Utility lingo

Tainted

Tainted

Senior Member
Location
New York
Occupation
Engineer (PE)
I received a service determination from Con-Edison, they give me the inrush current frequent and infrequent amps

What is the difference between frequent inrush current and infrequent inrush current? see below

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My understanding is it has to do with when the breaker closes and core saturation. Frequent inrush would be the breaker closing at the peak on the sine wave. Infrequent would be it closing on the zero crossing.
 
Is this from a load study of your customer by the POCO ?
Seems like the utility was recording the Inrush current seen *to* the customer for power quality purposes.
If they are running a large single phase load requiring a frequent inrush current above a certain number, the POCO might want capacitors or something installed to cap inrush to a value acceptable for their network, apparently your customers values are acceptable. Problem customers might be metal fab with lots of single phase welders, or a Hospital imaging like MRI or X-rays, that equipment might have a frequent inrush that causes issues for other customers. Just my guess.
 
Never heard of a "Service Determination", but I think they are giving limits for allowable inrush current from the customer. You'll have to ask them to define "frequent" vs "infrequent".
 
Hv&Lv said:
My understanding is it has to do with when the breaker closes and core saturation. Frequent inrush would be the breaker closing at the peak on the sine wave. Infrequent would be it closing on the zero crossing.
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I don't know whether the utility has a breaker before the service end box

Elect117 said:
I had never heard of the term either.

Maybe this will help?


Sounds like a way to plot damage curves.
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The link you showed talks about frequent vs infrequent faults, but this is about inrush current

tortuga said:
Is this from a load study of your customer by the POCO ?
Seems like the utility was recording the Inrush current seen *to* the customer for power quality purposes.
If they are running a large single phase load requiring a frequent inrush current above a certain number, the POCO might want capacitors or something installed to cap inrush to a value acceptable for their network, apparently your customers values are acceptable. Problem customers might be metal fab with lots of single phase welders, or a Hospital imaging like MRI or X-rays, that equipment might have a frequent inrush that causes issues for other customers. Just my guess.
Click to expand...

How it works is I give utility the load and they give us these statements on how they will reinforce the service at their end, so I don't know what they do on the backend. This is a residential and commercial building, not with any complicated loads
 
Tainted said:
How it works is I give utility the load and they give us these statements on how they will reinforce the service at their end, so I don't know what they do on the backend. This is a residential and commercial building, not with any complicated loads
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You check your main breaker with values by Con Edison for fault interrupting capacity', not trip frequent and infrequent inrush currents
 
Tainted said:
I don't know whether the utility has a breaker before the service end box


The link you showed talks about frequent vs infrequent faults, but this is about inrush current



How it works is I give utility the load and they give us these statements on how they will reinforce the service at their end, so I don't know what they do on the backend. This is a residential and commercial building, not with any complicated loads
Click to expand...
What is the calculated load? 1200A?
 
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