Temperature Rise Standard and Overload Capacity of 1500 kVA Dry Type Transformer

We know that the temperature rise standard and overload capacity of 1500 kVA dry type transformer units are not just technical afterthoughts-they are the decisive factors determining whether your power asset will deliver decades of trouble-free service or fail prematurely under stress.

 

Producing high-quality dry-type transformers for over 18 years, our factory engineers every Three-Phase Dry-type Transformer to meet and exceed IEC 60076-11 thermal requirements, bringing certified, reliable cast resin power transformer solutions to projects in over 60 countries.

 

Dry-type Transformer Power Frequency Withstand Voltage Test
 

 

For any dry distribution transformer, insulation aging is a thermal process: the hotter the winding runs, the faster the epoxy and conductor materials degrade. The temperature rise standard of 1500 kVA dry type transformer units, as defined by IEC 60076-11, limits the winding hot-spot temperature to protect the insulation system and guarantee the contracted lifespan of a cast resin distribution transformer. Insulation aging roughly doubles for every 6–8°C increase in continuous operating temperature, so even a small deviation from the rated temperature rise can cut the life of a dry core transformer by half.

 

As a cast resin dry type transformer manufacturers with deep expertise, GNEE maintains strict control over the temperature rise limits in every 1500 kVA Three-Phase Cast Resin Transformer. Our standard design targets a 100 K average winding rise under rated load and 1.0 p.u. cooling, ensuring Class F insulation (155°C) operates with a generous safety margin. This directly correlates with superior overload capacity and an expected operational life exceeding 30 years for an Indoor Three-Phase Transformer installed in a properly ventilated substation.

 

Key Thermal Failure Modes Avoided by Proper Temperature Rise Design

• Accelerated epoxy embrittlement leading to cracking of the cast coil dry type transformer winding
• Hot-spot gas bubble formation within the resin, triggering partial discharge
• Permanent degradation of inter-turn insulation, making the unit vulnerable to short-circuit forces
• Reduced overload capacity, turning a low loss dry-type transformer into a thermal bottleneck

 

 

The overload capacity of a 1500 kVA dry type transformer is the ability to continuously or temporarily supply current beyond the nameplate rating without exceeding the permissible winding hot-spot temperature. This is not a single number; it varies with ambient temperature, pre-load history, and cooling configuration.

 

GNEE's dry cast resin transformers are engineered with conservative thermal time constants, allowing substantial short-term overloads without triggering forced cooling or emergency load shedding.

 

Short-Time Emergency Overload Performance for Cast Resin Type Transformer

The following table presents the permissible overload durations for our 1500 kVA cast resin type transformer at different overload percentages, assuming natural air cooling (AN), 40°C maximum ambient, and an initial load of 50% of rated capacity. These values are validated through factory thermal testing on every Three-Phase Cast Resin Transformer batch.

 

Overload (% of Rated)	Permissible Duration (minutes)	Winding Hot-Spot Limit	Notes
10% (1650 kVA)	Continuous	130°C max	Requires ambient ≤ 30°C, low pre-load
20% (1800 kVA)	120 minutes	140°C	Allowable during N-1 contingency
30% (1950 kVA)	60 minutes	150°C (Class F limit)	Emergency only, expect reduced insulation life
40% (2100 kVA)	30 minutes	155°C	Not recommended for repetitive operation
50% (2250 kVA)	10 minutes	170°C (Class H winding)	Requires Class H insulation upgrade

 

 

The relationship between temperature rise standard and overload capacity of 1500 kVA dry type transformer products is fundamentally governed by the insulation thermal class. A dry cast resin transformer built with Class F materials (155°C maximum hot-spot) can operate at higher temperatures than a Class B unit, thus offering greater emergency overload headroom.

 

GNEE standardizes on Class F winding with Class H (180°C) upgrades available, allowing our cast resin distribution transformer to deliver significant overload flexibility.

 

Insulation Class vs. Temperature Rise Limits (IEC 60076-11)

Insulation Class	Maximum Winding Hot-Spot	Rated Average Winding Temperature Rise (AN)	Typical Overload Capability
B (130°C)	130°C	80 K	Moderate – limited overload margin
F (155°C)	155°C	100 K	High – standard for industrial dry-type transformer
H (180°C)	180°C	125 K	Very High – preferred for harsh environments, high-altitude, and frequent overloads

 

 

Below are the standard technical parameters for GNEE's 1500 kVA cast resin power transformer, which directly determine its temperature rise behavior and overload capacity.

Parameter	Specification
Rated Capacity	1500 kVA
HV Voltage	10 kV / 6.3 kV / 11 kV (customizable)
LV Voltage	0.4 kV / 0.69 kV
Insulation Class	F (155°C) / H (180°C) optional
Average Winding Temperature Rise (AN)	100 K (Class F) / 125 K (Class H)
Maximum Hot-Spot Temperature	130°C (F) / 150°C (H) under rated conditions
Cooling Method	AN (Air Natural) standard; AF (Air Forced) optional for +25% continuous overload
Short-Circuit Impedance	6% (standard)
No-Load Loss (SCB12)	≤ 1720 W
Load Loss at 120°C (SCB12)	≤ 8130 W
Acoustic Noise Level	≤ 62 dBA
Enclosure Protection	IP20 / IP23 / IP25 / IP31
Applicable Standards	IEC 60076-11, GB 1094.11

 

 

As a dedicated cast resin dry type transformer manufacturers, GNEE applies multiple proprietary techniques to ensure the thermal performance and overload capacity of every 1500 kVA Three-Phase Dry-type Transformer surpasses customer expectations.

 

Precision Winding and Cooling Duct Design for a Cast Coil Dry Type Transformer

Proper cooling of a cast coil dry type transformer relies on efficient heat transfer from the copper or aluminum conductors through the epoxy encapsulation to the ambient air. GNEE designs the winding with integrated axial and radial cooling ducts, which allow natural convection to carry heat away from the core and coils without dead zones. The result is a 1500 kVA dry core transformer with a uniform temperature distribution and no internal hot spots-critical for meeting the stringent temperature rise standard and preserving the overload capacity.

 

Vacuum Casting and Void-Free Insulation System

Our vacuum casting process for the cast resin distribution transformer ensures a homogeneous, bubble-free epoxy insulation layer around every conductor. Voids inside the resin act as thermal barriers and voltage stress concentrators, leading to localized overheating during overload conditions. By eliminating these imperfections, GNEE's dry distribution transformer maintains its rated temperature rise and full overload capacity even after years of thermal cycling.

 

Factory Temperature Rise Testing Protocol

Every 1500 kVA Cast Resin Power Transformer undergoes a comprehensive factory acceptance test including a simulated full-load temperature rise test. We measure winding resistance before and after applying a controlled current, calculating the average winding temperature rise by the resistance method. This test verifies that the temperature rise standard of the 1500 kVA dry type transformer is met and provides the baseline for the overload capacity curve included in the final documentation. Certificates from third-party laboratories can be provided for each batch, reinforcing the trust of our global customers in our cast resin type transformer quality.

 

Request A Quote

 

Ready to Specify a 1500 kVA Dry-Type Transformer with Full Thermal Performance Guarantee?

Contact GNEE today and receive a tailored solution, complete with overload curves and temperature rise test certificates specific to your project conditions.

 

Simply provide your project details:

• Ambient temperature and altitude at the installation site
• Desired overload scenarios (duration and percentage)
• Preferred insulation class and cooling method (AN or AF)
• Voltage ratings and required certification (IEC, CE, UL, GOST)
• Quantity and expected delivery timeline

 

FAQ

 

What is 1500 kVA transformer?

A 1500kVA transformer usually refers to apparent power (transformer capacity) of 1500kVA. Usually, its active power is 1200kw. Mostly used in power distribution systems, 1500 kVA distribution transformers can directly supply power to end-users. The high voltage of the transformer generally does not exceed 35kv.

 

What does 1500 kVA mean?

What Does kVA Mean on a Generator. A generator is one item where kVA is used as a measure of power. Essentially, the higher the kVA rating, the more power the generator produces. Kilovolt-amps (kVA) measure the Apparent Power of a generator, while kilowatts (kW) measure the Actual Power.

 

What is the voltage of A 1500kva transformer?

13200V

Transformer Features: With a transformer rating of 1.5 MVA (1500 KVA), the industrial transformer features a primary voltage of three-phase 13200V Delta and a secondary voltage of three-phase 480Y/277 Wye-n.

 

What is the full load current of a 1500kva transformer?

At 480V, a 1500 kVA three-phase transformer has a full load current of 1804.3 amps.