Important Points About Tariff

Tariff : The rate at which a consumer is charged for the consumption of electricity.

Following factors affect the framing of tariff : 

1. MD of the consumer. 
2. P.F. of consumer.
3. Load factor of consumer. 
4. Use during peak hours of load.
5. Purpose of use.
6. Supply system i.e. H.T.or L.T.
7. Paying capacity etc.

Following types of tariffs may be framed :

1. Simple flat rate.
2. Block rate.
3. Two part.
4. Maximum demand.
5. Power factor.
6. Three part tariff.

Load factor : The ratio of average load to maximum demand during a given period is known as load factor.
Maximum demand : It is the highest demand of load on the power station during a given period. 
Following types of specific tariffs can be employed by the electricity company for economical generation of electricity.

1. Time-off-day tariff.
2. Peak-off-day tariff. 
3. Maximum demand tariff.
4. Power factor tariff.
5. Load factor tariff.

In the time of day tariff, low rate are applied during off-peak hours and higher rates during peak load hours.
In the peak-off-day tariff, consumers are allowed to use electricity during off peak hours of the day at In the power factor tariff, consumers using energy at high pf given benefit while those using at low p.f. are penalized.
In the maximum demand, tariff consumers using energy at more than their maximum demand will be penalized In load factor tariff consumers using energy at high load factor are charged at low rate compared with those using energy at low load factor.
Causes of low power factor :

1. Induction motors work at lagging p.f.
2. Transformer connected to system work at lagging p.f.
3. Induction heating furnaces work at lagging p.f.
4. Arc lamps draw current at lagging p.f.

Effects of low power factor :

1. For same kW demand kVA rating of transformer, generator increases.
2. Due to increased current at low p.f., conductor size of transmission, distribution lines increases Cost of generation and transmission increases.
3. Line loss increases, line efficiency and regulation decreases.
4. kW capacity of transmission reduces, voltage drop will increase, regulation will be reduced.
5. Bus-bar conductor size will increase contact surface of switch gear must be increased. 
6. kW capacity of generator reduces.
7. Power required for exciter increases.
8. Car Copper losses of machines will increase causing more heating effect.
9. Prime mover efficiency will be reduced.

Following methods can be used for power factor improvement :

1. Using capacitor.
2. Using synchronous condensers (synchronous motor). 
3. Using phase advancers.

Advantages of installing IPFC :

1.  Protects equipment.
2. Field failures are reduced.
3. Contactors wear and tear is reduced. 
4. Switch off system for excessive harmonics, voltage and current.
5. Switches of capacitor bank on main fault. 
6. Intelligent alarm functions are included in IPFC.
7. It safeguards and increases the life of equipment.

Advantages of intelligent power factor controller for improvement in energy efficiency :

1. Increase in system voltage can be avoided with it.
2.  Capacitor’s life increases.
3. Plant efficiency increases.
4. Utilization of demand is optimized.
5. Line losses are reduced.
6. Extra load can be connected without sanction of additional demand.
7. Demand penalty can be avoided.
8. Zero cost maintenance is possible.