Difference in power factor in sending end and receiveing end 1

[masinha2]

We have 132/11KV substation .One meter of EB is connected at sending end of 132KV voltage and our meter is connected at receiveing end 132KV voltage .Even though we are maintaining average power factor of receiveing end 132KV voltage around 0.92 but the average power factor of sending end is low around 0.84 .Why such huge difference in average power factor occurs .We have already checked both end meters but no fault found .I am not able to understand why such difference is coming .Also during running condition running power factor on both side is same .

 

[davidbeach]

Please explain what "Also during running condition running power factor on both side is same" means in context with the rest of the question.

 

[masinha2]

Means instantaneous power factor on both meter are same but average power factor in sending end and receiving end meter differs.

 

[marks1080]

It means the phase angles at the sending and receiveing end are different...

 

[davidbeach]

The line is a capacitor, the power factor won't be the same at both ends. The lower the charging current, relative to the load current, the greater the difference between the power factors at each end. At heavy load there may not be much difference, but at a load at the receiving end just large enough to calculate power factor they will be quite different; the sending end will probably be a leading power factor even.

 

[Mbrooke]

Davidbeach is spot on. The line has capacitance which add reactive components (current). Most people think of transmission lines as simple I2R in terms of losses, however reactive components add currents (MVAR) which changes power factor and even voltage (Ferranti rise for example) at the receiving/sending ends.

 

[7anoter4]

I agree with davidbeach, of course. In my opinion a long transmission line is less inductive and sometime even capacitive so the sending power factor could be better -less lagging- even. But a short transmission it is more inductive. I am not involved in power factor measurements. However, in my opinion, the average difference from sending end to receiving ,in this case, is huge. It could be other reactive elements like reactors or else?

 

[ScottyUK]

7another4,

That could be explained by a relatively small active power component.

 

[7anoter4]

Thank you, Scotty. However, in my opinion, if the load increases the power factor decreases, theoretically at least.

 

[ScottyUK]

If the active load increases and the reactive components remain constant then the PF improves, i.e it gets closer to unity.

Is this a cable circuit or a line?

 

[7anoter4]

You are right, Scotty: my experience it is only with cables and not with overhead lines. So, do you think it is a shunt [lumped] reactance in an overhead transmission line? In this case, of course, part of the reactive power could be constant [depending only on supply voltage].If it is only a series reactance then the [ lost] reactive power depends on current [in my opinion].

 

[ScottyUK]

"So, do you think it is a shunt [lumped] reactance in an overhead transmission line?"

My crystal ball is broken. The OP needs to provide more detail.

 

[masinha2]

Davidbeach answer is quite matching .But I want to know that how to resolve this issue as EB meter is at sending end and due to lower power factor we have to pay heavy penalty in every month.Please explain.

 

[krisys]

masinha2,
It is a clear maths. The penalty what you pay could be due to a loophole in the power agreement. Normally, when the EB (Electricity Board?, Utility supplier)supplies you the bulk power at EHV, you shall define the location of Point of Common Coupling (PCC). Normally, it is in the customer premises. If you have agreed the PCC somewhere far away from your premises, you are getting penalised, which could be avoidable, by reviewing the tariff metering location and moving the same to PCC.

I am sure presently you are also paying for for the line losses.

 

[Skogsgurra]

OP doesn't say if the PF is capacitive or inductive (the latter seems to be assumed), but he says: "Even though we are maintaining average power factor of receiveing end 132KV voltage around 0.92 but the average power factor of sending end is low around 0.84"

If there's a capacitance involved, cable or overhead or otherwise, and very low load, this makes sense. But, if this is a line with normal load, it doesn't make sense at all if there is not a rather high reactive component in the transmission line.

My questions: Is the PF capacitive or inductive? How heavily is the line loaded?



Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[ijl]

The parameters of the line and load have not given by the OP. I have tried to guess the parameters, as

Load: 111 MVA, pf 0.92
Line: 100 km, modeled in 10 sections. X = 0.44 Ohm/km, R = 0.09 Ohm/km, B = 7.7e-5/Ohm km (realistic, or typical ? )

With these parameters the pf = 0.84 at the source and pf = 0.92 at the load.
See the attached picture.

 

[GTTofAK]

The line is a capacitive load.

 

[jghrist]

There will be I²X reactive losses that will result in a lower sending end power factor. If the line capacitance load V²/XC was higher than the reactive losses, then the sending end power factor would be higher than the receiving end.

The question is - why is the instantaneous pf the same, but the sending end average pf lower? Could be explained by the average load being higher on average than when the instantaneous metering was read.

 

[crshears]

If I'm understanding the OP and follow-up comments correctly, the customer is being [unfairly] billed for reactive power it is not consuming.

Is it not the case that customer charges are always calculated at the point of common coupling? If so, the customer's power factor [iow @ the receiving end] should be the determinant; providing the customer can prove it, being billed for reactive power that flows into said [express?] circuit without the customer's consuming it would provide legal grounds upon which the customer could IMHO take the supplier to court for overcharging.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[stevenal]

I'm not sure why it would necessarily be wrong for a customer to pay for the reactive losses necessary to serve his load. In the end, someone needs to pay. It all depends on the local regulations, rate class, terms of contract, etc.