parallel transmission lines 2

[msasd2020]

1-ATTACHED DIAGRAM IS SHOWING 2 LINE ARE GOING 2 STATION IN SAME TOWERS
2-SHUNT REACTOR L1 & L2 ARE REVERSED
3-TL1 IS LOADED
4-CBs of TL2 is off and shunt reactor is connected to the line and earthing switch not applied from both sides

we found the voltage on the line TL 2 is 150 kv & 150kv & 120 kv so the question is why this high voltage is appearing on the line ? due to shunt reactor phase reversing or there is another thing

 

[magoo2]

If the two lines are close to each other or share a common structure, you could be seeing what has been termed near resonant coupling. The energized line is the source and there is capacitive coupling to the "de-energized" line. With a shunt reactor on the open line, you can have a tuned circuit.

I remember seeing an IEEE paper on the subject where there was two 345 kV lines on the same structures and the de-energized line had a shunt reactor on it. Two of the authors were Hesse and Wilson. I'll search for the paper and give you the title.

 

[FPelec]

This is a well known issue when de-energized shunt compensated overhead lines are installed nearby other HV overhead lines.
You can find several technical papers dealing with failures caused by this issue:

http://uni-obuda.hu/journal/Samimi_Abedini_Mostajabi_Farokhzad_Ayoubzadeh_Akmal_Mohseni_47.pdf

http://www.esbi.ie/news/pdf/white-paper-transmission-line-construction.pdf

Si duri puer ingeni videtur,
preconem facias vel architectum.

 

[msasd2020]

what is the relation between 2 phases reversed in shunt reactor and increasing of line voltage
by other meaning what is effect of revering shunt reactor phases on the transmission line
attached photo for line relay reading

 

[FPelec]

what do you mean for "reversed phases" on the shunt reactor?
If you refer to different correspondances between shunt reactor bushings and overhead line phases, it should not have any significant effect, as the positive and negative sequence impedance of a shunt reactor are the same.
BTW, as you can see from the line relay reading, the induced voltage is almost all at zero sequence.


Si duri puer ingeni videtur,
preconem facias vel architectum.

 

[crshears]

Are there any transitions anywhere along the circuit length, meaning are the phases "rolled" to balance out mutual coupling between phases? Outside Ottawa, Ontario, Canada there is a very wide corridor with a pair of 500 kV lines in the centre, 230 kV lines on either side of that, and 115 kV lines on the very outside beyond those; causes major headaches on the lower tension lines due to capacitive/inductive coupling...

Hope this helps.

CR

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

 

[msasd2020]

You can see the voltage for L1&L2 is more than phase L3 . and as per the diagram there is different correspondence between the shunt reactor and line phases on L1&L2 .
Another thing I can add it when we disconnect the shunt reactor the voltage disappeared and became 10kv
I caould not energize the line with reactor because synchro check relay was blocked due to 150 kV which was appeared on the line. as per relay settings the OHT line voltage at dead case should not be more than 13kv
Please how can I solve this problem?
the problem is coming from the shunt reactor or another thing else .
Also no transitions anywhere along the circuit lenght

 

[FPelec]

Most shunt reactors have a 5-limb core. This means that there is negligible magnetic coupling between shunt reactor phases: as a consequence the correspondence between shunt reactor bushing and OHL phases does not cause any difference in induced line voltages.
Slight differences in induced voltages magnitudes could be caused by unbalanced capacitances between OHL phases.
As explained in Marta's paper, the only parameter you can change (assuming that line geometry cannot be changed) is the shunt compensation degree: if the shunt reactor is equipped with a tap changer, you may evaluate operation on a different tap or evaluate the installation of an additional reactor between reactor neutral and ground; some preliminary calculations should however be performed in order to avoid even more severe overvoltages.
Can you give us more detailed information, like line lenght and p.u.l. parameter, shunt reactor size and construction?
Otherwise, you could try to energize the line without the shunt reactor and to connect it after line energization. Obviously this is possible only if the shunt reactor is connected to the line with a circuit breaker.
Another simpler solution could be to manually bypass the synchro check relay.
By the way, given the relatively low transmission line voltage, IMHO the best solution should be to connect the shunt reactor to the busbars with a dedicated bay.

Si duri puer ingeni videtur,
preconem facias vel architectum.

 

[msasd2020]

Dear FPelec

line trap and coupling voltage transformer also connected to the OHTL . can you tell me what is the relation between line trap or ccvt and shunt reactor

 

[FPelec]

dear msasd2020,
line traps as well as capacitive voltage transformers have no impact on parallel resonance.

Si duri puer ingeni videtur,
preconem facias vel architectum.