Please, can you help? For many countries, I can't find a typical price per kilowatt-hour for industrial customers in 2005.
If you have some information that I could use, or even an estimate, please send me an e-mail - Alex@PowerStandards.com
In fact, I've become quite skeptical about many instruments that are "certified" for Class A.
If you would like a copy of PSL's Test Protocol, I would be glad to share it - just send me an e-mail - Alex@PowerStandards.com. Meanwhile, unless the instrument has a Certificate from an authoritative Calibration Lab, I would be scratch my head and think carefully before assuming it really is Class A.
My program for engineers and students, the Power Quality Teaching Toy, keeps on growing.
It's free, so there's no support - sorry...
In Europe, the Leonardo Power Quality Initiative (lpqi.org) tells me it is among their most popular downloads.
Some ideas for future updates: Mats Hager in Sweden has some interesting ideas about transformers and phase shift, and I think Willem Meijs in Holland would find transformer impedance simulations useful. Do you have ideas? Please send them to me.
Also, if you would like to translate the program into an additional language, I would be grateful. (At the moment, I can only work with translations in Roman characters, so Japanese, Arabic, Russian, Korean, Chinese, Thai, etc. will have to wait.)
Free Windows-based power quality teaching program
from Power Standards lab
In my last newsletter, I asked if anyone could explain the mechanism that links forest fires and voltage interruptions.
Richard Schomburg of Electrict=E9 de France provided the most concise answer. He remembered an old report from CESI (Italy) that said the first cause of dielectric rupture is in fact the air temperature at about 800=B0C because of a much lower gas density, the second cause is the presence of carbon particulates that fragment the interval, finally the ionization if much higher temperature are reached. Xavier Momo, also of EDF, points out another mechanism: dilatation of cables actually makes them hanging closer to the ground......and creates a dielectric insulation reduction. He is not sure that 800=B0C would be enough to have a significant ionization effect.
I did a little web-based research myself on plasma -- gases that are sufficiently hot that their electrons travel freely, i.e. the gas is a conductor. Research papers on plasma consider "low temperature" to be in the range of 2000 degrees C, and "low voltage" to be in the range of 5 million volts (!). It appears that plasma in air requires at least 1500 degrees C at atmospheric pressures. The temperature of a forest fire at its hottest point is about 800 C - only half the temperature necessary for plasma. So I would be inclined to look towards the carbon particulates and cable droops, and not so much towards plasma, for the initiation of an arc. Of course, once the arc starts, the temperatures can certainly rise to plasma levels.
P.S. During an informal conversation last week in Sweden, Ulrich Minnaar of ESKOM (South Africa) mentioned an interesting solution that I don't quite understand. Apparently transmission line voltage dips can be reduced by encouraging sugar cane farmers to burn their fields at a different time of day - a simple, low-cost solution. If only it could be applied to forest fires!
PSL uses a custom transformer to make 200-amp, 3-phase power
at every world-wide voltage from 100 volts to 600 volts. Useful for
testing industrial equipment...
I have continued to receive interesting correspondence on the topic, and I think I will let my old friend Francois Martzloff have the final word, who writes:
"My own recommendation in a surge-prone environment, dating back to GE days and taught to me by Frank Fisher and Keith Crouch, was definitely to ground both ends of the cable, but to do that at one end via a pair of two or three series-connected power-rated diodes in anti-parallel connection: the forward drop of each string is sufficient to block the power-frequency current that tries to flow between distant grounds at different potentials, but in case of a difference caused by a surge, the diodes allow part of the surge current to flow in the shield, producing the zero-sum effect so well described by some of the contributors. This produces a glitch in the data transmission during the surge, but protects the connected equipment during that surge."
Francois's very useful archive covers almost everything that is known about surge protection in low-voltage AC circuits. I recommend it.
In the next few months I will be in Hong Kong, Malaysia, Canada, France, China - perhaps we will get to say hello somewhere. In any case, I will always be glad to hear from you via e-mail.
With best wishes -