LOAD MANAGEMENT & TARIFF
Objective type questions
Objective type questions
From the economic point of view , a power system should have a load factor
From the economic point of view , a power system should have a diversity factor
Peak load hydro power plants compared to base load thermal plants have plant capacity factor
Run-of-river plants are used for
The two-part tariff is based on
Assessment of electrical energy requirements
Past developmental patterns: Local forecasting (short term & long term) using historical data & future projections
Definition of terms used in Power System Planning:
Number & size of generating units
Factors in selection:
The thumb rule is; select a minimum number of units fitting the load curve as closely as possible
Definitions of some factors used in unit selection:
Plant capacity factor: Gives an idea of reserve available.
Plant use factor: considers actual period of operation.
For hydro plants, plant capacity and plant use factors are much lower than those for thermal plants. Due to water availability restrictions hydro units are shut down for prolonged periods. Loading also varies substantially for the same reason.
Base load & peak load plants
Base load exists for 100% of the time
Criterion for selecting units to operate in a portion of the load duration curve:
Generally hydro plants are used for peak shaving replacing high incremental cost thermal generation. Gas turbine plants although very costly are also used during peak period due to quick start/stop and loading. Nuclear plants are used for base load due to difficulty in frequent load variation.
Run of river plants without pondage are obviously base loaded.
The costs can be broadly classified as
Fixed cost is the capital investment on all types of assets.
The cost per unit (kWh) chargeable to the consumer depends on
This consists of
Single-part tariff- is based only on energy consumption
Two-part tariff- is based on energy consumption and on a component linked to maximum demand (kVA or MVA).
If a demand more than previous level remains sustained for say half an hour then this becomes the established maximum demand until some other demand crosses this limit during the month. The second component is sometimes the fixed cost. MD influences the installed capacity, and hence, tariffs on MD are justified. KVA or MVA is more appropriate than kW/MW due to thermal considerations for lines, transformers, etc. The consumer automatically pays more for poor power factor. There is thus an incentive to improve the power factor.
Sometimes penalty clauses are also built in to prevent excessive and unscheduled maximum demand. This is particularly important in developing countries with generation shortages