rayp1
Member
- Location
- Phoenix, Az, USA
New 11-300kVA dry type transformers,480/480V, 3PH, installed side by side at one location. Upon energizing how do we ensure no issues with unwanted tripping from:
a. In rush without significant load.
b. Sympathetic inrush currents from adjacenttransformers.
c. Cold load pickup issues for startups when load ready to start(load profile is mainly resistive circuits).
Here are our settings:
Primary protection is set at125% of transformer rating even though code does allow 150% for secondaryconductor lengths up to maximum of 100 feet and we need to ensure ourconductors are protected by these overcurrent devices.
300kVA, CB 600A but we putthe set at 450A
225kVA, CB 400A needs to be setat 340A
150kVA, CB 250A needs to be setat 225A
75kVA, CB 160A needsto be set at 112A
Do you recommend a certain timedelay setting for source breaker?
a. In rush without significant load.
b. Sympathetic inrush currents from adjacenttransformers.
c. Cold load pickup issues for startups when load ready to start(load profile is mainly resistive circuits).
Here are our settings:
Primary protection is set at125% of transformer rating even though code does allow 150% for secondaryconductor lengths up to maximum of 100 feet and we need to ensure ourconductors are protected by these overcurrent devices.
300kVA, CB 600A but we putthe set at 450A
225kVA, CB 400A needs to be setat 340A
150kVA, CB 250A needs to be setat 225A
75kVA, CB 160A needsto be set at 112A
Do you recommend a certain timedelay setting for source breaker?