Instrument Transformers
Instrument Transformers - CT/PT Ratio + Polarity
Practice CT and PT/VT ratio and polarity testing as one instrument-transformer workflow. The sequence emphasizes secondary safety, fuse isolation, burden awareness, and documenting what was lifted or left connected.
CT ratio shot
Use the CT ratio set, verify shorting, isolate burden per plan, source P1-P2, and sense X1-X2.
Current Objective
CT ratio shot
A common field mistake is finding the right CT but landing on the wrong multi-ratio secondary tap.
Why
Ratio proves the installed CT matches drawings, relay settings, and metering expectations before energization.
Safety
A CT secondary can produce hazardous voltage if open-circuited. Keep the shorting path controlled.
Tip
If the ratio is off by a clean multiple, look for window passes, tap selection, or a drawing mismatch before calling the CT bad.
Safety Hold Point
This simulator starts after the real-world LOTO and live-dead-live check. In the field, use the properly rated tester, prove it on a proving unit or known live source, test for absence of voltage, then prove it again before installing test leads.
Loadout
Test Bench
Required Now
Test Instrument
RequiredCT Secondary
RequiredRelay / Meter Burden
RequiredPT Fuse Path
PT Secondary
Sim Workbench
Lead Placement
Select a lead, then hit the highlighted target nodes.
Expected for Current Step
Source / primary lead: CT P1-P2 primary. Sense / secondary lead: CT X1-X2 secondary.
CT primary
CT secondary
CT polarity
CT safety
PT primary
PT secondary
PT polarity
PT safety
Source / primary lead
Not placed
Sense / secondary lead
Not placed
Step Checklist
Field Intel
Never open-circuit a CT secondary; prove shorting and burden condition before ratio testing.
Isolate PT primary and secondary fuse paths before applying a ratio/polarity test.
Use ratio, polarity, drawings, relay settings, and nameplate data together rather than trusting one reading.
Mistakes Tracked
No mistakes yet. Good simulator runs come from correct setup, lead placement, and sequence discipline.
Readings
Correct the setup, place leads, and run the current step to generate simulated readings.
Profile History
No saved attempts yet. Completed reports show up here and on the simulator landing page.