How to Perform a VAT: Complete Voltage Absence Test Procedure

The Voltage Absence Test (VAT) is an essential step for securing any intervention on an electrical installation. It follows 3 steps:

• Initial test of the Voltage Absence Tester: probes in contact → OK signal
• Measurement: 3 checks (phase/neutral + phase/earth + neutral/earth)
• Final test of the Voltage Absence Tester: probes in contact → OK signal

⚠️ If you are working in a NON-IP2X environment, you must wear your PPE throughout THE ENTIRE procedure (insulating gloves + face shield)

---

Bernard, a building caretaker, needs to replace a faulty socket. He switches off the corresponding circuit breaker. The lighting stops working. Before intervening, he takes out his Voltage Absence Tester (VAT).

Phase/neutral measurement: no signal. Phase/earth measurement: audible signal and LED. The VAT detects 230V on the phase.

Returning to the panel, Bernard discovers he switched off the wrong circuit breaker due to incorrect labelling. The VAT identified the error before any contact with the conductors.

In this article, you will follow the complete VAT procedure compliant with the NF C18-510 standard, from the initial test to the 3 mandatory measurements, following Bernard’s intervention.

💡 To go further: Our BS BE Switching training prepares you in 2 days with practical hands-on scenarios.

Accidents related to electrical risks constitute a real danger in France (INRS source). A tripped circuit breaker ≠ absence of voltage.

What is a VAT and why is it mandatory?

Definition: Voltage Absence Test

The VAT is a procedure that confirms no dangerous voltage remains on an installation. Unlike a multimeter which measures a potential difference between two points, the Voltage Absence Tester detects the presence of voltage on each conductor independently.

The VAT answers a binary question: voltage present (beep + LED) or voltage absent (no signal). This dual indication maximizes alert chances even in difficult conditions (noise, low light, confined space).

VAT in the lockout procedure (step 4/5)

The Voltage Absence Test is never performed in isolation. It is part of an electrical lockout or de-energization procedure, which comprises 5 successive steps:

Step	Action	Why
1. Separation	Switch off the circuit breaker or disconnector	Physical disconnection from the electrical network
2. Locking	Apply padlock + circuit breaker lockout device	Prevents accidental re-energization
3. Identification	Identify the circuit as close as possible to the work zone	Avoid any confusion about the equipment involved
4. VAT	Verify absence of voltage with a compliant VAT	Confirm no dangerous voltage remains
5. MALT (Optional in LV)	Grounding and short-circuiting	Mandatory only in High Voltage or specific risks

💡 In Bernard’s case: for a simple intervention such as replacing a domestic socket, you follow steps 1 to 4. Step 5 (MALT) is not required in Low Voltage (230V), except in certain specific cases.

The VAT confirms that the first three actions (separation, locking, identification) have been correctly carried out and that no dangerous voltage remains. Without this verification, you cannot guarantee your electrical safety.

The NF C18-510 standard is the French regulatory reference for safety during operations on electrical facilities and installations. It precisely defines what a VAT is and how it must be performed.

Requirement	What this means
❌ Multimeter prohibited	“Under no circumstances may a MEASURING device be used to perform a VAT” (NF C18-510, page 74). A multimeter measures a potential difference, not the presence of voltage on each conductor.
✅ Compliant VAT mandatory	The tester must comply with the NF EN 61243-3 standard. It must provide “indisputable proof of the absence of nominal voltage”.
🔄 Test before AND after	The VAT must be checked immediately before and immediately after each verification. This ensures it is functioning correctly and has not been damaged during the operation.
🧤 Mandatory PPE in NON-IP2X environments	Insulating gloves + face shield minimum throughout the entire VAT when working in a non-IP2X environment.
📌 IP2X probes only	Mandatory since the standard was published. These probes have an insulating sleeve that limits the exposed metal part to 4mm (instead of 2cm). This prevents accidentally touching two terminals simultaneously in an electrical panel where conductors are closely spaced.

What equipment to use for a VAT?

The risks of using a multimeter

Scenario: Bernard wants to replace a faulty socket. He switches off what he thinks is the correct circuit breaker. To check, he takes out his multimeter and measures between the phase and neutral of the socket: 0 volts displayed. He thinks he is safe and touches the wires with bare hands.

Result: electrification at 230V.

What happened? Bernard cut the neutral instead of the phase (identification error or mislabelled circuit breaker). The multimeter measures a potential difference between two points. Phase cut + neutral cut = open circuit = 0V difference. The device displays zero.

But the phase remains energized at 230V relative to earth.

The multimeter does not lie: it does exactly what it is designed for (measuring a difference). But it cannot tell you whether an individual conductor is dangerous.

With a Voltage Absence Tester, this trap does not exist.

The Voltage Absence Tester detects the potential of each conductor independently, not a difference between two points. If Bernard had used a VAT:

1. Phase/neutral measurement: No signal (both are cut)
2. Phase/earth measurement: BEEP + LED → The phase is still energized at 230V!
3. Bernard stops immediately and returns to the panel to switch off the correct circuit breaker

VAT vs multimeter vs VPD: comparison table

There are three types of devices that workers use (sometimes incorrectly) to check for the presence or absence of voltage. Here are their fundamental differences:

Criterion	VAT (Voltage Absence Tester)	Multimeter	VPD (Voltage Presence Detector)
Primary function	Certify total absence of voltage	Measure a potential difference	Signal voltage presence
Device type	Safety device	Measuring device	Detection device
NF C18-510 compliance	✅ Mandatory for VAT	❌ Prohibited for VAT	❌ Insufficient for VAT
Potential detection	Yes, with a single probe	No, requires two points	Yes, contactless detection possible
Self-test function	✅ Mandatory before/after use	❌ No built-in self-test	Varies by model
Battery-free operation	✅ Yes, powered by the circuit under test	❌ No, requires batteries	❌ No, requires batteries
Calibration error risk	✅ None (no adjustment needed)	❌ Yes (AC/DC selection, range)	✅ None
Warning signal	Dual: audible + visual	Digital display only	Varies (audible, visual)
Average price	€100 to €300	€30 to €200	€20 to €80

Errors to avoid during a VAT

What PPE is required to perform a VAT?

Understanding the Low Voltage reinforced vicinity zone (Zone 4)

The reinforced vicinity zone is a safety perimeter of 30 cm around any live bare part in Low Voltage. If you enter this zone, you are exposed to electrification and PPE becomes mandatory.

Switchboard type	Is there a Zone 4?	PPE upon opening?
IP2X Switchboard Conductors protected by covers	❌ No Live parts are not accessible	❌ No PPE optional
NON-IP2X Switchboard Visible bare conductors	✅ Yes As soon as you are within 30 cm	✅ Yes Gloves + face shield mandatory

💡 Simple test: Can you touch a bare conductor by reaching out from where you are standing? If yes → you are in Zone 4 → PPE mandatory.

Insulating gloves: inspection and required class

Insulating gloves are the first barrier of protection against electrical risk during a Voltage Absence Test. Even if you think you have correctly de-energized the installation, you must wear your insulating gloves throughout the entire VAT. Why? Because this is precisely the moment when you will confirm whether or not there is voltage. Until the test is complete, you are potentially in the danger zone.

For a Low Voltage intervention (up to 1,000V AC), you must use class 0 insulating gloves (working voltage up to 500V AC) or class 00 (working voltage up to 1,000V AC).

Face shield

The face shield (or protective visor) protects your face and eyes against the risk of electric arc. During a Voltage Absence Test, even though the risk is limited, an accidental short circuit or mishandling can cause an arc. This full protection is mandatory for any intervention in the reinforced vicinity zone or during a VAT on a non-IP2X switchboard.

For Bernard, who is working on a Low Voltage socket, insulating gloves and the face shield are essential.

Here is a summary table to help you identify when to wear your PPE:

Situation	IP2X Switchboard	NON-IP2X Switchboard
Opening the switchboard	Without PPE	With gloves + face shield
Identifying the circuit breaker	Without PPE	With gloves + face shield
Separation (disconnection)	Without PPE	With gloves + face shield
Locking	Without PPE	With gloves + face shield
VAT (verification)	With gloves + face shield	With gloves + face shield
Re-energization	Without PPE (optional)	With gloves + face shield

In Bernard’s case, he must therefore check whether his building’s electrical panel is IP2X. If not, he must put on his insulating gloves and face shield as soon as the panel is opened, even before identifying the circuit breaker corresponding to the socket he wants to replace.

The 3-step VAT procedure

Step 1 – Test the VAT before use (continuity self-test)

Before checking for the absence of voltage on your installation, the first thing to do is verify that your VAT is in working order. This is the step known as the self-test or continuity test.

Here is how to perform the self-test:

1. Take your Voltage Absence Tester
2. Bring the two test probes into contact with each other
3. The VAT must emit an audible signal (continuous or intermittent beep depending on the model)
4. Simultaneously, a visual signal (LED) must light up

Some professional VAT models incorporate a self-test button. In this case, simply press the button to verify the device is functioning. The result is the same: audible signal + visual signal = device operational.

If no signal appears (neither sound nor light), your VAT is out of service. Do not use it. First check that the test leads are correctly plugged into the device. If the problem persists, replace the batteries (if your model uses them) or replace the device. An important detail: a good VAT continues to work even if its batteries are dead, by drawing energy from the circuit under test.

Step 2 – Verify absence of voltage on all conductors

Your VAT is functioning correctly? Perfect. You can now verify the absence of voltage on the installation. This step takes place as close as possible to the work zone, not only at the electrical panel.

Let us return to Bernard’s example. He needs to replace a socket. He has switched off the corresponding circuit breaker and locked it with his padlock. He now stands in front of the faulty socket with his Voltage Absence Tester and his PPE.

You must verify the absence of voltage between all active conductors. In a standard domestic or commercial installation, this means three mandatory measurements:

1. Between phase and neutral – Place one test probe on the phase conductor (usually red, black or brown) and the other on the neutral conductor (usually blue).
2. Between phase and earth – Place one probe on the phase conductor and the other on the earth conductor (usually green/yellow).
3. Between neutral and earth – Place one probe on the neutral conductor and the other on the earth conductor.

Interpreting results:

• No audible or visual signal = Absence of voltage confirmed. You can proceed with your intervention safely.
• Audible signal + visual signal = Voltage detected. Do not intervene. Return to the electrical panel for further investigation.

Why check phase/earth? If the neutral is cut but the phase is still energized, the phase/neutral measurement could indicate absence of voltage (because the circuit is open). But the phase remains dangerous at 230V relative to earth. The phase/earth measurement will detect this problem.

Why check neutral/earth? In certain faulty installations, the neutral can be under voltage (phase/neutral inversion, voltage feedback from a connected appliance). The neutral/earth measurement detects this anomaly.

If you are working on a three-phase installation, you will need to perform more measurements: between each phase, between each phase and neutral, between each phase and earth, then between neutral and earth. The principle remains the same: verify all active conductors.

Step 3 – Re-test the VAT after use (final safety check)

You have verified the absence of voltage and no signal appeared. Can you intervene? Not yet. One crucial final step remains: re-testing your Voltage Absence Tester.

Why this additional check? Because it is possible that your VAT failed during the measurement. If the device burned out at the moment you touched the conductors (due to an overvoltage, fault, or shock), it would have emitted no signal even if voltage was present. You would then have believed in the absence of voltage while the danger persisted.

The final verification procedure is identical to the initial self-test.

This double verification (before and after) is a requirement of the NF C18-510 standard. It guarantees that your Voltage Absence Tester was functional at the precise moment you performed the measurement.

Complete summary of the 3-step VAT procedure:

Step	Action	Expected result	If problem
Step 1	Self-test: probes in contact	Audible + visual signal	VAT out of service: do not use
Step 2	Measurements phase/neutral, phase/earth, neutral/earth	No signal	Signal emitted = voltage present: do not intervene
Step 3	New self-test: probes in contact	Audible + visual signal	No signal = restart with another VAT

Practical case: performing a de-energization procedure per NF C18-510

Validating BS intervention conditions

Before intervening, Bernard verifies that he holds BS authorization for this type of intervention (socket replacement in LV ≤400V). His employer has confirmed he can carry out this operation. In case of doubt, he requests confirmation.

Separation, locking and identification

Before performing the VAT, Bernard must carry out the first three steps of electrical lockout: intervention analysis, separation, locking and identification.

Preliminary step: Intervention analysis

Bernard begins by analyzing the situation:

• Reinforced vicinity risk – He checks whether there is a reinforced vicinity risk near the socket. If neighbouring equipment remains energized within 30 cm, he will also need to de-energize it.
• Identifying the electrical panel – Bernard identifies the electrical panel to which the socket is connected. He checks whether this panel is IP2X (protection against the introduction of objects larger than 12.5 mm).

Step 1: Separation (de-energization)

Once the correct circuit breaker is identified, Bernard performs the separation by switching off the circuit breaker. The electrical circuit is now disconnected from the network.

Step 2: Locking

Switching off the circuit breaker is not enough. Someone could turn it back on during Bernard’s intervention, by mistake or ignorance. To prevent this, Bernard places a circuit breaker lockout device and a lockout padlock on the disconnection device.

Step 3: Identification

Bernard returns to the faulty socket (and any other equipment he has de-energized to eliminate the reinforced vicinity risk). He can now proceed with the Voltage Absence Test.

Performing the VAT: the 3 mandatory measurements

Bernard is now ready to perform his Voltage Absence Test. The VAT is always performed wearing personal protective equipment.

Preparing the Voltage Absence Tester

First, Bernard tests his VAT. He brings the two test probes into contact: the device emits an audible beep and a visual signal lights up. The VAT is functioning correctly. Bernard can proceed with the measurements.

The 3 mandatory measurements on the socket

For a standard single-phase AC socket, this means three measurements:

1. Measurement 1: Between phase and neutral
2. Measurement 2: Between phase and earth
3. Measurement 3: Between neutral and earth

These three measurements are essential. Never settle for checking only phase/neutral.

Final VAT verification

Bernard has completed his three measurements. No signal appeared. Can he intervene? Not yet. He must ensure his Voltage Absence Tester is still functioning. Bernard brings the two test probes into contact again: audible beep + visual signal. Perfect, the VAT was not damaged during the measurements.

The absence of voltage is now confirmed.

Interpreting results and next steps

✅ Scenario 1: No signal during all 3 measurements

The absence of audible and visual signal confirms that no dangerous voltage remains. Bernard can intervene safely.

He replaces the faulty socket, returns to the electrical panel, removes the padlock and lockout device, then resets the circuit breaker. If the panel is not IP2X, he puts his insulating gloves and face shield back on for this operation.

He tests that the new socket functions correctly and informs the electrical operations manager that the intervention is complete.

⚠️ Scenario 2: Signal emitted during one of the measurements

STOP IMMEDIATELY. DO NOT INTERVENE.

Audible signal + visual signal = voltage present = danger. Do not touch any conductor.

Possible causes:

• Wrong circuit breaker switched off – Return to the panel and verify the identification
• Faulty circuit breaker – Call a qualified electrician
• Voltage feedback – Inverter, backup generator or photovoltaic panels feeding power back
• Installation with multiple power sources – Identify and disconnect all sources

Under no circumstances should you intervene while the VAT detects voltage. Ignoring a VAT signal = fatal risk.

5 questions about the Voltage Absence Test