In simple words the HT/LT Ratio is the ratio between HT line (in Km) and LT line (in Km). In India, HT/LT ratio is barely 1:3 which is not a sign of a healthy power system. The ideal line length of 11kV HT line feeder is up to 20 KMs in urban areas and 3 KMs in rural areas. The length of LT lines more than 1.5 Km which is not considered as a balanced power system. There should be a limit while choosing length of LT lines and should not exceed beyond 1km. In recent years Government of India have come up with many schemes like R-APDRP, IPDS etc. to renovate & modernize the distribution network. Due to some loopholes in implementation & execution level the result is not as good as expected.
Improving HT/LT ratio:
The HT/LT ratio is improved by reducing the line length of LT distribution network and increasing the line length of HT distribution network. The conversion of LT lines to higher voltages may cost expensive initially but the system is beneficial in the long run. If we adapt High Voltage distribution System (HVDS) then the length of LT lines, the maintenance of both HT & LT lines reduces, which results reduction of losses and the power system will become more efficient. The concept of High Voltage distribution system (HVDS) is to reduce the length of LT lines, installing lower capacity distribution transformers in the load end & use of capacitor banks to maintain a healthy voltage level to make both LT & HT Power system balanced and stable. Therefore the power system formed will be a better HT/ LT ratio. Installation of distribution transformers of low capacity at consumer’s premises instead of cluster formation will decrease the voltage drops which results the reduction of losses. Installation of single phase transformers to feed residential and commercial customers in rural areas with Kiosks lead to reduction of losses. The use of Arial Bunched Cable (ABC) with suitable size in theft prone areas can reduce the commercial losses too. Installation of High tension and low tension Capacitor bank in appropriate location from the load centre improve the power factor as well voltage regulation of the system.