Do you also monitor and compare based on loading of the machines? I'm looking at putting a system in shortly and was thinking that machine loading would be important, but perhaps temp (stator I assume) would naturally compensate for this.
I don't think you'll find any "mini" 50KV cable. Even though your talking small power you need substantial insulation thickness for the voltage stress.
One method I've used is puttinng a drive E-stop button next to the disconnect with a label on the disconnect to push switch first. The E-Stop then did a drive shutdown before opening the disconnect.
Depending on the size and bonding of the system your L-G-L fault could have a signifigant impedance in the ground path to limit the fault current. Could the 4160V system have been affected by the path of fault current? If the 4160V is within the system (between the two faults) you could get...
I would think tour "ground" arcing evidence was caused by a L-L fault through earth as rraghunath suggested. The 50/51N could them have tripped on false relaying with the relatively heavy fault current.
What also sometimes occurs is that the phasing of the CT's is wrong, a CT is shorted, or...
I haven't tried to protect a high impedance grounded system but it could have challenges. Ie: discriminating between charging current during faults and ground fault current, at MV this could become a factor depending on the size of the system. Selectivity could also be a challenge.
Could it perhaps be a resonance condition at 17Khz being excited by the arc from the airblast breaker? (I don't think restrike is commom with air-breakers, vacuum mainly)
Generally every few posts there is a tap off of the ground grid that runs up the fabric to the the barbed wire. It is connected to the mesh,posts, and barbed wire with mechanical connectors.
Try these links to NETA standards. Although not in reference directly to power plants, they cover a lot of the equipement contained there in.
http://www.netaworld.org/Category.cfm?CategoryID=25
http://www.netaworld.org/Category.cfm?CategoryID=26
Regards,
Gord
This a real shot in the dark but:
Special breakers are often available which rack into empty cells to ground the load side stabs for maintenance purposes. This "integral ground" breaker may have this function built in such that load side stabs are automatically grounded after the breaker is open.
Transformers have very long thermal time constants, so the thermal affects of motor starting aren't a consideration. (If the motors are VFD controled than there is no large starting current)
10MVA of transformers is definetly enough for 5.25MVA of motors. If your aim is redundancy you may...
I would suggest you get a hold of IEEE Std. 421.4 "IEEE Guide for the Preparation of Excitation System Specifications"
For a generating station this large I would expect some sort of regulating authority would have requirements for reliability (redundancy), stability, response time, etc. I...
In Canada (and the US I beleive) there are three grades of cable used with low resistance grounded systems as we call them.
100% insulation - ground faults clear within 1 minute
133% insulation - ground faults clear within 60 minutes
173% insulation - ground faults can persist indefinitely
An...
In Canada (and the US I beleive) there are three grades of cable used with low resistance grounded systems as we call them.
100% insulation - ground faults clear within 1 minute
133% insulation - ground faults clear within 60 minutes
173% insulation - ground faults can persist indefinitely
