Controlled procedures for isolating and proving-dead CCRs, AGL series circuits, isolating transformers, primary cables, distribution equipment and control systems — lockout/tagout, absence-of-voltage testing, stored-energy discharge, temporary earthing, controlled re-energization, and electrical PPE and test-instrument safety. Applicable SOP range: SOP-26 to SOP-50.
Golden Rule — Never work on an AGL electrical circuit on the assumption that it is dead. Identify it, isolate it, lock it, test it, prove it safe, control stored energy, perform the work, inspect it and only then restore it to service.
Critical Rule — Never remove another person's personal LOTO device except under the organization's formally approved emergency/removal procedure.
To prevent accidental energization or release of electrical energy while AGL maintenance or testing is being performed.
Applicable to CCRs, distribution panels, AGL circuits, control equipment, cable systems and other equipment requiring electrical isolation.
Before Isolation
Isolation
Verification
Work
Only after isolation has been verified may work commence.
Restoration
To establish a safe method for isolating electrical equipment before maintenance.
IDENTIFY → NOTIFY → SWITCH OFF → ISOLATE → LOCK/TAG → PROVE → WORK
Isolation shall be maintained for the entire duration of the work unless a controlled testing procedure specifically requires temporary energization.
To safely isolate a Constant Current Regulator (CCR) before maintenance.
Verify:
Critical Rule — AGL series circuits shall not be assumed safe simply because the CCR output indication is zero. The actual safe condition must be verified using the approved test method.
To establish safe isolation of an AGL series circuit supplied by a CCR.
To safely isolate an AGL isolating transformer and connected light fixture/circuit.
Before removing the transformer:
To safely isolate AGL primary or secondary cables before cutting, disconnecting, repairing or testing.
Never cut or disconnect an AGL cable based solely on physical appearance or assumed routing.
Critical Rule — Do not touch conductors merely because the instrument indicates zero until the complete isolation procedure has been verified.
To verify that electrical equipment or a circuit is de-energized before work.
The approved sequence should be:
TEST INSTRUMENT → TEST CIRCUIT → RE-TEST INSTRUMENT
This verifies that the instrument was functioning before and after the measurement.
To establish a controlled procedure for measuring voltage on AGL electrical equipment.
Before testing:
During testing:
Unexpected voltage shall be treated as a potentially hazardous condition until investigated.
Critical Rule — Absence-of-voltage testing shall be performed at the actual point of work or an approved representative point, according to the site's electrical safety procedure.
To confirm that the intended work area is not energized before personnel begin work.
To control electrical energy that may remain after the primary source has been disconnected.
Stored energy may exist in:
Never short circuit capacitors or stored-energy devices using improvised methods.
Critical Rule — Temporary earthing requirements depend on system design and the applicable electrical safety rules. It shall not be improvised.
To establish controlled temporary earthing where required by the electrical safety procedure.
To prevent injury and equipment damage during restoration of electrical power.
Before energization:
Then:
To establish a controlled method of energizing equipment after maintenance or repair.
For AGL equipment, controlled energization should include verification of the associated circuit and operational indications where applicable.
To provide a rapid response to electrical emergencies.
Emergency shutdown may be required for:
To control access to electrical distribution and control panels.
Before opening:
During access:
After work:
To provide additional controls for maintenance access to CCR cabinets.
Do not:
To ensure PPE is selected according to the actual electrical hazard.
The assessment should consider:
Depending on the risk assessment:
PPE shall be inspected before use and maintained according to the manufacturer's requirements.
To prevent accidental electrical contact when using hand tools.
Insulated tools shall:
Damaged or questionable insulated tools shall be removed from service.
Insulated tools are not a substitute for electrical isolation.
To ensure electrical measurement equipment is used safely and correctly.
Check:
To control hazards associated with high-voltage testing of AGL equipment, cables or components.
HV testing shall be conducted only by authorized personnel using approved equipment and procedures.
Before testing:
During testing:
After testing:
Critical Rule — Insulation resistance testing can place a significant test voltage on a circuit even though its normal operating voltage may be lower.
To safely perform insulation resistance testing on AGL cables and electrical equipment.
Before testing:
During testing:
After testing:
Critical Rule — Never disconnect a protective earth or bonding conductor merely to perform a test unless the approved procedure specifically requires it and an equivalent safe arrangement is established.
To safely perform earth/ground resistance measurements associated with AGL electrical installations.
To identify and control hazards before electrical work begins.
Step 1 — Identify the Task
Example:
Step 2 — Identify Hazards
Consider:
Step 3 — Determine Controls
Apply the hierarchy:
Eliminate → Isolate → Engineer → Administrative Controls → PPE
Step 4 — Establish Safe Work Method
Document:
Step 5 — Review
The risk assessment shall be reviewed when:
To formally close an electrical work permit after the system has been made safe and the work is complete.
Before closure:
The responsible authorized person shall:
An electrical permit shall not be closed merely because the physical repair is complete.
To provide a final electrical safety verification before equipment is returned to normal operation.
Check:
Electrical
Mechanical
Safety
Functional
INSPECT → TEST → CLEAR → AUTHORIZE → ENERGIZE → VERIFY → DOCUMENT
Record:
Core electrical safety rules, the master isolation sequence, and the golden rule that governs all 25 Division 02 procedures.
For applicable AGL electrical maintenance:
"Never work on an AGL electrical circuit on the assumption that it is dead. Identify it, isolate it, lock it, test it, prove it safe, control stored energy, perform the work, inspect it and only then restore it to service."
Technical references behind the procedures in this division:
References are given at document or chapter level for technical orientation. Confirm the current edition, amendments and national adoption (for example DGCA CAR Section 4, FAA Advisory Circulars or EASA material) for each project. Approved project specifications, manufacturer instructions and the airport's own procedures take precedence, as stated in the precedence note above.
Quick answers about Electrical Safety, LOTO & Isolation SOPs in the AGL SOP Library.
Division 02 is a set of 25 procedures (SOP-26 to SOP-50, Rev 0) for isolating and proving dead CCRs, AGL series circuits, isolating transformers, primary cables, distribution equipment and control systems. It covers lockout/tagout, absence-of-voltage testing, stored-energy discharge, temporary earthing, controlled re-energization, and electrical PPE and test-instrument safety.
Never work on an AGL electrical circuit on the assumption that it is dead. Identify it, isolate it, lock it, test it, prove it safe, control stored energy, perform the work, inspect it and only then restore it to service.
No. Rule 04 (Prove Dead) says not to rely only on a switch position, indicator lamp, CCR display or control-system status. Isolation must be verified by testing, and LOTO is required where the task calls for it, because isolation without the required LOTO controls is incomplete.
The approved sequence is test instrument, test circuit, re-test instrument (SOP-32). This shows the tester worked before and after the measurement. Absence-of-voltage testing is done at the actual point of work or an approved representative point, covering phase-to-phase and phase-to-earth points where required (SOP-34).
No. SOP-26 states that another person's personal LOTO device must never be removed except under the organization's formally approved emergency/removal procedure. LOTO removal during restoration is done only by authorized personnel under the approved sequence.
Capacitors, CCR power electronics, DC control circuits, filters, UPS systems, batteries, cable capacitance and electronic components may retain energy after the supply is disconnected. SOP-35 requires allowing the manufacturer-specified discharge time, using approved discharge equipment where required, verifying the energy has gone, and never short-circuiting capacitors by improvised methods.
Confirm the work is complete, inspect the equipment, verify covers and guards, remove tools and temporary materials, confirm personnel are clear, confirm permits allow restoration and verify protective devices. Notify affected personnel, remove LOTO under the approved sequence, energize, monitor for abnormal noise, smell, indication or alarm, verify electrical parameters and perform functional testing (SOP-37).
Stop work, warn personnel, operate the emergency isolation device if safe and authorized, and keep people away from the hazard. Notify Airport Operations or emergency response, do not touch an injured person who may still be energized, prevent unauthorized re-energization, and do not restore power until authorized (SOP-39).
Rule 08 says unexpected voltage means stop: treat it as hazardous until its source is identified and controlled. Rule 09 says safety interlocks, protective devices and emergency systems must not be bypassed unless specifically authorized under an approved procedure.
Not merely because the physical repair is complete (SOP-49). Work must be finished and inspected, tools and FOD removed, temporary earths and connections removed where authorized, covers and guards installed, electrical and functional tests completed, personnel accounted for and the operational authority notified. The authorized person then records outstanding defects and returns the system to the operational authority.
Knowing the isolation procedure is essential. Understanding why LOTO works, how AGL circuits store and release energy, and how to apply engineering controls safely takes deeper technical knowledge.
Learn through structured training covering:
Develop the technical foundation to work with AGL systems systematically, safely and confidently.
Please read before relying on any content on this page or on any SOP downloaded from it.