KVAh Metering Basics

1 09/20/06 Smart Energy Management © Copyright 1986-2005, ConZerv Proprietary & Confidential

kVAh Metering BasicskVAh Metering BasicsAshok HattangadyAshok HattangadyDirector Technology Development, Director Technology Development, Conzerv Systems Pvt Ltd, Bangalore, IndiaConzerv Systems Pvt Ltd, Bangalore, India

Smart Energy Management2 09/20/06 © Copyright 1986-2005, ConZerv Proprietary & Confidential

kVAkVA

kVA is already widely in use: kVA Demand PF Penalties. PF = kW / kVA Sizing of Transformers and Distribution

Any wrong definitions are detrimental and must be corrected, irrespective of billing kVAh directly


141 kVA141 kVA0.7 PF0.7 PF

Principle of kVAPrinciple of kVA

~~ MM100100 kWkW

100100kVAkVA1 PF1 PF

~~ MM

100 100 kVARkVAR

141 kVA141 kVA0.7 PF0.7 PF

100100kWkW

100100kVARkVAR

Reactive Energy Reactive Energy supplied by Sourcesupplied by Source

Reactive Energy Reactive Energy supplied by Capacitorsupplied by Capacitor

141141kVAkVA

0.7 PF0.7 PF

Eg. Motor Load needs 100kVAR of Reactive EnergyEg. Motor Load needs 100kVAR of Reactive Energy


Spectral Constituents of kVASpectral Constituents of kVA

VV

AA

kW, kVAR, kW, kVAR, SS

DD DistortionDistortion

kVA- kVA- UU ApparentApparent


Effect of D on kVA, PFEffect of D on kVA, PF Consider the Rectifier

Waveform- PCs, UPS, CFL etc

S (Vector) kVA gives a PF of 1.00

U (Apparent) kVA gives a PF of 0.5

VV

AA


Vector Constituents of kVA 1ΦVector Constituents of kVA 1Φ

P Active kWP Active kW

Q Reactive kVARQ Reactive kVAR

D Distortion kVA D Distortion kVA Polarity kept same as Q, not W per IEEE 100Polarity kept same as Q, not W per IEEE 100 IEEE 100IEEE 100

S Phasor kVAS Phasor kVA22 QP ++=

U Apparent kVAU Apparent kVA222 DQP +++=

rmsrms AV ×=


Six kVAsSix kVAsOne Apparent Power (U)One Apparent Power (U)UUaritharith = 3ph Arithmetic kVA = V = 3ph Arithmetic kVA = V11AA11+ V+ V22AA22+ V+ V33AA33

S S Phasor kVAPhasor kVA22 QP ++=F F

Fictitious Fictitious kVAkVA

22 DQ +=

N N Nonreactive kVANonreactive kVA22 DP +=D D Distortion kVADistortion kVA

22 SU −±=

U Apparent kVAU Apparent kVA222 DQP +++=

rmsrms AV ×=


3 Apparent Power UΦ3 Apparent Power UΦ

( ) ( ) ( ) 2321

2321

23213 DDDQQQPPPU ++++++++=φ

21

21

21 DQP ++

22

22

22 DQP ++

23

23

23 DQP ++


Vector & Scalar AdditionVector & Scalar Addition

4 km4 km

3 km3 km5 km “as the crow flies” 5 km “as the crow flies” Vector Add Vector Add

7 km “the fare you pay”7 km “the fare you pay”Scalar AddScalar Add

Example: How far has your Taxi gone?Example: How far has your Taxi gone?


Apparent kVA (U) vs Apparent kVA (U) vs Arithmetic kVA 3phArithmetic kVA 3ph

Apparent Apparent Vector addition in 3DVector addition in 3D

( ) ( ) ( ) 2321

2321


Arithmetic Arithmetic ScalarScalar

321Arith UUUU ++=332211 AVAVAV ++=

VV11AA11

VV22AA22

VV33AA33

Note that V2A2 & V3A3 are positive (no sign)



Apparent Apparent Vector addition in 3DVector addition in 3D

( ) ( ) ( ) 2321

2321


Arithmetic Arithmetic ScalarScalar

321Arith UUUU ++=332211 AVAVAV ++=



3ph Apparent kVA =

3ph Arithmetic kVA =

( ) ( ) ( ) 2321

2321


321 UUU ++=

332211 AVAVAV ++=

23

23

23

22

22

22

21

21

21Arith DQPDQPDQPU ++++++++=


kVAh (over intervals of time) =….

But Derived kVAh = kWh2 + kVARh2 is much smaller

kVAh Integration kVAh Integration

321 UUU ++=2

32

32

32

22

22

22

12

12

1 DQPDQPDQP ++++++++=

( ) ( )23212

321 QQQPPP +++++=

....PP2PP2PP2PPP 3231212

32

22

1 +++++=


Apparent kVA (U) vs Apparent kVA (U) vs Arithmetic kVAArithmetic kVA Apparent kVA includes Wh, PF, THD revenue

a “Vector” quantity, but always Positive

Arithmetic kVA in addition includes “Unbalance” revenue a Scalar quantity

Uarith ≥ U ≥ S. Uarith is higher than U especially for Delta loads with unbalance


Apparent kVA (U) vs Apparent kVA (U) vs Arithmetic kVAArithmetic kVA

kWh PF• Traditional Billing » kWH + PF Penalty

kWh PF THD• Apparent kVAh» + THD

kWh PF

Unbalance

THD• Arithmetic kVAh» + THD + Unbalance


Apparent kVA (U) vs Apparent kVA (U) vs Arithmetic kVAArithmetic kVA

Unbalance Penalization with Arithmetic kVA Placing a single Line-Line

Load (resistor) creates maximum Unbalance

Uarith is 15.5% more than W, PF=0.866 Arithmetic kVA penalizes Unbalance

Vy

Vr

Vb



Arith kVA, kVAh, Demand- insensitive to CT Polarity PT, CT Phase Shift errors Phase Sequence Better accuracies can be achieved.

Tariff meter need show only V, A, Freq, Arith kVA, Arith kVAh, Arith kVA Dmd

But Apparent kVA is degraded by these


Apparent kVA in Delta HT SystemsApparent kVA in Delta HT Systems

kVA (S), PF in Delta systems do not fully measure Harmonic energy with Non-sinusoidal Waveforms Unbalanced Voltage Vectors / Loads A limitation today in HT kVA Demand and PF values

In Meter, compute on equivalent Star vectors

19 09/20/06 Smart Energy Management © Copyright 1986-2005, ConZerv Proprietary & Confidential

ApplicationsApplications


Expected Growth OfExpected Growth OfElectric Energy DemandElectric Energy Demand

0

500

1000

1500

2000

2500

3000

3500

4000

1995 2020Asia

Rest of World

150% Growth

300% Growth

GWh/Yr


Electricity Cost Rising Fastest Electricity Cost Rising Fastest in Indiain India

1

2

3

4

5

6

1988 1990 1992 1995 1998 2001

Steam Coal Electricity

Cost in India. Normalised to 1988


Power Costs WorldwidePower Costs Worldwide

US Cents / kWh

Jap

an.

Indi

aG

erm

any

Aus

tria

.

Italy

.P

ort

ugal

.B

elgi

um.

Sp

ain.

UK

.Ir

elan

d.F

ran

ce.

Net

herl

ands

.

US

A.

Gre

ece.

Isra

el.

Aus

tral

ia.

S.K

orea

.D

enm

ark.

Fin

land

.N

ewze

alan

d.

Nor

way

.C

anad

a.S

wed

en.

S. A

fric

a.

0123456789

1011121314

2.5 MW supply, 40% Load


Electricity Usage in IndiaElectricity Usage in India

Others6%

Lighting13%Electrolysis

5%

Arc Furnaces

1%

Motors 75%Industrial + Agricultural


Sector – wise % ConsumptionSector – wise % Consumption

9

18.4

50.8

21.8

13

25.9

41.9

19.3

20

32

31

17

1984 1989 1999

Normalized % : IndiaSource: Annual Report on the Working of SEBs,

Planning Commission, June 2001

OthersIndustrialAgricultreDomestic



Arithmetic kVA Domestic (1ph) and Commercial billing Simplicity in meeting the cost of service

Apparent kVA Industrial and Grid metering Not possible for 1ph services Available in the meters?



Arithmetic kVA is suitable for Domestic and Commercial billing with simplicity in meeting the cost of service

Apparent kVA is probably better suited to Industrial and Grid metering. It would simplify billing if available in the meters. It is also more suitable for Energy Balancing than Arithmetic kVA.


Arithmetic kVA Insensitive to CT Polarity, Phase shift error, phase sequence. Not Vector kVA

Import / Export? kVA Polarity Star only, not Delta Energy Balancing when PF Caps added KVA Demand Includes PF, Harmonics, Unbalance


““Cost of Service” IndicatorCost of Service” Indicator

kWh + PF Penalty Historic origin of kWh

kVAh Metering Includes PF penalty.

Arithmetic kVAh Metering Includes unbalance penalty. True cost of service


KVA MeasurementKVA Measurement

3D VA Ideal

√(W2+VAR2+D2)

Arith VAEurope

VA1+VA2+VA3

2D VAPythogoras√(W2+VAR2)


Correct kVA Steps already knownCorrect kVA Steps already known

For 2E: Convert from Delta to Star IEEE 100

Then, VA is given by:

Polarity of D = Polarity of VAR, not W VAR must be directly calculated not from VA

( ) ( ) ( ) 2321

2321



kVA Test Case 1kVA Test Case 1

Unbalance Penalization with Arithmetic kVA Placing a single Line-Line

Load (resistor) creates maximum Unbalance

Uarith is 15.5% more than W, PF=0.866 Arithmetic kVA penalizes Unbalance

Vy

Vr

Vb


KVA Test Case 2 (UPS)KVA Test Case 2 (UPS)


Unbalanced kVAUnbalanced kVA

2191316412573 Phase

600 600268.3B

13641364452.4Y

12001200536.6R

3D VA Ideal

√(W2+VAR2+D2)

Arith VAEurope

VA1+VA2+VA3

2D VACBIP

√(W2+VAR2)Phase


Unbalanced PFUnbalanced PF

+ 0.376- 0.544- 0.9473 Phase

0.447 0.4470.999B

- 0.283- 0.283- 0.853Y

- 0.447- 0.447- 0.999R

3DIdeal

Arith Europe

2D CBIP

Phase

KVAh Metering Basics

Documents

Transcript of KVAh Metering Basics