Electrical Commissioning Procedures

circuit breaker, Current Transformer, Transformer
April 25, 2024

Picture this: You’ve just finished building a brand-new electrical system for a hospital, shopping mall, or factory. Everything is installed, the wires are connected, and it looks perfect. But here’s the million-dollar question: Will it actually work when you turn it on? More importantly, is it safe?

This is exactly why electrical commissioning exists. It’s the process of checking, testing, and verifying that your new electrical system works correctly and safely before anyone starts using it.

What Is Electrical Commissioning? (Explained Simply)

Think of electrical commissioning like taking a new car for a test drive before buying it. You don’t just look at the car and assume it works—you start the engine, test the brakes, check the lights, and make sure everything functions properly.

Electrical commissioning does the same thing for electrical systems. It’s a systematic checkup that answers two simple questions:

Question 1: Does everything work correctly right now?

This means testing every piece of equipment—transformers, circuit breakers, cables, switches, and controls—to make sure they work exactly as they should.

Question 2: Will we know when something starts going wrong in the future?

During commissioning, you record how everything performs when it’s brand new. These records become your reference point. Years later, when you test the same equipment during maintenance, you can compare the new results with the original ones. If the numbers have changed significantly, you know something is wearing out before it breaks completely.

Why Commissioning Saves Lives and Money

Let me give you a real example: During commissioning, you test a cable’s insulation and it measures 5,000 megohms (very good). Five years later during maintenance, you test the same cable and it now reads 500 megohms. That’s a big drop! The insulation is deteriorating. Without that original commissioning record, you wouldn’t know if 500 megohms is normal or dangerous for that cable.

Here are real problems that commissioning catches before disaster strikes:

Wiring mistakes: Someone connected the wrong wires, which could make motors spin backward or cause equipment damage
Faulty equipment: A circuit breaker might have a manufacturing defect that only shows up during testing
Safety hazards: The grounding system might be incomplete, creating shock risks for workers
Protection failures: Safety devices might not work together properly, causing unnecessary power outages

Finding and fixing these issues during commissioning is far cheaper and safer than discovering them after someone gets hurt or equipment fails during operation.

Step 1: Getting Ready (Pre-Commissioning Phase)

Before you test anything, you need to prepare thoroughly. Skipping preparation is like performing surgery without washing your hands—it’s dangerous and unprofessional.

Review All the Paperwork

Start by gathering every document about the electrical installation:

Check the Drawings Match Reality

Walk through the building with the electrical drawings in your hand. Does what’s actually installed match what the engineers designed on paper? Sometimes workers make changes during installation that never get written down. You need to find these differences.

Read the Instruction Manuals

Every piece of equipment comes with an instruction manual from the manufacturer. These manuals tell you exactly how to test the equipment safely. Follow these instructions carefully. The manufacturer knows their equipment better than anyone.

Verify All Permits Are in Order

Make sure all required permits have been obtained and that the installation follows local electrical codes. Check test certificates, especially for transformers, which must meet IEEE C57.12.90 standards.

Confirm the Diagrams Are Accurate

Single-line diagrams show how electricity flows through the system. These diagrams are crucial during testing. Make sure they’re updated with any changes made during construction.

Walk Through and Inspect Everything

Now put on your safety gear and walk through the installation carefully:

Does the Installation Match the Plans?

Are cables routed where the drawings show them? Are all the support structures installed? Sometimes construction challenges force changes, but every change needs to be documented and approved.

Check How Cables Are Installed

Follow the cable paths throughout the building. Look for problems:

Cables rubbing against sharp metal edges (will damage insulation over time)
Cables without proper support that sag
Cables too close to hot equipment like motors or heaters
Cable trays that aren’t properly secured

Verify Equipment Is Mounted Properly

Every piece of equipment should be firmly attached and level:

Transformers must be anchored to withstand earthquakes
Electrical panels should be perfectly straight
Equipment that’s crooked or loose will develop problems

Check All the Labels

According to NFPA 70 (the National Electrical Code), every panel, breaker, and disconnect switch needs a clear, permanent label. During an emergency, proper labels help people respond quickly. Poor labeling can turn a minor issue into a major disaster.

Inspect Cooling and Fire Protection

Make sure ventilation openings aren’t blocked. Transformers generate heat and need air circulation. Also verify that fire-rated walls are intact—holes in fire walls can allow fires to spread.

Set Up Safety Procedures

Safety is not negotiable. Before testing any equipment, establish these procedures:

Implement Lockout/Tagout (LOTO)

This is how you prevent accidents. When someone works on equipment, they physically lock the power switch in the “off” position and attach a tag with their name. Nobody can turn the power back on until that person removes their lock and tag. This prevents someone from accidentally turning on power while others are working.

Prepare for Arc Flash Hazards

Arc flash is when electrical equipment fails catastrophically, releasing intense heat and light that can cause severe burns. Arc flash studies calculate how much energy could be released at different locations in your electrical system. Based on these studies, you determine what protective equipment workers need:

Special arc-rated clothing
Face shields
Insulated gloves
Safety glasses

Learn more about substation protection systems that help prevent arc flash incidents.

Create Safe Work Zones

Use barriers, caution tape, and warning signs to mark work areas. Only authorized people wearing proper safety equipment should enter these zones.

Prepare for Emergencies

Make sure everyone knows:

Where fire extinguishers are located
Who to call in an emergency
Where the first aid kit is stored
Basic first aid and CPR procedures
How to safely shut down equipment in an emergency

Step 2: Testing the Equipment (Verification Phase)

With preparation complete, it’s time to start testing. This phase checks that every component works correctly.

Testing Insulation: The Most Critical Safety Test

Insulation is like the protective coating on electrical wires. It keeps electricity flowing where it should and prevents dangerous situations. This test checks if that insulation is working properly.

What Equipment Gets Tested?

Using special meters called megohm testers, you check insulation on:

All power cables (both main power and control wires)
Motors and generators (the windings inside)
Transformers (both primary and secondary sides)
Electrical panels and switchgear (the bus bars and connections)

Understanding the Results

Insulation resistance is measured in megohms (millions of ohms). Think of it like this: higher numbers mean better insulation. You want readings in the hundreds or thousands of megohms.

For example:

5,000 megohms = excellent insulation
500 megohms = might be acceptable but much lower
50 megohms = warning sign, needs attention
5 megohms = dangerous, needs immediate repair

Write down every measurement carefully. These numbers become your baseline for future comparisons. Poor insulation is one of the main reasons why substation faults happen, making this test absolutely essential.

Checking Electrical Connections

Next, verify that electricity can flow through all the circuits as designed. This is called continuity testing.

Testing Power Circuits

Test every circuit from beginning to end:

Are all connections tight and secure?
Are wires broken anywhere?
Is everything connected to the right circuit breaker?
Are the phases connected correctly? (If Phase A connects where Phase B should be, motors will run backward!)

Testing Control Wiring

Control wiring is like the nervous system of your electrical system—it tells equipment what to do. Test every control circuit:

Do buttons and switches control the right equipment?
Do emergency stop buttons immediately cut power when pressed?
Do safety interlocks prevent dangerous situations?

Testing the Grounding System

Proper grounding protects both people and equipment. Test ground connections throughout the system:

Measure ground resistance (should be very low, typically under 5 ohms)
Verify all equipment frames are properly grounded
Check that ground connections are tight with no corrosion

Electrical substations depend heavily on good grounding for safety.

Measuring Voltages

Voltage testing confirms that the electrical supply is correct:

Check Incoming Voltage

Measure voltage where power enters the building:

Is it at the correct level? (480V, 208V, 120V, or whatever your system uses)
Does voltage stay steady, or does it bounce around?
Are all three phases present and balanced?

Verify Phase Sequence

Three-phase motors spin based on the order of the phases. If phases are swapped, motors run backward. Use a phase rotation meter to check this. This simple test prevents expensive motor damage.

Test Voltage Drop

When electricity flows through wires, some voltage is lost due to resistance. Test voltage at different points:

At the main panel
At distribution panels
At equipment connections

Voltage drop should typically be less than 3% for branch circuits and less than 5% total for the entire system. Higher voltage drop means wires might be undersized or connections are poor.

Analyze Harmonics

Modern buildings have lots of electronic equipment—computers, LED lights, variable speed drives—that create electrical “noise” called harmonics. Too much harmonic distortion can:

Overheat wires and transformers
Overload neutral conductors
Cause equipment to malfunction

Use a power quality analyzer to measure harmonics. If they’re too high, you might need filters to clean up the power.

Testing Protection Systems

Protection systems are your safety net—they must work perfectly when needed.

Testing Circuit Breakers

Circuit breakers are supposed to trip (turn off) when too much current flows. Test each breaker:

Does it trip at the correct current level?
Does it trip fast enough? (Must meet IEEE C37.90 standards)
Does it open all three phases at the same time?
Does it operate smoothly without sticking?

Testing Protective Relays

Modern protective relays are like smart guards that watch for problems. Test that they:

Detect overcurrent situations correctly
Respond to ground faults appropriately
Are timed correctly to work with other protective devices
Communicate properly with monitoring systems

Substation automation systems rely on these relays working correctly.

Checking Fuses

Verify every fuse is the correct type and amperage. Installing a 30-amp fuse where a 20-amp fuse belongs can create dangerous conditions.

Testing Emergency Shutdown Systems

Emergency power-off (EPO) buttons must work instantly and reliably. Test that pressing an EPO button:

Immediately cuts power
Triggers the correct alarms
Stays locked off until manually reset
Clearly indicates which EPO was activated

Testing Safety Interlocks

Safety interlocks prevent dangerous situations. For example:

An exhaust fan must run before certain equipment can start
A door switch cuts power when someone opens an access panel
Equipment won’t start if guards aren’t in place

Test every interlock to confirm it works under all conditions.

Step 3: Running the System (Functional Testing)

Now that individual components pass their tests, it’s time to run the complete system.

First Power-Up: No-Load Testing

The first time you turn on a new electrical system is exciting but potentially dangerous. Follow these steps carefully:

Turn Things On Gradually

Never energize everything at once. Instead, power up in stages:

Main switchgear first
Wait and check for problems
Distribution panels next
Wait and check again
Branch circuits
Finally, individual equipment one piece at a time

At each stage, watch and listen for:

Unusual sounds (buzzing, humming, crackling)
Strange smells (burning, melting plastic)
Visible problems (sparks, smoke, overheating)

If anything seems wrong, immediately shut down and investigate.

Check Motor Rotation

Start each motor individually and verify it spins the correct direction:

Does it accelerate smoothly?
Is rotation in the right direction?
Is it unusually noisy?
Does starting current look normal?
Does temperature rise normally?

Test Control Systems

Test every control function:

Do start/stop buttons work?
Are indicator lights accurate?
Do displays show correct information?
Do automatic sequences work properly?

Verify Monitoring Systems

Check that monitoring systems work correctly:

Current readings match actual loads
Voltage displays are accurate
Temperature sensors read correctly
Communication with building systems works

Test Alarm Systems

Trigger each alarm and verify:

Alarms activate at the right time
Alarm messages are clear
Alarms get logged properly
Visual and audible alarms work
You can acknowledge and clear alarms

Load Testing: Running Under Real Conditions

Once no-load tests pass, gradually add electrical load:

Increase Load Slowly

Don’t jump to full load immediately. Instead:

Start at 25% of maximum load
Monitor everything
Increase to 50% load
Keep monitoring
Increase to 75% load
Continue monitoring
Finally test at 100% load

At each step, watch for problems before going higher.

Watch These Important Things

Current Balance: Check that current is equal across all three phases. Significant imbalance means wiring problems or unbalanced loads.

Voltage Stability: Voltage should stay steady as load changes. Big voltage drops indicate undersized wires, poor connections, or inadequate transformer capacity.

Temperature: Use infrared cameras to find hot spots:

Hot connections mean loose hardware
Transformers should heat evenly
Hot spots in conductors mean problems
Motors should stay within normal temperature rise

Vibration: Excessive vibration means mechanical problems. Use vibration meters to establish baselines and identify rough-running equipment.

Test the Complete Operating Range

If equipment can operate from 0-100%, test it at various points: 0%, 25%, 50%, 75%, and 100%. This prevents surprises when the system encounters unusual but normal operating conditions.

Integration Testing: Making Everything Work Together

Modern buildings have many interconnected systems. The electrical system must work with everything else:

Building Management System (BMS)

Test that electrical and building systems communicate:

Can the BMS see electrical loads?
Do electrical alarms show up in the BMS?
Can operators control lighting through the BMS?
Does historical data get recorded?

HVAC Coordination

Verify:

HVAC equipment starts and stops as programmed
Electrical interlocks prevent equipment damage
Power monitoring tracks HVAC energy use
Emergency conditions shut down HVAC properly

Fire Protection System

Test fire system interfaces:

Fire alarms shut down designated equipment
Smoke detectors trigger correct responses
Elevator recall works
Emergency lighting activates during fire alarm

Security System

Confirm:

Access controls work with electrical systems
Security cameras have backup power
Intrusion alarms trigger lighting responses
Emergency lockdown procedures function

Backup Power Systems

If you have backup generators or UPS systems, test them:

Simulate utility power failure
Verify backup starts within the specified time
Confirm automatic transfer switches work
Test switching back to utility power
Verify critical loads never lose power

Understanding what substations do helps coordinate backup power with utility feeds.

Step 4: Documentation and Training

Testing is done and everything works perfectly. But you’re not finished yet! Good documentation and training are crucial.

Creating Complete Test Reports

Documentation serves several important purposes:

Record Everything

For each test, write down:

Equipment details (manufacturer, model, serial number)
When the test was done (date, time, weather conditions)
What test equipment was used (with calibration dates)
Who did the testing
What procedures were followed
The actual test results
Whether it passed or failed
How results compare to manufacturer specifications

Take Photos

Pictures are extremely valuable. Include:

Equipment installations showing nameplate information
Test setup photos
Thermal images showing heat distribution
Photos of any problems found
Photos proving repairs were completed

Document Problems and Fixes

If testing found problems:

Describe what was wrong
Explain how it was fixed
Include retest results proving the fix worked
Note any design changes required

Collect All Certificates

Include sign-off certificates from:

The commissioning agent
Licensed electricians
Third-party testing companies (if used)
The electrical engineer
Local inspectors

Training People How to Use the System

Even the best electrical system needs knowledgeable people operating it.

Train Operators

Teach operators about:

Normal operating procedures
How to read monitoring displays
Recognizing when something looks wrong
Emergency response procedures
When to call maintenance vs. when to shut down
What to write in their log books

Use hands-on training whenever possible. Let people actually operate the equipment with supervision.

Train Maintenance Staff

Maintenance teams need deeper technical knowledge:

How to perform preventive maintenance
How to use test equipment
How to interpret test results
How to troubleshoot common problems
Safety procedures including lockout/tagout
Arc flash protection requirements
Emergency response protocols

Review Emergency Procedures

Everyone should understand:

How to safely shut down in an emergency
Who to call for different emergencies
Where emergency equipment is located
When and how to evacuate
How to prevent small problems from becoming big ones

Distribute Documentation

Give complete documentation to:

Operations staff (simplified procedures)
Maintenance department (full technical details)
Engineering files (design drawings)
Safety officer (arc flash studies and PPE requirements)
Management (summary reports and warranties)

Step 5: Final Handover Package

Organize everything for the building owner:

As-Built Drawings

Provide updated drawings showing exactly what was installed:

Single-line diagrams
Three-line diagrams
Panel schedules
Lighting and outlet plans
Connection details

Mark any differences from the original design clearly.

Equipment Settings

Document all configuration settings:

Protective relay setpoints
Variable frequency drive parameters
Control system programming
Network and communication settings
Access codes and passwords

Maintenance Schedules

Create schedules showing:

What maintenance is needed
How often to do it
What test equipment is required
Expected test values based on commissioning baselines

Warranty Information

Compile warranty details:

Warranty certificates for all equipment
When coverage starts and ends
Terms and conditions
How to make warranty claims
Manufacturer contact information

Emergency Contacts

Provide a list of:

Equipment manufacturers (24-hour support)
Utility company emergency line
Electrical contractor
Commissioning agent
Engineering firm
Parts suppliers

Quality Control Checklist

Before declaring commissioning complete, verify everything on this list:

Documentation ✓

All drawings show as-built conditions
Permits obtained and inspections passed
Compliance records verified
Test reports complete with signatures

Physical Installation ✓

Visual inspection passed
All equipment properly labeled per NFPA 70
Cable paths verified correct
Fire barriers and cooling properly installed

Safety Systems ✓

Lockout/tagout procedures posted
Arc flash labels installed
Protective equipment available
Emergency procedures documented
First aid supplies and fire extinguishers in place

Testing ✓

Insulation resistance tests passed
Continuity tests successful
Voltage measurements acceptable
Harmonics analysis completed
Protection system testing passed
Circuit breakers tested
Ground resistance acceptable

System Function ✓

No-load tests completed
Motor rotation verified
Control systems working
Monitoring displays accurate
Alarm systems functional
Load testing completed at 100%
Temperature and vibration recorded

Integration ✓

Building management system working
HVAC coordination verified
Fire protection working
Security system integrated
Backup power tested

Training and Handover ✓

Test reports assembled
As-built drawings delivered
Equipment settings documented
Maintenance schedules created
Warranty information compiled
Operators trained
Maintenance staff trained
Emergency procedures reviewed
All manuals delivered
Owner acceptance obtained

Following Industry Standards

Professional electrical commissioning follows standards from ANSI/NETA (American National Standards Institute / InterNational Electrical Testing Association). These standards represent decades of best practices.

ANSI/NETA ECS (Electrical Commissioning Specifications)

Describes the systematic process for placing new or updated electrical systems into service.

ANSI/NETA ATS (Acceptance Testing Specifications)

Defines tests and inspections before initial startup. Covers switchgear, transformers, cables, and protective devices.

ANSI/NETA MTS (Maintenance Testing Specifications)

Specifies tests for existing systems. Maintenance results are compared to commissioning baselines to identify deterioration.

Following these standards ensures:

Consistent testing nationwide
Qualified technicians do the work
Proper documentation
Safety practices followed
Equipment meets specifications

Projects also reference IEEE standards:

IEEE C57.12.90: Transformer testing standard
IEEE C37.90: Protective relay standards

The Benefits of Proper Commissioning

Thorough commissioning pays off for years:

Immediate Safety: Verifies safety systems work before people depend on them.

Reliability from Day One: Properly commissioned systems have fewer failures and unexpected shutdowns.

Lower Maintenance Costs: Baseline data makes maintenance more effective by showing exactly how equipment is aging.

Longer Equipment Life: Equipment operating within specifications lasts longer.

Warranty Protection: Many warranties require professional commissioning. Without documentation, claims may be denied.

Regulatory Compliance: Verifies code compliance, protecting owners from liability.

Predictive Maintenance: Baseline measurements enable scheduling repairs before failures occur.

Peace of Mind: Confidence that the system will perform safely and reliably.

Common Problems and Solutions

Problem: Incomplete Documentation Solution: Require progressive documentation during construction. Don’t wait until the end.

Problem: Schedule Pressure Solution: Build adequate commissioning time into schedules from the start. Rushing causes mistakes.

Problem: Access Issues Solution: Coordinate with operations to schedule testing when safe and non-disruptive.

Problem: Equipment Fails Specifications Solution: Document clearly and work with manufacturers and contractors to resolve. Don’t accept substandard equipment.

Problem: Inadequate Test Equipment Solution: Use properly calibrated equipment. Consider hiring specialized testing firms for complex systems.

Final Thoughts

Electrical commissioning is essential—not optional. It ensures electrical systems operate safely and reliably from day one. Following systematic procedures, adhering to ANSI/NETA standards, and thoroughly documenting results creates a solid foundation for years of dependable operation.

Remember These Key Points:

Prepare thoroughly – Review documents, inspect carefully, establish safety procedures
Test systematically – Go from individual components to complete systems
Document everything – Baseline data is invaluable for future maintenance
Train people – Systems need knowledgeable operators
Follow standards – ANSI/NETA and IEEE standards are industry best practices

Proper commissioning reduces maintenance costs, prevents safety problems, minimizes downtime, and provides essential baseline information for ongoing operations. It’s an investment that pays returns throughout the system’s life.

Whether commissioning a small building or a large electrical substation, these procedures ensure success. Time spent in careful commissioning prevents countless hours of troubleshooting and repairs later.

For more information about electrical systems, protection, troubleshooting, and maintenance, visit SubstationFaults.com.

Common Questions About Electrical Commissioning

Q: How long does commissioning take?

It depends on size and complexity. A small commercial building might take 1-2 weeks. A large industrial facility or substation could take several months. Never rush commissioning to meet deadlines—it leads to problems later.

Q: Who should do the commissioning?

Qualified electrical professionals, ideally NETA-certified technicians or experienced licensed electricians. For large projects, owners often hire independent commissioning agents for unbiased verification.

Q: Can you commission a system that’s already running?

Yes, this is called “retro-commissioning.” While you won’t have baseline data from startup, comprehensive testing establishes current baselines and identifies problems that developed over time.

Q: What’s the difference between commissioning and acceptance testing?

Acceptance testing verifies individual equipment meets specifications. Commissioning is broader—it includes acceptance testing plus system integration, functional testing, documentation, training, and complete system verification.

Q: Is commissioning required by code?

Many codes reference commissioning requirements, especially for critical facilities like hospitals, data centers, and high-rises. Even when not required, it’s strongly recommended and often required by owners or insurers.

Q: What if commissioning finds major problems?

Document everything clearly and work with contractors and suppliers to fix issues. Don’t sign off until significant problems are corrected. Finding problems during commissioning is good—it prevents failures during operation.

Q: How much does commissioning cost?

Typically 1-3% of total electrical construction costs. This is small compared to the cost of failures, downtime, or safety incidents that commissioning prevents.

Learn More on SubstationFaults.com

Industry Standards and Resources

Fazli wahid
April 25, 2024