Controlled procedures for AGL series-circuit isolating transformers installed in transformer pits, base cans, ducts or other approved locations — covering selection, positioning, primary and secondary connection, nameplate and polarity verification, insulation/continuity/ratio/output testing, water protection, handling, storage, replacement, removal and final acceptance.
Important — Transformer ratings, primary/secondary characteristics, insulation requirements, test voltages, acceptable test limits, polarity/phase relationships and installation details shall be taken from the approved transformer datasheet, manufacturer's instructions, project specification and applicable standards. Generic test values shall not be substituted for manufacturer/project requirements.
To ensure that the correct isolating transformer is selected for the intended AGL fixture and series-circuit application.
Verify:
To ensure isolating transformers are installed correctly and protected against mechanical and environmental damage.
Verify:
To establish requirements for installing transformers within approved transformer pits.
The pit shall be:
Critical Rule — The transformer shall not be positioned in a manner that places continuous mechanical stress on the primary or secondary cables.
To ensure that the transformer is correctly positioned within the approved installation location.
To establish a controlled method for connecting the AGL primary series circuit to the isolating transformer.
Before connection:
To establish the correct connection between the transformer secondary and AGL fixture circuit.
To control all cable connections associated with an AGL isolating transformer.
Verify:
To ensure every isolating transformer has a unique and traceable identification.
The identification system should link:
Transformer ID → Circuit ID → Fixture ID → Location
To verify that the installed transformer matches the approved equipment.
To verify the required polarity/terminal relationship of the transformer in accordance with the manufacturer's documentation and approved AGL circuit design.
Important AGL Note — AGL series circuits are not equivalent to conventional single-phase distribution systems. Polarity verification shall therefore follow the actual transformer design and manufacturer's approved test method.
Critical Rule — The test voltage and acceptance criteria shall not be invented or assumed; use the approved equipment/test specification.
To assess insulation condition of the transformer and associated accessible connections where specified.
Before testing:
To verify electrical continuity of appropriate transformer windings/circuit paths.
To verify the transformer ratio where required by the equipment specification, factory acceptance procedure or commissioning procedure.
The measured ratio shall fall within the manufacturer's/project-defined tolerance.
To verify that the transformer provides the intended secondary output under the approved test conditions.
Important — Output verification shall be conducted using the manufacturer-approved method and appropriate AGL test conditions.
To verify that the installed transformer is correctly rated for the connected AGL fixture/load.
Critical Principle — Do not treat transformer wattage as an isolated number. Verify the complete Fixture → Secondary Lead → Transformer → Primary Series Circuit compatibility.
To identify visible conditions that may compromise transformer reliability.
Check:
To verify mechanical integrity and installation security.
The transformer shall remain mechanically stable during normal operation and maintenance activities.
To prevent water ingress and water-related deterioration of isolating transformers and associated connections.
Inspect:
If water is present:
To safely replace a defective or obsolete isolating transformer.
To establish a controlled method for removing an isolating transformer.
To preserve transformer condition before installation or after removal.
Provide:
To prevent damage during transportation, lifting and installation.
Critical Rule — Never lift or carry a transformer by its cable or connector assembly unless the manufacturer explicitly provides for that method.
To establish the final acceptance process before an isolating transformer is placed into service.
Verify:
The transformer should be classified as ACCEPTED / ACCEPTED WITH COMMENTS / REJECTED according to the approved project QA/QC process.
To establish a standardized method for preparing the final isolating-transformer test report.
Record:
Where applicable, record continuity, insulation resistance, ratio, output and other manufacturer/project-specified tests. For each test, record the instrument used, test condition, result, acceptance criteria and PASS/FAIL status.
Attach, where required:
The report shall clearly state whether the transformer is PASS / FAIL / ACCEPTED WITH COMMENTS for the applicable test scope.
Master transformer workflow, quality hold points, master acceptance checklist, common transformer failure modes and required records that apply across all 24 Division 07 procedures.
The following sequence should be applied whenever applicable:
Work shall not proceed past a hold point until the associated inspection or verification has been completed and released.
The following items should be confirmed before a transformer is released to service:
The following conditions should be specifically monitored during AGL maintenance:
The AGL installation/maintenance organization should maintain, as applicable:
"An isolating transformer is a critical interface between the AGL series circuit and the individual light. Correct selection, correct rating, correct connection, effective water protection, proper connector installation, controlled testing and complete documentation are essential for reliable AGL operation."
Transformer ratings, primary/secondary characteristics, insulation requirements, test voltages, acceptable test limits, polarity/phase relationships and installation details shall be taken from the approved transformer datasheet, manufacturer's instructions, project specification and applicable standards.
Generic test values shall not be substituted for manufacturer/project requirements — approved project specifications and the transformer manufacturer's instructions shall always take precedence.
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 Isolation Transformer SOPs in the AGL SOP Library.
Division 07 is a set of 24 procedures (SOP-141 to SOP-164, Rev 0) for AGL series-circuit isolating transformers in transformer pits, base cans, ducts or other approved locations. It covers selection, positioning, primary and secondary connection, nameplate and polarity verification, insulation, continuity, ratio and output testing, water protection, handling, storage, replacement, removal and final acceptance.
From the approved transformer datasheet, manufacturer's instructions, project specification and applicable standards. This includes ratings, primary and secondary characteristics, insulation requirements, test voltages, acceptable limits and polarity or phase relationships. Generic test values must not be substituted.
No. The test voltage and acceptance criteria must not be invented or assumed; they come from the approved equipment or test specification (SOP-151). Testing requires authorization, isolation, LOTO, verification of absence of voltage and discharge of the tested circuit afterwards.
AGL series circuits are not equivalent to conventional single-phase distribution, so polarity verification follows the actual transformer design and the manufacturer's approved test method (SOP-150). Identify the terminals, review the documentation, use an approved test method and record the result.
Do not automatically re-energize (SOP-158). Identify the source, isolate the equipment as required, remove standing water by an approved safe method, inspect the components, test insulation and electrical condition as required, correct the drainage or sealing problem and obtain technical clearance before return to service.
SOP-163 checks manufacturer, model, rating, nameplate and serial number, physical condition, location, primary and secondary connections, connector condition, cable identification, pit condition, drainage and water protection. Insulation, continuity, ratio and output tests are confirmed where required, and documentation must be complete.
Incoming inspection, pit release, transformer position, primary connection, secondary connection, electrical testing, water protection, controlled energization and final acceptance.
Knowing the transformer procedure is essential. Understanding how isolating transformers protect the series circuit, and how to test and troubleshoot them, 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.