USD
EUR
GBP
CAD
AUD
CHF
HKD
JPY
RUB
BRL
CLP
NOK
DKK
SEK
KRW
ILS
MXN
CNY
SAR
SGD
NZD
ARS
INR
COP
AED
Home
Products
Current Transformer
Three phase CT Protection Current Transformer High Voltage Current Transformer
Indoor current transformer Outdoor current transformer Indoor voltage transformer Outdoor voltage transformer
Summation Current Transformer Mini Current Transformer
Combined Current Transformer Loading-Type Current transformer Bus Bar-Type Current transformer Pin-type Current Transformer Current-Voltage Transformer DC Immune CT Voltage Power Transformer Zero-Sequence Current Transformer Special Current Transformer
Low Voltage Current Transformer
Residual Current Sensor
Flexible Rogowski coil
Split Core Current Transformer
Current transducer
Current Sensor
Closed Loop Hall Effect Current Sensor DC leakage current sensor Hall Effect Current Transmitter Hall Effect Voltage Sensor & Transmitter Open Loop Hall Effect Current Sensor
Shunt
Zero Sequence CT
Indicator lamp
Transformer
Others
Overvoltage And Undervoltage Protector Digital Meter Insulator Inverter Controller Voltage Stabilizer Meter Socket Smart Circuit Breaker
Case
Case Example
Download
About Us
Contact Us
Contact Us
News
Company News
Industry News
Technical Standard
Feedback

Technique used in temperature rise test of oil-immersed transformers to determine the thermal constant by an experimental estimation

Views : 622
Update time : 2024-09-27 08:41:19
List of symbols: 

Temperature in °C

Oil temperature, varying with time (this may be the temperature of the oil at the top, or average oil temperature

External cooling medium temperature (ambient air or water) assumed to be constant

Oil temperature rise above
Ultimate values in steady state

Remaining deviation from steady-state value
Time constant for exponential variation of bulk oil temperature rise

Time interval between readings

Three successive temperature readings with time interval h between them. 

In principle, the test should continue until the steady-state temperature rise (of the oil) is ascertained.  
It is considered that: 

– the ambient temperature is kept as constant as possible; 

– the oil temperature will approach an ultimate value along an exponential function with a time constant of To; 

– the equation (2D.2) is a good approximation of the temperature curve (see Figure 2D.1). 

Given three successive readings, the exponential relation of equation (2D.2), is a good approximation of the temperature curve, then the increments will have relation.

Successive estimates are to be made and they should converge. In order to avoid large random numerical errors the time interval h should be approximately To should be not less than 0.95. 

A more accurate value of steady-rate temperature rise is obtained by a least square method of extrapolation of all measured points above approximately 60 % (estimated by the three point method). 
Previous :
Next :
Related News
Read More >>
Where Is the HK-58 Current Transformer Used in Malaysian LV Projects? Where Is the HK-58 Current Transformer Used in Malaysian LV Projects?
Sep .28.2026
HK-58 current transformer is designed for Malaysian LV switchboards, busbar panels and energy monitoring upgrades, enabling easier current measurement in factories and commercial buildings without major wiring changes.
Together Under the Same Moon: Celebrating Mid-Autumn Festival with Our Team Together Under the Same Moon: Celebrating Mid-Autumn Festival with Our Team
Sep .24.2026
HEYI celebrates the Mid-Autumn Festival by preparing thoughtful gifts for employees, expressing appreciation for their dedication, teamwork, and contribution while highlighting a warm and people-centered company culture.
Where Is the LMK5-100 Current Transformer Used in Australian Electrical Projects? Where Is the LMK5-100 Current Transformer Used in Australian Electrical Projects?
Sep .18.2026
Explore where the LMK5-100 current transformer is used in Australian switchboards, energy meters, busbar systems, factories, solar projects and infrastructure for accurate high-current energy monitoring.
Where Is a Current Transformer Used in South Africa’s LV Electrical Projects? Where Is a Current Transformer Used in South Africa’s LV Electrical Projects?
Sep .14.2026
Discover where a current transformer can be used in South Africa’s LV projects. Learn how DP-23 supports electrical panels, energy meters, motors, HVAC, and LV busbars with split-core installation, flexible ratios, and easy retrofit.