BS 137-1:1982

Foreword
Cooperating organizations
Methods of test
Section one. General
1 Scope
2 References
3 Definitions
4 Classification
5 Values of voltage
6 Values which characterize a string insulator unit or
    a rigid insulator
7 Values which characterize an insulator string or an
    insulator set
8 Marking
Section two. General requirements for tests
9 General requirements for electrical tests
10 Lightning impulse voltage tests
11 Switching impulse voltage tests
12 Wet power-frequency voltage tests
13 Wet tests
14 Standard atmospheric conditions for tests
15 Correction factors for atmospheric conditions
16 Classification of tests
Section three. Tests in group I (type tests)
17 General
18 Methods of mounting
19 Time intervals between consecutive applications of
    the voltage
20 Dry lightning impulse withstand voltage test
21 Wet switching impulse withstand voltage test
22 Wet power-frequency withstand voltage test
Section four. Tests in group II (sample tests)
23 General
24 Verification of dimensions
25 Temperature cycle test
26 Electromechanical failing load test (on type B
    string insulator units only)
27 Mechanical failing load test
28 Thermal shock test (for toughened glass insulators
    only)
29 Power-frequency puncture test (for type B insulators
    only)
30 Porosity test (for ceramic insulators only)
31 Galvanizing tests
32 Re-test procedure
Section five. Tests in group III (routine tests)
33 General
34 Visual examination
35 Mechanical routine test
36 Electrical routine test (only on type B insulators
    of ceramic material)
37 Thermal shock routine test (for toughened glass
    parts only)
Figures
1 Temperature correction factor alpha for resistivity
    of water as used in wet tests, where rho20 and rhot
    indicate resistivity at 20 deg C and t deg C
2 Corrections for air density: exponent m versus
    insulating distance d
3 Corrections for humidity: factor kh versus absolute
    humidity
4 Section through very large insulators indicating the
    greatest thickness phi of the insulator