JB/T 10181.5-2000 Calculation of cable current carrying capacity Part 3: Sections related to operating conditions Section 1: Reference operating conditions and cable selection
Some standard content:
ICS29.060.20
Standard of the Machinery Industry of the People's Republic of China
JB/T10181.110181.6-2000
idtIEC60287
Calculation of the current rating of electric cables2000-04-24Release
State Bureau of Machinery Industry
Easy to process one website to PDF
Set other
2000-10-01Implementation
Standard of the Machinery Industry of the People's Republic of China
Calculation of the current rating of electric cables
Part 3: Sections on operating conditions
Section 1: Benchmark operating conditions and cable selectionCalculation of the current rating ofelectric cables Part 3: Section on operating conditions Section 1: Reference operating conditions and selection of cable type 1 Scope
JB/T10181.5-2000
idtIEC60287-3-1:1995
This standard applies to the steady-state operating conditions of all AC voltage and DC voltage cables of 5kV and below laid in air or soil. The soil includes cables laid directly in the ground, in pipelines, cable trenches or steel pipes with or without local soil drying. The term "steady state" means that the continuous constant current (100% load factor) is just enough to asymptotically reach the maximum temperature of the conductor under the condition that the surrounding environment is assumed to be unchanged. This section contains reference operating conditions and cable selection. 2 Reference standards
The provisions contained in the following standards constitute the provisions of this standard by reference in this standard. At the time of publication of the standard, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest version of the following standards. JB/T8996—1999 Guidelines for the Selection of High Voltage Cables JB/T101812000 Calculation of Cable Current-Carrying Capacity
3 Reference Ambient Temperature and Soil Thermal Resistivity in Different Countries 3.1 Standard Operating Conditions
In order to use the formulas given in the various parts of this standard, the values of the selected physical quantities are related to the operating conditions. Obviously, only when the assumed conditions and parameter values are known can two current-carrying capacity calculation results be compared. In particular, the values related to the operating conditions of the cable vary greatly from country to country. Various countries have been consulted on this issue, and many countries have responded.
Chapter 4 and its clauses summarize the operating conditions used in different countries. Note that Chapter 4 is intended to serve as a design guide for cables when the data provided by the user is incomplete. Care must be taken not to draw unreasonable conclusions from comparing the values of different countries. It should be remembered that the data used in any particular country are subject to many factors, some of which have different importance in different countries. Chapter 4 gives the numerical values of operating conditions for the following countries: Australia
Austria
Canada
France
Approved by the State Machinery Industry Bureau on April 24, 2000Netherlands
Implemented on October 1, 2000
Italy
JB/T10181.5-2000
3.2 Method for determining operating conditions when there is no such data in the country's data When there is no reference ambient temperature and soil thermal resistivity in the country's data, the following values are recommended: 3.2.1 Ambient temperature at sea level (see Table 1). Table 1
Ambient air temperature
Subtropical
Minimum
Maximum
Soil temperature at 1 (m) depth
Minimum
Maximum
The current carrying capacity given for the maximum operating temperature is necessary. If necessary, for the winter current carrying capacity, the lower value shall be adopted. These values
correspond to the temperature limits for winter and summer, or the extreme temperature values for rainy and dry seasons. When the laying depth is not specified, the standard depth is 1m. 3.2.2 Soil thermal resistance coefficient (see Table 2).
Thermal resistance coefficient (K·mW)
4 Values related to operating conditions in different countries 4.1 Australia
1) Standard conditions
Soil thermal resistance coefficient
Ambient soil temperature
2) Burial depth
Soil conditions
Very humid
Very dry
1.2K·m/W
25℃ (summer)
18℃ (winter)
Distance from the ground to the center of the cable or the center of the triangular cable group: low-voltage cable
1kV cable
33kV cable and high-voltage cable
Under the sidewalk
Under the lane
Under the sidewalk
Under the lane
Under the sidewalk
Under the lane
1000mm
1000mm
Weather conditions
Continuous humidity
Regular rainfall
Infrequent rainfall
Little or no rainfall
3) Ambient temperature in the air
Maximum value
4.2 Geographical conditions
1) Thermal properties of soil
a) Thermal resistance
30kV or less, average value
30kV average value
b) Temperature
Maximum value
Minimum value
2) Cable burial depth
All cables below 1kV
All cables below 10kV
10kV paper insulated cable
Oil-filled cable below 220kV
3) Ambient air temperature
Average value
4.3 Canada Large
JB/T10181.5—2000
40℃ (summer)
30℃ (winter)
0.7K·m/W
1.0K·m/W
(maximum 1.2; minimum 0.7K·m/W)
1000mm
1200mm
20℃ (maximum 40: minimum -20℃)
Although Canada has no recognized national values for soil thermal resistivity, ambient temperature and burial depth, the following values are representative. 1) Thermal characteristics of soil for direct buried or pipeline cables a) Thermal resistance coefficient:
Maximum value
Minimum value
Average value
Soil thermal resistance coefficient
1.2K·m/W
0.6K·m/W
0.9K·m/W
Not as a basis for design
In the absence of direct measurement data, a thermal resistance coefficient of 0.9K·m/W is usually assumed. However, if it is foreseen that the thermal characteristics of the surrounding soil will continue to deteriorate over the years and the climatic conditions may cause significant seasonal changes, it is recommended that the current carrying capacity be determined based on a thermal resistance coefficient of 1.2K·m/W.
The lower thermal resistance coefficient value in winter is not quoted as the basis for system design in any valid range. 83
2) Buried depth 1)
JB/T10181.5-2000
a) For viscous impregnated and non-drip paper insulated cables with voltages up to 69kV b) Extruded insulation (factory-based, EPDM, PVC, polyethylene, cross-linked polyethylene, etc.) cables with voltages up to 46kV c) Voltages up to 345kV
d) Steel pipe cables with voltages up to 345kV (air pressure or oil pressure) 3) Ambient air temperature
Maximum value
Minimum value
Average value
4.4 Finland
1) Thermal properties of soil
a) Thermal resistance coefficient:
The average value is used to calculate the current carrying capacity
-40℃
Not used as the design basis
1.0K·m/W
The soil of submarine cable is completely saturated with water
b)Temperature
Maximum value
Minimum value
(Average 5℃ to 10℃, abnormal maximum value is 20℃)2)Burial depth of direct buried cable or cable laid in pipelineAll cables with voltage of 36kV and below
All cables with voltage of 52kV and below
All cables with voltage of 123kV and below
All cables with voltage of 245kV and below
The actual depth depends on local conditions.
3) Ambient air temperature
Basic value for calculating current carrying capacity
Maximum value
Minimum value
4.5 France
1) Soil thermal characteristics
1000mm
1300mm
1500mm
—20℃
Direct burial
1100mm
1100mm||tt ||1100mm
In pipeline
1100mm
1100mm
a) Thermal resistance coefficient Summer: 1.2K·m/W, Winter: 0.85K·m/W (Direct measurement for trunk lines, 225kV and 400kV, in order to achieve the specified thermal resistance coefficient, artificial backfill soil is used if necessary): b) Temperature
1) This is actually the "minimum coverage" requirement. In the case of drainage, it corresponds to the drainage pipe without benefit requirement. 84
20kV cable
63, 255 and 400kV cable
JB/T10181.5-2000
In the Mediterranean region, it is recommended to add 5℃ to the value. 2) Buried depth
20kV distribution network cable:
Paris:
1400mm
Provinces - generally: 800~1400mm
—63, 255 and 400kV transmission network cable: Underground trench or pipeline: 1300mm
Substation:
The above figures represent the distance from the ground to the center of the cable in a flat arrangement and the center of the triangle in a triangular arrangement. (These values may vary according to local regulations.) 3) Ambient air temperature
The number is set on the cable bracket when calculating the cable current carrying capacity. The base value: summer
-winter
Unless there are specified requirements for soil thermal resistance, bZxz.net
temperature and burial depth, these values are listed as the basis and standard values for calculating the current carrying capacity.
1) Thermal characteristics of soil
a) Thermal resistance
Average value
The calculation takes into account the dry area adjacent to the cable. b) Temperature
Maximum value
Minimum value
Average value
2) Cable burial depth
Cables of 60kV and above
Cables below 60kV
3) Ambient air temperature
Maximum value
Minimum value
Average value
1.0K·m/W
2.5K·m/W
Minimum 12 00mm
700mml)
-20℃
1) Although calculated based on a laying depth of 700mm, 20kV to 30kV cables are usually laid at a depth of 900mm to 1000mm85
4.7Italy
1) Thermal properties of soil
a) Thermal resistance
Maximum value
JB/T10181.5-2000
1.0K·m/W
If the thermal properties of the soil are found to be poor, use a suitable backfill soil, the quoted thermal resistance value is between the backfill soil and the surrounding soil.
b) Temperature
Maximum value (for calculation)
Minimum value
2) Depth of laying of straight cables
Unless otherwise specified, the depth is taken as the maximum value. 12kV and below
17.5kV and below
24kV and below
36kV and below
72kV and below
220kV and below
3) Ambient air temperature
Maximum value (for calculation)
Minimum value
Daily maximum deviation
1000mm
1200mm
1500mm
1800mm
2200mm
In summer, the maximum value may be 5℃ higher than the above maximum value for a few hours every day (even more than 5℃ higher in special cases). Since its process is very short, such a situation is allowed. 4.8 Japan
1) Soil thermal characteristics
a) Thermal resistivity
Average value
1.0K·m/W
(One manufacturer uses 1.2, 0.8 and 0.4K·m/W for dry, normal and moist soils respectively). b) Temperature
Maximum value
Minimum value
2) Direct buried cable or pipeline cable laying depth a) Direct buried:
33kV and below paper insulated cable and extruded insulated cable oil-filled and steel pipe cable
b) In pipeline:
1200mm
1500mm
Less than 66kv
66kV and above
3) Ambient air temperature
Maximum value
4.9 Netherlands
1) Soil thermal characteristics
a) Thermal resistance
Groundwater table near the cable
Eastern region of the country| |tt||b) Temperature
Maximum value
Minimum value
Average value
2) Direct buried cable laying depth
Cables of 10kV and below
Cables above 10kV
3) Ambient air temperature
Maximum value
Minimum value
Average value
4.10 Norway
1) Soil thermal characteristics
a) Thermal resistance
Average value used for calculation
b) Temperature (℃)
2) Laying depth, minimum value
Above 1kV
3) Ambient air temperature||tt ||Maximum value (used for calculation)
4.11 Poland
1) Soil thermal characteristics
JB/T10181.5-2000
1200mm
1500mm
30℃ in winter
0.8K·m/W
1000mm
Maximum value
Minimum value
a) Thermal resistance coefficient
Used to calculate the average value
b) Temperature
Used to calculate the average value
Minimum value
2) Direct buried cable laying depth
1kV and below cables
1 Cables of 5kV and below
Cables of 15kV and above
3) Ambient air temperature
Average value used for calculation
4.12 Sweden
1) Soil thermal characteristics
a) Thermal resistance
Average value used for calculation
JB/T10181.5-2000
1.0K·m/W
1000mm
1.0K·m/W
(The thermal resistance of the submarine cable whose soil is completely saturated with water and whose bottom is covered with sand is 0.4K·m/W.) In other cases, it can be found that the thermal resistance is as high as 1.0K·m/W. For important cables, it is recommended to measure the thermal resistance of the seabed and the condition of the seabed soil. In cases where nothing is known, 0.6K·m/W is used. b) Temperature
Maximum value
Minimum value
(for most of the year between 5℃ and 15℃). 2) Laying depth of straight cables and short-distance cables in pipelines 24kV and below all cables
52kV and below paper insulated cables
420kV and below oil-filled cables
4.13 Switzerland
1) Soil thermal properties
a) Thermal resistance
Used value used for calculation
(1.3K·m/W in case of rock soil)
b) Temperature
Maximum value used for calculation
Minimum value
1000~1500mml
1.0K·m/W
Generally: -10℃
Mountainous area: -15℃
1) Depth depends on local conditions, and values less than 1000mm are not used. 88
JB/T10181.5-2000
Note: The additional condition is that the maximum soil temperature near the power plant is 50℃ under constant load (to avoid soil drying). 2) Burial depth
Under normal conditions
3) Air ambient temperature
Maximum value used for calculation
Minimum value
4.14 United Kingdom
1) Standard conditions
a) Soil thermal resistivity
b) Temperature
2) Burial depth
1000mm
25℃ (30℃ in some places in the country)-25℃
1.2K·m/W
a) 1kV cable - from the ground to the center of the cable, to the center of the pipeline or to the center of the cable or pipeline group laid in a triangular pipeline
b) 3.3 to 33kV cables (except pressure cables) - from the ground to the center of the cable, to the center of the pipeline c) 33kV pressure cable
3) Ambient air temperature
Outdoor1)
Inside a building
4.15 USA
1) Soil thermal properties
a) Thermal resistance
- The depth from the ground to the top surface of the cable, pipe or the triangular-laid cable or pipe is 900mm
Average value used for calculation when there is no data b) Temperature
2) Direct buried cable laying depth
3) Ambient air temperature
Design value
0.9K·m/W
(including the maximum air temperature caused by solar radiation heat is 40℃ to 50℃). 5 Information required from the purchaser to select the appropriate cable type 5.1 Background
This chapter refers to JB/8996 and gives the data required to select the appropriate cable type so that the purchaser can provide the manufacturer with the required data when the cable manufacturer selects the correct size and type of cable for a specific application. The purchaser should provide the manufacturer with as much information as possible 1) This temperature is also assumed as a standard condition for determining the current carrying capacity of cables in some indoor situations, such as for cables installed in basements of power stations and other factories.
JB/T10181.5-2000
and pay attention to some questions that they do not know or cannot be sure of the answer. In the absence of definite data, the manufacturer must make some assumptions, so any relevant information provided by the purchaser is helpful. 5.2 Operating conditions
a) The nominal voltage of the system U The rated power frequency voltage between any two conductors for the design of cables and their accessories: b) The highest voltage of the three-phase system U. Under normal operating conditions, the highest phase-to-phase voltage that occurs at any time and at any point in the system. It does not include voltage transients (such as those caused by system switching operations) and transient voltage changes due to abnormal system conditions (such as transient voltage changes caused by fault conditions or sudden disconnection of large loads) c) Lightning overvoltage:
d) System frequency;
e) Grounding method and the maximum allowable duration of any ground fault state and the total duration per year when the neutral point is not effectively grounded:
f) Environmental conditions should be given when determining the use of terminals, such as: altitude exceeding 1000m above sea level:
-Indoor or outdoor installation:
-Whether excessive atmospheric pollution is expected: -SF. Terminals in switches:
-Design safety distances and insulation used for the connection method between cables and equipment (transformers, switch motors, etc.). For example, safety distances and surrounding insulation should be specified.
g) Maximum rated current:
1) Continuous operation:
2) Cyclic operation;
3) Emergency operation or overload (if it occurs). Note: Load curves are essential when determining conductor dimensions if cyclic loads are considered. h) Symmetrical and asymmetrical short-circuit currents expected to flow when short-circuited between phases and between phases and ground: i) Maximum flow time of short-circuit current.
5.3 Installation information
5.3.1 General conditions
a) Line length and cross-section;
b) Installation details (such as flat or delta arrangement) and metal sheath interconnection and grounding method: c) Special laying conditions, such as cable laying in water. Individual installations require special considerations. 5.3.2 Geotechnical Cables
a) Details of the laying operation (e.g. direct burial, pipeline, etc.) to determine the metal sheath composition, armor (or required) type and outer sheath type, such as anti-corrosion, flame retardant or termite-resistant; b) Burial depth:
c) Thermal resistivity and type of soil along the route (e.g. sand, clay and man-made soil), and whether the data is derived from measurements, surveys or just assumptions;
d) Minimum, maximum and average soil temperature at the burial depth: 902 Operating conditions
a) The nominal voltage of the system U The rated power frequency voltage between any two conductors for the design of the cable and its accessories: b) The highest voltage of the three-phase system U. Under normal operating conditions, the highest phase-to-phase voltage effective value that occurs at any time and any point in the system. It does not include voltage transients (such as due to system switch operation) and transient voltage changes caused by abnormal system conditions (such as transient voltage changes caused by fault conditions or sudden disconnection of large loads) c) Lightning overvoltage:
d) System frequency;
e) Grounding method and the maximum allowable duration of any ground fault state and the total duration per year when the neutral point is not effectively grounded:
f) When determining the use of the terminal, the environmental conditions should be given, such as: Altitude exceeding 1000m above sea level:
-Indoor or outdoor installation:
-Whether excessive atmospheric pollution is expected: -SF. Terminals in the switch:
-The designed safety distance and insulation adopted by the connection method between the cable and the equipment (transformer, switch motor, etc.). For example, safety distances and surrounding insulation should be specified.
g) Maximum rated current:
1) Continuous operation:
2) Cyclic operation;
3) Emergency operation or overload (if it occurs). Note: Load curves are essential when determining conductor size if cyclic loads are considered. h) Symmetrical and asymmetrical short-circuit currents expected to flow when short-circuited between phases and between phases and ground: i) Maximum flow time of short-circuit current.
5.3 Installation information
5.3.1 General
a) Line length and cross-section;
b) Detailed information on laying and installation (such as flat or delta arrangement) and metal sheath interconnection and grounding method: c) Special laying conditions, such as cable laying in water. Individual installations require special considerations. 5.3.2 Geotechnical Cables
a) Details of the laying operation (e.g. direct burial, pipeline, etc.) to determine the metal sheath composition, armor (or required) type and outer sheath type, such as anti-corrosion, flame retardant or termite-resistant; b) Burial depth:
c) Thermal resistivity and type of soil along the route (e.g. sand, clay and man-made soil), and whether the data is derived from measurements, surveys or just assumptions;
d) Minimum, maximum and average soil temperature at the burial depth: 902 Operating conditions
a) The nominal voltage of the system U The rated power frequency voltage between any two conductors for the design of the cable and its accessories: b) The highest voltage of the three-phase system U. Under normal operating conditions, the highest phase-to-phase voltage effective value that occurs at any time and any point in the system. It does not include voltage transients (such as due to system switch operation) and transient voltage changes caused by abnormal system conditions (such as transient voltage changes caused by fault conditions or sudden disconnection of large loads) c) Lightning overvoltage:
d) System frequency;
e) Grounding method and the maximum allowable duration of any ground fault state and the total duration per year when the neutral point is not effectively grounded:
f) When determining the use of the terminal, the environmental conditions should be given, such as: Altitude exceeding 1000m above sea level:
-Indoor or outdoor installation:
-Whether excessive atmospheric pollution is expected: -SF. Terminals in the switch:
-The designed safety distance and insulation adopted by the connection method between the cable and the equipment (transformer, switch motor, etc.). For example, safety distances and surrounding insulation should be specified.
g) Maximum rated current:
1) Continuous operation:
2) Cyclic operation;
3) Emergency operation or overload (if it occurs). Note: Load curves are essential when determining conductor size if cyclic loads are considered. h) Symmetrical and asymmetrical short-circuit currents expected to flow when short-circuited between phases and between phases and ground: i) Maximum flow time of short-circuit current.
5.3 Installation information
5.3.1 General
a) Line length and cross-section;
b) Detailed information on laying and installation (such as flat or delta arrangement) and metal sheath interconnection and grounding method: c) Special laying conditions, such as cable laying in water. Individual installations require special considerations. 5.3.2 Geotechnical Cables
a) Details of the laying operation (e.g. direct burial, pipeline, etc.) to determine the metal sheath composition, armor (or required) type and outer sheath type, such as anti-corrosion, flame retardant or termite-resistant; b) Burial depth:
c) Thermal resistivity and type of soil along the route (e.g. sand, clay and man-made soil), and whether the data is derived from measurements, surveys or just assumptions;
d) Minimum, maximum and average soil temperature at the burial depth: 90
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