Delta-Delta Transformer bank, Phase loss and Ground fault
Delta-Delta Transformer bank, Phase loss and Ground fault
(OP)
I have a Delta-Delta transformer bank, 13,200-480. I would like to monitor both phase loss(ie. loss of a primary fuse) and ground fault on the secondary.
I would like to send a signal to trip a shunt trip molded case circuit breaker during a phase loss to prevent single phasing loads and alarm for a ground fault.
Any ideas. I know I can use the Ground Detection Lights for the ground fault, but is there a relay that can handle both.
Whats the best way?
I would like to send a signal to trip a shunt trip molded case circuit breaker during a phase loss to prevent single phasing loads and alarm for a ground fault.
Any ideas. I know I can use the Ground Detection Lights for the ground fault, but is there a relay that can handle both.
Whats the best way?






RE: Delta-Delta Transformer bank, Phase loss and Ground fault
See http://www.schneider-electric.ca/www/en/products/ground...
For loss of phase detection, see
http://basler.com/downloads/practical.pdf
RE: Delta-Delta Transformer bank, Phase loss and Ground fault
As implied in the original post, there are two conditions that should be handled in different manners. The problem with low-voltage ungrounded-system transient overvoltage and consequent insulation damage {often in motors} has been acknowledged in power-systems publications for 50 years. Adaptation/retrofit to high-resistance grounding and associated indication/annunciation is well recognized in various electrical publications.
Phase “loss” or imbalance is a bit trickier. Voltage-imbalance detection is adequate to inhibit starting of a group of motors, but has significant limitations in protecting motors once they are running. Unfortunately, once motors have accelerated and settle to namplate current, voltage-imbalance sensing has serious limitations, and in many cases is quite useless. Current-imbalance protection is far more effective, but cannot reliably be applied to groups of motors.
There are a number of “ice-cube” type devices that promise to protect against electrical ills and look good in advertisements, but in terms of reliably protecting against equipment damage and production loss leave a lot to be desired.
A search in electrical topics at Eng-Tips under ‘ungrounded’/’high-resistance grounding’ and ‘phase loss’/‘phase imbalance’ will yield discussion on the matter.
RE: Delta-Delta Transformer bank, Phase loss and Ground fault
I have a Delta-Delta transformer bank, 13,200-480. I would like to monitor both phase loss(ie. loss of a primary fuse)
///Some disconnect switch manufacturers offer the blown fuse monitor with their product as an option. E.g. see
http://www.pringle-elec.com/bolted.html
\\\
and ground fault on the secondary.
///Modern electronic circuit breakers do have this feature available via the electronic trip unit, e.g. Square D Micrologic.\\\
I would like to send a signal to trip a shunt trip molded case circuit breaker during a phase loss to prevent single phasing loads and alarm for a ground fault.
///See the Pringle Blown Fuse Detector. It can open the switch.\\\
Any ideas. I know I can use the Ground Detection Lights for the ground fault, but is there a relay that can handle both.
///See above comments\\\
RE: Delta-Delta Transformer bank, Phase loss and Ground fault
For ground detection, I recommend you use the wye connected resistors approach rather than PTs. The latter can develop ferroresonance effects under certain conditions and the resistors work just fine in a 480V application. I'm away from the office and can't think of a brand name but there are companies who offer them in a NEMA 12 or other enclosure with audible and visual alarms and dry contacts for remote indication or tripping.