IEC 61378-2 pdf download – Convertor transformers — Part 2: Transformers for HVDC applications

IEC 61378-2 pdf download – Convertor transformers — Part 2: Transformers for HVDC applications
9.3Sound-power level at site
A correlation between the convertor transformer sound levels measured at the factory andthose on site has not been identified. The difference may be 10 dB(A) to 20 dB(A). lt isimportant that this difference is recognized by the purchaser when specifying sound levels.
10 Testing
10.1 General
The tests and measurements shall be made in accordance with IEC 60076-1 except for thosetests described in 10.3 to 10.6.
10.2 Tests
10.2.1 Routine tests
The following tests shall be performed on all transformers, not necessarily in the order given;- vector group (10.3 of lEC 60076-1);
– voltage ratio (10.3 of lEC 60076-1);
winding resistance (10.2 of lEC 60076-1);no-load losses and currents;
losses and impedances (main taps) (10.4 and 10.5 of lEC 60076-1);oil samples (lEC 60567);
switching impulse test (clause 15 of lEC 60076-3);-lightning impulse test (clause 13 of IEC 60076-3);
d.c. separate source-voltage withstand test including partial discharge and acousticdetection measurements;
polarity reversal including partial discharge measurements;
a.c. separate source-voltage withstand test and partial discharge measurements(clause 11 of IEC 60076-3);
– induced overvoltage test and partial discharge measurements (clause 12 of lEC 60076-3);- insulation resistances;
– test of the magnetic circuit insulation and associated insulation.
il samples shall be taken for analysis at the beginning,during and at the end of the testsequence.The samples taken during the test sequence shall be taken at the end of majortests as agreed between purchaser and supplier. The samples taken at the beginning and endof the test sequence shall be analysed. if a difference in the analysis of the oil is detected, theintermediate samples should then be analysed.
10.2.2 Type tests
The following tests shall be performed on one of each type of transformer, not necessarily inthe order given:
– temperature-rise test (IEC 60076-2);- sound-power level (IEC 60076-10);
-sound-power level of cooling equipment (IEC 60076-10).
10.2.3 Special tests
The following tests shall be performed，not necessarily in the order given, when specificallyrequested by the purchaser:
– recurrent surge oscillograph(RSO) measurements;-short-circuit withstand test (clause 2 of lEC 60076-5y:
– losses and impedances (other taps) (10.4 and 10.5 of lEC 60076-1 and lEC 61378-1);-zero-phase sequence impedances (10.7 of IEC 60076-1);
-load-current test.
10.2.4 Commissioning tests
Commissioning tests, as agreed between purchaser and supplier, shall be performed on site.10.3 Load-loss measurements
10.3.1 General
The load-loss test shall be made with currents of sinusoidal shape. In order to establish theloss under service conditions,two loss measurements are required.One measurement shallbe made at rated frequency and the second one at a frequency not less than 150 Hz.Basedon these measurements a calculation shall be made
a) to establish the distribution of additional stray losses inside and outside the windings;b) to determine the load loss during service.
The method of loss measurements shall be as prescribed in 10.4 of lEC 60076-1, with thecurrent magnitude at rated frequency equal to rated current and that at elevated frequencybetween 10 % and 50 % of the rated current. The measurements with the two frequenciesmake it possible to separate the stray losses into two components,one related to the straylosses in the windings. PwE. and the other in structural parts，PsE-
NOTE 1 The proportionality between the individual loss components can be assumed to be constant for currentharmonics in the winding current above 10 % of rated current.
NOTE 2 North American practice may allow an alternative method of load-loss determination based on themeasurement of losses at multiple frequencies.
10.3.2 Calculation procedure
The load losses obtained from measurements with the two different frequencies, f， and f,, andthe corresponding currents,land l, are denoted Pand P, giving
The two above equations permit the evaluation of the two eddy loss components，Pwe，andPsE1-