138 KV cap bank

[HamburgerHelper]

I am trying to figure out what kind of options I have for controlled VAR support at 138kv. I came across switches offered by Southern State that looked like they could be used to switch cap banks in and out but not break fault currents, which could reduce the number of breakers needed. Synchronous condensers and SVCs look nice and offer a lot of control but they are pretty spendy in comparison to cap banks. ($20/kvar, $40/kvar). What sorts of option are there and how is it usually done?

 

[marks1080]

Do you need variable control? If so you may need an SVC or synchronous condensor. If you use a load break switch then this implies that a fault on the cap bank would take out a significant part of your system. Is this correct? A breaker (or set of breakers) would be a better option if you need to protect against any single contingency affecting load.

 

[crshears]

SVC's are definitely "spendy" - - but you get what you pay for. Having separately isolateable [sp?] branches can be a really sweet feature that allows the SVC to return to service in a derated state if one branch fails, and do not under-appreciate the benefit of smoothly controllable voltage/reactive capability on system operation.

There are places where I wish the company had used two smaller HV caps instead of one big one; the grid has to be able to tolerate the all-or-nothing nature of switching big capacitors under various operating scenarios, and putting toomany eggs in one basket can be problematic.

As to switching caps, my utility only ever used a circuit switcher to switch a 230 kV cap in to and out of service in one location - and that was in a spot where the fault current infeed capability was within the capacity of the circuit switcher to clear a cap fault. There was also a separate SF6 breaker installed as a back-up to the circuit switcher, since all the other breakers in the yard were of the oil-interrupt type. However, due to planned future system reinforcement the circuit switcher was eventually replaced with another SF6 breaker [as part of upgrading all the other breakers in the yard from oil to SF6.



CR

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

 

[rterickson]

Southern States have some good literature on the website for their CapSwitcher line.