Substation commissioning is the ordered set of inspections and tests that proves each device arrived undamaged, was installed correctly and works with the rest before and during energization. It moves from the individual to the integrated: primary equipment, instrument transformers, wiring, protection, control and communications, end-to-end tests and, finally, energization and on-load checks.
What substation commissioning is
Substation commissioning is the stage that separates an installed substation from one in operation. It consists of proving with documented tests that each device arrived undamaged from transport, was properly installed and connected, and works together with the rest: transformers, breakers, disconnectors, instrument transformers, protection, control, communications and station service. How it differs from pre-commissioning and start-up is explained in pre-commissioning, commissioning and start-up.
Commissioning comes after pre-commissioning, with the equipment de-energized, and in industry it is followed by start-up when the process begins to run. What changes between projects is the scope the contract sets, not the name.
No single standard covers it from end to end. Each device has its product standard; ANSI/NETA ATS covers field acceptance testing of each device and ANSI/NETA ECS the commissioning of the system as a whole; IEEE C37.233 and CIGRE Technical Brochure 637 guide protection and automation testing. The full picture is in standards for commissioning, FAT and SAT.
The stages, from the individual to the integrated
The order is not arbitrary: each stage rests on the previous one. Testing a protection end to end before verifying the ratio and polarity of its current transformers is a waste of time, because any error below contaminates the tests above.
- 01Inspection and documentationCurrent drawings, factory test reports and installation complete
- 02Primary equipmentTransformers, breakers, disconnectors, cables and grounding grid
- 03CTs, VTs and wiringRatio, polarity, burden and point-to-point circuit checks
- 04Protection per baySecondary injection with the approved settings and real trip
- 05Control, SAS and communicationsCommands, interlocks, signals to the HMI and the control center
- 06End to endTeleprotection and schemes between substations
- 07Energization and loadPhasing, synchronism, directionality and on-load measurements
Inspection and document review
Before measuring anything, the installation is checked against the latest approved drawings, the factory test reports of each device are gathered and the installation is confirmed complete. The factory test reports are the reference against which site tests are compared: without them, an isolated measurement says little.
Primary equipment tests
Each device is tested to confirm it was not damaged in transport and installation. On the power transformer, ratio, winding resistance, insulation resistance and power factor are measured, among others; what each one reveals is in turns ratio, polarity and vector group test and in the guide for each test. On breakers, timing, contact resistance and, depending on the technology, the gas or the vacuum. Cables, surge arresters and the grounding grid have their own tests. The list per device is in substation primary equipment tests, and the case of the transformer, with its accessories and no-load energization, in power transformer commissioning.
Instrument transformers and wiring
CTs and VTs feed all protection and metering. Ratio, polarity, excitation of the protection cores and connected burden are verified, and each circuit is checked to land on the right terminal. Point-to-point signal tests, from the device terminal to the IED and to SCADA, close this stage on the control side.
Protection of each bay
With the settings of the approved study loaded, each relay is tested by secondary injection: that it measures correctly, that each function operates as expected and that the trip reaches the right breaker. The tests and acceptance values follow the protection study and the utility’s requirements; the complete walk-through for each relay is in protective relay commissioning.
Control, SAS and communications
Local and remote commands, interlocks, the signal list to the HMI and the control center, time synchronization and, in IEC 61850 systems, the configuration files and GOOSE messages are verified. To prepare the interlocking test cases you can use our free interlocking table tool.
End to end
When a protection depends on the other end of the line (teleprotection, line differential, transfer trips), both substations are tested at the same time with synchronized sources. It is the only way to verify the complete scheme, channel included.
Energization and on-load tests
The last stage is energization coordinated with the utility or the transmission owner. Some checks can only be made with voltage and load: phase sequence, synchronism, protection directionality and consistency of the measurements. What is tested de-energized and what energized is covered in cold and hot commissioning, and the switching sequence in first energization of a substation.
What changes from one substation to another
| Factor | What it adds to commissioning |
|---|---|
| Voltage level | More equipment per bay, more demanding dielectric tests and redundant protection at high and extra-high voltage |
| Configuration | Single bus, double bus or breaker-and-a-half change the interlocking, the bus differential and the breaker failure scheme |
| Technology | In an IEC 61850 substation, verification of SCL files and GOOSE is added and, in a digital substation, sampled values |
| New substation or extension | An extension requires clearances and tests on existing protection, such as the bus differential |
| Connected generation | Tests of the interconnection functions the utility requires, under the local grid code (in North America, IEEE 1547 or IEEE 2800 depending on the connection) |
| Industry | Interfaces with switchgear, motors, drives and the plant SCADA |
What is delivered at the end
The result of commissioning is a set of documents, not just an energized substation: approved test plan, test records per device and per function with their measured values, a log of non-conformities and their closure, a copy of the settings loaded, verified signal lists and a final report. Those records are also the maintenance baseline. For protection, the minimum content is in what to ask for in a protection test report, and the complete organization of those documents in commissioning dossier.
The procedure for each test, the switching sequences and the acceptance values of a project depend on the client’s specification, the manufacturer and the applicable standard, and are set in the test plan.
We commission your substation
Our team carries out complete commissioning, from primary equipment tests to energization, in medium, high and extra-high voltage substations and in industrial plants, in Colombia, or elsewhere on request. For the rest of the scope, see our testing and commissioning service and send us the single-line diagram through contact: we will propose a plan.
Related guides
- Infrared thermography in substations and switchgear
- Substation SCADA and HMI
- Turns ratio, polarity and vector group test
- What substation commissioning includes
- Standards for commissioning, FAT and SAT testing
- Substation primary equipment tests
- Interlocking tests
- Switchgear and MCC commissioning: tests
- BESS commissioning: tests and requirements
- Electrical commissioning of an industrial plant
- Commissioning levels 1 to 5: what they are
- Electrical substation: what it is, parts and how it works
- Substation automation system (SAS): functions and levels
References
- ANSI/NETA ATS-2025, Standard for Acceptance Testing Specifications for Electrical Power Equipment and Systems.
- ANSI/NETA ECS-2024, Standard for Electrical Commissioning Specifications for Electrical Power Equipment and Systems.
- IEEE C37.233-2023, IEEE Guide for Power System Protection Testing.
- CIGRE TB 637, Acceptance, commissioning and field testing techniques for protection and automation systems, 2015.
- IEC 61850-4, System and project management.
- IEC 60076 series, Power transformers; IEC 62271 series, High-voltage switchgear and controlgear; IEC 61869 series, Instrument transformers.
Frequently asked questions
Are commissioning and acceptance testing the same thing?
They overlap. Acceptance testing (ANSI/NETA ATS) proves each device in the field; commissioning (ANSI/NETA ECS) proves that the devices work together as a system, up to energization. Many contracts call the whole stage commissioning. The scope is set by the contract, not by the word.
Which standard governs substation commissioning?
There is no single standard. Each device has its product standard (IEC 60076 / IEEE C57.12, IEC 62271 / IEEE C37, IEC 61869 / IEEE C57.13), field practice is collected in ANSI/NETA ATS and ECS, protection and control rely on IEEE C37.233 and CIGRE TB 637, and the utility or transmission owner adds its own interconnection requirements.
In what order is a substation commissioned?
From the individual to the integrated: first each piece of primary equipment and each instrument transformer, then the wiring and protection of each bay, then control, the SAS and communications, end-to-end tests when there is teleprotection and, finally, energization and on-load checks.