Harmonics In Electrical Networks


The harmonic is defined as one of the components obtained from the breakdown of a periodic wave in the Fourier series. The order of a harmonic is further defined as the ratio between the frequency of the harmonic and the fundamental frequency of the periodic wave considered. 

Harmonics In Electrical Networks

In the case of the perfectly sinusoidal waveform (as should characterize the voltage supplied by the utility) only the fundamental harmonic of the first order will be present, which in India has a frequency of 50 Hz.

If a sinusoidal voltage is applied to a load, the circulating current will also have a sinusoidal waveform only in the presence of loads with “linear characteristics”.

In the presence of a “non-linear” load the current waveform will deviate from the ideal pattern and breaking down the wave according to the Fourier theorem will show evidence of harmonics whose number and amplitude will increase with the degree of distortion in the current waveform.

The increasingly frequent use of non-linear loads in industrial facilities (inverters, fluorescent lamps, welders, DC drives etc.) Creates elevated distortions in the waveform of circulating current.

This is true in the case of ac/dc converters, for which the input current theoretically displays only harmonics of the order.

h=mp±1

The parameter used to determine the level of harmonic distortion presents in an electrical network is THD% of voltage & current.
 

Negative Effects Of Harmonics

 
  • The capacitors are subjected to a voltageoverload and their lifetime is drastically reduced.
  • Connection of the capacitor causes a large increase in the distortion factors THD(V) & THD (I).
  • Motors; Reduced motor life, inability to fully load motor.

  • The user transformers, wires and loads are affected by this increase in current, which leads to increased I R 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.
  • Interference in computers, microprocessor & solid state controlled equipment because of distorted 240 V supply. Increased neutral to ground voltage may cause hardware problems which may initially look like software problem.
  • High voltage distortion shall also be encountered when shifting from mains to emergency generator as they offer high impedance than supply transformer.
  • Large current in neutral wires of power distribution system. This is a real fire hazard as usually phase wires are 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. Utilities put penalties on consumers with low P. F., less than 0.9.
  • Over heating in fuses resulting in false blowing. False / spurious operations of breakers, which may lead to variation in other characteristics.

What do P. F. Correction Capacitors have to do with Harmonics ?

In an industrial plant containing power factor correction capacitors, harmonics distortions can be magnified due to the interaction between the capacitors and the service transformer. This is referred to as harmonic resonance or parallel resonance. It is important to note that capacitors themselves are not main cause of harmonics, but only aggravate potential harmonic problems. Often, harmonic-related problems do not show up until capacitors are applied for power factor correction.

What do P. F. Correction Capacitors have to do with Harmonics

Components of Detuned Systems Controller - Single Phase or 3 Phase
 

  • Measurement of A, V, PF, CosΦ, W, Var, VA (W,VA,VAr etc.)

  • Sense1%of load current

  • Auto/Manual mode selection with indicator light

  • Automatic calculation of C/k value

  • Program entry for targeted CosΦ value

  • Number of capacitor steps are user definable

  • The consequent switching time between capacitor steps is adjustable from 2 to 50 sec.

  • C+/NORMAL/C- condition lights indicate actual system state.

  • Over Voltage Insufficient Compensation, Over Compensation state alarm indicator lights with output contact

  • Adjustable programmable Over Voltage protection for capacitor banks.

  • Micro Controller based digital design complying with international standards.

  • Flush mounting with rear panel connectors.

  • Designed to use with Current T/F (.../5A)   

Data Logger Module with Energy Analyzer (Optional)

Energy Analyzer with Data Logger is having facility to record and display all the 3 Phase parameters of
mains where P.F.C. system is connected.

Capacitors Banks

Neptune-Ducati ranges of Capacitor Banks are using Capacitor Modules from M/s Ducati energia s.p.a,Italy. Ducati energia is a leading company in production of power factor correction capacitors. Following this tradition, continuous investments in research and development of new products have represented the policy of the company.

The result of this philosophy is the new range of Long Life Capacitors MONO16 and MODULO50. Thanks to the technological innovation of self-healing metallized polypropylene; the rated power of 50 KVAR is achieved in just one 3- phase element with very compact dimensions & a much higher life expectancy in comparison with other models. These new Long-Life Capacitors Mono16 & Modulo50 reach an expected life of more than 160,000 hours and a size reduction up

to 40% against the technologies so far applied with low loss of 0.2W/KVAR with 4 In capabilities and oil impregnation, the performance of these capacitors are much better in comparison to other technologies
available in market like gas filled & dry type.

Harmonic Reactors

Neptune Filter Circuits are designed as three-phase reactors with an iron core and air gap. Harmonic Filter Reactors are made out of high quality material and very stringent quality control. It has been designed with properties like low temperature rise and lower flux density so that it can operate in worst conditions of ambient and harmonic overloads.

They offer very good degree of linearity and low losses.Cheaper and non- linear reactors may trigger undesirable chain phenomena during periods of operation with high harmonic values, such as reduction in the inductance with consequent increase in the resonance frequency of the LC group, which would drain off more harmonic current, further reducing its inductance and overload the reactor more and more. Reactors are available with filtering factor of 5.6%, 7% and 14% as per standard ratings. Any other filtering factor and rating can be developed on request.

Other parts of Detuned systems.

  1. Other parts of Detuned systems.
  2. HRC Fuses
  3. ACB and MCCB as Incomer
Activcomp

Neptune can also offer fast Thyristor switched transient free system for power factor correction & Harmonic Filter.
 

Activcomp

 

Rating
440V,
50Hz
Capacitor Power at Un In (A) Main Switch Item Code
NDSL
Item Code
NDLL
10 20 30 40 50 60 70 80 90 100 110 120 A Icc
(kA)
KVAR KVAR KVAR KVAR KVAR KVAR KVAR KVAR KVAR KVAR KVAR KVAR

125

12.5 12.5 25 25 25 25             163 250 35 601.125 701.125

150

12.5 12.5 25 25 25 25 25           196.5 315 35 601.150 701.150
175 12.5 12.5 25 25 25 25 25 25         229 400 35 601.175 701.175
200 25 25 25 25 25 25 25 25         262 500 50 601.200 701.200
225 25 50 50 50 50               295 500 50 601.225 701.225
250 25 25 50 50 50 50             327 630 50 601.250 701.250
275 25 50 50 50 50 50             360 630 50 601.275 701.275
300 25 25 50 50 50 50 50           393 630 50 601.300 701.300
350 25 25 50 50 50 50 50 50         458.5 800 50 601.350 701.350
400 25 25 50 100 100 100             524 800 50 601.400 701.400
450 25 25 50 50 100 100 100           589.5 1000 63 601.450 701.450
500 25 25 50 100 100 100 100           655 1000 63 601.500 701.500
550 50 100 100 100 100 100             720.5 1250 63 601.550 701.550
600 50 50 100 100 100 100 100           786 1250 63 601.600 701.600
 
Capacitor Specifications   Harmonic Block Filter Specifications
Standard Voltage(Un) 525 V
Other Volt. on request (Un) 415V - 550V
Rated Frequency 50Hz
Capacitance Tolerance -0 + 5%
AC Test Volt. between term. 2.15 Un x 10"
AC Test Volt. between term and case 3kV x 10"
Dielectric losses <0.2W / KVAR
Ambient air temp. category -40 + 550 C
Temperature class -40 D
Service Continuous
Discharge Resistor 10% of Un in 20 Sec.
Over Heating <600 C
Inrush Current withstand capability 200 ln
Expected life 150,000h
Max. permissible current  4 ln
Connection Delta
Terminals 1 x M12 (upto 50 KVAR)
Installation Internal
Reference Standard EN 60831-1/2
   
 
Rated Voltage 3 x 415 / 440 V
Frequency 50 Hz
Constructional Max. Voltage 1000 V
Test Voltage  2500 V
Filtering Factors / Tuning Freq. 5.6% (210 Hz)
  7% (189 Hz)
  14% (133 Hz)
Tolerance of Inductance + 2%
Linearity 200 %
Ambient Temperature  + 550 C
Winding material Cu
Insulated class H
Cooling method Natural cooling (AN)
Installation Indoor
Temp. sensor (normally closed) 1550 C
Reference standard IEC 61558-2-20
   

Electrical & General Characteristics:
 

  • Power range: 125 - 1000 KVAR (440V)
  • Mains working voltage- 415-440V (other
    voltages on request)
  • Rated frequency :50 Hz
  • Altitude: 2000ma.s.l.
  • Relative humidity: 70% max. at 20 C
  • Duty :continuous
  • Ambient temperature class:-5+ 45 C
  • Power supply line: Three-phase + ground +
    neutral (for control only) in 3 phase controller
  • 3 phase + ground in single phase controller.
  • Relay current input signal: from 3 no’s or 1no.CT on line.../5A as per controller type.
  • Relay voltage input signal: picked up internally.

 

 
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