The quality of the power supply in electrical power systems can have significant impact on management and utilization of power. Electrical power systems function as nonlinear loads, resulting in a waveform deformed that is comprised of current and voltage harmonics. Current and voltage harmonics produced by these loads can cause issues like the increase in power losses, and degrading conductors, and, as a consequence, having a negative effects on distribution systems as well as other electrical components. Therefore, it is crucial to analyze the total impact on these harmonics.
The sum of different harmonics that are present within a given system known as total harmonic Distortion (THD). THD allows you to assess the degree of distortion present in the system. The concept of distortion with total frequency in distribution networks is described below to assist users.
What's Total Harmonic Distortion (THD)?
THD is a very difficult phenomenon to grasp. But, it gets easier when divided into the most fundamental definitions of distortion and harmonics. Other devices for switching, such as solar PV inverters could create distortions in the voltage of the system and also create abnormal conditions in sensitive loads.
Despite the current economic challenges electricity providers and end-users are still buying new space and purchasing more loads. Other facilities with a limited or no capacity will be converted to the grid over the coming years. The raging competition in many industries will cause more loads to enter the grid. The increased load could create other issues with power quality. The power quality issue will be the first to develop. Harmonics in the power distribution network is among the issues with power quality.
This is related to the rising use of PV solar panels. The introduction of a power inverter into the power conservation networks' front-end can affect the quality of power in relation to harmonics of voltage. The same as harmonic distortion is surges and voltage fluctuations. Many end users could be the source of these issues.
Power System that includes AC supply and load
The electrical load can be linear or non-linear and influence the power quality that the device receives in either way. Linear loads draw sinusoidal currents, and as a result, they do not cause distortion.
Idea Sine wave that has zero harmonics
Nonlinear loads on the contrary, draw current which is not sinusoidal. The waveform of the current is different in the direction of the sine wave, and because of this distortion in the voltage develops. The distortion can alter the behaviour of the sinusoid as depicted. This is known as harmonics.
Harmonics comprise frequency components that correspond to the fundamental frequency of the waveform. For instance, if the 6Hz fundamental waveform is used then the third, second and fourth harmonic elements are equal to 120Hz, 180Hz 300Hz and 240Hz respectively. A perfect sinusoidal wave has zero harmonics consequently, the wave is not distorted.
Harmonics related to power factor correction
The existence of power factor corrections in the current harmonics and voltage is a bit of a mystery. The total installation current is comprised of two parts which are the real power as a function the voltage, and that of the power source that is represented by.
Itotal2 is Ipower2 and Reactive power2
The power factor can be determined by
New South Wales Service and Installation regulations (March 1999) For instance, it stipulates that users must keep their power factor between 0.9 in lagging and one. Other sectors of power are subject to tariffs that requires end-users to keep their power factors as equal as they can, thus limiting reactive current. This can be accomplished through the installation of a Shunt capacitor.The the presence of harmonics triggers the frequency component of the current to increase and the equation above is altered as follows:
Itotal2 = Ipower2 + Ireactive2 + Iharmonic2
In a variety of scenarios, such as the installation of a computer Ireactivegets is close to zero, but Iharmonic can be massive which means that the power factor will be less than the unity value. If the user installs the power factor correcting capacitors they will cause the power factor to rise due to the current flowing through the capacitor, increasing the total current of installation Itotalto to increase, making the power factor less effective or worse.
How do you determine the Total Harmonic Distortion?
The end-users must consider two aspects of harmonics, specifically, susceptibility of equipment and emission.Equipment susceptibility refers to the degree that harmonic distortion could harm or destroy equipment. It is dependent on the voltage that is accepted by the equipment. Equipment emission is the speed of the supply being dependent on the device, and it is dependent on the current of harmonics drawn.
The sum of all harmonics from either the current or voltage waveform divided by the fundamental component of the voltage and current sinewave is referred to as THD.
The percentage of THD is the measure of distortion that is present on the image.
For example: If an harmonic voltage 20 volts are combined with the sinewave voltage of 240 volts the rms value of the two voltages is calculated by:
V2 = V12 + VH 2
V2 = 2402 + 202 = 24O.8 volts
THD is then expressed as a percentage. THD will then appear in percentage and is determined by:
Field measurements of power quality on PV inverters allow the assessment of their behavior under real operating conditions.
How do you analyze Harmonics?
- Receive data via the source system. The information is in a form of short-circuit current which could be utilized to determine the resistance of equipment.
- Examine the primary harmonic sources of the installation.
- Based on the harmonic order of each it is possible to simulate the electric power network and its installation. Inductive reaction increases with the increasing frequency, while capacitive reactance decreases and resistivity becomes remain constant.
- Analyze and evaluate that voltage which is at the junction of the coupling between the harmonic current and harmonic impedance that has been calculated.
How to cut down on Harmonics in an electronic system?
If you are planning to install huge distorting loads and harmonics that are in line with those of Australian standards AS 2279.2 is to be considered. If you don't have any prior experience in the analysis of the complete harmonic distortion consult a local professional or a professional. In the event of an overly harmonics after calculation it is possible to consider these options.
- Request for a concept of the harmonic current that is smaller with the nearby supplier
- Installation of excess devices that draw a variety of harmonic currents. This can prevent the spread of your power supply system. It is possible to use an harmonic filter, which is composed of resistors, capacitors and inductor.
- If the distortion is caused by an expansion of power factor capacitors or power factor capacitor, a suitable detuning inductor should be connected to it, which will prevent the capacitor from absorbing huge harmonic currents
- If the project is massive The local power provider can alter the system to lessen the resistance of the power system.
The above factors and analysis can be used when constructing commercial facilities.