BS IEC 60076-8:1997

FOREWORD
1 General
2 Characteristic properties of different three-phase
    winding combinations and magnetic circuit designs
3 Characteristic properties and application of auto-
    connected transformers
4 Zero-sequence properties - neutral load current and earth
    fault conditions, magnetic saturation and inrush current
5 Calculation of short-circuit currents in three-winding,
    three-phase transformers (separate winding transformers
    and auto-connected transformers) with earth neutrals
6 Parallel operation of transformers in three-phase systems
7 Calculation of voltage drop for a specified load,
    three-winding transformer load loss
8 Specification of rated quantities and tapping quantities
9 Convertor applications with standard transformers
10 Guide to the measurement of losses in power transformers
Annex A Basic relations for single-phase and two-phase
          earth faults

Information to help in determining and selecting characteristics of transformers complying with BS 171. Covers tapping quantities, winding connections, parallel operation, loading capability of the neutral point and calculation of voltage drop or rise for a specified load condition.

This Standard applies to power transformers complying with the series of publications IEC 60076.

It is intended to provide information to users about:

• certain fundamental service characteristics of different transformer connections and magnetic circuit designs, with particular reference to zero-sequence phenomena;

• system fault currents in transformers with YNynd and similar connections;

• parallel operation of transformers, calculation of voltage drop or rise under load, and calculation of load loss for three-winding load combinations;

• selection of rated quantities and tapping quantities at the time of purchase, based on prospective loading cases;

• application of transformers of conventional design to converter loading;

• measuring technique and accuracy in loss measurement.

Part of the information is of a general nature and applicable to all sizes of power transformers. Several chapters, however, deal with aspects and problems which are of the interest only for the specification and utilization of large high-voltage units.

The recommendations are not mandatory and do not in themselves constitute specification requirements.

Information concerning loadability of power transformers is given in IEC 60354, for oil­ immersed transformers, and IEC 60905, for dry-type transformers.

Guidance for impulse testing of power transformers is given in IEC 60722.