Basics about kWh Vs kVAh Billing System & Comparison

This Article provides a detailed technical understanding of the kWh vs kVAh regime and charts out the need for reactive power in the electricity distribution system and importance of reduction of reactive power. 

Power Factor: Power factor (pf) is defined as the ratio of active power to the apparent power of the system  i.e. pf = kWh/kVAh 

As shown in Fig, the quantities P, Q and S are represented by a power triangle.

Ideally the power factor is required to be unity. However, the power factor is leading if the load is predominantly capacitive and lagging if the load is predominantly inductive. PF incentives are given on electricity bill if the Power Factor is between 0.95 to 1. On other hand, penalties are levied if the Power Factor is below 0.9. It is therefore required that consumer should maintain higher power factor above 0.95 through proper compensation.

Power factor ratio is also equal to the cosine of the phase angle between true power and apparent  power. It should be noted that power factor, like all ratio measurements, is a unitless quantity.

As can be seen from the figure above, “power factor” can also be defined as the cosine of the electrical angle between the voltage and current vectors in an AC electrical circuit. However, power factor is not dependent upon the magnitude of the voltage and current but the phase angle between the voltage and current vectors.

The active power (kWh) is actually consumed by the electrical equipment and converted into work for creating heat, light, motion etc. However the reactive power (kVArh) is just used to provide the electromagnetic field in the inductive equipment, stored up in the windings of the equipment. Therefore while the kWh power is actually put to work, the kVArh power is just required to convert the electrical power into work.

Two Part Tariff:-

Generally, the two-part tariff is followed by distribution utilities for the billing of electrical energy. The two parts are – fixed charges based on installed capacity and variable charge which is based on energy utilized actually.

Further, the two additional components namely Electrically Duty which is usually some % of billed energy and Fuel Cost Adjustment (FCA) charges are included in the bill. Thus, the total billed amount is calculated as follows- 16% – Example value

What is kWh billing system:-

At present, in Maharashtra and  some states, the consumers are billed on Active Energy Consumption measured in kWh along with other components such as ED and FCA described above.

In kWh billing system, the incentives/ penalties are levied on Power Factor.

What is  kVAh Billing System:-

Electric power has two components – active power (kWh) and reactive power (kVArh). The active and reactive power components combine to form the apparent power (kVAh). The apparent power can be calculated as a Pythagoras sum of active power (kWh) and reactive power (kVArh).

In kVAh based billing system, the fixed charges or demand charges are levied on apparent power (kVA) and energy charges are levied on apparent energy (kVAh).
Because of kVAh billing system, Real and Reactive energies need not be charged separately.

Utilization of energies 

Necessity of kVAh billing:-

Both Active (kWh) and Reactive (kVArh) energies are consumed simultaneously. Reactive Energy (kVArh) occupies the capacity of electricity network and reduces the useful capacity of system for generation and distribution & hence its consumption also needs to be billed. kWh based billing is associated with PF incentive /penalty mechanism. Considering that the kVAh based billing has an inbuilt incentive /penalty mechanism and separate mechanism for the same is no more required; instead of billing two energies separately, billing of kVAh energy is preferred as a commercial inducement.

The consumer is encouraged to draw/inject minimum reactive power.

Implementation of kVAh billing system:-

State Electricity Regulatory Commissions in various States viz. Himachal Pradesh, Delhi, Uttar Pradesh, Jammu & Kashmir, Andhra Pradesh, Chhattisgarh, Bihar, Haryana, Punjab etc. have already introduced kVAh based tariff for various categories.

In the state of Maharashtra, as per MERC Order in Case no. 195 of 2017 dated September 12, 2018, The Commission intends to implement kVAh billing to all HT consumer and LT consumers having load above 20 kW from 1st April 2020.

Advantages of kVAh billing system:-

Advantages to consumer:-

1. kVAh billing will ensure that the consumers who will utilize the power efficiently will be paying less energy charges as compared to others who are not using the power efficiently.
2. The new billing methodology will be much simpler to understand as number of parameters viz. PF, rkVAh (lead/lag), kWh units) will be reduced.

Advantages to utility:-

1. Good system stability, improved power quality, improved voltage profile and reduced capital expenditure.
2. Complete recovery of cost of active and reactive powers.
3. Zero/ minimal drawl of reactive power by consumers.
4. Reduction in power purchase cost

Thus, considering the larger benefit of consumers as well as the utility, it is important that the existing billing regime can be migrated to kVAh based billing.

Comparison between kWh and kVAh billing systems:-

Source - MSEDCL Presentation on KVAH

Emerich Energy's AVG - IGBT Based Power Factor Correction & Benefits

The Emerich Energy's AVG (Active Var generator) represents the latest generation technology in the power factor correction field. By eliminating the need for switched capacitors and providing dynamic step-less compensation, the AVG offers high performance in a single Cubicle 

It operates by detecting the load current on a real-time basis through external CT’s and determining the reactive content of the load current. The data is analysed and the AVG’s controller drives the internal IGBT’s by using pulse width modulation signals to make the inverter produce the exact reverse reactive current of the corresponding load reactive content. This is injected to the grid to compensate the reactive content of the load current.By adjusting the output voltage amplitude and phase angle or by directly controlling the AC side current, the AVG can absorb or generate var according to the load reactive power or the grid 

AVG  OPERATING PRINCIPAL

Load current is detected through external CTs and fed to the internal DSP and CPU where an Instantaneous Reactive Power algorithm separates the active power from the reactive power. A compensating reactive power requirement is dynamically and accurately calculated and sent to the IGBT control where a 
PWM signal is generated at a switching frequency of 20kHz. A compensating capacitive reactive power or inductive reactive power is controlled by the manipulation of the DC bus voltage in comparison to the AC line voltage. 

Thus a capacitive current or inductive current will flow, creating a reactive power
exchange with the network voltage level

-->Excellent power factor correction performance

      Can maintain a PF of 0.99 lagging or unity if required

-->Compensates both inductive and capacitive loads

      Corrects lagging and leading power factor (-1 to +1)

Eliminating the weakest link 

This new method of Advanced Power Factor Compensation  takes away the most vulnerable and weakest link in a traditional APFC system–the switched capacitors. Various environmental conditions (eg.excessive temperature,over-voltage, harmonic distortion) may cause capacitors to rupture and ignite. 

The average life span of a switched capacitor is heavily dependent on the ambient temperature in which it is operated – requiring careful selection with respect to permissible operating temperature range. These temperature limits work well in colder climates but may not necessarily work well in all regions. The new generation technology in the Emerich AVG eliminates the operational limitations, safety concerns, space demands and life span issues of capacitor banks. 

Operates in all 3 phases 

A traditional switched capacitor type PFC system measures one phase and then

provides stepped kVAr compensation to all phases based on the measurements

taken from the one phase being measured. The other two phases all receive the same  compensation, irrespective of what the other two phases actually need. The Emerich AVG measures all 3 phases and provides specific dynamic kVAr compensation each phase.   

Greater longevity 

With traditional capacitor type systems, the physical cabinet space required for

the compensation steps is the same, weather the steps are 6.25kVAr or up to

50kVAr steps. This results in requiring  large cabinet space even for small

adjustments. The other disadvantage for having a small step for fine adjustment is that it gets over used (frequently switched). The PFC controller uses an

algorithm that evenly distributes the work load among the available steps except when one or two of those steps are of a smaller capacity. This brings into play the actual usable lifetime of the components used, for example the life of the contactor!

Not affected by resonance 

The system is not susceptible to existing harmonics and therefore does not need a blocking reactor and is unaffected by resonance whereas for the traditional

PFC system this is very much a problem. 

• Corrects load imbalance

• Can operate at low voltages

• Dynamic step-less compensation

• Profiles the load and operates with a response speed of <15ms

• Dynamic reaction time is less than 50µs

• No possibility of over-compensation or under-compensation

• Only injects the kVAr that is needed in that moment

BENEFITS of Emerich AVG

• Dynamic, Step-less Compensation

         + Adds exactly what is required to meet your Power Factor

         + Targets. No More, No less.

• Results in better Power Factor, for less costs

         + Better results for your critical load

         + Less money spent on power bills

• Better Knowledge of your own network

         + Far more detailed reporting

         + Corrects Power factor changes within 15ms

         + Reacts to changes in less than 50 micro seconds

• Virtually Maintenance Free

         + No capacitors to replace

• Far Safer

         + No capacitors to ignite

LONG LIFE WITH EXTREME DURABILITY 

• 100% solid state with latest generation IGBTs. 

• Electronics free from contaminated air flow 

• Long life cooling fans are simple to replace 

• Capacitor free. No Need for  constantly checking capacitors for degradation or failure 

• Low risk – no swollen or leaking capacitors. Reduced fire risk. 

• No contactors to replace 

• Design service life of more than 100,000hrs, without maintenance. That’s more than 10 years operation in a plant that operates 24/7. Capacitor based systems can last as little as three years. 

• High power density means less precious switchboard room is use

CONCLUSION 

Emerich Energy’s AVG is an entirely new approach to power factor correction. The AVG utilizes a high speed three level inverter that reacts to changes in reactive power, exchanging corrective reactive power into the system. Full correction is made in 3/4 of a cycle. This rapid response provides stable accurate real-time power factor correction without the drawbacks of traditional capacitor based systems. The AVG can continuously adjust reactive power dynamically and bidirectionally (leading or lagging). There is no chance of system resonance and even under low voltage conditions AVG will provide full reactive power compensation. The Emerich Energy's AVG is 100% inverter based so there are no AC capacitors to failure.

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Power Factor Incentive/Penalty: Revision in Maharashtra Electricity Tariff

The Maharashtra Electricity Regulatory Commission, in exercise of its power under Sections 61 and 62 of the Electricity Act (EA), 2003, and in pursuance  of the MYT Regulations and all other  powers enabling it in the behalf,  and  after  taking into consideration  MSEDCL’s  submission, the  written  and  oral suggestions  and objections received and the  responses  of MSEDCL, and all other  relevant  material,  has issued Mid-Term Review Order dated 12 September, 2018 in Case No. 195 of 2017.

Accordingly, the guidelines as under are issued for replacement  of the said order of the commission without prejudice to the rights of MSEDCL to take any actions as provides in the law.

Power Factor Incentive/Penalty:

In view of MERC Tariff order 195 of 2017 dt. 12.09.2018, Penalty for leading Power Factor is introduced, whereas incentive is applicable in case of lag PF only.

Penalty for leading power factor also introduced. This penalty will be applicable from prospective effect. As a first step  towards  the  kVAh billing system, which is devoid of any separate  incentive / penalty for power factor,  the  Commission has  decided  to  reduce  the  existing PF Incentive/ Penalty  by 50%. Accordingly, maximum PF Incentive, which is 7% at the Unity Power Factor, has been reduced to 3.5%. Similarly, Penalty for the lower power factor has been penalized.

Whenever the avg P.F. is more than 0.95 Lag and upto 1, an incentive shall be given at the rate of percentage in Tariff order at the amount  of monthly electricity bill, excluding taxes and duties. And whenever average P.F. is less  than  0.9 (Lead or Lag), Penal Charges shall be levied at the  rate  of percentage  of amount  of monthly electricity bill, excluding taxes and duties.

There is change in % of PF Penalty and Incentive as below. 

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