another FP stab-loc

[Paul W. Abernathy]

Originally Posted by dmacy

I have a panel I can send you. What address should I use for shipping?

Paul W. Abernathy
180 Crestridge Court
Harrisonburg,VA 22802

Include a few breakers if you have them....I will do a nice presentation on them....

[George P. Wells, CMI]

Originally Posted by jszczesny

I had one in my house 5 years ago, I was changing out a outlet without killing the circuit, I shorted it, no circuit trippped.
Later that night my house lights are fading in and out. I call out my electricial, we open the meter case, meter sockets is melted in half and arcing. I almost burned down my house.

Need I say more, looked like a clean panel when I moved in.

That is a classic example of what can happen when a breaker fails. The breaker should have tripped, thus clearing the original fault. In a system that is properly designed and assembled, the protective device nearest to the load or the point of the fault, will clear the fault. Available fault current in a residential system is usually assumed to be 10,000A. That actual AVC is going to be something less than that. It is determined by the combined impedance of the transformer and the service conductors.

The current that flows during a fault also depends on the nature of the fault. Assuming it was a very low impedance fault, it is likely that at least 5,000A was flowing for a short time. It doesn't take long for 5,000A to do some serious damage. You probably cleared the fault yourself. The meter socket should not have been damaged but the stab locks on meter sockets are among the most likely points for a fault to clear. All faults will eventually clear.

Transformers are fuses on the primary side. They will easily clear a transformer fault but usually will not clear a fault in a house. Consequently, meter socket failures are not all that uncommon. All residential loads have two protective devices in series. In the event that the one closest to the fault does not clear the fault, the next one upstream should.

Another contributing factor to meter socket damage is that the meter socket is not a vacuum. As soon as the fault current begins to flow, connections can loosen and the surrounding air is ionized. Ionized air is conductive. Normally, it is extremely difficult to establish an arc at low residential Voltages. However, once an arc is started, it will continue until it is extinguished. At such low Voltage, an arc cannot bridge more than a millimeter or two. The arc is usually extinguished by expanding metal separating enough to break the arc or by enough metal melting away to break the arc.

You mentioned that everything looked clean before the fault occurred. That is also common. One thing you can do is a white-glove test. Faults leave carbon deposits that are not always visible. Wipe the breakers with a white tissue or cloth. If you pick up carbon, there is a chance that there may have been a fault at some time in the past. However, the white-glove test is far from definitive.

[George P. Wells, CMI]

Originally Posted by dmcmullen

Unfortunately, I have two of these installed in our house as of now. About three years ago a critter got into the sub station, about two blocks away and shorted things out. The power surge that followed was out of this world when PG&E turned the power back on before investigating. We had three or four appliances blow the internal fuses and thermistors. With the amount of power that was flowing through the house there was not a single breaker that opened. They suddenly moved up on the old to do list.

David

David,

The problem you experienced was more likely a sudden rise in Voltage than power. In order for there to be power, there needs to be a load and both Voltage and current. The Voltage and current also have to be in phase. Breakers are designed primarily to interrupt the flow of current.

Some devices are more susceptible to a sudden rise in Voltage than others. Generally speaking, any device with an inherently high input impedance is at greater risk than one with a lower input impedance. That may seem counter-intuitive but the reason is that a lower impedance input component can clamp the Voltage but a higher input impedance component cannot. That is why static electricity can damage certain electronic components even though there is almost no current flow.

The important thing to understand is that there is a difference between a fault current and a Voltage rise. Breakers are intended clear faults that involve current flow, not high Voltage. Other types of devices clamp Voltage. It is much easier to predict and control fault currents than Voltages.

[David C. Macy]

Originally Posted by pabernathy

Paul W. Abernathy
180 Crestridge Court
Harrisonburg,VA 22802

Include a few breakers if you have them....I will do a nice presentation on them....

Just noticed your post, I will ship tomorrow, should get next week. I have breakers for you as well.

[Brian E. Kelly]

New Fangled Electric Fence

[Jeffrey R. Jonas]

Originally Posted by bkelly2

New Fangled Electric Fence

Zoned also! Reminds me of Jurassic Park!