I got a job in foundry industry due to the experience of power factor monitoring.
During joining days, monthly power factor was 0.97. Managing director of the Industry demanded a power factor of 0.999. I assured him that I will reach that mark as soon as possible.
After a month or two, power factor drops down to 0.96. A critical situation was arises. I checked power factor panel properly, Every single capacitor was working precisely. Even power factor controller mounted on the panel Which was installed for general loads; was showing power factor 0.99 or even 1 sometimes.
I talked to panel manufacturer about this. He guided me that “Capacitor banks are sufficient for general loads but for Induction furnaces, harmonic filter is must. Induction furnaces produces harmonics into the system which lowers the power factor & connecting only capacitors further makes the situation even worse. Harmonic filter reactors eliminates harmonics from the circuit.”
HARMONICS
” Harmonics are the signals with higher frequencies multiple of fundamental frequency. Harmonics superimposed on fundamental frequency & Provides distortions in power flow.”
In India, Working frequency is 50hz. It means basic fundamental frequency is 50. Harmonics are the multiple of 50.
50*1=50
50*2=100 //2nd order Harmonics
50*3=150 //3rd order Harmonics
50*4=200 //4th order Harmonics
Before joining foundry industry I was working in hand tools industry. Total running load was general load. There was only capacitor banks are available for power factor improvement. I didn’t observe the working of harmonic filter reactor before. After a suggestion from panel manufacturer, I talked to the MD. He said we have harmonics filter available.
(“One more thing I just want to share that never ever neglect; even a single machine or instrument in industry. Every single thing is important. I was working there from last two months I didn’t notice the reactor panel which was placed just near to the transformer. The reactor was not connected to the transformer, it was covered with 2inches of dust.
A reactor panel was always Infront of my eyes I didn’t even noticed it.
That’s why I’m saying never ever neglect a single machine or equipment in industry. If it is there; occupying some space; it means it has a value.“)
That’s why I’m saying never ever neglect a single machine or equipment in industry. If it is there; occupying some space; it means it has a value.“)
HARMONIC FILTER REACTOR
Harmonic filter reactor which is going to be discussed in this post; is a type of passive filter Which is a series combination of inductor(tuned reactor) & capacitor. Harmonics filter reactor shown in an image below having a protective rotary switch with 200 Amps HRC fuses. Two series combination of inductor & capacitor are connected parallelly.
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NAME PLATE ON REACTOR PANEL
Name plate is very important, It tells the safe operating ranges. Likely, There were two nameplates; One on inductor coil (tuned reactor) & another one; on capacitor.
Name plate on inductor coil
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Name plate on capacitor
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MAINTENANCE OF REACTOR PANEL
Reactor was covered with inches of dust. First, I cleaned it. Than I used series test lamp method for continuity & Insulation test with working voltage of 230VAC. Reactors insulation is fine & reactor’s each coil is continuous. (I should prefer megger at this point but i do not have that one at that time)
Outcomes of visual inspection :
- I observed that 200 Amps rotary switch was heated up badly Which needs replacements.
- No ampere meter; No CT coils.
Steps after the observations :
- Old heated rotary switch replaced with new-one. Rotary handle tightened.
- 3 CT coils with ratio of 100/5 were being installed.
- Analog ampere meter fitted on the reactor.
- Inductor coils(Reactors) were being varnished.
- Aluminum conductor connections were cleaned properly.
- All the connections tightened & checked twice. (In Electrical, Nut-Bolts should be tightened properly at rated required torque. One loose bolt can damage the whole panel)
- After all, I performed some test on the reactor panel.
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TESTINGS ON REACTOR PANEL
Series Lamp Test
This test was performed to check the insulation of the panel again. In This test, One conductor of series test lamp, is connected with the panel body While another conductor is connected with all the three conductors one by one. While performing this test, Bulb showed no indication which means panel was insulated. The series test lamp method was quick; not the standard test for insulation testing Which does not provide numerical insulation value.
This test was performed to check the insulation of the panel again. In This test, One conductor of series test lamp, is connected with the panel body While another conductor is connected with all the three conductors one by one. While performing this test, Bulb showed no indication which means panel was insulated. The series test lamp method was quick; not the standard test for insulation testing Which does not provide numerical insulation value.
For insulation testing, megger is the best device! I didn’t have megger at that time.
Test at Loading condition
- Panel connected with earthing first.
- Then I connected the panel with 200 Amps MCCB.
- Rotary switch of reactor panel placed to on position while 200Amps MCCB at off position.
- 200 Amps MCCB is switched on.
- Clamps meter shows amps reading around 50 Amps on all the three phases & line to line Voltage was 415 Volts across all three phases.
- Panel’s ampere meter was also working which was showing loads on all the three phases by changing the selector switch.
- No sparking while switching on-off. Panel was working perfectly.
CONCLUSION
- General types of loads like 3 phase Induction motors, 1phase induction motors, lighting loads, Fans, pumps all are inductive loads which generates lagging power factor in the power system. This lagging power factor can be cured by connecting the shunt capacitors.
- Variable frequency drives, rectifiers & induction furnaces are examples of non linear loads which generates harmonics into the circuit & Harmonics lowers the power factor. Only capacitors can not improve the power factor of harmonics carrying system rather it worse the power factor.
- To eliminate the harmonics from the circuit; There are multiple methods like active filter, passive filter, line reactor, arrangement of loads & much more. These methods should be adopted after a deep analysis of the system.
- Harmonics filter reactors is a type of passive filter which are the series combination of line reactor(choke) & shunt capacitor.
Hope! You like the post. If you have any doubt, query or suggestion please do comments !