Meter Socket SCCR

J

Juandsriv

Member
Location
Costa Rica
Occupation
engineer
¡Claro! Aquí tienes la traducción al inglés de tu consulta:
Hello, greetings from Costa Rica. I'm always very grateful for the valuable contributions I get from this forum.
I have a case with a meter socket that is located very close to the source, a 75 kVA transformer, 240 V, with an impedance of 2.2. The meter base is a UL-listed Milbank Class 200, and right downstream of it is a 200 A, 22 kA Square D breaker, also UL-listed in its respective cabinet.
The problem is that the calculated short-circuit current at the meter base location is around 13,200 A, while the meter base has a 10 kA SCCR. I have seen on some Class 200 meters that there is a note stating that the base can withstand up to 18 kA when paired with a 200 A breaker. However, it does not specify the interrupting rating that the breaker should have, nor whether the breaker must be from the same manufacturer, or if there is a list of compatible breakers for this meter socket.
In summary, I would like to know if it is indeed safe to use this base in this scenario, considering the short-circuit values I have.
In that case, Could this be related to the passing energy limitation that the breaker offers when tripping in a maximum of one cycle, versus the three cycles of support that the meter socket has at 10 kA?
Thank you in advance for your help!
 
Juandsriv said:
¡Claro! Aquí tienes la traducción al inglés de tu consulta:
Hello, greetings from Costa Rica. I'm always very grateful for the valuable contributions I get from this forum.
I have a case with a meter socket that is located very close to the source, a 75 kVA transformer, 240 V, with an impedance of 2.2. The meter base is a UL-listed Milbank Class 200, and right downstream of it is a 200 A, 22 kA Square D breaker, also UL-listed in its respective cabinet.
The problem is that the calculated short-circuit current at the meter base location is around 13,200 A, while the meter base has a 10 kA SCCR. I have seen on some Class 200 meters that there is a note stating that the base can withstand up to 18 kA when paired with a 200 A breaker. However, it does not specify the interrupting rating that the breaker should have, nor whether the breaker must be from the same manufacturer, or if there is a list of compatible breakers for this meter socket.
In summary, I would like to know if it is indeed safe to use this base in this scenario, considering the short-circuit values I have.
In that case, Could this be related to the passing energy limitation that the breaker offers when tripping in a maximum of one cycle, versus the three cycles of support that the meter socket has at 10 kA?
Thank you in advance for your help!
Click to expand...
Did some calculations. Your computed 13.2 kA come from using 3/0 (rated 205A) service drop conductor that is 12 feet long. You can reduce the short-circuit available at the meter socket down to below 10 kA by transferring your watthour meter 74 feet from the transformer pig. Basically, that's like having your service wires UG from the 20-foot 75 kVA transformer pole, across the 10-foot setback from the utlity pole plus a 40-foot building width; meaning the meter will be transferred to the back portion of the building.
 
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