EXERCISE NUMBER 4 – ELEARNING SUBJECT ELECTROMAGNETIC TRANSIENT PROCESS MISSION CALCULATE, SOFTWARE SIMULATION

VIETNAM GENERAL CONFEDERATION OF LABOUR TON DUC THANG UNIVERSITY FACULTY OF ELECTRICAL & ELECTRONICS ENGINEERING EXERCISE NUMBER 4 – ELEARNING SUBJECT: ELECTROMAGNETIC TRANSIENT PROCES

VIETNAM GENERAL CONFEDERATION OF LABOUR

TON DUC THANG UNIVERSITY FACULTY OF ELECTRICAL & ELECTRONICS ENGINEERING

EXERCISE NUMBER 4 – ELEARNING

SUBJECT: ELECTROMAGNETIC TRANSIENT PROCESS

MISSION: CALCULATE, SOFTWARE SIMULATION

ADVISED BY: Dr NGUYỄN CÔNG TRÁNG

BY: NGUYỄN NGỌC HOÀNG VŨ, StudentID code: 41900916

NGUYỄN VĂN THẮNG, StudentID code: 41900877 NGUYỄN MINH THUẬN, StudentID code: 41900891 TRANG THANH TUẤN, StudentID code: 41900912

LÊ MINH THẮNG, StudentID code: 41900875

HO CHI MINH CITY, 2021

I Introduce the problem and calculate

The figure:

Detailed specifications:

Generator: SrG1 = 117,5 MVA; UrG1 = 10 KV; Cosφ = 0.85; 𝑋𝑑′′= 0.1593 , 𝐸𝐺1′′ = 6.6 kV

System: 𝑆𝑘.𝑠𝑦𝑠′′ = 176.5 MVA;

Transformers: SrT1 = SrT2 = 125 MVA; Uđm = 10.5/115 KV; UkT1 % = UkT2 % = 10.5%;

T3: SrT3= 200 MVA; Uđm = 15.75/242 KV; UkT3% = 11%;

Lines: l1 = 45 km; l2 = 23km; l3= 40km; All 4 lines have X’= 0.4 Ω/km, R’ = 0.3 Ω/km, 110kV

Loads: stuck on busbar 22kV, SrL = 15 MVA, Cosφ = 0.8; 𝑋𝑟𝐿′′ = 0.4

Calculate short circuit:

Choose 𝑈𝑏𝑠=10KV

Ta có:

System: 𝑋𝑠𝑦𝑠= 𝑈2𝑏𝑠

𝑆′′𝑘.𝑠𝑦𝑠= 10

2

176,5=0.57 𝛺 Line 1: 𝑋𝐿1=𝑋′𝐿*𝑙1∗(𝑈𝑏𝑠

𝑈𝑙)2=0.4*45*(10

110)2=0.15 𝛺

𝑅𝐿1=𝑅′𝐿*𝑙1∗(𝑈𝑏𝑠

𝑈𝑙)2=0.11 𝛺 Line 2:𝑋𝐿2=𝑋′𝐿*𝑙2∗(𝑈𝑏𝑠

𝑈𝑙)2=0.6*23*(10

110)2=0.08 𝛺

𝑅𝐿2=𝑅′𝐿*𝑙2∗(𝑈𝑏𝑠

𝑈𝑙)2=0.06 𝛺 𝐿𝑖𝑛𝑒 3: 𝑋𝐿3=𝑋′𝐿*𝑙3∗(𝑈𝑏𝑠

𝑈𝑙)2=0.4*40*(10

110)2=0.13 𝛺

𝑅𝐿3=𝑅′𝐿*3 ∗(𝑈𝑏𝑠

𝑈𝑙)2=0.1 𝛺 Trans1, 2:

𝑋𝑇1 = 𝑋𝑇2 = 𝑍𝑇1 = 𝑍𝑇2=𝑈𝑘𝑇1%

100 *𝑈

2 𝑏𝑠

𝑆𝑟𝑇1=10,5

100 ∗102

125=0.084 𝛺

Trans3:

𝑋𝑇3 = 𝑍𝑇3=𝑈𝑘𝑇3%

100 *𝑈

2 𝑏𝑠

𝑆𝑟𝑇3=11

100∗102

200=0.055 𝛺

Loads:

𝑅𝑟𝑙=𝑈2𝑏𝑠

𝑆𝑟𝑙 * Cos(𝜑)= 10

2

15*0.85=5.3 𝛺

𝑋𝑟𝑙=𝑈

2

𝑏𝑠

𝑆𝑟𝑙 * Sin(𝜑)= 10

2

15*0.6=4 𝛺

𝐸𝐿=𝑉𝑟𝑙*√(𝑐𝑜𝑠𝑐𝑜𝑠 𝜑 )2+ (𝑠𝑖𝑛)2− 𝑋′′𝑟 =22* √(0,8)2+ (𝑠𝑖0.6 − 0.4)2− 𝑋′′𝑟

=17,1KV

Electromotive of system return to base voltage chosen: 𝐸𝑠𝑦𝑠 = 𝑈𝑏𝑠=10KV

Generator: 𝑋𝐺 = 𝑋′′𝐷=𝑈

2 𝑏𝑠

𝑆𝑟𝐺= 10

2

117,5=0.14 𝛺

𝑍1=𝑋𝐺 + 𝑋𝑇1=0.14j+0.084j=0.224j

𝑍2=𝑋𝑇3+ 𝑋𝑠𝑦𝑠=0.055j+0.57j=0.625j

𝑍3=𝑋𝑇3+ 𝑋𝑟𝑙=0.084j+5.1+4j=5.3+4.084j

𝑍𝐿12=𝑍 𝑍𝐿1∗𝑍𝐿2

𝐿1 +𝑍𝐿2+𝑍𝐿3= (0.11+0.15𝑗)∗(0.06+0.08𝑗)

0.11+0.15𝑗+0.06+0.08𝑗+0.1+0.13𝑗 = 0.025+0.03j

𝑍𝐿13=𝑍 𝑍𝐿1∗𝑍𝐿3

𝐿1 +𝑍𝐿2+𝑍𝐿3= (0.11+0.15𝑗)∗(0.1+0.13𝑗)

0.11+0.15𝑗+0.06+0.08𝑗+0.1+0.13𝑗 = 0.04+0.05j

𝑍𝐿23=𝑍 𝑍𝐿2∗𝑍𝐿3

𝐿1 +𝑍𝐿2+𝑍𝐿3 = (0.06+0.08𝑗)∗(0.06+0.08𝑗)

0.11+0.15𝑗+0.06+0.08𝑗+0.1+0.13𝑗 = 0.02+0.03j

𝑍4 = 𝑍𝐿13 + 𝑍2=0.04+0.05j+0.625j=0.04+0.675j

𝑍5 = 𝑍𝐿23 + 𝑍3=0.02+0.03j+5.3+4.084j=5.32+4.114j

𝑍6= 𝑍4+ 𝑋𝐿12+𝑋𝐿12∗ 𝑍4

𝑍5 =0.025+0.03j+0.04+0.675j+(0.025+0.03𝑗)∗(0.04+0.675𝑗)

5.32+4.114𝑗 =0.06+0.7j

𝑍7=𝑍5+ 𝑋𝐿12+𝑋𝐿12∗ 𝑍5

𝑍4 =5.32+4.114j+0.025+0.03j+(0.025+0.03𝑗)∗(5.32+4.114𝑗)

0.04+0.675𝑗 =5.7+4.15j

𝑌1=1

𝑍1= 1

√0.224 2=4.46

𝑌7=1

𝑍7= 1

√5.7 2 +4.15 2=0.14

𝑌7 = 𝐸𝐺∗𝑌1+𝐸2∗𝑌7

𝑌1+𝑌7 =6.6∗4.46+18.1∗0.14

4.46+0.14 =6.95

𝑍1,7=𝑍1//𝑍7=5.54*10−3+0.22j

𝑌1,7= 1

√(5.54∗10−3)2+0.222=4.54

𝑌6=1

𝑍6= 1

√0.062+0.72=1.42

𝐸𝑒𝑞=4.84∗4.54+10∗1.42

4.54+1.42 =6.07

𝐼𝑠𝑐.𝑒𝑞𝑘3 = 𝐸𝑒𝑞

√3∗𝑍 𝑧.𝑠𝑐= 6.07

√3∗√(6.63∗10−3) 2 +0.17 2=20.6kA 𝐼′′𝑘3=𝐼𝑠𝑐.𝑒𝑞𝑘3 * 𝑈𝑏𝑠

𝑈𝑐𝑜𝑛𝑠𝑖𝑑𝑒𝑟𝑖𝑛𝑔=20.6*10

10=20.6kA

II Simulate the problem by software

Introduction about software MELSHORT2

● The Melshort provided by Mitsubishi is nearly perfect It provides all functions and information about short circuits

● The software can calculate short circuits at all times of breakers

● Help to choose a suitable CB (Circuit Breaker)

● The software is used to design a short circuit diagram easily In addition, the difference between two types of CBs is clearly shown through their routing curve diagram

● Because it is Mitsubishi’s software, the data information of each type of CB is shown very clearly in detail along with other data to make the calculation easier

Simulation

1

2 Start Melshort, software interface shown

Click the icons on the toolbar to create the diagram following the problem

3 Enter the parameters

○ Generator

○ System

○ Transformers (T1, T2, T3)

○ Lines

Tick in Calculation point to calculate short circuit at Line 2

4 Click Number 2 to auto check the diagram

The software notification

Click OK then click Number 3 to calculate automatically and show the result.

The result: Isc =22.427kA

III Comment, compare the results

Compare

Actual short circuit current

Comment

● Manual calculation and software simulation is not too different

● Rounding by manual calculation