A relay test plan defines what will be tested, in what order and with what expected result. It is built from the approved settings and the project logic, not from a generic template for the model. It covers hardware, inputs and outputs, metering, each enabled function, the logic, the actual trips and communications, following the IEEE C37.233 approach: components first, then the complete scheme.
What a test plan is
It is the document that states, before anyone reaches the panel, what will be tested on a protective relay, in what order, with what values and what result is expected in each test. At the end it becomes the final test report: the same plan, with the measured values and the verdict.
A well-made plan has three properties:
- It comes from the approved settings and the project logic, not from a template for the model.
- It tests what the relay does in that installation, including the functions that depend on other bays or on the remote end.
- It writes the acceptance criterion before the test.
The IEEE C37.233 approach
The IEEE C37.233-2023 guide for power system protection testing proposes a bottom-up approach: first the basic behavior of each component is verified, and then the interconnected components as a functional whole. Applied to a relay, the general order is:
- 01IdentificationHardware, firmware and loaded settings against the approved ones
- 02Inputs and outputsBinary inputs, outputs and LEDs
- 03MeteringMagnitude and angle of currents and voltages
- 04FunctionsEach enabled function, one by one
- 05LogicThe project's blocking, permissives, reclosing and interlocks
- 06TripsOpening and closing of the actual breakers
- 07CommunicationsSCADA, IEC 61850 and teleprotection
- 08Close-outRecords, time synchronization and final restoration
What it should cover
| Block | What is verified, in general terms |
|---|---|
| Identification | Model, serial number, firmware and settings file; comparison with what was approved |
| Hardware | Self-test, auxiliary supply, internal alarms |
| Inputs and outputs | Each binary input with its real signal, each output to its destination, each LED |
| Metering | Magnitude and angle of currents and voltages against what was injected |
| Functions | Pickup, time and characteristic of each enabled function with the study settings |
| Logic | Each equation or block of the project logic, in its normal and blocking cases |
| Trips | Trip command to each breaker and coil, closing and reclosing, 50BF to its destinations |
| Communications | Signals to SCADA, GOOSE published and received, teleprotection with the remote end |
| Records | Events, oscillography with its triggers, synchronized time |
| Restoration | Final settings equal to the approved ones, test blocks closed, test modes off |
For functions, the plan does not stop at one point: it tests the pickup, several points of the characteristic (for example, several multiples of an inverse-time curve, or points on the boundary of a distance zone) and the blocking that affects it, with a secondary injection test set that reproduces each case. You can calculate the expected times of an IEC or IEEE curve with our free inverse-time curves tool.
Based on settings, not on a template
Test software templates are useful so nothing is forgotten, but they have three problems:
- They test functions that are not enabled, which fills the report with results of no value.
- They do not know the project logic: which input blocks which function, which output goes to which breaker, which signal arrives by GOOSE.
- They use example settings, which are not those of the study.
The plan is built from the approved settings file, the protection coordination and setting criteria study and the control and protection drawings. If the relay has several settings groups, the plan says which one is tested and how the group change is verified.
Acceptance criteria
Each test needs an expected result and a tolerance written down before injecting:
- The manufacturer’s tolerance, which the relay manual states for each function (pickup and time).
- The uncertainty of the test set, according to its calibration certificate.
- The requirements of the contract or the utility, if any. Generation interconnections, for example, often come with test scopes of their own set by the utility.
The functional parts of the IEC 60255 family (such as part 151 for overcurrent, with IEEE C37.112 for inverse-time curves, or part 121 for distance) define how the performance of a function is expressed; the applicable standards are in standards for protection testing and secondary injection.
Commissioning and maintenance
The commissioning plan covers all of the above plus the actual trips and the scheme tests with other bays and the remote end, including end-to-end testing. The maintenance plan is shorter: it confirms that the settings have not changed, that the main functions and the trips still respond and that the alarms arrive. In both cases, the bay is isolated with its test blocks before injecting and restored at the end.
Common mistakes in test plans
- Testing only the pickup. A function with the right pickup can have the wrong time, curve or direction.
- Leaving out the blocking. The plan tests that the function trips, but not that it is blocked when it should be, for example by second harmonic, by loss of potential or by a signal from another bay.
- Testing trips only up to the relay contact. If the plan does not include opening the actual breaker, a broken wire in the trip circuit goes unnoticed.
- Not testing the recording. Oscillography and events are the evidence for the next trip; if their triggers are badly configured, the future analysis starts without data.
- Not writing down the restoration. An active test mode, an open test block or a forgotten test setting leave the bay unprotected.
What the plan does not do
It does not replace the settings review. A relay that passes every test with a wrong setting is well tested and badly set.
We prepare and run your test plan
At Tiza Group we prepare the test plan from your settings and your logic, and run it in the field with secondary injection testing in medium, high and extra-high voltage substations and industrial plants, in Colombia, or elsewhere on request. You receive the report with each result, its tolerance and its verdict.
Related guides
- What to ask for in a protection test report
- Standards for protection testing and secondary injection
- OMICRON CMC 356, CMC 430 and Test Universe
- Line differential 87L testing: what is verified
- Test blocks and bay isolation for testing
- Protection coordination and setting criteria
- Primary vs secondary injection testing
References
- IEEE C37.233-2023, Guide for Power System Protection Testing. https://standards.ieee.org/ieee/C37.233/6676/
- IEC 60255-151:2009, Functional requirements for over/under current protection.
- IEEE C37.112, Standard for Inverse-Time Characteristics Equations for Overcurrent Relays.
- IEC 60255-121:2014, Functional requirements for distance protection.
- ANSI/NETA ATS-2025 and MTS-2023, acceptance and maintenance testing specifications.
Frequently asked questions
Can I use the test template that comes with the test set software?
As a starting point, yes. But a template tests the generic relay, not yours: it does not know which functions are enabled, with what settings, what logic the project has or which breakers it trips. A useful plan is built from the approved settings and the project logic, and removes whatever does not apply.
What tolerance do I use to decide whether a test passes?
The one the manufacturer states for each function in the relay manual, plus the uncertainty of the test set. The functional parts of IEC 60255 define how that performance is expressed. The plan must state the tolerance of each test before it is run, not adjust it afterwards to what was measured.
Is the maintenance plan the same as the commissioning plan?
No. The commissioning plan tests everything the relay does in the project, including wiring, logic and actual trips. The maintenance plan focuses on confirming that nothing has changed: settings equal to the approved ones, main functions, trip outputs and alarms. Its scope depends on the maintenance program and on the relay's self-monitoring.