The whole purpose of such capacitors is to produce reactive required by the
load. In the case of loss of load, there can be overvoltages due to these
capacitors. Look at a line with inductive impedance and a load at the end.
Put reactive compensation at the load end and look at the voltage. Now drop
the load and keep the reactive compensation and see what happens to the
In some cases it can be quite drastic- near series resonance.
Don Kelly email@example.com
remove the X to answer
This is mention in a book that I don't quite understand how it happens
"There are several disadvantages to mechanically switched
capacitors. ... If voltage collapse results in a systems in a system
breakup, the stable parts of the system may experience damaging
overvoltages immediately following separation. "
As Don pointed out, having capacitors at the end of an inductive line is a
common practice to compensate for any inductive loads placed on the line.
(having an inductive load on an inductive line results in pretty severe
voltage drop without any compensation)
Mechanical switches that are automatically controlled to maintain line
voltage at the load end will switch caps in/out as load increases/decreases.
But they react rather slowly, they are designed to 'follow' with normal load
When a system starts to trip lines and 'break up', the inductive load can be
lost much faster (like a single breaker tripping). The mechancial switch
won't disconnect the caps fast enough and the large capacitance at the end
of an inductive line can result in very high voltages.
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