F.2 MOTORS, MOTORS, GENERATORS, GENERATORS, TRANSFORMERS TRANSFORMERS (COIL (COIL WOUND WOUND EQUIPMENT) EQUIPMENT) F
H.5.2 MOVABLE MOVABLE EQUIPMENT EQUIPMENT .1
H.5.2 MOVABLE MOVABLE EQUIPMENTEQUIPMENT H.5.2.1
H.5.2.1 Hand Hand ToolsTools
Insulation resistance
H.5.2.2 Distribution Distribution equipment equipment (cables, (cables, distribution distribution boards,boards, transformers)
transformers)
Insulation resistance:
Insulation resistance: 5 M5 MΩΩ
NOTES:
NOTES: 1. 1. These vThese values alues are are considered considered the lthe lowest owest acceptable acceptable to ato allow llow energisation energisation of exof existing isting equipment.equipment.
Corrective action shall be taken where lower values are found.
Corrective action shall be taken where lower values are found.
2.
2. The above figures are to The above figures are to be used unless local be used unless local regulations are more regulations are more stringent in which stringent in which case thecase the latter shall prevail.
latter shall prevail.
3.
3. IR to IR to be measube measured with red with load diload disconnected.sconnected.
Example: Required value for maintenance (M
Example: Required value for maintenance (MΩΩ) is kV rating of cable/length in km.) is kV rating of cable/length in km.
4.
4. Minimum insulation reMinimum insulation resistance values are gsistance values are given for 25 °C (77 iven for 25 °C (77 °F) equipment temperature; app°F) equipment temperature; applyly corrections for differing temperatures.
corrections for differing temperatures.
5.
5. For machines < 10 MVFor machines < 10 MVA energisation is pA energisation is possible if IR or Possible if IR or PI is above the miniI is above the minimum given.mum given.
6.
6. PI values beloPI values below those givw those given may ben may be accepted ie accepted if IR is > f IR is > 100(kV+1) M100(kV+1) MΩΩ..
7.
7. For test For test method anmethod and voltage d voltage see (Appesee (Appendix F)ndix F) 8.
8. PI measurements on insulPI measurements on insulation class 'F' ation class 'F' machines with IR in the machines with IR in the GGΩΩ range may be difficult to range may be difficult to obtain due to
obtain due to meter scale compression.meter scale compression.
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APPENDIX Ia
APPENDIX Ia EARTEARTH (GROUND) ELECTRODE RESISTH (GROUND) ELECTRODE RESIST ANCEANCE 1
1 An An alternating current alternating current of a of a steady steady value ivalue is pas passed between ssed between the earth the earth electrode electrode T andT and an auxiliary earth electrode T
an auxiliary earth electrode T11 placed at such a distance from T that the resistance placed at such a distance from T that the resistance areas of the two electrodes do not overlap.
areas of the two electrodes do not overlap.
2
2 A A second second auxiliary auxiliary earth earth electrode electrode TT22, which may be a metal spike driven into the, which may be a metal spike driven into the ground, is then inserted half-way between T and T
ground, is then inserted half-way between T and T11 and the voltage drop between T and the voltage drop between T and T
and T22 is measured. is measured.
3
3 The resistance The resistance of tof the he earth electrodes earth electrodes is is then then the volthe voltage tage between T between T and and TT22, divided, divided by the current flowing between T and T
by the current flowing between T and T11, provided that there is no overlap of the, provided that there is no overlap of the resistance areas.
resistance areas.
4
4 To check To check that that the resistance the resistance of the of the earth electrodes earth electrodes is a is a true value, true value, two furthertwo further readings are taken with the second auxiliary electrode T
readings are taken with the second auxiliary electrode T22 moved 6 m (20 ft) further moved 6 m (20 ft) further from and 6 m (20 ft) nearer to T, respectively.
from and 6 m (20 ft) nearer to T, respectively.
5
5 If the If the three three results results are are substantially substantially in in agreement, the agreement, the mean of mean of the the three three readings readings isis taken as the resistance of the earth electrode T. If there is no such agreement the taken as the resistance of the earth electrode T. If there is no such agreement the tests are repeated with the distance between T and T
tests are repeated with the distance between T and T11 increased. increased.
6
6 The test The test is is made eimade either wither with current th current at at power power frequency, in frequency, in which which case case the resithe resistancestance of the voltmeter used must be high (of the order of 200
of the voltmeter used must be high (of the order of 200 ΩΩ per volt), or with alternating per volt), or with alternating current from an earth tester comprising a hand-driven generator, a rectifier (where current from an earth tester comprising a hand-driven generator, a rectifier (where necessary), and a direct-reading ohmmeter.
necessary), and a direct-reading ohmmeter.
7
7 If the If the tests are tests are made at made at power frequency power frequency the source the source of the of the current used current used for the for the test itest iss isolated from the mains supply (e.g., by a double-wound transformer), and in any event isolated from the mains supply (e.g., by a double-wound transformer), and in any event the earth electrode T under test is disconnected from all sources of supply other than the earth electrode T under test is disconnected from all sources of supply other than that used for testing.
that used for testing.
APPENDIX Ia
APPENDIX Ia EARTEARTH (GROUND) ELECTRODE RESISTH (GROUND) ELECTRODE RESIST ANCEANCE 1
1 An An alternating current alternating current of a of a steady steady value ivalue is pas passed between ssed between the earth the earth electrode electrode T andT and an auxiliary earth electrode T
an auxiliary earth electrode T11 placed at such a distance from T that the resistance placed at such a distance from T that the resistance areas of the two electrodes do not overlap.
areas of the two electrodes do not overlap.
2
2 A A second second auxiliary auxiliary earth earth electrode electrode TT22, which may be a metal spike driven into the, which may be a metal spike driven into the ground, is then inserted half-way between T and T
ground, is then inserted half-way between T and T11 and the voltage drop between T and the voltage drop between T and T
and T22 is measured. is measured.
3
3 The resistance The resistance of tof the he earth electrodes earth electrodes is is then then the volthe voltage tage between T between T and and TT22, divided, divided by the current flowing between T and T
by the current flowing between T and T11, provided that there is no overlap of the, provided that there is no overlap of the resistance areas.
resistance areas.
4
4 To check To check that that the resistance the resistance of the of the earth electrodes earth electrodes is a is a true value, true value, two furthertwo further readings are taken with the second auxiliary electrode T
readings are taken with the second auxiliary electrode T22 moved 6 m (20 ft) further moved 6 m (20 ft) further from and 6 m (20 ft) nearer to T, respectively.
from and 6 m (20 ft) nearer to T, respectively.
5
5 If the If the three three results results are are substantially substantially in in agreement, the agreement, the mean of mean of the the three three readings readings isis taken as the resistance of the earth electrode T. If there is no such agreement the taken as the resistance of the earth electrode T. If there is no such agreement the tests are repeated with the distance between T and T
tests are repeated with the distance between T and T11 increased. increased.
6
6 The test The test is is made eimade either wither with current th current at at power power frequency, in frequency, in which which case case the resithe resistancestance of the voltmeter used must be high (of the order of 200
of the voltmeter used must be high (of the order of 200 ΩΩ per volt), or with alternating per volt), or with alternating current from an earth tester comprising a hand-driven generator, a rectifier (where current from an earth tester comprising a hand-driven generator, a rectifier (where necessary), and a direct-reading ohmmeter.
necessary), and a direct-reading ohmmeter.
7
7 If the If the tests are tests are made at made at power frequency power frequency the source the source of the of the current used current used for the for the test itest iss isolated from the mains supply (e.g., by a double-wound transformer), and in any event isolated from the mains supply (e.g., by a double-wound transformer), and in any event the earth electrode T under test is disconnected from all sources of supply other than the earth electrode T under test is disconnected from all sources of supply other than that used for testing.
that used for testing.
Measurement of earth electrode resistance Measurement of earth electrode resistance T
T - - earth earth electrode electrode under under test, test, disconnected disconnected from from all all other other sources sources of of supply.supply.
T
T11 - - auxiliary auxiliary earth earth electrode.electrode.
T
T22 - - second second auxiliary auxiliary earth earth electrode.electrode.
X
X - - alternative alternative position position of of TT22 for check measurement. for check measurement.
Y
Y - - further further alternative alternative position position of of TT22 for check measurement. for check measurement.
ski ski d d
plant earth/ground grid plant earth/ground grid
measurement of bonding of measurement of bonding of skid to plant earth/ground skid to plant earth/ground
grid grid
measurement of measurement of earth/ground electrode earth/ground electrode against the impedance of against the impedance of the plant earth/ground grid the plant earth/ground grid
Earthing / grounding Earthing / grounding electrode with electrode with inspection pit inspection pit loop impedance Z
loop impedance Zbb via bonding via bonding connections and plant connections and plant earth/ground grid earth/ground grid
Earthing/grounding impedance Z Earthing/grounding impedance Zr r
of earth/ground rod against plant of earth/ground rod against plant earth/ground grid impedance earth/ground grid impedance Earth/Ground clamp meters should have:
Earth/Ground clamp meters should have:
Self-calibration Self-calibration Overload protection Overload protection
AC current measurement > 10 A AC current measurement > 10 A
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APPENDIX J EXAMPLES OF DELTAEXAMPLES OF DELTA /STAR TRANSFORMER CONNECTION/STAR TRANSFORMER CONNECTION
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APPENDIX K
APPENDIX K TRANSFORMTRANSFORMER OILER OIL K.1
K.1 OIL OIL CONDITIONING CONDITIONING AND AND SAMPLINGSAMPLING