fault analysis

[guest111]

hello

im currently doing a project which is "fault analysis on the power system of marine vessels"

because of the inrease in electrical supply, generation will have to increase to meet demand which will cause unaceptable high fault current a low voltage levels in the power network

the area ive started looing into is variying the z% of the lv transformers and analysing whch % will give the lowest fault current while still operating with in spec (Defstan and Stanag)

ive analysed the effect that will have in the steady state ( voltage reduction and recovery times)and transient states(oscillation etc..)

now im analysing the cost of this against the cost of just upgrading the complex protection circuity

I would love to here your views and made get some pointers of u guys on things that i might have overlooked or not consiered

ps
I`ve heard that the cables have to be extremly secured because at high current the force generated is also high
is this the case?

 

[DougMSOE]

The last time that I did any fault analysis for a marine application was about 20 years ago.
What was found was the typical utility gird fault analysis is not appropriate for marine applications. Each circuit needs to be handled as an ungrounded circuit and with the same tools i.e. mesh, nodal, etc. that other circuits might be analyzed by.
The ship that I helped do the circuit analysis on is still in service and for the most part (if I remember correctly) had a number of inductors as fault current limiters. The thought was that it is easy to replace or go without an inductor but not a transformer. All of the circuit breakers were of the highest fault rating that we could find.
Hope this helps.

 

[jbartos]

Suggestions to guest111 (Electrical) Feb 12, 2004 marked ///\\im currently doing a project which is "fault analysis on the power system of marine vessels"

because of the inrease in electrical supply, generation will have to increase to meet demand which will cause unaceptable high fault current a low voltage levels in the power network
///When it comes to electrical propulsion, higher voltages may be considered to reduce weight, amount of copper, and in some cases dimensions of the electrical hardware. The fault levels will decrease; however, current limiting devices still should be considered, e.g. reactors.\\the area ive started looing into is variying the z% of the lv transformers and analysing whch % will give the lowest fault current while still operating with in spec (Defstan and Stanag)
///The high transformer Z% decreases the short circuit currents; however, it causes an increase in voltage harmonics content.\\ive analysed the effect that will have in the steady state ( voltage reduction and recovery times)and transient states(oscillation etc..)
///Yes, it will cause higher voltage drops and longer recovery times. The voltage drops should not be a major problem since distances on within shipboards are short.\\ now im analysing the cost of this against the cost of just upgrading the complex protection circuity
///The cost will vary since there are not that many marine equipment suppliers, which leads to high dispersions in prices.\\I would love to here your views and made get some pointers of u guys on things that i might have overlooked or not consiered
///If you have nonlinear loads, e.g. motor speed drives, electronics, etc., the harmonic mitigation will be required.\\ps
I`ve heard that the cables have to be extremly secured because at high current the force generated is also high
is this the case?
///Probably, DC cables running separately. The AC cables are supposed to be multi-conductor cables, where forces balance inside because of symmetry.\\