By what the low-voltage side connects to. The distribution type has a fixed 0.4 kV low voltage feeding terminal loads directly, covers 50–1600 kVA and holds 6.5% impedance throughout. The power type has a medium-voltage low side of 3.15, 6.3 or 10.5 kV feeding the next level of switchgear, and starts at 630 kVA. The 630 to 1600 kVA stretch is in both tables with identical loss figures; only the low voltage and the vector group differ.
35 kV Oil-Immersed Power Transformer
For distribution contractors, panel builders and industrial project owners: the ETENZ 35 kV oil-immersed power transformer covers 50–1600 kVA in the distribution table and 630–31500 kVA in the power table, with off-circuit or on-load tap changing — for step-down main transformers on a 35 kV incomer, industrial captive substations and renewable plant step-up duty.
Primary Equipment E-HousePV Inverter Step-Up StationRenewable Energy Collector Station Support
Key Metrics
50–1600kVA
Distribution
630–31500kVA
Power
2000–20000kVA
On-load
6.5–8.0%
Impedance
Product Features
Two rating tables
The distribution type runs 50–1600 kVA with a 0.4 kV low voltage feeding terminal loads directly, at 6.5% impedance throughout. The power type runs 630–31500 kVA with a medium-voltage low side of 3.15, 6.3 or 10.5 kV, supplying the next level of switchgear. The two differ in low voltage and in vector group, so the first step in selection is settling which one applies.
Two rating tables
The distribution type runs 50–1600 kVA with a 0.4 kV low voltage feeding terminal loads directly, at 6.5% impedance throughout. The power type runs 630–31500 kVA with a medium-voltage low side of 3.15, 6.3 or 10.5 kV, supplying the next level of switchgear. The two differ in low voltage and in vector group, so the first step in selection is settling which one applies.
Two rating tables
The distribution type runs 50–1600 kVA with a 0.4 kV low voltage feeding terminal loads directly, at 6.5% impedance throughout. The power type runs 630–31500 kVA with a medium-voltage low side of 3.15, 6.3 or 10.5 kV, supplying the next level of switchgear. The two differ in low voltage and in vector group, so the first step in selection is settling which one applies.
On-load switching
The on-load type covers 2000–20000 kVA with a ±3×2.5% tapping range and adjusts voltage under load, with no outage. The off-circuit type reaches 31500 kVA with ±5% or ±2×2.5%, and the transformer has to be de-energised to change taps.
Capacity boundaries
Crossing 3150 kVA changes the high-voltage range from 35 kV to 35–38.5 kV. Crossing 8000 kVA changes the vector group from Yd11 to Ynd11, the tapping range to ±2×2.5%, and adds low-voltage options. Impedance steps at 3150, 8000 and 12500 kVA. The three sets of boundaries do not fall on the same capacity.
Only no-load differs
Load loss, no-load current and impedance are cell for cell the same across the two performance levels; the difference sits in no-load loss — 940 W against 830 W at 630 kVA, and 22.75 kW against 20.22 kW at 31500 kVA. The same holds for SZ10 against SZ11 on the on-load side.
Special conditions
High altitude, seismic and anti-corrosion seismic service each carry their own product code. Normal conditions are altitude not above 1000 m, maximum +40 °C and minimum −25 °C; where the site falls outside that range it is raised at the ordering stage and settled as a special service condition.
Product Details
The leading S is three-phase oil-immersed; a Z in the second position means on-load tap changing and its absence means off-circuit — that position decides whether taps can be changed under load, and it is the first fork in selection at this class. The digits that follow are the performance-level code, and M means the fully sealed construction. Rated capacity and rated high voltage follow the code, written as "-capacity/voltage". SZ11-M-6300/35 therefore reads: three-phase oil-immersed, on-load tap changing, performance level 11, fully sealed, 6300 kVA, 35 kV. GY is the suffix for high altitude, WZ for seismic and WFZ for anti-corrosion seismic duty.
The distribution type covers 50 to 1600 kVA with the low voltage fixed at 0.4 kV, vector group Dyn11 or Yyn0 and 6.5% impedance throughout, feeding terminal loads directly. At 500 kVA and below, load loss is tabulated separately by vector group; above 630 kVA it no longer is. The power type starts at 630 kVA with a medium-voltage low side of 3.15, 6.3 or 10.5 kV, feeding the next level of switchgear rather than terminal loads; the vector group is Yd11 up to 6300 kVA and Ynd11 from 8000 kVA. The 630 to 1600 kVA stretch appears in both tables with identical loss figures, and the only differences are the low voltage and the vector group. On a project it comes down to one question, and ETENZ settles it from the low-voltage connection on the single-line diagram before quoting any value: is the low side a 0.4 kV distribution board or a medium-voltage busbar.
The high-voltage range changes at 3150 kVA: below it, 35 kV; at and above it, 35–38.5 kV. Vector group, tapping range and low-voltage options all change together at 8000 kVA: up to 6300 kVA it is Yd11, ±5% taps and 3.15/6.3/10.5 kV; from 8000 kVA it is Ynd11, ±2×2.5% taps, and 3.3, 6.6 and 11 kV are added to the low-voltage list. Short-circuit impedance has four bands with boundaries at 3150, 8000 and 12500 kVA: 6.5% for 630–2500 kVA, 7.0% for 3150–6300 kVA, 7.5% for 8000–10000 kVA and 8.0% from 12500 kVA up. The three sets fall on different capacities, so take the values item by item from the row selected rather than applying a whole capacity band at once.
Off-circuit tap changing is simple in construction and lower in cost, requires an outage to switch, and suits sites where the supply voltage is steady and taps are adjusted once or twice a year. It reaches 31500 kVA. On-load tap changing switches under load with a ±3×2.5% range and suits loads where voltage swings or voltage quality matters — metallurgy, chemicals, data centres, and renewable plant connection points where both the direction and the magnitude of power flow change. The on-load table covers 2000 to 20000 kVA; the two capacity steps above that have no on-load version. An on-load unit has slightly higher losses than the off-circuit unit of the same rating: at 2000 kVA the SZ11 is 2.30 kW no-load and 19.24 kW load loss, against 2.18 kW and 18.38 kW for the S11. The tap changer itself also needs periodic inspection and contact-life management, and that maintenance cost belongs in the selection arithmetic.
Delivery Scope Options
Scope 1
Single Unit or Complete Package Supply
Scope 1Single Unit or Complete Package Supply
Transformers are supplied as single units against the order schedule, or as a complete package together with the protective enclosure, the temperature controller and the cooling fans. The active part is wound, assembled and routine-tested at the works and shipped as a complete unit; the assembly interface for the accessories follows the transport conditions. Where the transformer is to arrive together with a prefabricated power module, the E-House line takes on the enclosure, the internal arrangement and the foundation fixing, and the transformer is delivered as equipment housed within it.
Scope Includes:
Single unit or complete package
Complete-unit shipment and assembly interface
Foundation and fixing interface
In-cabin delivery handled by the E-House line
Scope 1
Single Unit or Complete Package Supply
Scope 1Single Unit or Complete Package Supply
Transformers are supplied as single units against the order schedule, or as a complete package together with the protective enclosure, the temperature controller and the cooling fans. The active part is wound, assembled and routine-tested at the works and shipped as a complete unit; the assembly interface for the accessories follows the transport conditions. Where the transformer is to arrive together with a prefabricated power module, the E-House line takes on the enclosure, the internal arrangement and the foundation fixing, and the transformer is delivered as equipment housed within it.
Scope Includes:
Single unit or complete package
Complete-unit shipment and assembly interface
Foundation and fixing interface
In-cabin delivery handled by the E-House line
Technical Specifications
Product form
35 kV class three-phase two-winding oil-immersed transformer, off-circuit or on-load tap changing
Rated capacity, distribution type
50–1600 kVA
Rated capacity, power type
630–31500 kVA (off-circuit)
Rated capacity, on-load type
2000–20000 kVA
Rated high voltage (below 3150 kVA)
35 kV
Rated high voltage (3150 kVA and above)
35–38.5 kV
Rated low voltage, distribution type
0.4 kV
Rated low voltage, power type
3.15, 6.3, 10.5 kV; 3.3, 6.6 and 11 kV added from 8000 kVA
Off-circuit tapping range
±5% (≤6300 kVA); ±2×2.5% (≥8000 kVA); ±2×2.5% available on the distribution type on request
On-load tapping range
±3×2.5%
Vector group, distribution type
Dyn11 or Yyn0
Vector group, power type
Yd11 (≤6300 kVA); Ynd11 (≥8000 kVA)
Short-circuit impedance, distribution type
6.5% throughout
Short-circuit impedance, power type
6.5% (630–2500); 7.0% (3150–6300); 7.5% (8000–10000); 8.0% (12500–31500 kVA)
No-load loss (630 kVA)
S10 940 W; S11 830 W
Load loss (630 kVA)
7870 W, the same for S10 and S11
No-load loss (31500 kVA)
S10 22.75 kW; S11 20.22 kW
Load loss (31500 kVA)
112.86 kW, the same for S10 and S11
On-load type losses (2000 kVA)
SZ10 2.59 kW no-load / 19.24 kW load; SZ11 2.30 kW no-load / 19.24 kW load
No-load current
1.10% at 630 kVA falling to 0.32% at 31500 kVA
Cooling
ONAN oil-immersed natural cooling; ONAF forced air available at larger ratings
Overall dimensions and weight
Designed specifically to the project requirement and confirmed with the drawings
Service conditions
Outdoor; maximum +40 °C, minimum −25 °C, hottest month average +30 °C, altitude not above 1000 m
Special service conditions
High altitude, seismic and anti-corrosion seismic duty carry their own product codes and are raised when ordering
| Parameter | Specification |
|---|---|
| Product form | 35 kV class three-phase two-winding oil-immersed transformer, off-circuit or on-load tap changing |
| Rated capacity, distribution type | 50–1600 kVA |
| Rated capacity, power type | 630–31500 kVA (off-circuit) |
| Rated capacity, on-load type | 2000–20000 kVA |
| Rated high voltage (below 3150 kVA) | 35 kV |
| Rated high voltage (3150 kVA and above) | 35–38.5 kV |
| Rated low voltage, distribution type | 0.4 kV |
| Rated low voltage, power type | 3.15, 6.3, 10.5 kV; 3.3, 6.6 and 11 kV added from 8000 kVA |
| Off-circuit tapping range | ±5% (≤6300 kVA); ±2×2.5% (≥8000 kVA); ±2×2.5% available on the distribution type on request |
| On-load tapping range | ±3×2.5% |
| Vector group, distribution type | Dyn11 or Yyn0 |
| Vector group, power type | Yd11 (≤6300 kVA); Ynd11 (≥8000 kVA) |
| Short-circuit impedance, distribution type | 6.5% throughout |
| Short-circuit impedance, power type | 6.5% (630–2500); 7.0% (3150–6300); 7.5% (8000–10000); 8.0% (12500–31500 kVA) |
| No-load loss (630 kVA) | S10 940 W; S11 830 W |
| Load loss (630 kVA) | 7870 W, the same for S10 and S11 |
| No-load loss (31500 kVA) | S10 22.75 kW; S11 20.22 kW |
| Load loss (31500 kVA) | 112.86 kW, the same for S10 and S11 |
| On-load type losses (2000 kVA) | SZ10 2.59 kW no-load / 19.24 kW load; SZ11 2.30 kW no-load / 19.24 kW load |
| No-load current | 1.10% at 630 kVA falling to 0.32% at 31500 kVA |
| Cooling | ONAN oil-immersed natural cooling; ONAF forced air available at larger ratings |
| Overall dimensions and weight | Designed specifically to the project requirement and confirmed with the drawings |
| Service conditions | Outdoor; maximum +40 °C, minimum −25 °C, hottest month average +30 °C, altitude not above 1000 m |
| Special service conditions | High altitude, seismic and anti-corrosion seismic duty carry their own product codes and are raised when ordering |
Product FAQs
It follows the voltage swing and how often taps are adjusted. Off-circuit switching needs an outage and suits sites where the supply voltage is steady and taps move once or twice a year; it reaches 31500 kVA. On-load switches under load with a ±3×2.5% range and suits metallurgy, chemicals and data centres, and renewable connection points where the direction and magnitude of power flow both change; it covers 2000–20000 kVA. The price is slightly higher losses (SZ11 at 2000 kVA is 2.30 kW no-load against 2.18 kW for the S11) and a tap changer that needs periodic inspection and contact-life management.
Three sets, and their boundaries are not in the same place. The high-voltage range changes at 3150 kVA (35 kV becomes 35–38.5 kV); vector group, tapping range and low-voltage options change together at 8000 kVA (Yd11 becomes Ynd11, ±5% becomes ±2×2.5%, and 3.3/6.6/11 kV are added); short-circuit impedance has four bands with boundaries at 3150, 8000 and 12500 kVA. Take the values item by item from the row selected rather than applying a whole capacity band at once.
At this voltage class the radiator arrangement, conservator position, bushing orientation and transport gauge all follow the project conditions, so dimensions are designed specifically to the requirement and there is no standard table. In practice that adds one round of design confirmation: foundation dimensions, wheel gauge, lifting hole positions, oil pit volume and the transport plan can only be fixed once the drawings are confirmed, so allow for that round in the project programme.
Only in no-load loss. Load loss, no-load current and impedance are cell for cell the same — 7870 W load loss at 630 kVA for both, 112.86 kW at 31500 kVA for both. No-load is 940 W against 830 W at 630 kVA and 22.75 kW against 20.22 kW at 31500 kVA. The same holds for SZ10 against SZ11. The saving follows directly from the annual energised hours and is independent of load factor.
There are product codes for it. Normal service conditions are altitude not above 1000 m, maximum +40 °C, minimum −25 °C and hottest month average +30 °C. Where high altitude, seismic or anti-corrosion seismic duty takes the site outside that range, it is raised at the ordering stage, and insulation distances, cooling capability and external protection are settled again as a special service condition rather than taken from the standard table.
Yes. Where it travels with the module, the prefabricated power module line takes on the enclosure, the internal arrangement and the foundation fixing, and the transformer leaves the works as equipment inside it. The overall shape at this class is designed specifically anyway, which makes it natural to merge that with the module layout drawing into a single round of confirmation — transformer outline, oil pit volume, maintenance aisles, cooling air path and lifting hole positions settled at once, saving a cycle against confirming them separately.
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