1. Define Type tests, Acceptance tests, Routine tests and Optional tests.
2. What are the typical tests performed as
   Type/ Routine/ Acceptance / Optional tests ?
3. What is the significance of following tests?
   
   
1. Annealing test
2. Armour resistance test
3. Bending test
4. Cold bend test
5. Conductor resistance test
6. Flammability test
7. High voltage test
8. Insulation resistance
9. Impulse Test
10. Loss of Mass Test
11. Partial Discharge Test
12. Tensile test
13. Wrapping Test (for Aluminium wires)

The tests performed on the cables are grouped as :

• Type Tests :
  These are the tests required to be made before supply on a general commercial basis a type of cable in order to demonstrate satisfactory performance characteristics to meet the intended application.
• Acceptance Tests :
  These are the tests carried out on samples taken from a lot for the purpose of acceptance of the lot.
• Optional Tests :
  These are the special tests which are to be carried out when required, by agreement between the purchaser & the supplier.
• Routine Tests :
  These are the tests made by the manufacturer on all finished cable lengths to demonstrate the integrity of the cable.
  

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a) Tests on conductor

• Annealing test (for conductor)
• Tensile test (for Aluminium)
• Wrapping test (for Aluminium)
• Conductor resistance test

b) Test for armouring wires/ strips

c) Test for thickness of insulation and sheath

d) Physical tests for insulation and outer :

• Tensile Strength and elongation at break
• Ageing in air oven
• Shrinkage test
• Hot deformation
• Loss of mass in air oven
• Heat Shock Test Thermal Stability

e) Insulation Resistance Test

f) High Voltage Test (water immersion test )

g) High voltage test at room temperature

h) Flammability Test

Acceptance tests

Various test performed under this group are:

a) Annealing test (for Copper)

b) Tensile test (for Aluminium)

c) Wrapping test (for Aluminium)

d) Conductor resistance test

e) Test for thickness of insulation and sheath.

f) Tensile strength and elongation at break of insulation and sheath.

g) Insulation resistance test .

h) High voltage test at room temperature.

Routine tests

Various tests performed under this group are:

a) Conductor resistance test

b) High voltage test at room temp.

c) Armour resistance test (for mining cables )

Optional tests :

Various tests performed under this group are:

a) Cold bend test

b) Cold impact test

c) Armour resistance test (for other than mining cables)

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• Annealing test :
  As the conductor of a cable is subjected to twisting & bending, it is necessary that it should be flexible enough to take any desired bend without breaking. This test takes into consideration the extent of work hardening which may be caused during the stranding & laying up the process.
  
  
• Armour resistance test :
  In case of short circuit faults the armour has to carry the short circuit current. The resistivity of the armour must be maintained within the designed value so that there is no excess temperature rise above the designed value & also there is no excess voltage rise , to the unsafe level.
  
  
• Bending test :
  All electrical cables are subjected to bending operation during handling & installation. The minimum radii are specified in the relevant specifications. In order to ensure that the cables withstand, without damage or showing any cracking of the sheaths, the recommended bending radii during installation & handling, it is necessary to conduct a bending test which is more rigorous than what is likely to be subjected to in actual practice.
  
  
• Cold bend test :
  Sometimes the cable have to be laid in the area of low temperature climatic conditions or frost. Due to constant exposure of the cable to the low temperature or frost conditions, the insulation or outer sheath of the cable will become hardened & stiff. However, this is a long term effect. Such hardening or stiffness causes cracking of the insulation or outer sheath & may lead to the failure of the cable. In order to ascertain the suitability or withstandability of the insulating or sheathing materials at low temperature or frost conditions (when usage of the cable so warrants), this cold bend test is carried out.
  

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• Conductor resistance test :
  Accurate control of resistance is necessary to meet system design parameters. Resistance is influenced by conductor dimensions & construction, processing, conditions, temperature, resistivity (composition/ impurity & temper of the material). It is expressed in terms of ohms per kilometre corrected to 20 0C.
  
  
• Flammability test :
  For certain location it may be important to use a cable which retards flame in case of a fire & is self-extinguishing when the source of the fire is removed. This test is therefore carried out on finished cables to verify this property.
  
  
• High voltage test :
  The insulation material in a cable is used to isolate the conductors from one another and from ground, as well as provide the necessary mechanical strength. The fundamental requirement of the insulation in an electric cable is that it withstands the voltage imposed on it in service. It is necessary that evaluation of the condition of the insulation be made by imposing a higher voltage stress for a short duration.
  
  
• Insulation resistance :
  The test is performed to determine insulation resistance, calculate volume resistivity and insulation resistance constant of the dielectric material of electric cable by direct current method. The dielectric material in a cable is used to insulate the conductors from one another and from ground as well as to provide mechanical support for the components. For this purpose it is desirable to have the insulation resistance as high as possible consistent with acceptable mechanical, chemical and heat resisting properties. During the manufacturing process non-uniformities may develop in the dielectric either in the form of conductive impurities in the material or in the form of mechanical imperfections in the dielectric affecting the quality of the cable. This test helps in detecting these imperfections.
  

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• Impulse Test :
  This test involves impulse testing ( simulated lightning impulse ) of electric cables. Insulating material used in high voltage cable may be subjected to transient voltages resulting from nearby lightning strokes. The ability of the insulating material to withstand these transient voltages is important in establishing the reliability of the cable insulation
  
  
• Loss of Mass Test:
  This test is performed to determine the thermal effect on the mass of thermoplastic insulation and sheath. Themoplastic insulation and sheath exposed to heat are subjected to many types of physical and chemical changes. The severity of exposure , in both time and temperature, determines the extent and type of change that takes place. Extended periods of exposure of insulation and sheath to elevated temperature cause degradation with progressive changes. These changes are assessed by measuring the loss of mass on subjecting the material to accelerating ageing.
  
  
• Partial Discharge Test:
  This test involves detection and measurement of partial discharge occurring in screened electric cables. Partial discharges remain unnoticed in the normal high voltage tests and could be harmful to the life of the insulants. Extruded dielectric tends to deteriorate very fast due to discharge in very small voids and cavities. It is therefore necessary that such voids should be avoided in the extrusion process. Still certain minute voids are unavoidable and these remain in the insulation. The magnitude of the discharge in such voids are measured so as to determine whether these are within permissible limits
  
  
• Tensile test :
  This test is performed on conductor material to determine the strength of the material when subjected to tensile stress. Since cable conductors to be pulled from one end along trenches are subjected to considerable force during pulling as well as manufacture, it is necessary to ensure that the conductor material has adequate tensile strength.
  
  
• Wrapping Test (for Aluminium wires) :
  This test is performed to determine the ductility of aluminium wire used as conductor for electric cables. This test brings out the property of the material, which makes it suitable for winding and twisting. Cable conductors during the process of manufacture as well as during installation are subjected to torsion due to axial twist and might break, if material is not sufficiently ductile. The properties checked by wrapping test ensure the suitability of material as cable conductor.

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