Recommended Practice for Performing Temperature Rise Tests on Oil-Immersed Power Transformers at Loads Beyond Nameplate Ratings
|Publication Date:||7 May 2018|
This recommended practice covers temperature rise test procedures for determining those thermal characteristics of power transformers needed to appraise the transformer's load carrying capabilities at specifi c loading conditions other than rated load.
These recommended test procedures for performing temperature rise tests on power transformers are for the purpose of the following:
a) Determining the thermal characteristics of a transformer needed to appraise the thermal performance of a transformer at loads other than nameplate rating
b) Verifying that a transformer can be loaded with a specified load profile without exceeding specified temperature rise
c) Assessing a transformer's performance during transient loading, simulating a load cycle that includes loads in excess of nameplate rating
Tests performed in accordance with Clause 9 are for the purpose of determining transformer thermal characteristics in a consistent manner. Data may then be accumulated from a large number of transformers and used to evaluate the accuracy of the equations and the empirical constants used in the loading guides.
Tests performed in accordance with Clause 10 are for the purpose of demonstrating the thermal effects of loading a transformer with a specified sequence of loads, including loads beyond nameplate rating.
Tests performed in accordance with Clause 11 are for the combined purposes of determining the thermal characteristics of a transformer and demonstrating the thermal effects of loading with a designated load cycle. This is accomplished by performing temperature rise tests at three loads, similar to Clause 9, except the three loads are selected to simulate the thermal effects of a specific load cycle.
It is not intended that all of these procedures be performed on a transformer design. It is intended that only one of the following combinations of test procedures be specified:
- Clause 9 only, when thermal characteristics are to be determined
- Clause 10 only, when only verification of complying with temperature limits when loaded to a specific load profile is needed
- Clause 9 plus Clause 10, when both thermal characteristics and verification of compliance with temperature limits when loaded to a specific load profile are needed
- Clause 11 when both thermal characteristics and verification of compliance with temperature limits when loaded to a specific load profile are required, and the load profile can be represented with three steady state loads
The user should specify which of the test procedures are required at the time of specification.
A further purpose of these procedures is to obtain information with respect to possible loading limitations imposed on the transformer by liquid levels and ancillary equipment when the transformer is operated at loads beyond nameplate rating.