Transient and subtransient reactance of alternators

In summary: Generator fault current is caused when there is a problem with the generator. The generator creates electrical power, but sometimes there is a problem with it and the power isn't as good as it should be. This can happen with a lot of different things, but the most common reasons for generator fault current are problems with the rotor or the stator. If the rotor or stator isn't working properly, then the generator can't generate the correct amount of current and that will cause fault current to flow.
  • #1
arun babu
8
0
please explain the transient and subtransient reactance of synchronous machines
 
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  • #2
I assume you're referring to Fortescu's analysis of 3 phase machines. Its a mathematical representation of 3 phase systems that makes analysis easier in some respects. There are other, more experienced members on this forum who could answer your question better.

As an example, I think the Buccholz relay in transformers measures negative sequence currents within a range to raise alarms. This is only possible because we can measure the negative sequence current accurately. Practically it is useful, so we translate the known quantities to better understand the system. Another example is that zero sequence current interfers with communication lines. Thus, we can attribute that interference to a particular component of electrical power. Sorry if this doesn't help.
 
  • #3
oops...that was not what i was looking for...anyways thanks for the info..in fact i hope to get a very down to Earth and easy to understand explanation on the said topic ie transient and sub transient reactance of alternators...
 
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  • #4
arun babu said:
oops...that was not what i was looking for...anyways thanks for the info..in fact i hope to get a very down to Earth and easy to understand explanation on the said topic ie transient and sub transient reactance of alternators...

Well, you need to start by telling us what you know so far, and what sources of information you have used.
 
  • #5
berkeman said:
Well, you need to start by telling us what you know so far, and what sources of information you have used.
i have learned that it is concerned with the induced current in damper winding and field winding of synchronous machines..which is divided into transient period and sub transient periods
 
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  • #6
Generator fault current is normally discussed in terms of “subtransient,” “transient,” and “synchronous” currents and impedances. These terms refer to various time periods during the decay of the AC component of current. Attached Figure plots the envelope of the AC current for a typical machine. The subtransient current, reactance and related time constant defines the AC current component from the inception of the fault and the following cycle or two. This is the maximum available AC short-circuit current from the generator. Synchronous quantities define the final or steady-state current. The transient parameters define the interim current.:rolleyes:

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Creative thinking is breezy, Then think about your surrounding things and other thought products. http://electrical-riddles.com
 

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  • #7
thank you m.s.j. could you please explain how generator fault current arises?
 
  • #9
is there any kind of flux variation during the transient state n in the final steady state ??
 
  • #10
Any emf without flux variation is impossible. Please more explain.

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Creative thinking is breezy, Then think about your surrounding things and other thought products. http://electrical-riddles.com
 

1. What is the difference between transient and subtransient reactance?

Transient reactance is the measure of the ability of an alternator to withstand sudden changes in load, while subtransient reactance is the measure of its ability to withstand short-circuit faults. Transient reactance is higher than subtransient reactance, as short-circuit faults are more severe and require a stronger response from the alternator.

2. How are transient and subtransient reactance values determined?

Transient and subtransient reactance values are determined through testing and analysis of the alternator's electrical and mechanical characteristics. This includes measurements of inductance, resistance, and other parameters that affect the alternator's ability to respond to sudden changes in load or short-circuit faults.

3. Why is it important to know the transient and subtransient reactance values of an alternator?

Knowing the transient and subtransient reactance values of an alternator is crucial for properly designing and operating a power system. These values are used to calculate the alternator's response to transient events and short-circuit faults, which can affect the stability and reliability of the entire system.

4. Can the transient and subtransient reactance values change over time?

Yes, the transient and subtransient reactance values of an alternator can change over time due to factors such as aging, wear and tear, and changes in operating conditions. It is important to regularly monitor and update these values to ensure the continued safe and efficient operation of the alternator and the power system.

5. How can the transient and subtransient reactance values be improved?

The transient and subtransient reactance values of an alternator can be improved through design modifications, such as increasing the number of turns in the rotor windings or using different materials. However, these changes must be carefully considered to avoid negative impacts on other parameters and overall performance of the alternator.

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