Skip to Content

SiePortal

The integrated platform for your product selection, buying and support workflow - bringing together Industry Mall and Online Support.

SiePortalDeutsch

Search

Home
Support Support
{{(apiData.Support | filter:{'rank':1}:true)[0].title}} Support
- Menu temporary not available
- Menu temporary not available
- Menue temporary not available
- {{item.title}}

Products & Services
- Menu temporary not available
- Menue temporary not available
- {{item.title}}
Support Support
{{(apiData.Support | filter:{'rank':1}:true)[0].title}} Support
- Menu temporary not available
- Menue temporary not available
- {{item.title}}
MySiePortal MySiePortal
{{(apiData.MySiePortal | filter:{'rank':1}:true)[0].title}} MySiePortal
- Menu temporary not available
- Menue temporary not available
- {{item.title}}
Cart ({{apiData.CartCount}})

Navigation

mians voltage contain harmonics

Created by: viralpatel at: 7/11/2013 8:51 AM (5 Replies)

Rating (0)

Thanks 1

6 Entries

7/11/2013 8:51 AM	Rate (0)
viralpatel Silver Member Joined: 11/18/2010 Last visit: 8/5/2022 Posts: 523 Rating: (32)	Hi i just want to know that whether mains supply voltage contain any harmonics? VP

Suggestion To thank Quote Answer

7/11/2013 9:01 AM	Rate (0)
Ste39 Platinum Member Joined: 1/21/2013 Last visit: 11/20/2024 Posts: 4620 Rating: (710)	Hi VP Have a look, Part 1: Harmonics Harmonics of the mains supply in electrical power distribution ... Harmonics (electrical power)
	Last edited by: Ste39 at: 7/11/2013 9:02 AM
Suggestion To thank Quote Answer
This contribution was helpful to 1 thankful Users m@nju

7/11/2013 11:22 AM	Rate (0)
Scorpio31 Posts: 47 Rating: (8)	Hey, I have gone thru a complete IEEE page.. but i need some basic info like wether harmonics is beacuse of Voltage or Current? Its effects on the selection of protection device like ACB? I think VP also needs to know the simple reply which can be co-related. please help !
Scorpio31 Posts: 47 Rating: (8)
Suggestion To thank Quote Answer

7/11/2013 11:53 AM	Rate (0)
viralpatel Silver Member Joined: 11/18/2010 Last visit: 8/5/2022 Posts: 523 Rating: (32)	yes Scorpio31, i want to know basic only as you havemention, I am not sure but Voltage harmonics generatedue to developing source and current harmonics generate due to load am i right ? VP

Suggestion To thank Quote Answer

7/11/2013 11:59 AM	Rate (0)
Ste39 Platinum Member Joined: 1/21/2013 Last visit: 11/20/2024 Posts: 4620 Rating: (710)	Hi Harmonics are sinusoidal voltages or currents with a frequency equal to an integer multiple of the frequency of the distribution system, called the fundamental (50 or 60 Hz). If added, respectively, to the fundamental sinusoidal current or voltage, harmonics distort the waveform of the current or voltage. Effects on Circuit Breakers: As announced, the circuit breakers are equipped with two overcurrent protection: thermal nature (bimetal) each and electromagnetic (coil) the other. The joint action of the two devices is to limit as much as possible through energy (the so-called I2t) defined by the integral Joule evaluated between the instant of start and end of the current. The functionality of each circuit breaker is expressed by curves that provide the operating time of the device in function of the current that interests him. The value of the integral of Joule current changes in the presence of highly distorted compared to the case sine wave. If, as sometimes happens, the circuit breaker should be sized on the basis of measurements made in the field on the current transit, and the equipment is not a true rms is possible that the device is triggered in the presence of currents other than those provided . Effects on Residual Circuit Breakers: The sensitivity of intervention of a differential switch is determined, other conditions being equal, the type of material used for the construction of the toroidal core and in particular by the value of its reluctance to the frequency of use. The dependence of the reluctance of the frequency means that the materials with standard operation is guaranteed only at the nominal frequency or, in the limit, for small variations of the same. At higher frequencies the reluctance of the magnetic circuit increases, and this leads to a decrease, with the same fault current, the induced voltage on the third winding, and then the signal in the current product towards the relay tripping. Under these conditions the value of the operating current increases to, at frequencies of about 400 Hz (harmonic order 8) values of up to 4 or 5 times higher than those found at 50Hz. When the fault current is highly distorted and has most of its energy away from the fundamental, the differential may behave improperly or become unstable. This happens especially in the presence of loads consist of rectifiers (especially power) that absorb pulsed currents. For these switches are running special, in which the value of the differential current intervention is kept constant as the frequency increases (at least within certain ranges). In all other cases, the decrease in sensitivity that occurs (increase in the threshold of intervention) generally does not involve particular problems in terms of protection.

Suggestion To thank Quote Answer

7/11/2013 12:01 PM	Rate (0)
N. Vijay Silver Member Joined: 3/17/2013 Last visit: 4/28/2025 Posts: 481 Rating: (43)	Hi Scorpio and V Patel, Harmonics are generated in the line supply systemdepending on the equipment connected to the grid.Non linear systems like UPS, VFDs, Rectifiers cause these harmonics while drawing current from line system. More commonly it's association is defined in terms of line current. Its understanding is easy when you define harmonics w.r.t power factor. More briefly, a VFD with good power factor utilizes most part of the line current in generating real power to motor than a VFD with low pf which often generate square wave shaped line currents THD is a direct measurement of harmonics. For 6 pulse it is around 25%, for 12 puls it is 8.8% It results in voltage distortions also to the extent of 10% and 5.9% respectively There are proven drives taking care of harmonics to a value as low as 0.8% See thebrief definition in the attachment It is a very long subject to discuss. Hope this helps definetly to meaningful extent Regards, Vijay Attachment HARMONICS.JPG (336 Downloads)

Suggestion To thank Quote Answer

|

Share this page:

Share this page on...

Follow us on