NETA ETT Level 4 case studies
NETA ETT Level 4 · Put your knowledge to work in context.
The NETA ETT Level 4 credential is the fourth tier in the InterNational Electrical Testing Association's Electrical Testing Technician certification ladder, aimed at field technicians who commission, maintain, and troubleshoot power systems and who already carry substantial hands-on test experience. It signals that a technician can work independently on complex apparatus, interpret test results against standards, and take responsibility for acceptance and maintenance testing decisions. The NETA ETT Level 4 case studies are 5 cases and about 3,174 words.
1Arc Flash PPE Decision at a 480 V Motor Control Center
A 480Y/277 V, 2000 A motor control center (MCC) at an industrial plant is fed by a 2500 kVA, 13.8 kV/480 V transformer with 5.75% impedance. The utility reports 42 kA available at the MCC line side, and the upstream main breaker clears in 6 cycles.
726 words, about 4 min2Shunt-Trip Circuit Fails to Trip at 125 VDC
A 125 VDC station battery with 60 lead-acid cells floats at 132 V and supplies the shunt-trip coils for a 15 kV metal-clad switchgear lineup. One feeder breaker fails to trip during a routine trip test.
607 words, about 3 min3Rising Acetylene in a 20 MVA Substation Transformer
A 20/26.7 MVA, 138/13.8 kV conservator transformer with a nitrogen bladder supplies the only feed to a refinery process line. It has a separate-compartment OLTC, and the main-tank sample is taken from the bottom valve.
581 words, about 3 min4One Slow Pole on a 138 kV SF6 Breaker
A 138 kV, 2000 A, 40 kA SF6 dead-tank circuit breaker with three independent poles and spring-operated mechanisms is due for its six-year timing test. At rated control voltage (125 VDC) the trip times are A 32 ms, B 33 ms, and C 46 ms.
655 words, about 3 min5Nuisance Ground Fault Trips on a 480 V Service
A 480Y/277 V, 2000 A, 4-wire service entrance has a main ground-fault protection relay with a 1200:1 zero-sequence CT window encircling all three phases and the neutral. The pickup is 100 A with a 0.1 s delay.
605 words, about 3 min