1. IEC/NEC 접지비교 및 개정된 뇌 보호 시스템(KS C IEC 61024) 주요 내용
IEEE DETAIL DESIGN
공학박사/기술사
IEC TC 81 전문위원
발표 : 정 용 기
㈜의제전기설비연구원
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BRITISH STANDARD
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fig2. ILLUSTRATION OF EARTHING AND PROTECTIVE CONDUCTOR TERM Part 2 DEFINITIONS
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4. Voltage rating a 100kV/20kV/0.4kV system
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5. Building current in a TN-C system and TNS system
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6. TN-C system with several infeeds(distributed arrangement)
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7. fig 1.1/13 TN-S system with several infeeds (distributed arrangement)
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Fig 1.2/1 Designation of fault types and short-circuit currents to IEC / DIN VDE 0102
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Fig 2.6/1 External (red) and internal (blue) protection against lightning stroke current with arresters of requirement categories B, C, and D
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Fig 2.6/2 Overvoltage category (IEC / VDE 0110 Part 1 and impulse voltage withstand level
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11. Lightning stroke current and Surge arrester
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12. 5.9 General information on special areas, locations, and installations
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Fig 5.9/1 Zoning with special requirements in rooms with bath tubs or shower basins to HD / IEC /DIN VDE
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14. Fig. 5.9/2 Example of zoning in rooms with shower basin or shower
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Fig 5.9/3 Zoning for swimming fools and foot-baths to HD / IEC / DIN VDE
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Diversity of grounding systems around the world
Type
Power distribution side
Consumer side
TN-S
에스토니아, 스웨덴, 남아프리카, 영국
네델란드, 유고슬라비아
오스트리아, 독일, 핀란드, 러시아, 남아프리카
오스트레일리아, 덴마크, 프랑스, 스웨덴
스위스, 스페인, 네덜란드, 영국
TN-C
오스트리아 체코 에스토니아 헝가리 러시아
영국, 오스트레일리아, 독일, 핀란드
네덜란드, 스웨덴, 유고슬라비아, 스위스
덴마크, 크로아티아, 노르웨이, 슬로바키아
USA, Korea
오스트리아 벨기에 스위스 체코 독일 덴마크
에스토니아 스페인 프랑스 크로아티아 헝가리
네덜란드 노르웨이 러시아 스웨덴 영국 USA
TN-C-S
벨기에, 에스토니아, 뉴질랜드, 노르웨이
스웨덴, 영국, 유고슬라비아, 남아프리카
오스트리아, 오스트레일리아, 벨기에 , 네덜란드
독일, 덴마크, 스페인, 핀란드, 프랑스 , 러시아
크로아티아, 스웨덴, 영국, 남아프리카, 스위스 TT
(중성선 무)
벨기에, 스위스, 체코, 덴마크, JAPAN
네덜란드, 영국
오스트리아, 스위스, 독일, 덴마크, JAPAN, Korea
네덜란드, 러시아, 슬로바키아, 영국
(중선선 유)
오스트리아, 독일, 스페인, 프랑스, 헝가리
크로아티아, 네덜란드, 영국, 유고슬라비아,
스페인, 프랑스, 헝가리, 네덜란드, 영국
오스트리아, 프랑스, Korea
IT(중성선유) 영국
영국, 유고슬라비아, 오스트리아, 독일, 덴마크
IT(중선선무)
벨기에, 에스토니아, 노르웨이
스페인, 프랑스, 네덜란드, 슬로바키아, 영국
IT(중성)
TN : 다중접지방식 TT : 개별접지방식 IT : 고저항 접지방식
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THE OFFICIAL GROUNDING LESTED IN INTERNATIONAL IEC CODES
separate neutral and protective conductors throughout the system
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THE OFFICIAL GROUNDING LESTED IN INTERNATIONAL IEC CODES
Neutral and protective functions combined in a single conductor in a part of the system.
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THE OFFICIAL GROUNDING LESTED IN INTERNATIONAL IEC CODES
Neutral and protective functions combined in a single conductor throughout system.
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THE OFFICIAL GROUNDING LESTED IN INTERNATIONAL IEC CODES
All exposed-conductive-parts of an installation are connected to an earth electrode which is electrically independent of the source earth
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THE OFFICIAL GROUNDING LESTED IN INTERNATIONAL IEC CODES
All exposed-conductive-parts of an installation are connected to an earth electrode
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THE OFFICIAL GROUNDING LESTED IN INTERNATIONAL IEC CODES
L1, L2, L3 : 상도체 PEN:PEN도체
M : 노출도전성 부분 Ia : 고장전류
RA : 설비의 노출도전성 부분 접지저항
RB : 전원중성점 접지저항 UC : 접촉전압
ZL : 인체 임피던스 Ut : 추정접촉전압
Us : Rs를 뛰어넘는 전압 강하 Uf : 고장전압
E : 대지(정의는 IEV )
Rs : 사람이 접촉하는 표면 또는 설비의 기준점 B(주요 등전위 본딩점)에 연결된 계통의 도전성 부분간의 저항
주) Rs는 사람이 이런 계통외 도전성 부분과 접촉했을 때 0이 될 가능성이 있다.
C: 보호도체 및 주접지 단자와 연결된 계통외 도전성 부분
B : 기준점(예를 들어 주요 등전위 본딩)
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THE OFFICIAL GROUNDING LESTED IN INTERNATIONAL IEC CODES
L1, L2, L3 : 상도체 N:중성선 도체
M : 노출도전성 부분 Ia : 고장전류
RA : 설비의 노출도전성 부분 접지저항
RB : 전원 중성점 접지저항 UC : 접촉전압
ZL : 인체 임피던스 Ut : 추정접촉전압
Us : Rs를 뛰어넘는 전압 강하 Uf : 고장전압
E : 대지(정의는 IEV )
Rs : 사람이 접촉하는 표면 또는 설비의 기준점 B(주요 등전위 본딩점)에 연결된 계통의 도전성 부분간의 저항
주) Rs는 사람이 이런 계통외 도전성 부분과 접촉했을 때 0이 될 가능성이 있다.
C: 보호도체 및 주접지 단자와 연결된 계통외 도전성 부분
B : 기준점(예를 들어 주요 등전위 본딩)
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THE OFFICIAL GROUNDING LESTED IN INTERNATIONAL IEC CODES
All exposed-conductive-parts of an installation are connected to an earth electrode
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Distribution Chart of international Grounding systems
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Regulation of Grounding System of Korea (1)
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Regulation of Grounding System of Korea (2)
Diameter of Grounding Wire
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Comparison in Concept of Grounding System Designs (America/Korea)
KOREA
AMERICA
Characteristic
Limitation to ground resistance based on each types(main design of grounded electrode)
Reduction by potential considering step and touch voltage, mesh voltage
Method
Installing separately in isolated grounding
Installing separately in common grounding
Pattern
General example
: steel
structure
: bonding
network
: Information
equipments
ERP : Equipotential
Separate System S
(Star Bonding) M
(Mesh Bonding)
Common System Ss Mm
Disconnection of S, M from structure → Isolated grounding(1 point by disconnector)
Vulnerable to outside noises, and simple repair and inspection.
Ss, Mm is called integrated grounding(Common relay)
Easy equipotentialization but vulnerable to external noises.
Value of Resistance
E1 : Less than 10[]
E2 : ground fault 150V/phase
E3 : Less than 100[]
Es3 : Less than 10[]
Recommended NEC application : Less than 5[] 〃
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Resistance response characteristics per Frequency
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Revised edition JIS 1996
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Revised edition JIS 1996
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Revised edition JIS 1996
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Regulation of Grounding System of Korea (5)
PROTECTIVE SYSTEM IN AC ELECTRIC POWER SUPPLY
Grounding System of Buildings based on IEC , IEC and IEC 61024
Telephone
Electrical System of house and Building
Horizontal equipotential of Bonding System in Local area
AC Power Supply System
PE : Protective Conductor of AC Power Supply System
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An American National Standard
IEEE Guide for Safety in AC Substation Grounding
Regulation of Grounding System of Korea (5)
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An American National Standard
IEEE Guide for Safety in AC Substation Grounding
Regulation of Grounding System of Korea (5)
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Fig 9 Basic Shock Situations
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Fig 10 Typical Situation of External transferred Potential
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Fig 5. Step Voltage Circuit
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Fig 6. Touch Voltage Circuit
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Step and Touch Voltage Criteria
ANSI/IEEE
Std
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The Basic Concept of American Grounding Method (IEEE)
VALUE OF CONSTANT k FOR EFFECTIVE RMS VALUES OF
FIBRILLATION
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The Basic Concept of American Grounding Method (IEEE)
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The Basic Concept of American Grounding Method (IEEE)
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Fault Within Local Station; Local Neutral Grounded (IEEE)
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Fault Within Local Station; Neutral Grounded at Remote Location
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Fault in Station; System Grounded at Local Station and Also at Other Points
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Typical Current Division for a Fault on High Side of Distribution Substation
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Equipotential Contours of a Typical Grounding Grid With and Without Ground Rods
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National Electrical Code
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National Electrical Code
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Example of GFCI installation in dwelling units
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The circuitry and components of a typical GFCI
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Small appliance branch circuits as applied to the requirements (b)
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A 15-ampere duplicate receptacle with integral GFCI that also protects downstream loads
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Design Procedure Block Diagram (IEEE)
FIELD DATA
A, 
IRg < Etouch
YES
CONDUCTOR SIZE
3t0, tc, d NO
MESH & STEP
Em, Es, Km, Ks,
Ki, kii, Kh
VOLTAGE
TOUCH & STEP CRITERIA
Etouch50 or 70, Estep50 or 70
INSTALL DESIGN
D, m, L, h
Em < Etouch NO
YES
MODIFY DESIGN
D, m, L, h
Es < Estep
GRID RESISTANCE
Rg, Lc, Lr NO
YES
GRID CURRENT
A, 
DETAIL
DESIGN
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Fig 9 Basic Shock Situations
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Table 8 Index of Design Parameters
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Design examples (IEEE )
설계 기본 Data
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Design examples(IEEE ) ( P80)
step 1), step 2)
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Nomogram for Conductor Sizing
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Table 2 Minimum per Unit Conductor Sizes (cmils / A)
Fault
Time(s)
100% Cu
Only
97% Cu
40% Cu
30% Cu
97%Cu/Temperature Limits
(450℃)
(250℃)
30.0
4.0
1.0
0.5
38.4
14.0
7.0
4.9
38.7
14.2
7.1
5.0
57.0
20.8
10.4
7.4
65.8
24.0
12.0
8.5
51.1
18.7
9.3
6.6
64.5
23.5
11.8
8.3
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62. Design examples(IEEE 80-1996) (1997. 6.15. P80)
에서Table 1 data를 이용
Table 1. Material Constants
↑ ↑ ↑ ↑
r= K0 = r = TAPC=3.846
여기에서, Tm=700℃, Ta = 40℃, I = 3.18[kA], tc = 0.5[sec] 이므로
4.46[mm]는 약 0.005[m] 이므로 d=0.01[m]로 한다.
용해온도
열용량
Description
Material Conductivity
[%] r
Factor
@ 20 [℃] K
(1/0)
@ 0 [℃]
Fusing
Temperature
[℃] r
[Ω/츠]
TCAP Factor
Effective Value
[J/cm3/℃]
Copper-Clad Steel Core Wire
40.0
245
1084/1300
4.397
3.846
30.0
5.862
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Review of leakage current in TT and TN system
중성점 공통접지(미국)에서 접지고장
접지고장전류
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Review of leakage current in TT and TN system
중성점 접지 방식의 접지고장전류
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Review of leakage current in TT and TN system
중성점 독립접지(한국, 일본)에서 접지고장
접지고장전류
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Design examples (IEEE )
step 3)
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Reflections of Current in Two-Layer Soil With Current Source in Lower Soil
The abrupt changes in resistivity at the boundaries of each soil layer can be described by means of a reflection factor.
This reflection factor K is defined as
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Relation of Cs and h
0.74
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Design examples (IEEE )
step 4)
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Design examples (IEEE )
테이블로 구하면
Rg = (토양 저항[Ω•m] x graphical value) / 1000
Rg = (400 x 6.7 / 100 ) = 2.68  2.7
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Design examples (IEEE )
6.7
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Design examples (IEEE )
Fault Duration tf(s)
Cycles (60 Hz ac)
Decrement Factor Df
0.008
0.14
0.25
0.5 or more 6 15
30 or more
1.65
1.25
1.10
1.0
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Typical Current Division for a Fault on High Side of Distribution Substation
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The Example of American Grounding (NEC )
250-5(b)
250-94`
AWG #2
(30♢)
AWG #2
(30♢)
AWG #4
(22♢)
AWG #2
(30♢)
AWG #6
(14♢)
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Design examples (IEEE )
Ground Potential Rise
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Design Procedure Block Diagram (IEEE)
FIELD DATA
A, 
IRg < Etouch
YES
CONDUCTOR SIZE
3t0, tc, d NO
MESH & STEP
Em, Es, Km, Ks,
Ki, kii, Kh
VOLTAGE
TOUCH & STEP CRITERIA
Etouch50 or 70, Estep50 or 70
INSTALL DESIGN
D, m, L, h
Em < Etouch NO
YES
MODIFY DESIGN
D, m, L, h
Es < Estep
GRID RESISTANCE
Rg, Lc, Lr NO
YES
GRID CURRENT
A, 
DETAIL
DESIGN
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Design examples (IEEE )
step 8)
지형지수
테이블을 이용할 경우
Em  5,304 x 0.2  1,060V 로 개략 산정할 수 있다.
접지된 간격에 따른 조정계수
IG : 매설 도선의 최대전류
Km : 지형 지수
Ki : 조정 계수
LC : 메설 길이
LR : 접지 봉의 총길이
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Design examples (IEEE ) %
(11)
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Design examples (IEEE ) 참고
사각배치 경우 봉이 사각에 타입된 경우
Kii = 1
접지봉이 없거나 그리드 코너 또는 맨가의 접지 도선에 접지봉이 없는 경우
LR : 접지 봉의 총길이
LG : 매설 접지도선의 총길이
n=na, nb, nc, nd
사각매설의 경우 모두 1
사각 배치가 아닌경우
Ki = n
LC : 매설접지 도선의 총길이
LP : 매설 접지도선의 주변 길이
Lx : x방향 최장 길이
Ly : y방향 최장 길이
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Design examples (IEEE )
step 9)
접지봉이 있는 경우
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Design examples (IEEE )
B2 예제
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Design examples (IEEE )
B2 Step 5), 6), 7)
(0.03 감소)
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Design examples (IEEE )
B2 Step 8)
(0.89에서 0.77로 감소)
(1,002.1에서 로 감소)
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Design Procedure Block Diagram (IEEE)
FIELD DATA
A, 
IRg < Etouch
YES
CONDUCTOR SIZE
3t0, tc, d NO
MESH & STEP
Em, Es, Km, Ks,
Ki, kii, Kh
VOLTAGE
TOUCH & STEP CRITERIA
Etouch50 or 70, Estep50 or 70
INSTALL DESIGN
D, m, L, h
Em < Etouch NO
YES
MODIFY DESIGN
D, m, L, h
Es < Estep
GRID RESISTANCE
Rg, Lc, Lr NO
YES
GRID CURRENT
A, 
DETAIL
DESIGN
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Design examples(IEEE )
B2 Step 9)
= 7.5 x 20 개
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The Example of American Grounding (NEC )
250-5(b)
250-94`
AWG #2
(30♢)
AWG #2
(30♢)
AWG #4
(22♢)
AWG #2
(30♢)
AWG #6
(14♢)
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The Measures to Problems with Korean Grounding Systems and Methods
Problems
Korean grounding systems are utilizing American and Japanese grounding system.
Participating in WTO we should observe TBT though our domestic regulations and standards are not internalized.
The systemic and fundamental research for grounding have not been taken
The classification of grounding are found unreasonable
Measures
Positive consideration about NEC is required so that we should observe IEC codes
The Grounding system for Korean Electric Power and Consumer ought to be unified.
Inevitably the system of the regulations and standards in relation to electricity and its constructions should be modified.
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