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Case Study on Harmonics Mitigation in Newspaper Industry

Case Study on Harmonics Mitigation in Newspaper Industry
Updated: | 6 min read

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Background

M/s Uttar Banga Sambad is a regional Bengali daily newspaper published in the state of west Bengal, India. The case study presents harmonic analysis at this newspaper printing press.


The printing press, a drive based system (both AC and DC drives) is the major load in the factory and the major source of harmonics. The problem experienced was high current harmonics i.e. about 36.8% and consequent voltage harmonics of about 9.5%. As a result the customer experienced a poor power factor, and frequent tripping of circuit breakers of capacitor bank (due to high VTHD) leading to loss of incentive from electricity board.


This case study is presented in 4 different parts followed by the conclusions. The four parts are as follows:

  1. Harmonics study
  2. Solution sizing
  3. Harmonic Study post solution
  4. Tariff System & Bill Comparison


Part I - Harmonic study.


The initial harmonic analysis results were as below.

1. Harmonic Analysis was carried out at main LV incomer of 500KVA 11KV/433 V transformer.

2. 140 kVAr APFC Panel is installed at site (without detuned reactor)

3. Harmonic levels with capacitors ON and OFF were recorded.

a. With APFC On: VTHD = 9.5%; ITHD = 36%

b. With APFC Off: VTHD = 8%; ITHD = 22%

Analysis with APFC Panel ON

The following figures are of harmonic study with APFC panel ON.

Harmonic study with APFC panel ON
Voltage & Current Harmonic Spectrum

5th and 7th harmonic are dominant due to AC Drives & 11th harmonic is dominant dut to the Presence of DC drives

Load Current & Power Factor

From Figure 6 that the displacement power factor is 0.944 and the true power factor is 0.882. (True PF = Displacement PF X Distortion PF). In this case harmonics are responsible for low distortion PF leading to lower value of true PF


Considering observed harmonic level, it was decided to install AHF at site. Sizing decisions were done as follows

Part II — AHF sizing and installation


The summary of the conducted harmonic study prior to AHF installation is as follows:

  1. Max Load Current during survey=520A
  2. Maximum Load=319KW
  3. VTHD=11% which is beyond permissible limits of 8% as per IEEE-519 (5% for individual VTHD)
  4. TDD-l=38% (IEEE limit dependent on short circuit ratio)
  5. Average power factor is 0.89 (instantaneous PF = 0.882)
  6. 5th, 7th, 11th harmonic currents are predominant
  7. The above readings were taken with all the capacitors switched on and a reading of: VTHD = 8 % ITDD = 22 % was obtained with the bank switched off.


The actual AHF sizing can be calculated using the "Active Harmonic Filter Selection Tool" in etaPRO v3.O as indicated below. (etaPRO v3.0 can be downloaded from www.Lntebg.com/etaPRO)

etaPRO v3.0 AHF Selection Tool

It can be inferred from above software selection tool that a 300A, AHF is required for the considered input parameters

Indicative Installation arrangement

The Printing press load is a complete non linear load responsible for harmonic production. Aux load is the auxiliary load which mainly includes lighting fans etc.

Part III - Harmonic Study after AHF Installation.


A300 A, 3 phase 3 wire AHF was installed and following results were obtained.

VTHD & ITHD
Voltage & Current Harmonic Spectrum

It can be observed from Figure 13 that the load current waveform is much smoother than the before (Figure 5)


Due to reduction in harmonics, distortion PF has increased leading to the increase in the overall PF to 0.946, indicating distortion PF

Load Current & Recorded Power Factor
VTHD variation
ITHD Variation

Part IV - Tariff System & Bill Comparison


The West Bengal Electricity Board has kWh billing and penalty/ Incentive rates applicable as follows:

11 kV Industrial Consumer E (Bt) type tariff system

E (Bt) TYPE OF CONSUMERS Energy Charge P/kWh (Winter) Demand Charges (Rs./KVA/month)
Normal TOD 06.00 hrs-17.00 hrs All Units Normal 707 384
17.00 hrs-23.00 hrs All Units Peak 849
23.00 Hrs-06.00Hrs. All Units Off-Peak 530

Power factor Incentive Scheme Applicable

SLAB Power Factor (PF) Power Factor Rebate & surcharge On Energy Charge in Percentage for the Year 2015-16
Range For Consumers Under TOD Tariff
Normal Period (6.00 AM to 5.00 PM) Peak Period (5.00 PM to 11.00PM) OH-Peak Period (11.00 PM to 6.00 PM)
PF > 0.99 -8 -9 -6
Slab 1 PF > 0.98 & PF = ≤ 0.99 -7 -8 -5
Slab 2 PF > 0.97 & PF = ≤ 0.98 -5 -6 -4
Slab 3 PF > 0.96 & PF = ≤ 0.97 -4 -5 -3
Slab 4 PF > 0.95 & PF = ≤ 0.96 -3 -4 -2
Slab 5 PF > 0.94 & PF = ≤ 0.95 -2.25 -3 -1.5
Slab 6 PF > 0.93 & PF = ≤ 0.94 -1.5 -2 -1
Slab 7 PF > 0.92 & PF = ≤ 0.93 -0.75 -1 -0.05
Slab 8 PF > 0.86 & PF = ≤ 0.92 0 0 0
*Yellow Highlights indicate reference slabs as indicated in bill analysis below

The following section is the comparison of the bills of the month of July and September in order to evaluate the savings post AHF installation. The bill calculations are presented and actual bills are attached for the reader's reference. The first major column indicates the parameter and side by side comparison for the months of July and September with APFC Panel Switched ON.

APFC Panel Only APFC Panel + AHF
Parameter July September
Supply Voltage 11 kV 11 kV
Contract Demand 415 kVA 415 kVA
Fixed Demand charges (Rs./kVA) 384 384
Percentage Chargeable 85% 85%
Power Factor 0.8916 0.9743
Meter Reading MVAH
Time Normal Peak Off-Peak Normal Peak Off-Peak
Present Reading 417.77 527.26 1890.82 441.04 556.44 1991.6
Previous Reading 405.84 512.78 1830.66 429.9 543.35 1944.1
Units Consumed (MVAh) 11.93 14.48 60.16 11.14 13.09 47.5
Net MF 500 500 500 500 500 500
kVAh (Units Consumed * MF) 5965 7240 30080 5570 6545 23725
ITHD Variation
ITHD Variation

Conclusion

The conclusions that can be drawn out from the harmonic study are as follows:-

  1. TDD-I reduced from 36% to 3%
  2. THD-V reduced from 9.5% to 2.5%
  3. Harmonic Current reduced from 181 Amp to 14 Amp
  4. RMS current reduced by 4%
  5. Maximum demand on transformer reduced by 6%


The results of AHF installation can be seen from the electricity bill also. Following are the main observations.


  1. Demand charges - The maximum demand got reduced from 385 kVA to 343 kVA i.e. lesser than 85% of 415 kVA, leading to direct reduction of INR 13,961
  2. The average power factor improved from 0.8916 to 0.9743.
  3. The rebate slabs of PF increase from 0.75, 0, 0 to 7, 6, and 4 in Normal, peak & off- peak time periods respectively, each slab as a percentage of the EC.
  4. The number of units consumed also reduced considerably
  5. The overall bill reduced from INR 475715 to INR 424948.

Additional Scope for saving

The AHF can be used to improve the PF further to unity such that the percentage rebate for all times of day falls in Slab-1 as indicated by PF Incentive Scheme Table.

Additional savings of INR 4457 can be obtained from the same.

Payback Calculations

From the difference in the bill it can be seen than, the customer has a saving of INR 54768/ month (average). The 300 A AHF panel has an approximate cost of INR 10,00,000. Hence the payback period is 19 months. The same can be further be reduced if power factor is made unity.

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About the Author

author

Sourav Dasmodak,

Product Management & Marketing (Powergear - ACB)

Product Owner of Air Circuit Breaker (ACB) of Lauritz Knudsen for Domestic & International Market. I can talk to you about Electrical Products' Sales, Business Development, Market Expansion, Cracking Critical Strategic Account, handling Key Account & of course how to develop & motivate Channels along with the organizational growth. Having near about one and a half decade of experience across the country with major electrical manufacturers (Top 4).