Tank, Silencers
●
Problems – Power Factor, High KVAh consumption reported and Heavy
Bills from EB.
●
Solution – AHF + TVSS + Detuned Reactors + transformer
●
Problem Solved and Adopting all solutions in the new plant during
Project Level Itself.
●
Tank Leakage/Rejection % reduced from 30 % to 10 % in the process due
to improvement in the welding Quality.
73. Critical Problems Solved
Vijayshree Industries Limited, Tata Nagar – Transformer
Overheating and Power Factor Issue was there for 5 Years, PF
Improved From 0.55 to 0.85 and Above. Issue Solved. (13 Km
Feeder was separately allotted to the consumer by EB and Detuned
Reactors Installed.)
Electronic PCB Manufacturing Company, Pune –
EB Meter Malfunctioning and Excess billing problem resolved,
(EB - Meter Replacement )
Meter Mfg Company Modified the meter designs Suitable to work
in the high harmonic environment in the year 2001.
75. Some of the Symptoms of Poor Power Quality
1 High Demand Charges
2 Power Factor Penalties
3 Unable to Maintain Good Power Factor
4 Computers Crashing
5 Computers Locking Up
6 Computers Memory Losses
7 Dropped Telephone Calls
8 Erratic Equipment Operation
9 Equipment Running Hot
10 Nuisance Tripping
76. Some of the Symptoms of Poor Power Quality
11 Lights Flickering
12 Motor Failures
13 Nuisance Tripping
14 Speed/Setting Drifting
15 Component Failures
16 Equipment Running Hot
17 Power Supply Failures
18 Surge Suppressor/UPS Failures
19 Circuit Board Failures
20 Overheating Transformers
77. Some of the Symptoms of Poor Power Quality
21 Overheating Wires/Conduit / Cables
22 Excessive Neutral Current
23 Disturbed/Wavy Audio-Visual Displays
24 Over-Heating Conductors/Switchboards
25 Persistent Fuse Blowing
26 Short Life of Lamps
27 Mains-Based Timing (clocks run fast)
28 Buzzing/Crackling Audio Systems
29 General Equipment Malfunction
30 Motor Start Problems
78. Some of the Symptoms of Poor Power Quality
31 Erratic control of process performance
32 Weight Accuracy Problem in the Process
33 Dimensional Accuracy Problem
34 More % of Rejection due to Power Issues
35 Hum Noise in the Breakers / Substation
36 Transformer Over Heating / Hum Noise
37 Corona Effect in the HT Lines
38 Life of Equipments is Low
39 Maintenance Cost is High
40 Fault Finding Cost and time is High
79. Some of the Symptoms of Poor Power Quality
40 Fault Finding Cost and time is High
41 Problems due to Unknown Reasons
42 Product production cost High due to
Unknown Reason
43 Poor Product Quality due to Unknown
Reason
44 Frequent Earth Faults
45 Contactor Coil Failure rate is High
46 Any Other Problem ( Unknown Reason )
