On 8/25/21 10:25, Mel Beckman wrote:
Jay,
No, because transformers work in both directions :)
I think you mean, "Yes, because transformers work in both directions."
First of all, I absolutely agree that no one should attempt to energize
their home wiring with a standby generator unless there is a proper
transfer switch in place. I very much understand the safety concerns.
The question that Ethan raised makes sense, however. If power to several
blocks is out and I connect my little 2KW Honda to my house wiring
without a transfer switch, because transformers work in both directions
my generator will see the load of the whole neighborhood. This will
immediately and severely overload the generator and at best cause it to
stall out or trip its output breaker, at worst to fail catastrophically.
In the very rare case that the outage is at the fuse on the pole pig
feeding just my house or that of me and one or two neighbors, then
indeed the generator may continue to run and that transformer will have
distribution voltage of 4KV or so on the utility side, a very dangerous
condition. That's a pretty unusual situation, however. Typical power
outages are substantially more widespread. My little generator would be
looking at the load of the entire outage area reflected through the
(bidirectional as you note) transformers. The load of half the town
will, as Ethan speculated, completely overwhelm any practical
residential standby generator to the point that it stops producing power
either by failure or by tripping its breaker.
Even if the generator were massive and survived, its branch circuit
breaker or the house main would trip long before sufficient power to
feed a large area was able to flow back into the utility's wiring.
Yes, connecting a generator without a transfer switch is a horrible idea
and likely to get someone killed, agreed.* However, as the vast
majority of power failures involve more than a single residence, the
generator will fail to produce power immediately anyway due to looking
at essentially a dead short.
* Every time I've seen utility workers working on lines that are assumed
to be dead, the first thing they do is clamp them to ground to be
certain. When the lines are assumed to be live, massive insulation
sleeves, heavy gloves, insulated booms and the like are used.
--
Jay Hennigan - j...@west.net
Network Engineering - CCIE #7880
503 897-8550 - WB6RDV