A pre-dispatch inspection (PDI) checks that electrical equipment conforms to your purchase order, the specified standard and the approved drawings before it leaves the factory, when problems are still cheap to fix. A good PDI has three parts: documents verified before the visit, tests witnessed on samples the inspector selects, and a physical check of marking, packing and quantity. The checklists below cover cables, energy meters, distribution transformers and low-voltage switchgear.
Before the inspection: documents to have ready
Ask the supplier for these at least a few days before the call for inspection:
- Purchase order, technical specification and any amendments
- Approved drawings and guaranteed technical particulars (GTP)
- Manufacturing quality plan or quality assurance plan, if agreed
- Valid type test reports for the design offered, from an accredited or BIS-recognised laboratory, and within any validity period your specification sets
- BIS licence or registration details where the product is under compulsory certification, and BEE registration for star-labelled products such as distribution transformers
- Raw material and bought-out component certificates
- Calibration certificates for every instrument that will be used in the witnessed tests
- Internal routine test records for the lot offered
Red flag: a type test report for a different rating, design or factory than the one being supplied.
General checks for every inspection
- Lot offered matches the quantity and ratings in the call for inspection.
- Sampling is done by the inspector, at random, using the sampling plan in the standard or the specification.
- Instruments are within calibration and suitable for the range being measured.
- Witnessed tests are recorded with actual readings, not just “OK”.
- Marking (rating plate, Standard Mark and licence number, serial numbers) matches the drawings.
- Packing is suitable for transport and storage as specified.
- Sealing and identification of inspected items, so that what is dispatched is what was inspected.
Cables
Common standards include IS 694 for PVC-insulated cables up to and including 450/750 V, and the IS 7098 series for XLPE-insulated cables: Part 1 for low voltage, Part 2 for 3.3 kV up to 33 kV and Part 3 for 66 kV up to 220 kV.
Checklist
- Drum length, drum marking and sealing of cable ends
- Embossing or printing on the sheath (manufacturer, voltage grade, size, standard, year)
- Conductor construction and number and size of wires
- Conductor resistance at the specified temperature
- Thickness of insulation and sheath (minimum and average)
- Overall dimensions and ovality, where specified
- Tensile strength and elongation of insulation and sheath
- Insulation resistance
- High-voltage test
- Armour checks for armoured cables
- Additional tests specified for XLPE cables, such as hot set, where the standard or PO requires
Red flag: insulation thickness at the lower limit on most cores, which can indicate cost-cutting.
Energy meters
Static energy meters are generally specified to IS 13779, and smart meters to IS 16444 (Part 1) for whole-current meters and IS 16444 (Part 2) for transformer-operated meters. Utility specifications, such as those published by the Central Electricity Authority, add functional and communication requirements.
Checklist
- Rating plate details, meter constant and accuracy class
- Serial numbers matching the lot list
- Sealing arrangements on the body and terminal cover
- AC high-voltage test and insulation resistance
- Accuracy (limits of error) at the specified load points
- Starting current and no-load (creep) test
- Meter constant check
- Display parameters and sequence
- For smart meters: communication, tamper events and functions required by the specification
- Firmware version matching the version type-tested and approved
Red flag: firmware or hardware version different from the type-tested version.
Distribution transformers
Oil-immersed distribution transformers are commonly specified to IS 1180 (Part 1) along with the purchaser’s specification, such as the CEA’s standard technical specifications for distribution transformers. The BIS product manual for IS 1180 (Part 1) lists the routine tests, which include:
- Winding resistance
- Voltage ratio and phase displacement (vector group)
- Short-circuit impedance and load loss
- No-load loss and no-load current
- Insulation resistance
- Induced over-voltage withstand
- Separate-source voltage withstand
- Pressure and oil leakage tests on the tank, as specified
Also check:
- Losses against the guaranteed values and the BEE star rating claimed on the rating plate
- Core and winding material against the GTP (for example, CRGO grade and copper or aluminium windings)
- Oil quality certificates, and breakdown voltage where specified
- Fittings, bushings, tap changer operation and paint thickness
Note: BEE has issued an advisory on upgrading the star rating table for distribution transformers with effect from 1 January 2027 (see the BEE Star Label portal). For orders that will be delivered around that date, confirm with the supplier which table the rating plate and BEE registration will follow.
Red flag: measured losses that are consistently right at the guaranteed maximum across all units.
Low-voltage switchgear and controlgear
Products such as circuit breakers, switches and disconnectors, contactors and motor starters are specified under the IS/IEC 60947 series. Several of these are covered by the Electrical Equipment (Quality Control) Order under BIS Scheme-X, subject to the implementation dates notified for each item.
Checklist
- Ratings (rated current, breaking capacity, utilisation category) on the device match the PO
- Standard Mark and licence details, where the product is under compulsory certification
- Mechanical operation and interlocks
- Dielectric tests as specified for routine testing
- Trip or calibration checks for protective devices at the specified multiples
- For panels and assemblies: wiring as per drawings, busbar sizes and clearances, earthing continuity, component makes as approved, and functional checks
Red flag: approved component makes substituted without written approval.
When final inspection is not enough
Some defects cannot be seen once the product is finished. For transformers, core construction and winding work are hidden inside the tank; for cables, conductor and insulation quality is easier to verify during manufacture than on a finished drum. For large or critical orders, consider adding stage inspections, for example at core assembly or before tanking for transformers, alongside the final pre-dispatch inspection. Agree these hold points in the quality plan at the order stage, not after manufacturing has started.
After the inspection
- The report should state the lot, sample identities, tests witnessed with readings, instruments used, deviations and the decision.
- Rejections should identify the failed requirement and the re-offer conditions.
- Dispatch clearance should be issued only for the inspected and sealed lot.
How Aaditech can help
Aaditech is a NABCB-accredited Type A inspection body (IB 024) under ISO/IEC 17020, with an accredited scope limited to electrical equipment such as cables and conductors, energy meters, transformers, switchgear and controlgear, capacitors and motors. We carry out stage-wise and pre-dispatch inspections for utilities, EPC contractors and private buyers, witnessing tests and reporting what we see. See our pre-dispatch inspection service.