IEC 60076-21:2011 pdf – Power transformers – Part 21: Standard requirements, terminology, and test code for step-voltage regulators.
5.8 Losses
The losses specified by the manutaciurer shall be the no-load frwüation) lasses and ttl losses of a regulator, as defined in (‘lause 3.
5.8.1 Total losses
11w total losses of a voltage regulator shall be the sum of the no-load (excitation) and load losses.
5.8.2 Tolerance for losses
Unless otherwise specified, the losses represented by a test of a voltage regulator shall be subject to the lollowing tolerances: the no-load losscs of a voltage regulator shall not exceed the specified no-load losses by more than 10%. and the total losses of a voltage regulator shall not exceed the specified total losses by more than 6%. Failure to meet the loss tolerances shall not warrant immediate rejection but lead to consultation between purchascr and manufacturer about further investigation of possible causes and the conaeqocnccs of the higher losses.
NOTE—Smce losses will differ at different opcrating positions of tbc voltage regulator. care must be exercised in the consideration of map position with lasses Some sIyle of sicp-sobgc regulators will exhibit ajrcciablc ctiimgc in load loss when baouing versus bucking. or will exhibit apprcci4c change in no-load loss on alternate tap positions. See
5.8.3 DetermInation of losses and excitatIon current
No-load (excitation) losses md exciling current shall be determined for the rated voltage and frequency on a sine-wave basis, unless a dificrent form is inherent in the operation of the apparatus.
Load losses shall be determined for rated voltage. curreni and frequency and shall be corrected to a relerence temperature equal to the sum of the limiting (rated I winding temperature rise by resistaitce from Table 2 plus ‘0 ‘C.
Since losses may be very different at different operating positions and with various design options, losses shall he considered in practice as the sum of no-load md load kisses where:
a) No-load loss is the average olno-load loss in the neutral and next adjacent boost position with rated voltage applied to the shum or series winding for voltage regulators that do not include a series transformer,
NOTE—li will be appacnI. m the case of a Type B step-vohage regulator that is on the next adjacent boost position, that the excitation voltage applied at the source terminal will be higher at the shunt winding. Cat tmlst be exercised to ,sssure that rated excitation is present on the shuns winding; this may be accomplished b exciting the voltage rcgulatut from the load terminal.
b) No-load loss is reported for neutral position. mavimum boost position, and position adjacent-to- maximum boost position for voltage regulators that include a series transformer.
c) Load loss is the average load loss in both the maximum and adjacent-to-maximum buck positions. and the maximum and adjacent-to-maximum boost positions (that is. four positions) with rated current in the windings
5.9.3 Thermal capability of voltage regulators for short-circuit conditions
The temperature of the conductor material in the windings of voltage regulators under the short-circuitconditions specified in 5.9.1, as calculated by methods described in 8.9.4, shall not exceed 250 C for acopper conductor or 200 C for an electrical conductor (EC) aluminum. A maximum temperature of 250 Cshall be allowed for aluminum alloys that have resistance to annealing properties at 250 °C, equivalent toEC aluminum at 200 “C, or for application of EC aluminum where the charactceristics of the fully annealedmaterial satisfy the mechanical requirements. In setting thesc temperature limits, the following factors wereconsidered:
a)Gas generation from fluid or solid insulationb)Conductor annealing
c)Insulation aging
5.10 Tests
Tests are divided into two categories: routine and design.Routine tests are made for quality control by themanufacturer to verify during production that the product meets the design specifications. Design tests aremade to determine the adequacy of the design of a particular type,style,or model of equipment or itscomponent parts.Design adequacy includes but is not limited to: meeting assigned ratings, operatingsatisfactorily under normal service condition or under special conditions if specified, and compliance withappropriate standards of the industry.
5.10.1 Routine tests
Routine tests shall be made on all voltage regulators per the following list:
a) Resistance measurements of all windings (see 8.l)
b) Ratio test on all tap connections (see 8.2)
c) Polarity test (see 8.3)
d) Operational test of all devices.Controlled devices such as load tap changers,position indicators, fans, pumps, etc, shall be operated for proper functioning.
e) Leak test
f) No-load (cxcitation) loss at rated voltage and rated frequency (sec 8.4)
g) Excitation current at rated voltage and rated frequency (see 8.4)
h) lmpedance and load loss at rated currcnt and rated frequency (see 8.5)
i) Lightning impulse test (see 8.6.3)
j) Applied-voltage test (sec 8.6.5)kInduced-voltage test (see 8.6.6)
k) Insulation power factor test (sec 8.6.7).