harmonic study
There has been much discussion and interest in recent years on the subject of Harmonics under ambit of network power quality. More and more frequently, industrial and commercial users are finding they have to deal with the problem of "polluted power. Many seminars and awareness programs have been conducted to effectively deal with the problems of harmonics. Lot has been done but still there are gaps in knowledge of harmonics in network and methods to effectively deal with them. Therefore harmonic studies assume great significance to understand network power quality and negative impact they can have on network. Our company can offer continuous studies from 24 hours to many days by high end waveform and PQ recorders so that to comprehensively understand harmonics during various load cycles and their impact on network devices.
Every Electrical Engineer would like to have a power system having voltage and frequency at every point constant, no interference of one load with other, power factor is unity and wave form of both voltage and current is sinusoidal. But this is a theoretical perception which is not possible in practical situations.
Naac energy controls Pvt Ltd
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| Harmonic Study |
Presence of harmonics in electrical systems is gradually becoming more and more important with the spread of AC/DC conversion systems using SCRs, for example driving DC motors for metal rolling & extrusion lines, in the rubber, plastics, textile and paper industries and so on/ VFDS, UPS , Energy saving lighting and many other modern day efficient equipment’s. They offer energy efficiency but being nonlinear in nature pollutes the electrical network and creates different type of distortions & deviation to the parameters of electrical supply network.
Harmonics in electrical system results in wave form distortion. In general harmonics are periodic disturbances in voltage and current. Any non-sinusoidal periodic wave form can be considered as combination of sine waves of certain frequencies, amplitudes and phase angle (fourier series). In simple terms Harmonics are multiple of the normal main power frequency, like "3rd order" harmonics has got frequency of 150 Hz and "5th order" has to 250 Hz frequency. Harmonics causes pollution in electrical systems, which may affect the equipment at much larger distances from origin and if not controlled can become expensive preposition.
In a wave shape only the fundamental component of voltage and current contribute to power translation. The harmonics only load the translation system and cause increase in apparent power of source. This non-active power due to harmonics is referred as distortion power.
Power factor correction capacitor banks of such loads are put under considerable stress by presence of harmonics in network. Wrongly designed PF equipment can magnify or aggravate
harmonic distortion resulting in lot of operational problems therefore PF studies along with harmonic studies of harmonic infested network assume bigger significance.
Some significant problems because of high harmonic distortion are as follows
Overload and failure of capacitor banks used for Power factor correction .The capacitors are subjected to an overload and their lifetime is drastically reduced.
Overload and failures of Motors; Reduced motor life, inability to fully load motor.
Low efficiency of transformers and cables- The user transformers, wires and loads are affected by this increase in current, which leads to increased I2R losses and eddy current losses in transformer. This reduces the capacity of transformer resulting into economic loss as well. Apart from this transformer may also be subjected to excessive overheating and saturation. This will shorten the life of transformer. When transformer fails, the cost of loss of productivity during emergency repair time far exceeds the replacement cost of transformer itself.
Malfunctioning and failure in computers, microprocessor, solid state controlled and other Electronic equipment.
High voltage distortion shall also be encountered when shifting from mains to emergency generator as they offer high impedance than supply transformer.
Tripping of protection switchgear and relays without apparent reason.
Large current in neutral wires of power distribution system. This is a real fire hazard as usually phase wires are only protected by circuit breakers or fuses.
Poor power factor: As mentioned earlier the harmonic current caused by non-linear loads do not carry any real power (KW) even though they do increase the volt amperage (KVA). This lowers the power factor at (Pf=KW/KVA) the main distribution transformer.
Over heating in fuses resulting in false blowing and in some cases because of resonant condition result in burning of HRC or even fuse base because of resonant conditions. False / spurious operations of breakers, which may lead to variation in other characteristics.
Low efficiency of UPS- Reduction of power generated by UPS.
