Thanks for the replies.
The system is 600V, and proposed generation would be up to 5MVA (multiple parallel units), so the LG current would be quite significant.
No breakers would be spec'd as slant rated. However, a 4 pole ATS would be needed to separate the grounding systems.
Given this...
Hello,
I'm wondering if anyone can point out any obvious drawbacks to having a normal source (utility) solidly grounded (3P 4W system), with an emergency system (separately derived) impedance grounded. All circuit breakers within the main and emergency distribution would be 4 pole. There would...
Shunt trips can be used for remote tripping or allow another protection element to trip the breaker. For example, an LSIG MCCB will inherently provide phase and ground overcurrent protection but an external 27/47 to a shunt trip can add undervoltage/phase balance elements to the breaker.
Hi sajujsam,
The Lee (1982) equations shown in Table D.1 are for incident energy and not the bolted fault current. Keep in mind that the Lee method is theoretically derived and is very conservative. If you read the appendices of the IEEE 1584 standard, you can see how Lee's incident energy...
Arcing current is a function of voltage, conductor gap, enclosure type, and most importantly, the bolted fault current.
Clearing time is a function of the arcing fault current and the protective device time-current characteristics.
Arc flash energy is a function of clearing time and arcing...
Hello,
Has anyone ever seen or used an Arc Terminator or similar device (crowbar) in a switchgear lineup for arc flash/blast mitigation? I'm trying to see how prevalent the usage of these devices are, and if anyone think they will become more widely used.
Where do people think the arc flash...
What type of study? If you are doing a fault, coordination or arc flash study you will need the positive and zero sequence Thevenin equivalent impedance at the system connection point (which translates into the LLL and LG amps with the X/R ratios).
Okay, thanks for the responses. I now realize my question requires further info.
1. I have only seen relays which initiate a tripping signal based on the filtered rms value (ie. the signal sent by the CT and filtered for DC and harmonic components). Is this for the most part correct?
a...
This would be for medium and low voltage systems, instantaneous element (50), and probably between 1-10 times pickup. For high multiple values where CT saturation poses an issue, I'm also unsure how quickly the relay can recognize the actual rms current.
Hello,
I am wondering if anyone has run across any whitepapers or IEEE articles relating to ultrafast tripping times. I am trying to find, given our current technology, what the fastest time a relay can initiate a correct trip signal is.
As of right now I cannot find anything where the required...
