GB/T 15544.4-2017 in English
VALIDShort-circuit current calculation in three-phase a.c. systems―Part 4:Currents during two separate simultaneous line-to-earth short circuits and partial short-circuit currents flowing through earth
- Issued on:2017-12-29
- Implemented on:2018-07-01
- File Format:PDF
- Delivery:Via email within 5 business days
$592.00
《GB/T 15544.4-2017三相交流系统短路电流计算 第4部分：同时发生两个独立单相接地故障时的电流以及流过大地的电流》由TC424（全国短路电流计算标准化技术委员会）归口，主管部门为中国电力企业联合会。
Introduction
Analysis of the core content of the standard
| Calculation scenario | Key formula | Typical application |
|---|---|---|
| Dual independent single-phase ground short circuit | Formula (4): IKEE''=3cUn/[Z(1)A+Z(2)A+Z(1)B+Z(2)B+M(1)+M(2)+M(0)] | Fault analysis of ungrounded neutral point system |
| Overhead line reduction factor | Formula (33): r=1-ZQL'/ZQ' | Ground wire shunt calculation and grounding system design |
| Three-core cable current distribution | Formula (37): r1=RS'/[RS' + ωμ0/2π·ln(δ/rS)] | Cable sheath grounding current calculation |
Technical evolution and implementation points
Standard development background
This part is GB/T Part 4 of the 15544 series is equivalent to the IEC 60909-3:2009 international standard, and mainly solves the following problems:
- Current distribution problem of double ground fault in neutral point ungrounded system
- Calculation of ground potential rise in directly grounded system
- Quantitative method of current distribution in overhead line and cable system
Key technical innovations
- Reduction coefficient model: An accurate algorithm for the current split ratio of ground wire/sheath is established through equations (33)-(39)
- Infinite chain impedance theory: The ZP calculation method proposed in equation (1) simplifies the analysis of multi-tower system
- Soil resistivity classification: Table 2 gives the corresponding relationship between ρ and δ for 8 types of soil to improve the calculation accuracy
Engineering application guide
Implementation precautions
- For overhead lines, when the distance between towers is dT>δ/2, finite link impedance correction shall be adopted.
- Three-core cable systems shall check the maximum step voltage according to equations (45)-(46).
- Faults near the power station (DF<3√(RTdT)) shall be handled specially according to Chapter 6.4.
Typical calculation process
Step 1: Determine system topology and parameters (Z(1), Z(0), ρ, etc.)
Step 2: Calculate the reduction factor (Equation 33 for overhead lines and Equation 37/48 for cables)
Step 3: Establish an equivalent circuit (Figures 4/5/9/10)
Step 4: Solve the fault current distribution (Equation 13/22/42, etc.)
Step 5: Check the ground potential (Equation 18/24/30)
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