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[Utility / T&D Automation & Engineering Magazine, p35]

Transformer - Information required with enquiry and order "CHECKLIST" (IEC 60 076-1)

The list is not exhaustive.

I- Normal Information:

N°	INFORMATION	YES	NO
1	Particulars of the specifications to which the transformer shall comply (e.g : international & national standards, …)
2	Kind of transformer (separate winding, auto-transformer or booster)
3	Single or three-phase unit
4	Number of phases in system
5	Frequency
6	Dry-type (degree of protection) or liquid filled (mineral oil or synthetic insulating liquid) "see IEC 60529
7	Indoor or outdoor type
8	Type of cooling
9	Rated power (on the ONAN / ONAF)
10	Rated voltage for each winding
11	For a transformer with tappings : (see IEC 60 076-1)
-	Which winding is tapped
-	The number of tappings, and
-	The tapping range or tapping step
-	"Off - Circuit" or "On - Load " tap-changing is required
-	If the tapping range is more ± 5% :
-	The type of voltage variation (Constant Flux Voltage Variation, Variable Flux Voltage Variation or Normal operation is CbV V : Combined Voltage Variation)
-	The location of the maximum current tapping
12	Higest voltage for equipment (Um) for each winding (see IEC 60 076-3)
13	Method of system earthing (for each winding)
14	Insulation level (see IEC 60 076-3)
15	Connection symbol and neutral terminals (e.g : Y, Z or D …)
16	Any peculiarities of insulation, assembly, transport and handling. Restrictions on dimensions and mass
17	Details of auxiliary supply voltage (for fans and pumps, tap-changer, alarms, etc)
18	Fittings required and an indication of the side from which meters, rating plates, oil level indications, shall be legible
19	Type of oil preservation system
20	Capitalisation of losses.

II- Special Information:

N°	INFORMATION	YES	NO
1	If a lightning impulse voltage test is required, whether or not the test is to include chopped wavec (IEC 60076-3).
2	Whether a stabilizing winding is required and, if so, the method of earthing (neutral not isolated, limit the zero sequence impedance)
3	Short-circuit impedance, or impedance range
4	Tolerances on voltage ratios and short-circuit impedances as left to agreement in IEC 60076-1 table 1, or deviating from values given in the table
5	Whether a generator transformer is to be connected to the generator directly or through switchgear, and whether it will be subjected to load rejection conditions which can give up to 1.4 times normal voltage in 5 seconds
6	Whether a transformer is to be connected directly or by a short length of overhead line to gas-insulated switchgear (GIS) Also connection of large power transformer with high current isolated phase bus duct has to be mentrioned
7	Altitude above sea level, if in excess of 1000 m (3300 ft)
8	Special ambient temperature conditions (see IEC 60076-1 section 1.2.1b), or restrictions to circulation of cooling air.
9	Expected seismic activity at the installation site which requires special consideration
10	Special installation space restrictions which may influence the insulation clearances and terminal locations on the transformer also the maintenance
11	Whether load current wave shape will be heavily distorted. Whether unbalanced three-phase loading is anticipated. In both cases, details to be given.
	Load with abnormal harmonics current, harmonic factor above 5%, may cause excessive losses and abnormal heating.
	Other special operation conditions such as :
	Continuous load operation at voltage and voltage per Hertz avove 105% of rated values, and above 110 % in no-load condition.
	Continuous operation at load power factor less than 80%
12	Whether transformers will be subjected to frequent over-currents
13	Details of intended regular cyclic overloading other than covered by IEC 60076-1 clause 4.2 (to enable the rating of the transformer auxiliary equipment to be estabilished)
14	Any other exceptional service conditions (unusual strong magnetic fields)
15	If a transformer has alternative winding connections, how they should be changed and which connection is required ex works
16	Short-circuit characteristics of the connected systems (expressed as short-circuit power or current, or system impedance data) and possible limitations affecting the transformer design (see IEC 60076-5)
17	Whether sound-level measurement is to be carried out (see IEC 60551)
18	Vacuum withstand of the transformer tank and, possibly, the conservator, if a specific value is required.
19	Any tests not referred to above which may be required.
20	Any information ragarding the required corrosion resistance or colour of the surface treatment in reference to the geographic zone and pollution zone has to be stated

III- Parallel Operations:

If parallel operation with existing transformers is required, this shall be stated and the following information on the existing transformers gives :

N°	INFORMATION	YES	NO
1	Rated power
2	Rated voltage ratio
3	Voltage ratios corresponding to tappings other than the principal tapping
4	Load loss at rated current on the principal tapping, corrected to the appropriate reference temperature
5	Short-circuit impedance on the principal tapping and at least on the extreme tappings, if the tapping range of the tapped winding exceeds ±5%
6	Diagram of connections, or connection symbol, or both

Note: On multi-winding transformers, supplementary information will generall be required