Multiple Generators Onto Single Transformers
Multiple Generators Onto Single Transformers
(OP)
A client has a temporary installation of 4 x 600kw 400v generators connected to a 400/11,000v 3MVA step-up transformer.
The generators are self-contained mobile units, each with its own circuit breaker. Each generator is cabled from the load-side of its circuit breaker to the LV terminals of the transformer, making the LV transformer terminals a common bus. There is no other 400v load, and the 11,000v feeds into an MV switchboard.
The client has been advised by somebody that additional circuit breakers must be installed at the load-end (transformer-end) of each set of generator cables, but his advisor was unable to provide any reasons why, other than "it is bad industry practice".
Can anybody please confirm if these circuit breakers are required, and why/why not.
The generators are self-contained mobile units, each with its own circuit breaker. Each generator is cabled from the load-side of its circuit breaker to the LV terminals of the transformer, making the LV transformer terminals a common bus. There is no other 400v load, and the 11,000v feeds into an MV switchboard.
The client has been advised by somebody that additional circuit breakers must be installed at the load-end (transformer-end) of each set of generator cables, but his advisor was unable to provide any reasons why, other than "it is bad industry practice".
Can anybody please confirm if these circuit breakers are required, and why/why not.






RE: Multiple Generators Onto Single Transformers
RE: Multiple Generators Onto Single Transformers
But as David says, you may have code requirements which overrule engineering decisions.
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RE: Multiple Generators Onto Single Transformers
All four generators can operate in parallel. The client's concern is more about any potential protection issues (rather than loss of supply).
RE: Multiple Generators Onto Single Transformers
But back to the original question, there may be code issues and apart from code issues, the distance and cable installation details of this particular installation would probably influence the recommendations on the second breakers.
If the transformer is very close to the generators, the second breaker may not be recommended. With a long distance from the generators to the transformer and cables subject to possible damage, the second breaker would probably be recommended. In between, "It depends".
Bill
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