Season 9 Challenges

OPENED ON: 24 JUN 2020  |  CLOSED ON: 29 JUL 2020  |  REWARD: INR 8,00,000
Reward money is paid in exchange of legally acquiring the solution, implementing it to solve the problem and meeting the success criteria. Milestones for paying the reward money would depend upon the complexity of challenge and maturity of the proposed solution, which would be discussed with the solver as soon as the proposed solution is selected by us.

Short Description:

We are looking for solutions that will enable the use of APFC without causing voltage surge which tends to damage LED lighting systems.

Challenge Details

In one of our industrial areas we have replaced HPSV (High-Pressure Sodium Vapour) light fittings with LED light fittings. We are also using APFC (Automatic Power Factor Control) for improving the power factor. The power factor was around 0.8 with APFC was used along with  HPSV light fittings. 

The LED lighting system is getting damaged when APFC is in the circuit. On investigation of the failure of LED lights, it was found out that there is a surge in the Voltage in LT lines. The voltage is not expected to exceed 250 V in the LT lines. Thus, APFC had to be taken-off as it was causing high voltage in the LT line. However, removing APFC reduces the power factor and it is now around 0.68 to 0.70. LED lights are not getting damaged when APFC is removed from the circuit.

Note: HPSV light fittings had inbuilt surge voltage protection and hence they were not getting damaged.

APFC should be used as it improves power factor and helps receive subsidy from the local electricity board.

APFC unit has 16-stage capacitor bank. The technical details are provided in Table 1.

Table 1: APFC Details



Number of stages


Total Capacity of APFC

225 KVAR

Number of capacitors

Total 8 nos (50 KVAR – 3 nos., 25 KVAR – 02 nos., 10 KVAR – 02 nos., 05 KVAR – 1 no)


We are looking for solutions that will enable the use of APFC without causing voltage surge and subsequently damaging the LED lights.

System should be

  • Easy to manage.
  • Cost-effective.
  • Easily integrated into existing operations.

Additional information:

Details relating to LED ratings, Distribution Transformer capacity and its tap positions are as follows.

  1. LED ratings:  LED light fittings are from 100 to 350 Watt and voltage bandwidth is 130 – 245 V.
  2. DT (Distribution Transformer) capacity & rating: 200 KVA DT. (3 Ph, 3300 / 433 V, 50 Hz, Dyn11, H.V. Amp. – 34.88 & L.V. Amp. – 266.66, ONAN)
  3. DT Tap positions: 05 nos. taps are in the DT., now set at tap position no. 1 (The voltage rating in the primary side at tap position no 1 is 3465 V, no 2 is 3382.5 V, no 3 is 3300 V, no 4 is 3217.5 V & no 5 is 3135 V and secondary voltage rating is 433 Volt)
  4. Incoming voltages: Incomer voltage is 3.3 KV (from the port supply) which is converted into 415V for phase-phase and 240V for phase-neutral.
  5. DT Neutral earthing resistance value and other earth resistance values of installation: DT neutral earthing is solidly earthed and other resistance values of installations <1 ohm.

Have any query or need more clarification about this challenge?