Tamil Nadu Electricity Board [TNEB] — low voltage of only 150v during nights

Address:

Chennai, Tamil Nadu, 600054

I stay in avadi tamilnadu housing board lig i 4th sector. There is a huge voltage breakdown in nights of only 150v supply from the main line itself. My fan, tv and lights are fluctuating upon voltage decrease.
I have both three phase supply and single phase in my home, the voltmeter for 3 phase in all the phases is showing just 150-160v during nights and after 10pm the voltage drops to a maximum of only 150v despite in all the phases it is the same flow of voltage. I try to switch on different phases but all remain same. What is the benefit and use of getting three phase to not even have a minimal advantage among others residing in the street.
Tneb should ensure and please work on this to manage the voltage during nights atleast benefiting for three phase consumers. Please give voltage more than 160v in any one phase if not in all.