Relay Testing Chart

Use this worksheet after the calculator result to record relay ID, function number, pickup setting, measured pickup, timing value, percent error, test set, and coordination action.

Open calculator

Quick reference table

A relay testing chart is a calculator-led testing worksheet. It keeps pickup, timing, instantaneous, and coordination-test results tied to relay settings, test instruments, and protection-study follow-up.

Relay testing worksheet

Relay testing worksheet
Item	Record from calculator	Follow-up
Relay ID	Device, function, firmware, setting group	Confirm current active settings
Test type	Pickup, timing, instantaneous, or complete test	Match test plan
Measured result	Pickup, time, trip, or error	Compare with expected value
Instrument	Test set and injection method	Record calibration status
Coordination	Curve or margin note	Route to study or settings review

Relay test method routing

Relay test method routing
Relay test item	Record on worksheet	Why it matters
Secondary injection	Test set, injected current, expected pickup	The result depends on CT ratio and test-set setup
Timing test	Curve, time dial, current multiple, measured time	One point does not prove the whole curve
Instantaneous element	Pickup setting, measured pickup, tolerance note	Instantaneous behavior can control coordination
Trip circuit check	Output contact, target, breaker trip path	Relay pickup is not the same as complete trip-path operation

Formula basis

Percent error = (measured value - expected value) / expected value x 100.

Measured value is the relay pickup, time, or trip value observed during the test.
Expected value is the setting, curve point, or test plan value.
Percent error is a screening comparison, not a full calibration decision by itself.
Coordination follow-up connects the relay result to the protection study and device settings.

Worked examples

Overcurrent relay pickup recordRecord relay ID, function 51 setting, expected pickup, measured pickup, percent error, test set, setting group, and coordination follow-up note.

Instantaneous element timing noteKeep function number, active setting group, current multiple, expected operation, measured trip time, test set, and study follow-up in one worksheet.

Assumptions. Balanced load and line-to-line voltage assumptions behind this chart.

Relay testing depends on the active setting group, CT/PT ratios, firmware, wiring, test set, and approved test procedure.
A calculator result does not change relay settings or prove system coordination by itself.

Code and standard notes. Planning limits that should be checked before final equipment selection.

Use this chart as a maintenance log; verify NETA or IEEE relay testing practices, manufacturer manuals, protection-study data, OSHA safety controls, adopted NEC context, AHJ expectations, and qualified-person review before changing settings or returning equipment to service.

How to use this chart

1Identify relay contextRecord relay ID, function, setting group, CT/PT ratio, and test type before entering results.

2Compare expected and measuredUse the calculator result to document percent error, timing, and pickup differences.

3Route study follow-upList protection-study, setting, firmware, wiring, or manufacturer review items.

Worksheet checklist. Record source basis, review gaps, and assumptions before using the chart result.

Capture relay dataRecord relay model, function number, setting group, expected pickup or timing, and curve basis.
Capture test dataWrite measured pickup, timing, instantaneous operation, test set, injection method, and error.
Capture actionDocument accept, retest, settings review, wiring check, or coordination-study update.

Common mistakes to avoid. Review these before turning chart current into an equipment decision.

Testing the wrong setting group or curve and comparing it to the wrong expected value.
Changing relay settings from one test point without reviewing system coordination.
Recording pickup accuracy without CT/PT ratio, test set calibration, trip output status, and active setting group.

Frequently asked questions

These answers explain how to use the chart without turning a quick reference into a final design decision.

Can the relay chart approve a settings change?

No. It documents test results and follow-up. Settings changes need the protection study, owner procedure, manufacturer guidance, and approval from the responsible protection engineer.

Why record the setting group?

Many relays have multiple groups. A test result is only meaningful when tied to the active group and exact setting basis.