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Capactor banks on short circuit analysis
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Author:  js.cardenas170 [ Mon Nov 12, 2018 8:52 am ]
Post subject:  Capactor banks on short circuit analysis
Hi everyone!


I would like to know if you would disconnect the capacitor bank for short circuit analysis under ANSI C37.010, in order to design a more conservative scenario of the power system.


Thanks for your time and your answers


Juan.
Author:  Jim Phillips (brainfiller) [ Thu Nov 15, 2018 1:20 pm ]
Post subject:  Re: Capactor banks on short circuit analysis
Capacitors are not typically modeled as part of a short circuit study. Below is a quote from IEEE 551 regarding capacitors and short circuit calculations:

Capacitor discharge currents from power factor correction capacitors or harmonic filters
have not previously been considered in the ANSI or IEC calculation procedures. The
stresses associated with capacitor discharge currents are different than typical fault
conditions due to the high-frequency components present within currents and the
extremely fast time constants of the capacitor circuits. These conditions may affect
equipment sensitive to high-frequency currents.

Based on the simulations shown in this chapter, capacitor discharge currents will have no
effect on breaker parting or clearing operations. Some small additional stresses may be
imposed for the closing and latching duty for very large capacitor banks. However, it
should be noted that the models developed in this chapter were sized larger than standard
design practices in order to determine any potential problems.
At this point, the standard cannot recommend that capacitors be added to system
simulations for breaker duty calculations. The existing ANSI C37 series fault calculation
methodologies remain adequate for the determination of breaker, fuse, and switch duties.

Hope this helps.
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