15-05-2013, 12:21 PM
SEMINAR REPORT ON POWER QUALITY
POWER QUALITY.pptx (Size: 503.93 KB / Downloads: 19)
POWER QUALITY
Power quality determines the fitness of electrical power to consumer devices. Synchronization of the voltage frequency and phase allows electrical systems to function in their intended manner without significant loss of performance or life. The term is used to describe electric power that drives an electrical load and the load's ability to function properly. Without the proper power, an electrical device (or load) may malfunction, fail prematurely or not operate at all.
CAUSES OF PQ PROBLEMS
1-Equipment failure in the power system network, storms and objects (trees, cars, etc) striking lines orpoles, fire, human error, bad coordination or failure of protection devices
2-Lightning, switching of lines or power factor correction capacitors, disconnection of heavy loads.
3-Faults on the transmission or distribution network (most of the times on parallel feeders). Faults in consumer’s installation. Connection of heavy loads and start-up of large motors.
4-Mainly due to the opening and automatic reclosure of protection devices to decommission a faulty section of the network. The main fault causes are insulation failures.
5-Classic sources: electric machines working above the knee of the magnetization curve (magnetic
saturation), arc furnaces, welding machines, rectifiers, and DC brush motors. Modern sources: all non-linear
loads, such as power electronics equipment including, switched mode power supplies, data processing equipment, high efficiency lighting
EFFECT
1-Direct costs. The costs that can be directly
attributable to the disturbance. These costs
include the damage in the equipment, loss of
production, loss of raw material, salary costs
during non-productive period and restart costs.
2-Indirect costs. These costs are very hard to
evaluate. Due to some disturbances and nonproductive
periods, one company may not be
able to accomplish the deadlines for some
deliveries and loose future orders. Investments
to prevent power quality problems may be
considered an indirect cost.
Grid Adequacy
Many PQ problems have origin in transmisson ordistribution grid. Thus, a proper transmission, distribution grid, with adequate planning and maintenance, is essential to minimize the occurrence of power quality problems.
Noise filter
Noise filters are used to avoid unwanted frequency
current or voltage signals (noise) from reaching sensitive
equipment. This can be accomplished by using a
combination of capacitors and inductances that creates a
low impedance path to the fundamental frequency and
High impedance to higher frequencies, that is, a low-pass
F ilter. They should be used when noise with frequency in
the kHz range is considerable.