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difference frequency for sychronization

difference frequency for sychronization

difference frequency for sychronization

(OP)
IEEE C50.12 – 2005 define Synchronizing limits:
4.2.2 Synchronizing
Generators shall be designed to be fit for service without inspection or repair after synchronizing that is
within the limits listed in Table 2.
—Synchronizing limits
Breaker closing angle ±10º
Generator side voltage relative to system 0% to +5%
Frequency difference ±0.067 Hz.
Additional information on synchronizing practices can be found in IEEE Std C37.102™-1995 [B8].

We have seen 0.1 or 0.2 Hz as frequency difference. Have you seen another limit?



 

RE: difference frequency for sychronization

IEEE 1547 "Standard for Interconnecting Distributed Resources with Electric Power Systems" shows 0.3, 0.2, and 0.1 Hz frequency differences for 0-500, 500-1500, and 1500-10000 kVa aggregate generator ratings, respectively, when making a synchronous connection to an energized system from one or more distributed resources. Obviously this is meant as a different application than that in C50.12.

xnuke
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RE: difference frequency for sychronization

(OP)
Thank you xnuke.
The 0.067 limit is endorsed by the standard C37.102-1995-item 5.
Interestingly, generator could be fit for service without inspection or repair after synchronizing.

 

RE: difference frequency for sychronization

(OP)
Our PT has accuracy class of 0.3%.
measuring 60Hz wee have an error of 0.18Hz.
How can I measure 0.067Hz ?

RE: difference frequency for sychronization

A PT is not capable of changing the frequency. Frequency in = Frequency out. Accuracy class of a PT relates to voltage.
Regards
Marmite

RE: difference frequency for sychronization

(OP)
marmite,
We measure Frequency by PT, that means we convert voltage TPs value in Hz. (Hz= k * Vpt). All error in PT will be transfered to measuring.
 

RE: difference frequency for sychronization

I'm kind of lost with this post.  I'll assume the referances are to conditions before synchronizing.  If that is the case the extremely small frequency deviations can be measured with a "stop watch"

for a o.o67 hertz error, that would be 15 second "sweep" on the synch scope.

the 0.2 hertz error would be a 5 second clock. While I'm not an operator, that seems pretty fast to be closing in

RE: difference frequency for sychronization

Any frequency measuring error is in the device computing frequency, it is not in the PT.  The PT could have a 50% magnitude error and a 90 degree phase shift and still not make a whit of difference in the determination of frequency.  Find your problem elsewhere.

RE: difference frequency for sychronization

(OP)
-some fellow engineers from the maintenance area say the tests will prove difficult difference values below 0.12 Hz frequency in the synchronizers.
- I know of no electric utility that adopts 0.067 Hz limit.
-The national electric system operations in Brazil (ONS) suggests values of 0.1 or 0.2Hz.

Do you know any colleague or concessionary questioning the viability of this limit (0.067)?

 

RE: difference frequency for sychronization

(OP)
extracted from "Fundamentals and Advancements in Generator Synchronising Sistems- Thompson, Schweitzer
.."IEEE Standard 67.................. However , in practice, wider limits are often applied because the prime mover control is not fine enough to reliably achieve a 0.067 slip.

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