Transcript POWER QUALITY -- An Indian Perspective

POWER QUALITY
-- Bhanu Bhushan --
April, 2011
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Simple examples around us :
• Ceiling fan regulators
• Tube lights
• Lap-tops & peripherals
• Domestic inverters
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Ceiling fans -- 1- ph Induction motors,
shaded - pole or split - winding, inverted.
Fan regulators -- Choke, Resistor or
Electronic (wave - chopping) type.
i) Weighty, costly, low PF;
ii) Energy loss, heating;
iii) Voltage & current distortion, harmful
on both sides.
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Tube lights : non-linear discharge lamps.
Smoothening & PF improvement by choke
and capacitor. Not a serious problem.
Electronic ballasts : V & I distortions.
Lap-tops & peripherals : AC / DC adapters
draw non-sinusoidal current.
Domestic inverters : Battery charging
current is always non-sinusoidal.
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POWER QUALITY
in a wider, Indian perspective
GRID - Level
& CONSUMER - Level
1) SUPPLY CONTINUITY
2) FREQUENCY
3) VOLTAGE
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SUPPLY INTERRUPTIONS
a) LOAD - SHEDDING due to own or others’
over-drawal : Maximize generation, &
Allow over-drawal, as long as grid can
sustain it, and it is paid for.
b) LOAD - SHEDDING to curtail over-loading
or under-voltage :
If too frequent, ask for
system augmentation.
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c) TRIPPING due to a fault or equipment
failure : Minimize outage duration,
: Reliable protection, Auto-reclosing,
: Ask for building redundancies.
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VOLTAGE PROBLEMS
• HIGH / LOW : Can be corrected by
transformer tap-changing and reactive
compensation : shunt / series capacitors,
reactors, SVC, MVAR generation change.
• SWELLS & SAGS, SPIKES & DIPS,
FLICKER : Caused by switching on / off of
large loads, capacitor banks, electric
furnaces, welding machines.
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• PHASE UNBALANCE : Caused by single
- phase or unbalanced loads (e.g. railway
traction), pole - discrepancy, break in a
phase (conductor snapping), break in
neutral, hanging faults, non-transposition.
• WAVE FORM DISTORTIONS
(HARMONICS and DC offset) : caused by
HVDC, SVC, FACTS, Converters, UPS,
power / speed controllers, computers,
TVs, chargers, printers, tube-lights, CFLs,
fan regulators, electronic ballasts,
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communication equipment, arc furnaces,
welding, railway traction, etc.
Circuit breaker and isolator operation
(switching transients), L.A., transformer
magnetizing current inrush, lightning,
Faults and their clearance, insulator flashover, corona, faulty grounding.
Adverse effects : Over-heating & noise,
resonance, telephone interference, hum,
capacitor failure, control device
maloperation.
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Harmonic restraint in transformer
differential relays.
SOLUTION : Circuit segregation and
Harmonic filters.
INDUSTRIAL U.P.S.
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SOLAR FLARES --- transient
fluctuations in Earth’s magnetic field
(geomagnetic storms) --- potential
difference between different points on
Earth’s surface --- DC enters one
transformer neutral and exits at another -half-cycle saturation of transformer cores
--- unwanted trippings & grid disturbance.
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