Lakhasly

Here are some examples of problems that may be associated with harmonics.The total harmonic distortion value is often applied in terms of power quality validity to the voltage.Total harmonic distortion is the sum of all harmonic effects; (.Possible sources of flickering lights include machines with rapid fluctuations in load current or voltage, machines with rotary transformers such as mill motors and mine coils, and machines that use fixed frequency converters such as AC motors and electric Overheated transformers and tripped circuit breakers, Dips swells - voltage lower or higher than expected frequency effects caused either by the power supply or by equipment operating within the system Unbalance - the effect of voltage or current variations on each of the electrical phases may be signs of harmonic problems, with harmonic currents flowing back to other parts of the power system.-The state of harmonics in a system can be expressed in several ways.Flickering lights are a common symptom of a power quality problem.

Here are some examples of problems that may be associated with harmonics.
Flickering lights are a common symptom of a power quality problem. Possible sources of flickering lights include machines with rapid fluctuations in load current or voltage, machines with rotary transformers such as mill motors and mine coils, and machines that use fixed frequency converters such as AC motors and electric Overheated transformers and tripped circuit breakers, Dips swells – voltage lower or higher than expected
frequency effects caused either by the power supply or by equipment operating within the system
Unbalance – the effect of voltage or current variations on each of the electrical phases
may be signs of harmonic problems, with harmonic currents flowing back to other parts of the power system.-The state of harmonics in a system can be expressed in several ways. Total harmonic distortion is the sum of all harmonic effects; (. The total harmonic distortion value is often applied in terms of power quality validity to the voltage. The guidelines state that the harmonic effects of the voltage should be less than 8 percent relative to the fundamental.)
The first level of investigation is to determine the percentage of each individual harmonic, this is indicated either directly on a measuring instrument or on a chart of recorded and downloaded data - this is visualized as a "harmonic spectrum
the power losses in conductors are caused by the Joule effect due to load flow. If a distribution network has nonlinear loads, the current contains harmonics and the conductor resistance becomes frequency-dependent [
The injected harmonic currents and the resulted harmonic voltages can cause power quality problems and affect the performance of the consumers connected to the electric power network
Excessive and heat in equipment, components aging and capacity decrease, malfunction of protection and measurement devices, lower power factor and consequently reducing power system efficiency due to the increasing losses are some main effects of harmonics in power distribution systems. Harmonic distortions also increase the monetary costs in power systems by increasing energy losses, premature aging or de-rating of electrical equipment
The energy loss due to harmonics caused by a large number of nonlinear loads used in different power system sectors can be estimated.
The difference between the generated power and the consumed power us considered as the energy loss. However, energy losses in distribution networks are generally estimated rather than measured, because of inadequate metering in these networks and also due to high cost of data collection. Moreover, power system distribution loss estimation methods are reliable ways to determine the technical losses
the solution to the harmonics problem is
1-Reduce the harmonics by installation of filter
(active filter, passive filter)
2-Replace the transformer with a high K factor which can handle the distortio
, users must limit the number of harmonic currents generated by their receivers
-try to distribute electricity in their plants with low impedance per metre of cable

Harmonics represent the voltages and currents that appear in the network at frequencies which are integer multiples of the generated frequency. In the last decades, a massive penetration of nonlinear receivers has been seen, with strong effects in the alteration of the form of currents absorbed from the network. The increased use of nonlinear loads in all domains has resulted in an increasingly high level of harmonics, especially in the distribution networks.

1. Harmonics in distribution networks cause additional power loss, shorter insulation lifetime, higher temperature and insulation stress, reduced power factor
   . 2-Real power distribution networks are characterized by nonlinear loads that cause harmonic current flows. Also, when a combination of linear with nonlinear loads is supplied from a sinusoidal source, the total supply current will have harmonics
   3-In a three-phase symmetrical and balanced system with harmonics (distorted waveforms), a notorious rule provides that for each harmonic, a specified sequence exists (positive, negative or zero). In this ideal case, the current in the neutral conductor contains harmonics
   4-With the development of power electronics technology, the harmonic pollution in the network is getting increasingly serious, more obviously in the low voltage areas. Previous analyses have revealed that the harmonics distortion increase is one of major problems affecting power quality

5-in short distribution feeders, the distortion power losses caused by the third order harmonics in the line is the most significant, while other harmonics have a negligible share. In the design and operation stages of a network, the power losses are computed considering the ideal case (sinusoidal and balanced), an approach that brings many disadvantages. Recent studies show that harmonics suppression can result in improved supply quality and energy savings
6-The power losses in conductors are caused by the Joule effect due to load flow. If a distribution network has nonlinear loads, the current contains harmonics and the conductor resistance becomes frequency-dependent

• 7-Load variations increase the power losses. In the literature, the influence of harmonics on power losses was assessed using several specific computation methods
  9-uses an equivalent resistance, taking into account the frequency dependency and using a correction factor dependent only on the conductor cross section, ignoring the current harmonic spectrum. Also,
  9-proposes a set of equations where the temperature rise in the low voltage conductors is caused by power losses due to the presence of harmonic components, taking into account that the frequency components in the current modify the value of the AC resistance, due to the skin and the proximity effects. This project investigates the impact of harmonic distortion on power losses in electricity distribution networks due to the significant increase of nonlinear loads. In this way, the project tries to assess the harmonics amount generated by nonlinear loads in residential distribution feeders and estimates the additional power losses due to these harmonics.