Line voltage drop
09.08.2008 12:54
I was looking at the input and output voltage history of my server's UPS the other day and I noticed this line voltage drop or around 10 volts that occurred sometime in July:
Digging some more into logs I found out that this drop coincides with an hour long black-out in the morning of 14 July. Being a bit suspicious about the quality of the voltmeter built into a cheap UPS I also checked the current UPS input voltage reading against a multimeter and they matched to within 1 V.
It looks like this is still well within the allowed limits though. According to my electrical engineering handbook Slovenian distribution network complies with IEC 60038 standard, which permits tolerances of +6% and -10% from the nominal 230 V. So as long as the there is more than around 200 V in the sockets, I can't complain.
Still it's interesting why this happened. I find it hard to believe that such a consistent drop would be caused by a large load being connected to the network. This is a residential area and people don't tend to run large machinery in their basements. The time of the blackout (from 11 to 12 am) suggests that it was because of planned maintenance (they don't usually tell you about those).
It's possible that the ratio of the local transformer got changed for some reason. Someone closer to it could have complained that they're receiving voltage that is too high. Or perhaps the cause is somewhere further upstream. Maybe a transmission line is out somewhere and they are providing power to our neighborhood through some new route that is has a higher load.
Zanimivo bi blo se frekfenco vidt... ceprov jo je tezko tok natancno zmert, ker ko je omrezje preobremenjeno (recimo da izpade par vecjih elektrarn v evropi), razn padca napetosti pride tud do zmanjsanja frekfence (sicr zelo zelo malo, sam izmerljivo).
Je pa zanimivo da se je tok spustil... ponavad na trafoju pred zimo dvignejo napetost, spustijo jo pa cim je konc grelne sezone,... ne pa tok pozn. Razn ce niso zaostajal s cem... :)
Hm. Nisem se slišal, da bi se zaradi obremenjenosti znižala frekvenca. Veš mogoče, kakšen je vzrok za to?
UPS sicer tudi meri frekvenco, ampak še zdaleč ne dovolj natančno, da bi se karkoli videlo (kaže ali 50.0 ali 49.9 Hz).
Kokr se jst spomnm (ker sm mal spau na predavanjih).... amm.. ce je omrezje preobremenjeno, morjo generatorji proizvajat vec moci/energije, torej se poveca navor, in pri isti zunanji (vhodni) moci se zmanjsa frekfenca vrtenja generatorja. Ker so to sinhronci se spremeni tud frekfenca. Seveda ker je use skupi povezano na togo omrezje, se to dogaja samo kadar je celo omrezje preobremenjeno (drugace tece energija od drugje, kjer ni preobremenjeno). Seveda zarad regulacije je ta frekfenca ponavad zlooo zloo blizu 50Hz, al pa se celo omrezje sesuje (kar se je ze dogajalo :)) ce bom nasu knjigo lahk pogledam ce je se tm kj bl natano napisano, ker sm pr strojih kr dost spau, se pa spomnm da je prfoks omenju tud spremembo frekfence pr preobremenjeni mrezi.
