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NUE 505A Electrical systems safety Assessment preparation
Protection devices
10 -1 1 10 10 2 10 3 4.5 Time (sec) Current (x I RATED ) B Magnetic Section Thermal Section Circuit Breaker Types
10 -1 1 10 10 2 10 3 Time (sec) Current (x I RATED ) 7.5 C Thermal Section New Magnetic operation Circuit Breaker Types
10 -1 1 10 10 2 10 3 Time (sec) Current (x I RATED ) 12 D Thermal Section New Magnetic operation Circuit Breaker Types
RCD,s
Residual Current Device  RCD Safety Switch LOAD N A/s Supply When the circuit is in good condition. (No Earth Faults) (I  ...
RCD with Earth Fault LOAD N A/s Supply  When an Earth Faults occurs. (I  active     I  neutral) = Flux in Core = Induced...
Safety Switch N A/s Supply Not Earthed A person can receive a shock with a “Safety Switch” installed Another point to cons...
3   RCD  3   LOAD  N L1 Supply LOAD L2 L3
3   RCD  1   LOAD  N Supply LOAD A
 
 
 
 
Max Demand Calculations Domestic Lighting
 
 
 
 
Max Demand Calculations Domestic Power
 
 
 
 
Max Demand Calculations Domestic Appliances
 
 
Max Demand Calculations Domestic Multi-phase
 
 
 
Max Demand Calculations Non-Domestic Lighting
A Small motel installation contains the following
 
 
 
Max Demand Calculations Non-Domestic Power
A factory has the following loading, calculate the maximum demand consideration.
 
 
Max Demand Calculations Non-Domestic Appliances
A factory has the following three-phase loads,what would be the loading for a maximum demand calculation.
 
 
Cable selection
 
 
 
 
 
Cable selection based on voltage drop
 
 
 
 
 
 
Voltage drop Single-phase
 
 
 
 
 
Voltage drop Multi-phase
 
 
 
Conductor size based on voltage drop
 
 
 
 
 
 
 
Overall multi-phase voltage drop calculation
 
 
 
Fault loop impedance
AS/NZ 3000:2000 - 1.7.4.3.3 <ul><li>The  earth system impedance , and the  Trip characteristic of the protective device  m...
The Fault Loop  1. The impedance needs to be low enough, to allow a high enough fault current, to operate the protective d...
Earth System <ul><li>   There are three ways to determine whether fault loop impedance is OK: </li></ul><ul><li>1. Measur...
Earth System 1 Measure the Fault Loop Impedance… <ul><li>There are three ways to determine whether  </li></ul><ul><li>faul...
Earth System ♦  Z LOOP  =  Z ACTIVE  + Z EARTH  + Z  NEUTRAL  + Z  TX ♦  All these will limit current and dictate the faul...
Earth System AS3000: Wiring Rules
Earth System
10 -1 1 10 10 2 10 3 4 Time (sec) Current (x I RATED ) B Circuit Breaker Types 1x Magnetic Section Thermal Section
10 -1 1 10 10 2 10 3 Time (sec) Current (x I RATED ) Circuit Breaker Types 1x 7.5 C Thermal Section New Magnetic operation
10 -1 1 10 10 2 10 3 Time (sec) Current (x I RATED ) Circuit Breaker Types 1x 12.5 D Thermal Section New Magnetic operation
Earth System Load 16A N/L MEN Link must be left intact
Earth System Load 16A N/L Active Earth MEN Link must be left intact
 
<ul><li>Total maximum allowable  </li></ul><ul><li>Fault Loop Impedance = 1.92 Ω </li></ul><ul><li>Cold  Fault Loop Impeda...
Earth System 1 Measure the Fault Loop Impedance… <ul><li>There are three ways to determine whether  </li></ul><ul><li>faul...
Earth System Load 16A N/L With 80% of voltage drop here in a fault,  the FSC must have 80% of the total Fault Loop Impedan...
0.8 x V NOM  x CSA ACTIVE  x CSA  EARTH L MAX  =  I TRIP  x    x (CSA ACTIVE  + CSA  EARTH )    = 22.5 x 10 -3   ohm-mm ...
 
Earth System 1 Measure the Fault Loop Impedance… <ul><li>There are three ways to determine whether  </li></ul><ul><li>faul...
AS3017: Testing and Inspection Guidlines <ul><li>Notes: </li></ul><ul><li>It is cold resistance. </li></ul><ul><li>It is f...
MAIN SWITCHBOARD Load
But what if the cable/CB size is not there on that table?
Say, 300mm 2  orange circ. cable supplying a 415V, 350A, 3-phase motor through underground conduit 140mtrs away.  C/B is 4...
Say, 300mm 2  orange circ. cable supplying a 415V, 350A, 3-phase motor through underground conduit 140mtrs away…  7.  Meas...
<ul><li>But what if you are wanting to install the cable, and you want to know if everything is OK? </li></ul><ul><li>Size...
<ul><li>But what if you are wanting to install the cable, and you want to know if everything is OK? </li></ul><ul><li>Size...
<ul><ul><li>Earth :  X L   = 0.0743  /km  </li></ul></ul><ul><ul><ul><li>=  0.010402   for 140mtrs </li></ul></ul></ul><...
<ul><ul><li>Active X L   =  0.010248    </li></ul></ul><ul><ul><ul><ul><li>R =  0.0087136    </li></ul></ul></ul></ul><u...
4.  Is Loop Z < Maximum Allowable Z? Last Step…: <ul><li>Remember that a type C breaker trips at 7.5 times its rating?  Th...
Remember the last question? Q:  Why do we want a low resistance earth wire?  To CREATE a high enough fault current to tri...
AS3017: Testing and Inspection Guidlines
A Simplified  Circuit We need to look at a complete loop (circuit) 3 Phase Supply The current path includes the: Supply Tr...
B5.1 Maximum Circuit Length <ul><li>This process is used to calculate the maximum circuit length (FSC) taking into conside...
3 Phase Supply There will always be more than 80% of the Nominal Voltage AS/NZ3000:2000  B5.2.1 b Zext Zint Zint =  0.8 Uo...
Isolation, disconnection and reconnection procedures
Safe Isolation   <ul><li>Assess the need for isolation </li></ul><ul><li>Notify others </li></ul><ul><li>Determine how to ...
 
MEN Connection
MEN SYSTEM
Recent studies have shown that 95% of electricians do not fully understand the MEN system.  This figure comes from the Ele...
MEN Connection Consumer Mains MAIN SWITCHBOARD Circuit Protective Devices Earth Link Neutral Link Main Switch
MEN Connection Circuit Protective Devices Consumer Mains MAIN SWITCHBOARD Neutral Link Main Switch So why do we earth the ...
Load Direct Earthing System 16A Q: Will the  fuse blow? FAULT R TOTAL = 23.5  I FAULT  = V/R = 240/23.5    10A 0.3  0.2...
Load MEN Earthing System 0.3  0.2  16A R TOTAL = 1  Q: Will the  fuse blow? 0.5  I FAULT  = V/R = 240/1 = 240A N/L FAU...
Q:  Why do we want a low resistance earth wire?  To CREATE a high enough fault current to trip the protective device.
MAIN SWITCHBOARD MEN Connection Circuit Protective Devices Earth Link Neutral Link NORMAL LOAD CURRENT Typical  Earth stak...
MAIN SWITCHBOARD MEN Connection Circuit Protective Devices Earth Link Neutral Link FAULT CURRENT Main Switch Load A Low Re...
MAIN SWITCHBOARD MEN Connection Circuit Protective Devices Consumer Mains Earth Link Neutral Link What are the values give...
MAIN SWITCHBOARD MEN Connection Circuit Protective Devices Consumer Mains Earth Link Neutral Link 2   maximum 2   maximu...
MAIN SWITCHBOARD MEN Connection Circuit Protective Devices Consumer Mains Earth Link Neutral Link Main Switch < 0.5  (6.3...
Why Test
MAIN SWITCHBOARD Circuit Protective Devices Main Switch Earth Link Neutral Link Load OPEN  CIRCUIT MEN Connection
MAIN SWITCHBOARD Circuit Protective Devices Main Switch Earth Link Neutral Link NORMAL LOAD CURRENT Everything operates  O...
THEREFORE FAULT  CURRENT WILL BE VERY LOW MAIN SWITCHBOARD MEN Connection Circuit Protective Devices Main Switch Earth Lin...
MAIN SWITCHBOARD MEN Connection Circuit Protective Devices Main Switch Earth Link Neutral Link FAULT CURRENT AND PROTECTIO...
MAIN SWITCHBOARD MEN Connection Circuit Protective Devices Main Switch Earth Link Neutral Link FAULT CURRENT NOTE  THAT IF...
MAIN SWITCHBOARD MEN Connection Circuit Protective Devices Main Switch Earth Link Neutral Link FAULT CURRENT NOTE  ALSO TH...
Open Circuit MEN Connection MAIN SWITCHBOARD Circuit Protective Devices Neutral Link Sub Mains Sub Mains Neutral Link DIST...
<ul><li>What happens when incoming Active and Neutral are swapped? </li></ul>
MAIN SWITCHBOARD MEN Connection Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link A N LIVEN UP...
MAIN SWITCHBOARD Circuit Protective Devices Neutral Link Sub Mains Sub Mains ` Neutral Link DISTRIBUTION BOARD 3 Circuit P...
<ul><li>What happens when the Main Neutral </li></ul><ul><li>goes Open Circuit? </li></ul>
MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link OPEN  CIRCUIT Neutral Load
MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link LOAD CURRENT Load
MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link LOAD CURRENT Load
MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link Lo load Resistance Hi stake...
MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link Lo load Resistance Hi stake...
Q: What causes “tingles” on taps? MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutra...
Q: What causes “tingles” on taps? VD N =4V MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Li...
Q: What causes “tingles” on taps? MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutra...
Testing
TEST  EQUIPMENT  REQUIRED  (AS3017 1.6.2) <ul><li>High Voltage Insulation Resistance Tester </li></ul><ul><li>Low reading ...
TEST  EQUIPMENT  REQUIRED  (AS3017 1.6.2) <ul><li>Test for dead device. </li></ul><ul><ul><li>Category 1: electronic </li>...
TESTS <ul><li>Visual </li></ul><ul><li>Earth Continuity </li></ul><ul><li>Insulation Test </li></ul><ul><li>Polarity </li>...
<ul><li>General </li></ul><ul><li>Consumer Mains </li></ul><ul><li>Switchboards </li></ul><ul><li>Wiring Systems </li></ul...
General Requirements Clause No. What to look for 2.9.6  No exposed live parts.  E.g. no excessive removal of insulation at...
Consumer Mains Clause No. What to look for 3.4.1 Consumers Mains should be able to carry the maximum demand current of the...
<ul><li>Switchboard </li></ul><ul><li>Clause No. What to look for </li></ul><ul><ul><ul><li>Switchboard is in a suitable l...
<ul><li>Wiring Systems </li></ul><ul><li>Clause No. What to look for </li></ul><ul><ul><li>Correct conductor sizes.  E.g. ...
<ul><ul><ul><ul><li>Wiring fixed or passing through holes within 50mm of underside of roof material is protected by RCD or...
<ul><li>Electrical Equipment </li></ul><ul><li>Clause No. What to look for </li></ul><ul><li>4.3.11 Stove circuit has a ‘f...
<ul><li>Earthing </li></ul><ul><li>Clause No. What to look for </li></ul><ul><ul><ul><li>MEN link correctly installed. </l...
Initial Procedures <ul><li>Open all Main Switches. </li></ul><ul><li>Turn C/B’s off / remove fuse wedges. </li></ul><ul><l...
MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link Light
<ul><li>From Main Earth to Earth Electrode: <0.5  </li></ul><ul><li>Make sure all FSC earth resistance values are under t...
MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link Light Known resistance
STEP 3: Insulation Resistance <ul><li>Test between Main Earth and </li></ul><ul><li>1. Main Active  with main switch ON . ...
STEP 3: Insulation Resistance <ul><li>Test between Main Earth at Switchboard and: </li></ul><ul><li>The Active Conductors ...
MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link Light
MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link Light Switched Active
STEP 3: Insulation Resistance <ul><li>Where heater elements are tested:  >10k  </li></ul>
<ul><li>Checks: </li></ul><ul><li>1.  Polarity of mains or submains. </li></ul><ul><li>2.  C/B’s and single pole switches ...
STEP 5: Correct Circuit Connections <ul><li>Check that under normal operation earths do not carry current. </li></ul><ul><...
MEN Connection MAIN SWITCHBOARD Circuit Protective Devices Neutral Link Sub Mains Sub Mains ` Neutral Link DISTRIBUTION BO...
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Electrical Systems Safety

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Electrical Systems Safety

  1. 1. NUE 505A Electrical systems safety Assessment preparation
  2. 2.
  3. 3. Protection devices
  4. 4. 10 -1 1 10 10 2 10 3 4.5 Time (sec) Current (x I RATED ) B Magnetic Section Thermal Section Circuit Breaker Types
  5. 5. 10 -1 1 10 10 2 10 3 Time (sec) Current (x I RATED ) 7.5 C Thermal Section New Magnetic operation Circuit Breaker Types
  6. 6. 10 -1 1 10 10 2 10 3 Time (sec) Current (x I RATED ) 12 D Thermal Section New Magnetic operation Circuit Breaker Types
  7. 7. RCD,s
  8. 8. Residual Current Device RCD Safety Switch LOAD N A/s Supply When the circuit is in good condition. (No Earth Faults) (I active = I neutral) = No Flux = No Induced EMF Supply to the Load is Maintained I A I N
  9. 9. RCD with Earth Fault LOAD N A/s Supply  When an Earth Faults occurs. (I active  I neutral) = Flux in Core = Induced EMF The fault is Isolated
  10. 10. Safety Switch N A/s Supply Not Earthed A person can receive a shock with a “Safety Switch” installed Another point to consider: An RCD rated at 40Amps will not trip (like a C/B) if say 52Amps will to flow through the device.
  11. 11. 3  RCD 3  LOAD N L1 Supply LOAD L2 L3
  12. 12. 3  RCD 1  LOAD N Supply LOAD A
  13. 17. Max Demand Calculations Domestic Lighting
  14. 22. Max Demand Calculations Domestic Power
  15. 27. Max Demand Calculations Domestic Appliances
  16. 30. Max Demand Calculations Domestic Multi-phase
  17. 34. Max Demand Calculations Non-Domestic Lighting
  18. 35. A Small motel installation contains the following
  19. 39. Max Demand Calculations Non-Domestic Power
  20. 40. A factory has the following loading, calculate the maximum demand consideration.
  21. 43. Max Demand Calculations Non-Domestic Appliances
  22. 44. A factory has the following three-phase loads,what would be the loading for a maximum demand calculation.
  23. 47. Cable selection
  24. 53. Cable selection based on voltage drop
  25. 60. Voltage drop Single-phase
  26. 66. Voltage drop Multi-phase
  27. 70. Conductor size based on voltage drop
  28. 78. Overall multi-phase voltage drop calculation
  29. 82. Fault loop impedance
  30. 83. AS/NZ 3000:2000 - 1.7.4.3.3 <ul><li>The earth system impedance , and the Trip characteristic of the protective device must be such that if; </li></ul><ul><li>A fault of negligible impedance occurs (active to earth - short circuit) </li></ul><ul><li>Automatic disconnect of the supply (high enough fault current to operate the protective device) </li></ul><ul><li>Within a specified time </li></ul>6.3.3.2.1 6.3.3.2.2 Amendment AS/NZS 3000:2000
  31. 84. The Fault Loop 1. The impedance needs to be low enough, to allow a high enough fault current, to operate the protective device, within a given time period. (6.3.3.2.2) 2. The Earth Loop Impedance is matched to the Protective Device Tripping Characteristics. 3 Phase Supply N/L
  32. 85. Earth System <ul><li> There are three ways to determine whether fault loop impedance is OK: </li></ul><ul><li>1. Measure fault loop impedance at the load. </li></ul><ul><li>(Compare values against Table B4.1 of AS3000) </li></ul><ul><li>2. Calculate the maximum length allowable for the FSC, and come in under that. </li></ul><ul><li>3. Measure the A/A-E impedance. </li></ul><ul><li>(Compare it to Table 3.2 AS3017) </li></ul>
  33. 86. Earth System 1 Measure the Fault Loop Impedance… <ul><li>There are three ways to determine whether </li></ul><ul><li>fault loop impedance is OK: </li></ul>
  34. 87. Earth System ♦ Z LOOP = Z ACTIVE + Z EARTH + Z NEUTRAL + Z TX ♦ All these will limit current and dictate the fault current that will flow. Load N/L 16A MEN Link must be left intact
  35. 88. Earth System AS3000: Wiring Rules
  36. 89. Earth System
  37. 90. 10 -1 1 10 10 2 10 3 4 Time (sec) Current (x I RATED ) B Circuit Breaker Types 1x Magnetic Section Thermal Section
  38. 91. 10 -1 1 10 10 2 10 3 Time (sec) Current (x I RATED ) Circuit Breaker Types 1x 7.5 C Thermal Section New Magnetic operation
  39. 92. 10 -1 1 10 10 2 10 3 Time (sec) Current (x I RATED ) Circuit Breaker Types 1x 12.5 D Thermal Section New Magnetic operation
  40. 93. Earth System Load 16A N/L MEN Link must be left intact
  41. 94. Earth System Load 16A N/L Active Earth MEN Link must be left intact
  42. 96. <ul><li>Total maximum allowable </li></ul><ul><li>Fault Loop Impedance = 1.92 Ω </li></ul><ul><li>Cold Fault Loop Impedance = 1.92x0.8 </li></ul><ul><li> = 1.54Ω </li></ul><ul><li>If supply is 240V per phase, then multiply </li></ul><ul><li>Z by 240/230, or 1.04: </li></ul><ul><li>Fault Loop Impedance = 1.54 x 1.04 </li></ul><ul><li> = 1.60Ω </li></ul><ul><li>If RCD protection is used, AS3000, </li></ul><ul><li>rule 6.3.4.2.1 (2) states that if the RCD </li></ul><ul><li>operates during the FLI test, the test </li></ul><ul><li>result is considered satisfactory. </li></ul>
  43. 97. Earth System 1 Measure the Fault Loop Impedance… <ul><li>There are three ways to determine whether </li></ul><ul><li>fault loop impedance is OK: </li></ul>2. Calculate the maximum length allowable for the Final Sub Circuit and come in under that.
  44. 98. Earth System Load 16A N/L With 80% of voltage drop here in a fault, the FSC must have 80% of the total Fault Loop Impedance. Where the length and CSA of the mains is not known, we may assume that 80% of the voltage drop under fault conditions will occur in the final sub-circuit (B5.2.1b).
  45. 99. 0.8 x V NOM x CSA ACTIVE x CSA EARTH L MAX = I TRIP x  x (CSA ACTIVE + CSA EARTH )  = 22.5 x 10 -3 ohm-mm 2 /metre for Copper = 36 x 10 -3 ohm-mm 2 /metre for Aluminium <ul><li>This gives the maximum length allowable for </li></ul><ul><li>any given circuit. </li></ul><ul><li>Maximum length allowable for any given circuit </li></ul><ul><li>can be calculated from (B5.2.2): </li></ul>(Page 237 AS3000)
  46. 101. Earth System 1 Measure the Fault Loop Impedance… <ul><li>There are three ways to determine whether </li></ul><ul><li>fault loop impedance is OK: </li></ul>2. Calculate the maximum length allowable for the Final Sub Circuit and come in under that. 3. Measure the A/A-E impedance. (Compare it to Table 3.2 AS3017)
  47. 102. AS3017: Testing and Inspection Guidlines <ul><li>Notes: </li></ul><ul><li>It is cold resistance. </li></ul><ul><li>It is for FSC only. </li></ul><ul><li>There are still holes… </li></ul>
  48. 103. MAIN SWITCHBOARD Load
  49. 104. But what if the cable/CB size is not there on that table?
  50. 105. Say, 300mm 2 orange circ. cable supplying a 415V, 350A, 3-phase motor through underground conduit 140mtrs away. C/B is 400A type “C”. <ul><li>CCC of 300mm 2 cable = 415A </li></ul><ul><li>Determine the current required to cause instantaneous operation of the C/B. </li></ul><ul><ul><li>7.5 x 400 = 3000A </li></ul></ul><ul><li>Determine the (hot) fault loop impedance </li></ul><ul><ul><li>240/3000 = 0.08  </li></ul></ul><ul><li>Total circuit Cold FLZ = 0.08 x .8 = 0.064  </li></ul><ul><li>Final Sub-Circuit FLZ (cold) = 0.064 x 0.8 = 0.0512  </li></ul>
  51. 106. Say, 300mm 2 orange circ. cable supplying a 415V, 350A, 3-phase motor through underground conduit 140mtrs away… 7. Measure the actual loop impedance. MAIN SWITCHBOARD Load Z = V/I A V I  5A
  52. 107. <ul><li>But what if you are wanting to install the cable, and you want to know if everything is OK? </li></ul><ul><li>Size of earth: 120mm 2 (from AS3000 table 5.1) </li></ul><ul><li>Find Impedance actual of A-E loop on FSC. </li></ul>Say, 300mm 2 orange circ. cable supplying a 415V, 350A, 3-phase motor through underground conduit 140mtrs away… Note that including X L of the cable only comes into play above 120mm 2 Z R X L
  53. 108. <ul><li>But what if you are wanting to install the cable, and you want to know if everything is OK? </li></ul><ul><li>Size of earth: 120mm 2 (from AS3000 table 5.1) </li></ul><ul><li>Find Impedance actual of A-E loop on FSC. </li></ul>Say, 300mm 2 orange circ. cable supplying a 415V, 350A, 3-phase motor through underground conduit 140mtrs away… <ul><ul><li>Active : X L = 0.0732  /km (Table 30, AS3008) </li></ul></ul><ul><ul><li>= 0.010248  for 140mtrs </li></ul></ul><ul><ul><ul><ul><li>[email_address] 0 C = 0.0778  /km (Table 35, AS3008) </li></ul></ul></ul></ul><ul><ul><ul><ul><li>[email_address] 0 C = 0.0778 x 0.8 x 0.14 </li></ul></ul></ul></ul><ul><ul><ul><ul><li>= 0.0087136  for 140mtrs </li></ul></ul></ul></ul>
  54. 109. <ul><ul><li>Earth : X L = 0.0743  /km </li></ul></ul><ul><ul><ul><li>= 0.010402  for 140mtrs </li></ul></ul></ul><ul><ul><ul><ul><li>[email_address] 0 C = 0.188  /km </li></ul></ul></ul></ul><ul><ul><ul><ul><li>[email_address] 0 C = 0.188 x 0.8  /km </li></ul></ul></ul></ul><ul><ul><ul><ul><li>=0.1504  </li></ul></ul></ul></ul><ul><ul><ul><ul><li>R for 140mtrs = 0.021056  </li></ul></ul></ul></ul>Say, 300mm 2 orange circ. cable supplying a 415V, 350A, 3-phase motor through underground conduit 140mtrs away…
  55. 110. <ul><ul><li>Active X L = 0.010248  </li></ul></ul><ul><ul><ul><ul><li>R = 0.0087136  </li></ul></ul></ul></ul><ul><ul><li>Earth X L = 0.010402  </li></ul></ul><ul><ul><li>R = 0.021056  </li></ul></ul>Say, 300mm 2 orange circ. cable supplying a 415V, 350A, 3-phase motor through underground conduit 140mtrs away… R A + R E = 0.0298  X A + X E = 0.02065  Z = 0.0362  R ACTIVE R EARTH X ACTIVE X EARTH
  56. 111. 4. Is Loop Z < Maximum Allowable Z? Last Step…: <ul><li>Remember that a type C breaker trips at 7.5 times its rating? This figure is only an approximation. It can be anywhere between 5 and 10 times its rating… </li></ul><ul><li>Remember too, that we took the FSC as having 0.8 of the total circuit impedance? This is an approximation too. </li></ul>Z = 0.0362  Z = 0.0512 
  57. 112. Remember the last question? Q: Why do we want a low resistance earth wire?  To CREATE a high enough fault current to trip the protective device. To ensure that we do create a high enough fault current, fault loop impedance must be low enough.
  58. 113. AS3017: Testing and Inspection Guidlines
  59. 114. A Simplified Circuit We need to look at a complete loop (circuit) 3 Phase Supply The current path includes the: Supply Transformer, Distribution System, Mains, Protection Device, Final Sub-Circuit including the Load N/L
  60. 115. B5.1 Maximum Circuit Length <ul><li>This process is used to calculate the maximum circuit length (FSC) taking into consideration: </li></ul><ul><ul><li>The rating and type of Protection device </li></ul></ul><ul><ul><li>The CSA of the Active conductor </li></ul></ul><ul><ul><li>The CSA of the Earthing conductor </li></ul></ul><ul><ul><li>The route length of the Final sub-circuit. </li></ul></ul><ul><li>A variation of this process may be used to determine an exact value of the FSC’s impedance, and prove the earth continuity. </li></ul>
  61. 116. 3 Phase Supply There will always be more than 80% of the Nominal Voltage AS/NZ3000:2000 B5.2.1 b Zext Zint Zint = 0.8 Uo I a B5.2.1
  62. 117. Isolation, disconnection and reconnection procedures
  63. 118. Safe Isolation <ul><li>Assess the need for isolation </li></ul><ul><li>Notify others </li></ul><ul><li>Determine how to isolate the circuit </li></ul><ul><li>Test the supply is present & test meter </li></ul><ul><li>Isolate the supply. (switch, fuse, C/B etc) </li></ul><ul><li>Attach danger tags or locks </li></ul><ul><li>Test that you have isolated the correct circuit </li></ul><ul><li>Test your meter again </li></ul>
  64. 120. MEN Connection
  65. 121. MEN SYSTEM
  66. 122. Recent studies have shown that 95% of electricians do not fully understand the MEN system. This figure comes from the Electrical Contractors Association of Queensland who were conducting training sessions throughout Queensland during 1998. They asked electricians to draw a MEN system and explain it. Only 5% could!!! MEN System
  67. 123. MEN Connection Consumer Mains MAIN SWITCHBOARD Circuit Protective Devices Earth Link Neutral Link Main Switch
  68. 124. MEN Connection Circuit Protective Devices Consumer Mains MAIN SWITCHBOARD Neutral Link Main Switch So why do we earth the neutral at the board?
  69. 125. Load Direct Earthing System 16A Q: Will the fuse blow? FAULT R TOTAL = 23.5  I FAULT = V/R = 240/23.5  10A 0.3  0.2  23 
  70. 126. Load MEN Earthing System 0.3  0.2  16A R TOTAL = 1  Q: Will the fuse blow? 0.5  I FAULT = V/R = 240/1 = 240A N/L FAULT R RETURN = 0.5//23  0.5  23 
  71. 127. Q: Why do we want a low resistance earth wire?  To CREATE a high enough fault current to trip the protective device.
  72. 128. MAIN SWITCHBOARD MEN Connection Circuit Protective Devices Earth Link Neutral Link NORMAL LOAD CURRENT Typical Earth stake to Earth resistance = 30  - 2k  Main Switch Load Low R Consumer Mains
  73. 129. MAIN SWITCHBOARD MEN Connection Circuit Protective Devices Earth Link Neutral Link FAULT CURRENT Main Switch Load A Low Resistance earth CREATES A high fault current. Low R
  74. 130. MAIN SWITCHBOARD MEN Connection Circuit Protective Devices Consumer Mains Earth Link Neutral Link What are the values given by AS3000 on earth resistance? Main Switch Load
  75. 131. MAIN SWITCHBOARD MEN Connection Circuit Protective Devices Consumer Mains Earth Link Neutral Link 2  maximum 2  maximum Main Switch Load
  76. 132. MAIN SWITCHBOARD MEN Connection Circuit Protective Devices Consumer Mains Earth Link Neutral Link Main Switch < 0.5  (6.3.3.2.2) Load “ The resistance of the protective earthing conductors shall be low enough to permit the passage of current necessary to operate the overcurrent protective device” (6.3.3.2.2)
  77. 133. Why Test
  78. 134. MAIN SWITCHBOARD Circuit Protective Devices Main Switch Earth Link Neutral Link Load OPEN CIRCUIT MEN Connection
  79. 135. MAIN SWITCHBOARD Circuit Protective Devices Main Switch Earth Link Neutral Link NORMAL LOAD CURRENT Everything operates OK!!! Load
  80. 136. THEREFORE FAULT CURRENT WILL BE VERY LOW MAIN SWITCHBOARD MEN Connection Circuit Protective Devices Main Switch Earth Link Neutral Link FAULT CURRENT But RESISTANCE TO EARTH IS USUALLY HIGH. Load
  81. 137. MAIN SWITCHBOARD MEN Connection Circuit Protective Devices Main Switch Earth Link Neutral Link FAULT CURRENT AND PROTECTION WILL NOT TRIP. Load
  82. 138. MAIN SWITCHBOARD MEN Connection Circuit Protective Devices Main Switch Earth Link Neutral Link FAULT CURRENT NOTE THAT IF ACTIVE IS SHORTED TO EARTH, ALL EARTHS ARE LIVE!!! Load
  83. 139. MAIN SWITCHBOARD MEN Connection Circuit Protective Devices Main Switch Earth Link Neutral Link FAULT CURRENT NOTE ALSO THAT UNDER NORMAL CONDITIONS EVERYTHING ELSE WILL STILL WORK OK!!! Load
  84. 140. Open Circuit MEN Connection MAIN SWITCHBOARD Circuit Protective Devices Neutral Link Sub Mains Sub Mains Neutral Link DISTRIBUTION BOARD 3 Circuit Protective Devices Earthing Bar DISTRIBUTION BOARD 2 Circuit Protective Devices Neutral Link Earthing Bar Main Earthing Conductor Sub Mains Circuit Protective Devices Neutral Link Earthing Bar DISTRIBUTION BOARD 1 Main Switch What happens on Distribution Boards when the MSB MEN link open-circuits ? AS3000 5.6.6b(iv)
  85. 141. <ul><li>What happens when incoming Active and Neutral are swapped? </li></ul>
  86. 142. MAIN SWITCHBOARD MEN Connection Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link A N LIVEN UP: -Earth stake -Water pipes -Taps -Sink -Cases of appliances Load
  87. 143. MAIN SWITCHBOARD Circuit Protective Devices Neutral Link Sub Mains Sub Mains ` Neutral Link DISTRIBUTION BOARD 3 Circuit Protective Devices Earthing Bar DISTRIBUTION BOARD 2 Circuit Protective Devices Neutral Link Earthing Bar Main Earthing Conductor Sub Mains Circuit Protective Devices Neutral Link Earthing Bar DISTRIBUTION BOARD 1 Main Switch What happens on Distribution Boards when Main Active and Main Neutral are swapped? N A
  88. 144. <ul><li>What happens when the Main Neutral </li></ul><ul><li>goes Open Circuit? </li></ul>
  89. 145. MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link OPEN CIRCUIT Neutral Load
  90. 146. MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link LOAD CURRENT Load
  91. 147. MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link LOAD CURRENT Load
  92. 148. MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link Lo load Resistance Hi stake - earth Resistance: 30  - 2k  Load Voltages... High Voltage Low Voltage High Voltage on Earth System
  93. 149. MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link Lo load Resistance Hi stake - earth Resistance: 30  - 2k  High Voltage Low Voltage Livens: -Taps, -Sinks -Water pipes -Metal cases of appliances Load Voltages... High Voltage on Earth System
  94. 150. Q: What causes “tingles” on taps? MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link All Loads
  95. 151. Q: What causes “tingles” on taps? VD N =4V MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link All Loads
  96. 152. Q: What causes “tingles” on taps? MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link All Loads 4V 0V
  97. 153. Testing
  98. 154. TEST EQUIPMENT REQUIRED (AS3017 1.6.2) <ul><li>High Voltage Insulation Resistance Tester </li></ul><ul><li>Low reading ohmmeter (0.5-5  ) </li></ul><ul><li>Voltage Present Indicator </li></ul><ul><li>Trailing lead (of known resistance). </li></ul><ul><li>Fault Loop Impedance tester </li></ul><ul><li>RCD Tester </li></ul>
  99. 155. TEST EQUIPMENT REQUIRED (AS3017 1.6.2) <ul><li>Test for dead device. </li></ul><ul><ul><li>Category 1: electronic </li></ul></ul><ul><ul><li>Category 2: Single Phase boards </li></ul></ul><ul><ul><li>Category 3: Three Phase DB / MSB </li></ul></ul><ul><ul><li>Category 4: Three Phase power lines </li></ul></ul>
  100. 156. TESTS <ul><li>Visual </li></ul><ul><li>Earth Continuity </li></ul><ul><li>Insulation Test </li></ul><ul><li>Polarity </li></ul><ul><li>Correct circuit connections </li></ul><ul><li>Fault Loop Impedance check </li></ul><ul><li>RCD test </li></ul>
  101. 157. <ul><li>General </li></ul><ul><li>Consumer Mains </li></ul><ul><li>Switchboards </li></ul><ul><li>Wiring Systems </li></ul><ul><li>Electrical Equipment </li></ul><ul><li>Earthing </li></ul>Step 1: Visual Examination
  102. 158. General Requirements Clause No. What to look for 2.9.6 No exposed live parts. E.g. no excessive removal of insulation at terminations, terminal covers in place etc. Double insulation maintained where required. E.g. no single insulation in ceiling above light fittings, no more than 100mm single insulation in wall behind accessories, insulating shrouds installed where required. 1.9 All equipment is approved/compliant with Australian Standards and in good condition. E.g. no unsafe/damaged or non-compliant equipment installed.
  103. 159. Consumer Mains Clause No. What to look for 3.4.1 Consumers Mains should be able to carry the maximum demand current of the installation with some capacity to spare. As a guide: 16mm2 (or parallel 6mm2) for overhead mains, 10mm2 for underground mains.
  104. 160. <ul><li>Switchboard </li></ul><ul><li>Clause No. What to look for </li></ul><ul><ul><ul><li>Switchboard is in a suitable location. E.g. At appropriate height </li></ul></ul></ul><ul><li>2.4 Correct over-current protection is installed. E.g. Correct circuit breaker ratings for each sub-circuit conductor and fault level at switchboard. </li></ul><ul><ul><ul><ul><li>Main switch/es is/are appropriate for installation. E.g. current raring </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Neutral bars/links marked for identification. E.g. Main N/L, RCD N/L </li></ul></ul></ul></ul><ul><ul><ul><li>Switchboard wiring correctly fixed. E.g. to hinged panel and at back of board to minimise flexing at terminations. </li></ul></ul></ul><ul><ul><ul><ul><li>Consistency of switchboard layout and marking. E.g. Correct marking of main switch/es, circuit breakers and corresponding neutral link connections. </li></ul></ul></ul></ul>
  105. 161. <ul><li>Wiring Systems </li></ul><ul><li>Clause No. What to look for </li></ul><ul><ul><li>Correct conductor sizes. E.g. adequate current carrying capacity for circuit/load, 2.5mm2 minimum for socket outlets etc. </li></ul></ul><ul><ul><ul><li>Adequate support and fixing of cables where required. E.g. surface wiring. </li></ul></ul></ul><ul><ul><ul><ul><li>Wiring fixed or passing through holes within 50mm of underside of floor is protected by RCD or mechanical protection. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Wiring fixed or passing through holes within 50mm of ceiling material or ceiling fixing support is protected of by RCD or mechanical protection. </li></ul></ul></ul></ul>
  106. 162. <ul><ul><ul><ul><li>Wiring fixed or passing through holes within 50mm of underside of roof material is protected by RCD or mechanical protection. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Wiring fixed or passing through holes within 50mm of surface of wall is protected by RCD or mechanical protection if outside nominated ‘zones’. </li></ul></ul></ul></ul><ul><ul><ul><li>Wiring in location where it is ‘deemed likely to be disturbed is fixed to prevent undue sagging. </li></ul></ul></ul><ul><ul><ul><li>Single insulated wiring is enclosed in conduit/trunking or junction box, except for switchboard wiring and in wall cavities for up to 100mm behind accessories at which the wiring is terminated. </li></ul></ul></ul><ul><li>Connection and terminations are correctly made. E.g. stranded conductors twisted, single conductors doubled back, no excess insulation removed, damaged insulation reinstated, no undue mechanical stress on any connection. </li></ul>
  107. 163. <ul><li>Electrical Equipment </li></ul><ul><li>Clause No. What to look for </li></ul><ul><li>4.3.11 Stove circuit has a ‘functional switch’ installed in appropriate location. </li></ul><ul><ul><ul><li>Equipment and accessories installed in accordance with safe and sound practice. E.g. accessible for operation, adequately fixed and supported. </li></ul></ul></ul><ul><ul><ul><li>Equipment is suitable for the conditions to which it is likely to be exposed. E.g. weatherproof fittings on external walls. </li></ul></ul></ul>
  108. 164. <ul><li>Earthing </li></ul><ul><li>Clause No. What to look for </li></ul><ul><ul><ul><li>MEN link correctly installed. </li></ul></ul></ul><ul><ul><ul><ul><li>MEN link is correct size. </li></ul></ul></ul></ul><ul><li>2.9.4.4 MEN link terminated at extremity of Main Neutral Link and Main Neutral terminated in next adjacent terminal or both clearly marked. </li></ul><ul><ul><ul><ul><li>Correct location of Earth Electrode. i.e. outside, exposed to the weather. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Correct termination and protection of Main Earth at electrode. </li></ul></ul></ul></ul><ul><ul><li>Correct size of Main Earth and Protective Earthing Conductors. </li></ul></ul><ul><ul><ul><ul><li>Correct size Equipotential Bonding Conductor. </li></ul></ul></ul></ul><ul><li>5.5.4.2 Earth conductors protected against ‘becoming displaced, damaged or cut’ as appropriate to ‘expected conditions’. </li></ul><ul><ul><ul><li>All earth conductor terminations comply with clause 3.7. </li></ul></ul></ul><ul><ul><ul><ul><li>Correct use of 1 or 2 screw terminal connections as required. </li></ul></ul></ul></ul>
  109. 165. Initial Procedures <ul><li>Open all Main Switches. </li></ul><ul><li>Turn C/B’s off / remove fuse wedges. </li></ul><ul><li>Disconnect the Main Neutral, and Main Earth from the Neutral link. </li></ul>
  110. 166. MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link Light
  111. 167. <ul><li>From Main Earth to Earth Electrode: <0.5  </li></ul><ul><li>Make sure all FSC earth resistance values are under the value of table 3.2 of AS 3017. </li></ul><ul><li>OR </li></ul><ul><li>Make sure all FSC are under the maximum length allowable and have good continuity… </li></ul>STEP 2: Earth Continuity
  112. 168. MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link Light Known resistance
  113. 169. STEP 3: Insulation Resistance <ul><li>Test between Main Earth and </li></ul><ul><li>1. Main Active with main switch ON . </li></ul><ul><li>2. Main Neutral </li></ul><ul><li> Result: >1M  </li></ul>1. Consumer Mains: Disconnect any service bonding conductor:
  114. 170. STEP 3: Insulation Resistance <ul><li>Test between Main Earth at Switchboard and: </li></ul><ul><li>The Active Conductors of circuits which require testing: >1M  </li></ul><ul><li>The Neutral Conductors of circuits which require testing: >1M  </li></ul>2. Final Subcircuits: With all C/B’s ON or fuse wedges IN, and all switches in the installation ON:
  115. 171. MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link Light
  116. 172. MAIN SWITCHBOARD Circuit Protective Devices Main Switch Consumer Mains Earth Link Neutral Link Light Switched Active
  117. 173. STEP 3: Insulation Resistance <ul><li>Where heater elements are tested: >10k  </li></ul>
  118. 174. <ul><li>Checks: </li></ul><ul><li>1. Polarity of mains or submains. </li></ul><ul><li>2. C/B’s and single pole switches operate in Active. </li></ul><ul><li>3. Polarity socket outlets </li></ul>STEP 4: Polarity Tests
  119. 175. STEP 5: Correct Circuit Connections <ul><li>Check that under normal operation earths do not carry current. </li></ul><ul><li>There is no interconnection of conductors between different circuits. </li></ul>
  120. 176. MEN Connection MAIN SWITCHBOARD Circuit Protective Devices Neutral Link Sub Mains Sub Mains ` Neutral Link DISTRIBUTION BOARD 3 Circuit Protective Devices Earthing Bar DISTRIBUTION BOARD 2 Circuit Protective Devices Neutral Link Earthing Bar Sub Mains Circuit Protective Devices Neutral Link Earthing Bar DISTRIBUTION BOARD 1 Main Switch A N Thank You The End

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