why energy metering

8/3/2019 Why Energy Metering

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WHY ENERGY METERING?

The per capita energy consumption is the best measure of

the prosperity of a nation. Per capita energy consumption in

India is 360KWh per year.

Although power generation in India is far too insufficient to

meet the requirement, the most important fact is the major

chunk of the energy generated goes down the drain due to

transmission and distribution loss (T&D LOSS) .The official

figure of transmission and distribution losses in India is

22%.The real transmission and distribution loss in India is

somewhere around 45-50%.

Unless this huge amount of untapped energy could be

converted into revenue, the real growth of the nation is not

possible. What is requ ired, a systematic energy audit such

that T&D loss could be accurately measured, monitored and

allocated properly. This needs an effective and efficient



measurement of energy starting from the generating station

up to the end user. Only a reliable energy metering solves

this problem.



INTRODUCTION

1. ELECTRONIC ENERGY METER:

A watt-hour meter in which current and voltage act on a solid state elements to

produce an output proportional to energy is called electronic energy meter. The

electronic energy meter can be classified into two groups:

• ASIC

• MICRO CONTROLLER based energy meter

The ASIC based energy meter has no memory and is used for accurate and reliable

energy measurement. Micro controller based energy with memory are used for

advance metering.

Micro controller based energy meter has following advantage:-

• Software calibration helps achieving better accuracy with less effort.

• Tampering details are easily recorded.



• Extra facilities like multiple parameters display multi tariff arrangements, time

of day metering facility etc. can be easily corporate with the same hardware by

changing software and peripheral circuit.

PRINCIPLE OF OPERATI ON OF ELECTRONIC ENERGY METER

A S I C b a s e d e n e r g y m e t e r c o n s i s t s o f t h e

f o l l o w i n g b l o c k s :

A c u r r e n t s e n s i n g e l e m e n t w h i c h c o n v e r t s t h e

a c t u a l l i n e c u r r e n t t o a p r e d i c t ab l e l o w v a l u e

s i g n a l a n d i s f e d to c u rr e n t i n pu t c h a n n e l o f

e n e r g y m e a s u r i n g d e v i c e . i n f a c t i n o r d e r t o

a v o i d t a m p e r i n g t w o c u r r e n t s e n s i n g e l e m e n t s

a r e u s e d o n e f o r n o r m a l c i r c u i t a n d t h e o t h e r

f o r n e u t r a l c i r c u i t a n d t w o c u r r e n t i n p u t s

c h a n n e l s a r e u s e d .

A v o l t a g e s e n s i n g e l e m e n t w h i c h c o n v e r t s t h e

l i n e v o l t a g e t o a p r e d i c t a b l e l o w v a l u e s i g n a l

a n d i s f e d t o t h e v o l t a g e i n p u t c h a n n e l o f

e n e r g y m e a s u r i n g d e v i c e



A n a l o g t o d i g i t a l c o n v e r t e r f o r b o t h c u r r e n t

a n d v o l t a g e c h a n n e l , w h i c h c o n v e r t s i n p u t

a n a l o g c u r r e n t a n d v o l t a g e s i g n a l i n d i g i t a l

f o r m A m u l t i p l i e r c o n t i n u o u s l y m u l t i p l y i n p u t

c u r r e n t a n d v o l t a g e . T h e i r p r o d u c t i s

p r o p o r t i o n a l t o i n s t a n t a n e o u s p o w e r . V o l t a g e

t o f r e q u e n c y c o n v e r t e r w h e r e t h e o u t p u t o f

m u l t i p l i er i s c o n v e r t e d t o f r e q u e n c y . T h u s t h e

f r e q u e n c y b e c o m e s p r o p o r t i o n a l t o p o w e r . T w o

d i f f e r e n t s e t s o f o u t p u t f r e q u e n c i e s a r e

p r o d u c e d . L o w f r e q u e n c y s i g n a l a r e u s e d t o

d r i v e e l e c t r o c h e m i c a l c o u n t e r a n d h i g h

f r e q u e n c y s i g n a l a r e u s e d t o d r i v e L E D

r e q u i r e d f o r c a l i b r a t i o n p u r p o s e .

A r e v e r s e p o l a r i t y l o g i c s i g n a l i n d i c a t e s w h e n

t h e m e a s u r e d i n s t a n t a n e o u s p o w e r g o e s

n e g a t i v e .

A c o m p a r a t o r c i r c u i t w h i c h t a k e s t w o c u r r e n t

c h a n n e l i n p u t s o n e f r o m m a i n c t a n d o t h e r f r o m

n e u t r a l c t . w h e r e t h e n t h e r e i s a d i f f e r e n c e i n



c u r r e n t b e t w e e n t h e t w o c h a n n e l s i s m o r e t h e n

1 2 % , e a r t h d e t e c t i o n p i n b e c o m e s h i g h .

A p o w e r s u p p l y c i r c u i t r y w h i c h m a k e s r e q u i r e d

d c v o l t a g e f r o m l i n e v o l t a g e a n d i s f e d t o

s u p p l y p i n s o f a c t i v e d e v i c e s

A n i m p u l s e c o u n t e r / s te p p e r m o t o r c o u n t e r

c o n n e c t e d t o t h e o u t p u t o f e n e r g y m e a s u r i n g

d e v i c e w h i c h r e g i s t e r s t h e e n e r g y.

WHOLE CURRENT AND CT OPERATED METER

When the whole amount o f cur rent to be

measured passes through the current sens ing

e lements o f the energy meter i s ca l l ed the whole

current meter . Th i s type of meter i s a l so ca l led

d i rect connect ion meter but i f the amount o f

cur rent to be measured i s fa i r l y h igh then i t i s



d i f f i cu l t to hand le such h igh amount o f current .

Usua l l y what i s done i s to s tep down the current

at in i t i a l s tage through the use o f cur rent

t ransformer and the sca led down current ac tua l l y

passe s through the e ne rgy me te r . Th i s t ype o f

energy meter i s ca l l ed CT operated meter .

MEASURMENT OF CURRENT INPUTS:



Current inputs are normal ly measured us ing the

fo l lowing three techniques :

• By us ing current t ransformer

• By us ing shunt

• By us ing Ha l l e f fect sensor

The essent ia l requi rements o f cur rent sens ing

e lement should be :

• The output should be ext remely l inear and

proport iona l to input over a lon g range .

• The output produced should not be

abnormal ly l ow.• Env i ronmenta l fac tor does not produce any

adverse e f fect on i t s per formance .

Current transformers:-

The t ransformers used for measurement o f

cur rent are ca l led cur rent t ransform er or CT . The

use of CT i s very common among h igh current

so l id s tate energy meter . I t i s a pass ive dev ice

wi th no ext ra dr iv ing c i rcu i t ry needed to use i t .

I t consumes l i t t l e power how ever the saturat ion

of fe r r i te mater ia l used in core can occur when

the pr imary cur rent i s very h igh or when there i s

substant ia l dc component in the c i rcu i t .

By the use o f CT two types o f e r rors are

int roduced in s tat i c meter :a. RATIO ERROR

b. PHASE ANGLE ERROR

SHUNT:-



I t i s a very low va lue res i s tance when current

passes through i t , the vo l tage drop i s produced

The essent ia l requi rement o f shunt i s :

• I t should be very low va lue accurate and

s tab le

• The temp. coe f f i c ient o f the shunt should be

very low

• The res i s tance of the shunt should be as

c losed to a wi re as poss ib le to min imize the

ef fect o f any at tempt to d i rect the cur rent

us ing externa l w i re .

Hal l E f fect sensor: -

I f a s t r ip o f conduct ing mater ia l car r ies cur rent

in the presence of t ransverse magne t i c f i e ld , an

emf i s produced between two edges o f the

conductor . Th i s property o f the conductor i s

ca l led Ha l l E f fect

The Ha l l e f fect EMF i s very smal l i n condu ctor but in some semiconductor such as germanium,

the i s suf f i c ient ly l a rge .

Advantage:-

1 . Size i s very smal l .2. Phase e r ror not int roduced.

3.Outstand ing f requency response .

4 . capab le o f measur ing ve ry la rge current

Disadvantage:

1. H igh temp. Dr i f t .

2 . Requi rement o f ex terna l dr iv ing c i rcu i t ry .

3 . Re lat ive ly h igh cost .



9. Part of electronic energy meter:

1. Term inal bloc k : a support made of

insu lat ing mater ia l on a l l o r some o f the

termina ls o f the meter are grouped together .

Termina ls are usua l l y made of n i cke l p lated

brass . They should be h igh ly conduct ing and

cor ros ion f ree . Termina l w i th d i f fe rent potent ia l

which are grouped c losed together sha l l be

protected e le ct r i ca l shor t c i rcu i t ing .

The insu lat ing mater ia l o f the te rmina l b lock

should be o f h igh impact s t rength, n non



hygroscop ic f l ame re tardant mater ia l (usua l l y

bake l i te or po lycarbonate) .

The barr ie r between phases should be prov ided

in the te rmina l b lock so that proper

c learance /c reepage d i s tance between phases i smainta ined .

2. meter case : the meter sha l l have a case ,

which can be sea led in such a way that the

interna l par ts are access ib le on ly a f te r break ing

the sea l . the meter chamber , should be a l so dust

p roof and moisture proof . The mater ia l o f the

body i s e i ther o f the two types :

1.Enginee ring plast ic : the meter cas ing

mater ia l should be o f g lass re inforced , f l ame

retardant , unbreakab le eng ineer ing p last i c to

ensure h igh re l i ab i l i ty t roub le f ree l i fe , sa fe ty

aga inst e lec t r i ca l shock , spread of f i re and

e f fect o f excess ive temperature . The mater ia l

sha l l be cor ros ion res i s tant and inser t tochemica l and ox id i z ing agent , pet rochemica l

p roducts , ac ids , sa l t s and u l t rav io le t r ad iat ion.

The eng ineer ing p last i c should conform to

IS11731 bes ides meet ing the test requi reme nt o f

heat de f lec t ion test ISO75 and g low test as per

re levant s tandard .

2. Steel body : the meter cas ing i s a l so made of

sheet s tee l o f usua l l y 22SWG th i ckness .

Synthet i c rubber or any other not hygroscop ic

mater ia l i s used for gaske t and for f i x ing the

meter cover over the body. In order to permi t a



c lear v iew of counter and LEDs, toughened g lass

window i s used .

3. Count er : re g i s te r the to ta l e ne rg y c onsume d

norma l l y c ounte rs c ons i s t o f f i ve o r s i x f u l l d ig i t s

and 0 ,1 o r 2d e c ima l d ig i t s . Ac c ord ing the y a re

c a l l e d (5+ 0) , (5+ 1) , (5+ 2) , (6+ 0) , (6+ 1)&(6+ 2) a re

c ounte r . O d i s t ing u i sh the d e c ima l d ig i t , the

b ac k g round c o lour o f d e c ima l d ig i t i s d i f f e re nt f rom

f u l l d ig i t .

The mater ia l o f the counter drum i s normal ly o f

super ior qua l i ty thermoplast i c or h igh qua l i ty

synthet i c mater ia l po lyaceta l . The rat io gear

whee l sha l l be o f po lyaceta l or spec ia l synthet i c

mater ia l to reduce f r i c t ion& wear and tear . In

should be res i s tant to magnet i c f i e ld and

tamper ing . The reg is ter ing mechanism when

sub jected to bo i l ing water test sha l l w i th s tand

a temperature o f 100 c cont inuous ly for f i ve

minutes wi thout any d i s tor t ion or sof ten ing . The

externa l magnet i c f i e ld a f fect the counter

mechanism, hence they are encapsulated .



Energy Meter Testing

L ike a l l o ther types o f e lec t ron ic /e lec t r i ca l

equipment energy meter a l so undergoes three

types o f test ing :

1. Rout ine test ing: -

These are the test car r ied on each and every

meter to check conformi ty o f the meter wi th the

requi rement o f the s tandards . The purpose of

th i s test i s to check those po ints which may vary

dur ing product ion.

2. Acceptance test ing:-

These are the tests car r ied on sample bas i s over

a product ion lot /batch. The purpose of th i s test

i s to insure those po in ts which may vary in lo t to

lot dur ing product ion. Depend ing on the sample

resu l ts , the lot i s accepted or re jected .

3.Type test ing: -

These are the ser ies o f tests car r ied out on one

or a smal l numbers o f meters o f the same type

hav ing ident i ca l character i s t i cs to prove

conformi ty wi th the actua l requi rement o f the

standards . A l l the tests are bas i ca l l y to eva luate



that the des ign supports the spec i f i ed

s tandards .

Terminology

Resister : -

An e lect romechanica l or e lec t ron ic dev ice

compr is ing both memory and d i sp lay which



stores and d i sp lay in format ion. A S ing le d i sp lay

may be used wi th mul t ip le e lec t ron ic memor ies

to form mul t ip le res i s te rs .

Current c i rcu it : -

The interna l connect ion s o f the meter and par t

of the measur ing e lement through which f lows

the current o f the c i rcu i t to which the meter i s

connected .

Voltage c i rcu it : -

The interna l connect ion o f the meter , par t o f the

measur ing e lement and powder supp ly to the

meter supp l ied f rom the vo l tage of the c i rcu i t to

which the meter i s connected .



Auxi l iary c i rcu it : -

The e lements ( l amps, contacts e tc . ) and

connect ions o f an aux i l i a ry dev ice wi th in the

meter case intended to be connected to an

externa l dev i ce for example c lock , re lay , and

impulse counter .

Meter constant:-

Constant express ing the re lat ion between the

energy reg is tered by the meter and the

correspond ing pu lse count i f the test output .

Th is i s genera l l y expressed e i ther as pulse count

per wat t hour or pu lse count per k i l owat t hour or

wat t hour per pu lse .



Basic current : -

The va lue o f the cur rent in accordance wi th

which the re levant per formanc e of the meter i s

f i xed .

Rated maximum current : -

The h ighest va lue o f cur rent at which the meter

supports to meet the accuracy requi rement o f

th i s s tandard , when th i s cur rent f l ow

cont inuous ly in the meter .

Reference voltage:-



The va lue o f the vo l tage in accordance wi th

which the re levant per formanc e of the meter i s

f i xed .

Reference f requency: -

The va lue o f f requency in accordance wi th wh ich

the re levant per formance of the meter i s f i xed .

Percentage error : -

The percentage er ror i s g iven by the fo l lowing

formula : -

Pe rce ntage e r ro r =

Energy reg is tered - t rue energy x 100



True energy

Features of Electronic energy meter

• Sturdy const ruct ion



• Low wat t - loss e lect romagnets

• Tota l l y encapsulated vo l tage co i l

• Sturdy pressure d ies cast f rame

• Super ior grade bake l i te te rmina l b lock

• Low temperature r i se in e lec t romagnets

• Fronta l ad justments

• Machine wound Potent ia l & Current co i l s

• L ight we ight low f r i c t ion cyc lometer

• Meta l l i c /B lack Po lycarbonate Base wi th c ross

r ibs

• Ful l y t ransparent Po lycarbonate

Cover /Meta l l i c Cover wi th Toughened g lass

window/Complete G lass Cover



Specification of AC 4 Wires and Single PhaseKWH Electronic Meter

S.NO Parameters Single phase electronic KWHmeter

1. Model SPEM01

2. Standard applicable IS 13779/IEC: 1036

3. Rating 5 – 20A1. Accuracy Class 1.02. Rated voltage 240V (+20% - 40%)

3. Rated current Ib = 5AmpsImax = 20 Amps

4. Rated frequency 50Hz ±10%5. Power factor 90°Lag to unity to 90°Lead

6. Saturation current 200% of Imax

7. shall work within accuracy upto max loading

150% of Imax

4. Continuous current rating 30 Amps.5. Power loss at rated frequency

and reference temperature

a. Current circuit at ratedcurrent

Less than 1VA

b. Voltage circuit at ratedcurrent

Less than 1.5W/8VA

6. Transformers

a. Input CT and resistor network b. Output Stepper motor

counter/impulse counter

7. Cut-off voltage at which meterstop working

- 50%

8. Input voltage and frequencyvariation within which meterwork satisfactory

+ 20% to - 40% of Vref 50 Hz ± 5Hz

9. Relative humidity 95 %

10. Reference temperature 27°C

11. Temperature range of operation - 10°C to + 60°C12. Approximate weight of meter In sheet Steel – 1.1 Kg ±.2 Kg

In poly carbonate 1.1 Kg ±0.2Kg

13. Manufacturing Technology Mounting of component onPCB is SMT type and ASICtechnology

why energy metering

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