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The effect of zero sequence harmonics on cable Figure 2:
neutral is a matter of great significance in CESC
system due to the use of three and half core cables Figure 3:
in the LT distribution network. ➤ These results and analysis show patterns that

Relevance in Cesc System – A Brief Study support our theory and indicate that harmonics
in the system have a direct effect on these faults.
➤ In a quest to assess the relevance in THD w.r.t CESC However, further analysis must be done on system
system, a preliminary data crunching has been data before any conclusive statement can be made
carried out facilitated by the abrupt change in load in this regard.
profile in commercial areas during the period of
lockdown in 2020. TECHNIQUES TO MITIGATE
➤ Service fault figures in our system have been
studied to understand the effect of harmonics on ➤ Tuned Harmonic Filters: Passive harmonic filters
service cable neutrals. The number of service faults (PHF) involve the series or parallel connection of a
recorded over a few years due to fault in the neutral tuned LC and high-pass filter circuit to form a low-
of the service cable have been compared for three impedance path for a specific harmonic frequency.
LT districts:: CCD, ND and CSD. The filter is connected in parallel or series with the
nonlinear load to divert the tuned frequency harmonic
➤ In commercial areas (like CCD in our case), the current away from the power supply. Unlike series
amount of harmonics in the system is expected to line reactors, harmonic filters do not attenuate all
decrease during the nation-wise lockdown during harmonic frequencies but eliminate a single harmonic
April 2020 owing to the fact that most of the frequency from the supply current waveform.
commercial establishments were closed and same
has been reflected in the reduced number of service
faults due to neutral failure in the FY- 2020-21,
whereas the district with more number of domestic
consumers (ND in our case) saw a constant number
of service faults due to neutral failure in the FY-
2020-21, which can be explained by the unchanged
appliance usage pattern in domestic areas. In
CSD, containing both domestic and commercial
establishments, service neutral failure incidents have
been reduced in 2020.

Figure 1:

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