Shunt reactor impact on cable charging current

[aslamajec123]

we are working on cable ampacity calculations for 400kv 40km length HVAC subsea cable connecting offshore PV generation plant to the grid . Due to space restriction it will be possible to provide shunt reactor at the sending end only (generation end) . In this regard I would like to know if providing the adequately sized shunt reactor at sending end will compensate the capacitive charging current in the subsea cable and thereby reduce the overall current flow in the cable ? Do I still need to consider the capacitive charging current of the cable in addition to load current while sizing the cable ? Or is it that overall current in the cable will be reduced only if the shunt reactor will connected at receiving end since in this case unlike the previous case both capacitive charging current and inductive current drawn by the shunt reactor will flow through the cable and compensate each other which may reduce the overall current in cable ?

 

[waross]

Consider power factor correction of a motor.
This is a correction capacitor in parallel with induction, (The motor)
You are proposing an induction in parallel with a capacitor.(The cable)
The electrons will not know the difference.
Compared to the motor circuit:
Supply to connection point; current reduced.
Connection point to Induction; no change in current.
Connection point to capacitor; no change in current.

 

[aslamajec123]

Consider power factor correction of a motor.
This is a correction capacitor in parallel with induction, (The motor)
You are proposing an induction in parallel with a capacitor.(The cable)
The electrons will not know the difference.
Compared to the motor circuit:
Supply to connection point; current reduced.
Connection point to Induction; no change in current.
Connection point to capacitor; no change in current.

Thanks for your response . If I have understood rightly , providing the shunt reactor at sending end will not have any impact on total current flow in the cable ;rather it would be only useful if shunt reactor will be connected at receiving end which may reduce the current in cable as well as current drawn from the source and mitigate the Ferranti effect as well .not sure providing the reactor at sending end alone will be useful to control ferranti effect ?

 

[waross]

not sure providing the reactor at sending end alone will be useful to control ferranti effect ?

No effect.

400kv 40km length HVAC subsea cable

How much will 40 km of 3 conductor, 2500 sq. mm. cost?
Start considering multiple smaller cables in parallel as dpc has suggested in your other thread and cut your cable cost in half.

 

[bacon4life]

As a super simplified problem of how to maximize real power transfer across the cable, the transfer can be maximized by controlling voltage at each end of the cable to force half of the reactive current to flow from each end. Shunt inductors can be a tool control voltage, as well as to avoid having a local source for the inductive reactive power needed to offset the cable capacitance.

However, in a generator context, the generation plant likely need to be able to supply both real and reactive power at the Point of Interconnection. During times when the plant needs to supply power to an inductive load, having extra inductance on the generator end of the cable will not impact the cable ampacity.