How do shunt capacitors reduce losses, and what is a limitation?

Supply kVAR locally, cutting current; over-compensation at light load raises voltage

Raise resistance of lines; limited by cost

Increase kW demand; limited by metering

Reduce frequency; limited by harmonics only

Why does raising the voltage level reduce losses, and what limits it?

Loss is proportional to 1/V^2, but equipment must be changed so it is expensive

Loss is proportional to V, limited by land

Loss is independent of V, limited by tariff

Loss is proportional to V^2, limited by theft

Which measures target non-technical loss?

ABC conductor, proper/smart meters and inspection

Shunt capacitors and reconductoring

Which measures are usually done first because they are cheapest?

Capacitor placement and load balancing

Asked 2/20
2071 Magh · 6 marks
2067 Mangsir (old course) · 8 marks

Reducing power loss in distribution systems

Short answer

Shunt capacitors reduce I²R loss but risk overcompensation and harmonics. Reconductoring and raising voltage are effective but costly. Phase balancing, new substations near load, and loss-efficient transformers help. Non-technical loss reduction (ABC, smart meters) yields large gains but faces social resistance. Capacitors and balancing are cheapest first steps.

Briefly discuss the various options available with their limitations for power loss reduction on an already existing distribution network.

Losses in an existing distribution network are technical ( $I^2R$ in lines and transformers, core loss) and non-technical (theft, metering and billing errors). The main options, with their limitations, are:

Option	How it reduces loss	Limitations
Shunt capacitors at feeders/consumers	Supply kVAR locally, reducing current and $I^2R$ loss; improve voltage	Over-compensation at light load raises voltage; switching needed; harmonic resonance; cost
Reconductoring (larger conductor)	Lower $R$ reduces loss in proportion	High cost; poles may need strengthening; outage during work
Raising voltage level (e.g. 11 kV to 33 kV, more HT and less LT)	Loss ∝ $1/V^2$	Expensive; transformers, insulators and switchgear must be changed
Feeder/network reconfiguration	Open/close tie switches to balance feeders and shorten paths	Needs switches and loops; benefit limited in radial rural networks
New substation or transformer near load centre	Shortens LT feeders (loss ∝ length)	Land, cost, HT extension needed
Phase load balancing	Removes neutral current and overloaded-phase losses	Loads change with time; needs repeated monitoring
Replacing old/oversized transformers with right-sized, low-loss (CRGO, amorphous) units	Cuts no-load and copper loss	Capital cost; amorphous units are costly and bulky
Load management / improving load factor (ToD tariff)	Lower peak, lower $I^2R$ (loss ∝ peak²)	Depends on consumer response
Improving joints and connections, maintenance	Removes hot-spot losses	Needs continuous effort
Reducing non-technical loss: ABC conductor, proper meters, smart/prepaid meters, inspection	Stops theft and billing loss	Cost; social and political resistance

Notes on choice:

Capacitor placement and load balancing are the cheapest and are usually done first.
Reconductoring and voltage upgrading give large savings but need a cost–benefit study (energy saved × tariff vs capital cost).
In Nepal, where non-technical loss has been large, ABC, meter replacement and anti-theft drives (the NEA loss reduction campaign) have given the largest gains.

Every option should be justified by comparing the present worth of the energy saved with its investment.

✓ Answer checked by Claude Opus 5.5 (high effort)

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