NETA ETT Level 3 case studies
NETA ETT Level 3 · Put your knowledge to work in context.
The NETA ETT Level 3 credential - the Electrical Testing Technician Level III - is a tiered certification for field technicians who commission, maintain, and troubleshoot power systems. Level 3 signals that a technician can work independently on complex apparatus, interpret test results against standards, and make field decisions without close supervision. The NETA ETT Level 3 case studies are 5 cases and about 3,307 words.
1Energized 480 V Switchboard Voltage Verification at a Data Center
At a 24/7 data center, a 480Y/277 V, 1200 A switchboard main compartment cannot be de-energized because the critical load has no upstream bypass. The arc-flash label states 8.2 cal/cm² at an 18 in working distance and 35 kA available fault current.
731 words, about 4 min2Oil-Filled Transformer Insulation Resistance Drop Before Return to Service
An annual outage is testing a 1500 kVA, 13.8 kV delta–480Y/277 V oil-filled transformer. Last year's 5 kV insulation-resistance test at 24°C gave 4.8 GΩ at 10 minutes and a polarization index of 2.9.
646 words, about 3 min3Dry-Type Transformer Winding Resistance Imbalance
During acceptance testing of a 500 kVA dry-type transformer, 480 V delta primary and 208Y/120 V secondary, a technician measures primary winding resistance with a 10 A four-wire micro-ohmmeter. Nameplate primary current is 601 A.
614 words, about 3 min4Feeder CT Ratio Error After Relay Retrofit
After a relay retrofit on a 13.8 kV feeder, the new feeder relay displays 480 A while a calibrated clamp-on meter on the same phase reads 520 A. The CT is nameplate 600:5, multi-ratio 1200/600:5, connected on the 600:5 tap.
659 words, about 3 min5Intermittent Main Ground-Fault Protection Trips After VFD Installation
A 2000 A, 480Y/277 V service has a main ground-fault protection relay set at 600 A pickup with a 0.1 s delay. The building has a 200 hp VFD on a remote panel.
657 words, about 3 min