Technical Articles
In the previous two articles, we covered about ideal techno-commercial solution for high voltage harmonics issue in a paper & textile industry. It is a known fact that these industries employ high concentration of AC/DC Drive loads that can result in high current harmonics. Presence of high current harmonics along with high system impedance can result in high voltage harmonics. Many of us would think that high voltage harmonics is mainly possible in such industries and not in building loads.
However, it is not the case at one of India’s biggest malls, which is located in Ernakulam, Kerala. Due to vast build-up area, the presence of non-linear load content like VFD based HVAC, LEDs, escalators, etc., are also very high. The share of non-linear loads in this building is similar to the industrial loads mentioned above. In spite of multiple LT transformers for load sharing, both current & voltage harmonics were measured very high in few transformers that employed mainly the VFD based chiller loads.
Below are the initial readings recorded at the main incomer with APFC ON:
Maximum V-THD at the incomer: 10.6%
I-THD at the incomer during full load: 36%
APFC panels are with 300 kVAr capacitors without any detuned reactors. These capacitors were amplifying harmonics and getting overloaded.
Harmonics measured at the APFC incomer are:
V-THD at APFC incomer: 10.6% I-THD at APFC incomer: 66.7%
Current drawn by 25 kVAr 440 V capacitor: 40 A (against the rated value of 32 A).
This resulted in failure of capacitors in every 6 to 8 months, along with frequent failure of sensitive electronic equipment. They wanted to resolve this issue permanently with best possible techno-commercial solution.
To solve this complex issue, many firms offered different type of solutions, like with only Active Harmonic Filters, regular 7% & 14% reactors, etc. Whereas, LK suggested detuning the capacitors in APFC panel with special High VTHD reactors. To begin with, customer went for detuning with high-VTHD reactors in one of the transformers where Voltage harmonic is very high compared to all other transformers.
LK supplied 300 kVAr special reactors and 525 V Super Heavy Duty capacitors. Step sizes are 1x75 kVAr, 7x50 kVAr and 3x25 kVAr. After installing these reactors & capacitors, as expected, both voltage & current harmonics came down significantly.
Below are the readings at the main incomer after detuning with high V-THD reactors:
| Measurement location | Parameter | Before detuning the capacitors | After detuning with High VTHD reactors |
|---|---|---|---|
| Main incomer (LT side) | V-THD | 10.6% | 6.5% |
| I-THD | 36% | 25% | |
| APFC incomer | V-THD | 10.6% | 6.3% |
| I-THD | 66.7% | 10% |
As depicted in the above table, by avoiding resonance & harmonic amplification, overall current & voltage harmonics came down. At the APFC incomer, there is significant reduction in current harmonics. Also even at 6.3% voltage harmonics, the high-VTHD reactors are functioning normally without undergoing any humming noise or overheating.
Another advantage of detuning with these reactors is the rating optimization of Active Harmonic Filter. For the same site, one of the other firms offered 600 A AHF without detuning, to reduce the harmonics level. But now, with LK’s high-VTHD reactors, 300 A AHF alone would suffice to contain harmonics under limit.
Besides, in one of the other transformers, customer installed regular 14% reactor on trial basis. But those reactors did not perform satisfactorily resulting in overheated and burnt in a few months. Capacitors also started failing.
It is now evident that just by increasing the impedance (14% instead of 7%) alone cannot help in the cases of high VTHD. Special core design is required to withstand high voltage harmonics and LK can provide the same. This case is an apt example to the combination of proper application knowledge & unique superior products from LK. There are many other similar cases, were optimum techno-commercial solutions were given that ensured lesser life cycle cost.
Abhinav L Purkar,
Manager Product Management & Marketing (PMM)Abhinav Purkar is a Product Management, Marketing, and Application Engineering professional with over 10 years of experience in the Power Quality domain. He has extensive expertise in power quality analysis, harmonic mitigation, reactive power compensation, energy efficiency, and electrical system optimization, helping customers improve system reliability and operational performance. With proven experience in product lifecycle management, market development, portfolio growth, and go-to-market strategy, Abhinav has successfully driven initiatives that enhance customer value and strengthen market presence. His strong technical foundation, combined with strategic business acumen, enables him to bridge the gap between customer requirements and innovative product offerings.
Assistance Required?
Select an option to Contact Us
Contact Us 
