This part of GB 1094 specifies the requirement for power transformers to be undamaged under the action of overcurrent caused by external short circuits. This section describes the calculation program for characterizing the heat resistance ability of power transformers to withstand this overcurrent, as well as the special experimental and theoretical evaluation methods for withstanding the corresponding dynamic stability ability (see Appendix A). This section applies to transformers within the scope specified in GB1094.1. 2 Normative References: The clauses in the following documents are referred to in this part of GB 1094 and become the clauses of this part. For dated reference documents, all subsequent amendments (excluding erroneous content) or revisions do not apply to this section. However, parties to agreements based on this section are encouraged to study whether the latest versions of these documents can be used. For undated references, the latest version applies to this section. GB 1094.1-1996 Power Transformers - Part 1: General (eqv IEC 60076-1:1993) GB 1094.3-2003 Power Transformers: Part 3: Insulation Levels, Insulation test and external insulation air gap (IEC 60076-3; 2000, MOD) GB 1094.11-2007 Power Transformers: Part 11: Dry type Transformers (IEC 60076-11:2004, MOD) GB/T 13499-2002 Application Guidelines for Power Transformers (idt IEC 60076-8; 1997) 3 Requirements for the ability to withstand short circuits 3.1 General. Transformers, their components and accessories should be designed and manufactured to withstand external short circuits under the conditions specified in 3.2 of this part, with no damage to the thermal and dynamic stability effect surface. External short circuits include three-phase short circuits, interphase short circuits, two-phase ground faults, and phase to ground faults. The current caused by these faults in the winding is referred to as "overcurrent" in this section. 3.2 Overcurrent conditions 3.2.1 General conditions 3.2.1.1 Service conditions that require special consideration The following conditions have an impact on the magnitude, duration, or frequency of overcurrent and require special consideration and should be clearly specified in the transformer technical specifications: - For voltage regulating transformers with very small impedance, the impedance of the connected current limiting device needs to be considered; --- The generator transformer is susceptible to high overcurrent caused by the loss of synchronization between the generator and the connected system—— Transformers directly connected to rotating motors (such as electric motors or synchronous phase modulators), which operate in a generating state under system fault conditions and supply current to the transformers; - specialized transformers and transformers installed in high fault rate systems (see 3.2.6)- When a fault occurs, there is an operating voltage above the rated value on the non fault terminal
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