Picking 0.3333333333 of fault current
Picking 0.3333333333 of fault current
(OP)
Can anyone tell me the industry standard for protecting radial networks. Some publications for example base the "pick up" on a fraction of minimum fault current, typically 1/3 and the time dial settings based on maximum fault current. Still others use peak load current for pick up and fault currents for time dial settings. I really want to know the preferred method and the reasons for it.






RE: Picking 0.3333333333 of fault current
Pick your settings based on:
Coordination (source and load devices)
Arc-Flash hazard management
Equipment withstand
Fault detection for normal and contingent switching line length
Whatever you do, make sure the operators understand the settings and how you predict the system will respond to faults. It really helps with troubleshooting.
RE: Picking 0.3333333333 of fault current
Can you please advise where I can get the IEEE document.
MM
RE: Picking 0.3333333333 of fault current
Refer to the Red book and the Buff book. Look up color series of IEEE standards on the website.
Your question is too vague and at least to me does not make much sense. You do not even mention what type of over current protection you are taking about. Phase or ground? What does the device protect? Cable? transformer? Both? Motor? There are different consideration for different situations and applications.
Fault current comes into play only when setting instantaneous settings. What pick up are you referring to? I suspect it is long time pick up for phase overcurrent protection.
Setting relays is as much an art as science. Bottom line is you must strive to coordinate with upstream and downstream devices. You may not succeed all the time.
Have you compared the curvs of the devices in question on a common plot?? Are you using any software?
RE: Picking 0.3333333333 of fault current