# Calculation of Multiplication Factor of Energy Meters

Energy Meters are one of the important instrument to account for energy imported / exported in an industry. In Power Generating Stations, the cumulative reading of such energy meters are used for the calculation of total Million Units (MUs) of energy exported. On the basis of MUs, total revenue generated by the Station is calculated. Thus reading of Energy Meter is quite important to be recorded, accounted and audited.

As we know that,

Power = VICosØ where Ø is power factor.

Therefore, an Energy Meter shall take current and voltage as an input. Current and voltage input is extended through metering core of Current Transformer (CT) and metering core of Potential Transformer (PT). Based on this input, the energy meter calculates and display amount of energy imported / exported.

Let us take an example. Suppose the energy meter is connected in STAR connected system having CT ratio of 200/1 A & PT ratio of 220 kV / 110 V (phase to phase value). Assume power factor to be unity for the sake of easy understanding of Multiplication Factor. So, the current and voltage input to meter will be 1 A (phase to neutral current) and 110 V (phase to phase). Let us convert the input current and voltage to phase to neutral value.

Phase Voltage = 110/1.732 = 63.5 V

Phase Current = 1 A

Per phase power calculated by the Energy Meter assuming power factor to be unity

= 63.5 x 1 x 1 Watt = 63.5 Watt

Hence, total power as displayed in Meter = 3xPer Pahse Power

= 3×63.5 Watt

= 190.5 Watt

Energy Meter displays the cumulative energy imported / exported in Wh. Hence, energy displayed by meter assuming 190.5 Watt of power is supplied for 1 hour

= 190.5 Wh

Is this the actual power? Definitely not.

Actual power = 1.732x220x200x1 kW  (Three phase power)

= 76208 kW

Actual energy for 1 hour in watt hour = 76208 kWh

This discrepancy in the actual power and power displayed in energy meter is due to the fact that meter is taking CT and PT secondary value as input for its calculation. To overcome this discrepancy, we need to have a Multiplication Factor of Energy Meter.

### Calculation of Multiplication Factor:

Multiplication Factor of Energy Meter is calculated as below

Multiplication Factor = (External CT Ratio x External PT Ratio) / (Meter CT Ratio x Meter PT Ratio)

You can find the meter CT and PT ratio in the manufacturer manual. Usually both the ratios are 1.

Let us calculate the Multiplication Factor for our example.

Here,

External CT Ratio = 200/1

External PT Ratio = 220 kV / 110 V

Hence,

Multiplication Factor (MF) = (200×220 kV) / (1×110)

= 400,000

Thus the difference of meter reading must be multiplied by the above Multiplication Factor to get the actual amount of energy imported / exported for our example.

To conclude, as an energy meter shows the cumulative energy imported / exported in Watt Hour, therefore the difference of meter reading taken at two different point of time gives the net energy imported / exported. Let this difference in meter reading is n Wh for the given period.

Then the actual energy imported / exported during that period

= n x MF Wh

= n x MFx10-3 kWh

= n x MFx10-3 Units

### 87 thoughts on “Calculation of Multiplication Factor of Energy Meters”

1. Supposing my CT ratio is same but the PT ratio differs. Then how should i calculate the M.F. let as assume CT ratio is 200/1 external and meter side but PT ratio for external is 220/100 and at meter side 220/110. High light on it please.

Reply
• One meter will only have one CT and one PT input. Therefore the method for calculation of multiplication factor will remain same.

2. for multifunctional meter multiplication factor required or not

Reply
• For Multifunctional meter it is not required. But is better to refer the manufacturer’s manual.

3. hello friends. i need your opinion
i habe recently installed a 6kV switchgear, having doubts for the energy measyrement.
the old energy meter had a MF =100
The VTs are 6kv/100 V CTs are 300 A/5
so the MF should be (6 × 300 ) / ( 5× 100) = 3.6 ?
is this right??
the metter shows 1.2 kWh
so should i multiply this value with 3.6?

thanks

Reply
• U will get mf as 360 not 3.6

• Yes u r right Mr. Aurel made the calculation with 6. That should be 6000. Then the answer would be 360.

4. regarding my post of some minuits ago
a did a mistake in calculation.
for my switchgear PT ratio are 6000/100 CTs ratio 300/ 5A the meter ratio are both set at 1
so my MF is ( 6000 * 300)/(5* 100) =3600 ?
my new energy meter shows 2.2 kWh the last 24 hours
so the real value is 2.2 * 3600?

Reply
• Thank you Aurel for asking. Yes, you need to multiply the energy meter reading by 3600 (for kWh or Unit conversion) for getting the actual energy consumption by auxiliaries. You can download Multiplication Factor Calculator for Energy Meters for your future use and reference. Please share the post if you like it.

5. if you apply for 1MW at a plant, VT ratio 11kv/110,CT ratio 50/5. how do u find the multiplying factor

Reply
• Thank you for asking. You can download Multiplication Factor Calculator for Energy Meters for calculation.

6. Please help me.
the external CT ratio is 50/1A, external PT ratio is 33kV/110V
meter CT ratio is -/5A, meter PT ratio is -/110V.
What should be the multiplying factor?
Help will be highly appreciated

Reply
• The Multiplication Factor (MF) for Energy Meter will be 15,000. The MF to convert meter reading in kWh (Unit) = 15. You can download Multiplication Factor Calculator for Energy Meters for calculation for your future use.

7. external ct ratio 200/1,external pt ratio 66kv/110
meter ct ratio 400/1,meter pt ratio /110v
mf will be????

Reply
• Thank you for asking. You can download Multiplication Factor Calculator for Energy Meters for calculation. If you still find problem, please reply.

8. Please I have a question,
We have a meter at the at the transmission substation (132/33kv) and another meter on the 33kv feeder some kilometers away for inter-boundary metering.
The issues now is this, the reading from the inter-boundary meter is higher than that the meter at the transmission end is picking.
How can this be possible and how can I be able to resolve it? Those the CT rating has a part to play in this?
Thanks

Reply
• What is the CT and PT ratio for Substation Meter and feeder meter? Please revert so that I can help you. If possible can you send me a simplified single line diagram for Meter connection for both substation and feeder? Thank you!

• 132kv/33kv ka P.T. ratio kitne volt hoga

• PT kis side laga hai, agar 33 of side hai to ratio 33 kv/110 v hoga Aur agar 132 kv side hai to 132 kv/110v hoga

9. A Meter of /110v , / 5A having external CTR300/1 and PTR 66kv/110v and interposing Ct 1/5A. Pls advice whether Mf = 36000

Reply
• where does this interposing relay coming into picture in your system?

• The secondary of 300/1 CT is connected to the primary of interposing CT n secondary of interposing CT is connected to a HT meter of /5A

• In this case, the MF of Energy Meter will be = (300/5)x(66×1000) / 110 = 36000

10. 11kv feeder external CT ratio 300/5,external pt ratio 11 kv/110 v, meter ct ratio – /5,meter pt ratio /110 v, what is m. F.?

Reply
• It will be 6000.

11. Sir, your anser is not match in formula 11kv /110 v*300 /5/110 v*5=10.8
Your anser is 6000
We use 60m.f.in our 66kv substation in 11kv outgoing panel
What right 10.8,6000,60?
Please calculation me

Reply
• See, (11x1000x300) / (5×110) = 6000. It may be that you are using MF to convert into into million Units. Check where you are using MF and then change the data accordingly. Can you pls send me detail for your 66 kV substation so that I may check why the MF is 60 in that case?

• I have Schneider conzerv 6400NG energy meter.
CT is 75/5.5A
PT is 33000/110V
Please told me how to read unit in meter and what is multiple factor

• Have you made any setting of CTR and PTR in the meter?

12. I have to calculate MF of summation meter…yard CT ratio for feeder 1 is 300/1 and for feeder 2 is 300/1. Also, summation meter ke current transformer ka CT ratio 50/1 hai. And summation meter se pehle install 4 abt meter having CT ratio 600/1….
Then, how to calculate MF of summation meter?? Please reply with details

Reply
• Please send SLD.

13. I have a meter type MK6E with nominal current In= 1(10) Amps & Vn = 3*57-240 volt but the external CT = 100/5 & external PT = 20000/100 … please can you tell me how much is the multiplication factor ?

Reply
14. We have one 3 phase 4wire energy meter installed in our distribution network. On Energy meter facia MF-20 is written at bottom of meter 200/5A is written. There is no CT connected inside meter box. However we have connected one external CT of 300/5 in meter connection. Now what will be overall multiplying factor to calculate overall reading.

Pl reply

Reply
• What is the PT ratio connected to the Meter?

15. No PT is connected. three phase 415 V supply is directly connected to meter.

Reply
• It will be great if you can mention the meter make and model number so that i can check.

16. Great
Make- Capital,AC 3 Ph 4WIRE for unbalanced load
Type-RR47
Meter MF- 20 (written on meter facia)
At bottom of meter facia 200/5A is mention.
we have externally connected only CT having ratio 300/5. NO PT only 3 phase supply 415 V is connected. what will be the meter overall MF.

Reply
• I could not find the manual of the energy meter. However, if the power is being supplied through 415 V line and general calculation is considered then multiplication factor should be 60.

17. Hi
A
I’m k. Purushothaman
How can I identify PT Ratio in selec MFM376 Meter.. I’m using this meter in control panel. Please clear my doubt sir. CT RATIO is 250/5

Reply
• Is this the meter installed? If installed, then pls check in the meter console for voltage.

• if the input is 440/240 volt there is no need of PT ratio, your MF will be 50

18. Hi
Kindly clarify the correctness
The external CT ratio is 200/1A, external PT ratio is 132kV/110V and
meter (Secure Make) CT ratio is -/1A, meter PT ratio is 132kV/110V
We are using MF as 200
If not correct, please show detail calculation

Thanks & Regards
Lalthanzuala,

Reply
• The MF will be 240,000. However, the MF to convert meter reading into kWh (Unit) will be 240. For detailed calculation, you are requested to refer the article.

• Dear Sir,

External CT Ratio = 200/1

External PT Ratio = 220 kV / 110 V

Hence,

Multiplication Factor (MF) = (200×220 kV) / (1×110)

= 400,000

From the above calculation, how do you get 220 for External PT Ratio

• PT ratio is 132 kV/110V for your case. CT ratio is 200/1.

• Dear Sir,

what about the Meter CT and PT ratio. Why it is not considered in the MF calculation?

Thanks and regards

• As mentioned by you, it is 1. Meter CT and PT ratio is also considered. Please check the formula for multiplication factor.

19. Dear Sir,

what about the Meter CT and PT ratio. Why it is not considered in the MF calculation?

Thanks and regards

Reply
• It is considered.

20. MF=(33*50)/1*110=15
Meter reading should be multiplied by 15.

Reply
21. In our 33/0.415 KV 0.5MVA S/s Installed Elite 440-442 model. PT primary/Secondary = 33000/110 & CT primary/Secondary = 75/5 . Multiplying Factor is 4500 . But Why Installed Company Multiply with only PT Ratio (300) and KWH From meter.

Reply
22. 11kv Bank external CT ratio 800/1,external pt ratio 11 kv/110 v, meter ct ratio 200/1,meter pt ratio 66kv/110 v, what is m. F.?

Reply
23. What is the meaning of -/5A and -/110V meter? While counting m.f. why it is not considered?

Reply
24. A METER OF
MADE TO I.S.S. 2705/1992
(RATIO : 2000/5A VA : 15 CLASS : 1.0
FREQ : 50 Hz
LINE VOLTS : I.L.0.66/3.0KV

SO WHAT WILL BE M.F RATIO OF THIS

Reply
• What is line voltage and PT ratio used?

25. 11kv feeder eternal CT ratio 300/5 external PT ratio 11kv/110v meter CT ratio x/5 meter PT ratio 3×100/58v what is M.F?

Reply
• I have a meter written on it x/5A,3×58/100V externalC.T ratio300/5 ,external PT ratio11000/110V what will be the multiplying factor ?pl lam in need of this information

26. we had come a cross one issue at our plant. In CT panel, the connection which is going to meter, phase and neutral got interchanged. Hence though we use power, 1/3 only getting by meter. Inspection done by EB and they said , henceforth major changes in power cost. EB said they only did mistake while giving connection in few years back. Can you give some suggestion to how to tackle
thanks

Reply
• This is a big mistake by EB. The connection needs to be immediately changed. Also, ask EB to replace the meter as meter might have got damaged due to wring wring connection.

27. Hi. Hallo. HT METERING PANEL. 60 KVA CT RATIO 5/1A
PT RATIO 11KV/√3/110V/√3
VOLTAGE READING. 62.36
CURRENT IN AMPS 0.432
How to calculate input voltage.

Reply
• Your question is not clear. Can you please elaborate?

28. Please clarify the concept of meter CT and PT ratio -/1A and -/110V in calculation of M.F.

Reply
• Same question from me.

29. Sir can you explain in detail calculation of MF with
External CT ratio = 200/1A
External PT ratio= 11kv/110v
Meter CT ratio= -/1A
Meter PT ratio= 11KV/110v

Reply
• It will be 20,000 assuming meter PT ratio to be-/110V.

30. I am installing 440v 3phase 4 wire meter my mf ratio???

Reply
• Kindly use the excel to calculate the multiplication factor.

31. If the ctr of Meter is -/5A & ptr is 110v & ctr of mu is 200/5 & ptr is 11kv then what is MF of the consumer?

Reply
• It will be 4000.

32. If CMD changes CT coils are also to be changed , is it so. Why?

My CMD us 350Kva .derating to 250Kva.

Present CTR. 20/1,. ptr. 11kv/110v

Reply
• What is CMD?

33. Gcontracted Maximum Demand in KVA agreed mutually by user n supplier. RMD registered maximum demand in KVA.

Reply
34. HI I am vijayakumar i have one dought

my self have one DG (eg 500kva or 250 kva ) i want select the coil

how to select the ct coil if have any formula plse share me

Reply
• Can you please elaborate. Your doubt is not clear to me.

35. I have a 3 phase 415V kwhr meter where CT ratio is shown 100/5a and on kwhr meter , it mentioned 400/5a , what will be the multiplying factor ?

Reply
36. I have a 3 phase 4wire, 110v energy meter where CT ratio is 300/1A and the meter is installed on an 11KV panel. Can I use a P.T of 33000/110 volts to connect the meter ? what effect will it have on the reading?

Reply
37. my question is, we have connected CT of 100/5 with 3 phase 4 wire static meter of -/5 A. How the actual KWH will be calculated. pls help

Reply
• What is PT Ratio?

38. we have connected external CT Ratio 400/5 and external PT Ratio 11000/110 then meter CT ratio 400/5 and meter PT Ratio 11000/110 what will be the MF

Reply
39. 400volt 5(6)amp genus meter ct ratio200/5 amp.meter display show voltage r-110 v,y-300 v,b-300 v.amp average 78/phase.maximum femand-56kw.so how many kwh we loss.

Reply
40. my question is, we have connected CT of 100/5 & PT of 11KV/110 with 3 phase 4 wire static meter of -/10 A & -/110 How the actual KWH will be calculated. pls help

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41. I can’t understand what is n?? Pl. Explain with examples for easy understanding

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42. 33/110 SUB STATION
CT .
CTR= 500/1 AMP
PT.
PTR =33/110V
MF=1500
HOW TO POSSIBLE ?
NEED CALCULATE MF =???

Reply
43. Please help me in entering PT values in programmable energy meter.
Connecting meter in LT side having phase to phase voltage 440V and phase to neutral 220V.

Thanks in Advance.

Reply
44. Aoa dear all please tell me how to calculate multiplying factor for 400v LT energy meter
My CT ratio is 600/5 and phase voltage is 400v

Reply
• What is make and model of your energy meter?

45. Lesco Approved energy meter hy Creative electronics pvt.ltd model : CE-17

Reply