1 General
1.1 Scope
1.2 Normative references
1.3 List of symbols and definitions
2 Representative voltage stresses in service
2.1 Origin and classification of voltage stresses
2.2 Characteristics of overvoltage protective devices
2.3 Representative voltages and overvoltages
3 Co-ordination withstand voltage
3.1 Insulation strength characteristics
3.2 Performance criterion
3.3 Insulation co-ordination procedures
4 Required withstand voltage
4.1 General remarks
4.2 Atmospheric correction
4.3 Safety factors
5 Standard withstand voltage and testing procedures
5.1 General remarks
5.2 Test conversion factors
5.3 Determination of insulation withstand by type tests
6 Special considerations for overhead lines
6.1 General remarks
6.2 Insulation co-ordination for operating voltages
and temporary overvoltages
6.3 Insulation co-ordination for slow-front overvoltages
6.4 Insulation co-ordination for lightning overvoltages
7 Special considerations for substations
7.1 General remarks
7.2 Insulation co-ordination for overvoltages
Tables
1 Recommended creepage distances
2 Test conversion factors for range I, to convert required
switching impulses withstand voltages to short-
duration power-frequency and lightning impulse
withstand voltages
3 Test conversion factors for range II to convert required
short-duration power-frequency withstand voltages to
switching impulse withstand voltages
4 Selectivity of test procedures B and C of IEC 60-1
A.1 Correlation between standard lightning impulse withstand
voltages and minimum air clearances
A.2 Correlation between standard switching impulse withstand
voltages and minimum phase-to-earth air clearances
A.3 Correlation between standard switching impulse withstand
voltages and minimum phase-to-phase air clearances
C.1 Breakdown voltage versus cumulative flashover
probability - single insulation and 100 parallel
insulations
F.1 Corona damping constant Kco
F.2 Factor A for various overhead lines
G.1 Typical gap factors K for switching impulse breakdown
phase-to-earth
G.2 Gap factors for typical phase-to-phase geometries
H.1 Summary of minimum required withstand voltages obtained
for example H.1.1
H.2 Summary of required withstand voltages obtained for
example H.1.2
H.3 Values related to the insulation co-ordination
procedure for example H.3
Figures
1 Range of 2% slow-front overvoltages at the receiving end
due to line energization and re-energization
2 Ratio between the 2% values of slow-front overvoltages
phase-to-phase and phase-to-earth
3 Diagram for surge arrester connection to the
protected object
4 Distributive discharge probability of self-restoring
insulation described on a linear scale
5 Disruptive discharge probability of self-restoring
insulation described on a Gaussian scale
6 Evaluation of deterministic co-ordination factor Kcd
7 Evaluation of the risk of failure
8 Risk of failure of external insulation for slow-front
overvoltages as a function of the statistical co-
ordination factor Kcs
9 Dependence of exponent m on the co-ordination switching
impulse withstand voltage
10 Probability P of an equipment to pass the test dependent
on the difference K between the actual and the rated
impulse withstand voltage
11 Example of a schematic substation layout used for the
overvoltage stress location (see 7.1)
B.1 Earth-fault factor k on a base of Xo/X1 for R1/X1=0
B.2 Relationship between Ro/X1 for constant values of
earth-fault factor k where R1 = 0
B.3 Relationship between Ro/X1 et Xo/X1 for constant values
of earth-fault factor k where R1 - 0.5 X1
B.4 Relationship between Ro/X1 et Xo/X1 for constant values of
earth-fault factor k where R1 = X1
B.5 Relationship between Ro/X1 et Xo/X1 for constant values
of earth-fault k where R1 = X1
C.1 Conversion chart for the reduction of the withstand
voltage due to phasing insulation configurations in
parallel
D.1 Example for bivariate phase-to-phase overvoltage curves
with constant probability density and tangents giving
the relevant 2% values
D.2 Principle of the determination of the representative
phase-to-phase overvoltage Upre
D.3 Schematic phase-phase-earth insulation configuration
D.4 Description of the 50% switching impulse flashover
voltage of a phase-phase-earth insulation
D.5 Inclination angle of the phase-to-phase insulation
characteristic in range b dependent on the ratio of
the phase-phase-clearance D to the height Ht above earth
E.1 Distributed capacitances of the windings of a transformer
and the equivalent circuit describing the windings
E.2 Values of factor J describing the effect of the
winding connections rn the inductive surge transference
Annexes
A Clearances in air to assure a specified impulse withstand
voltage installation
B Determination of temporary overvoltages due to earth
faults
C Weibull probability distributions
D Determination of the representative slow-front over-
voltage due to line energization and re-energization
E transferred overvoltages in transformers
F Lightning overvoltages
G Calculation of air gap breakdown strength from
experimental data
H Examples of insulation co-ordination procedure
J Bibliography
ZA (normative) Normative references to international
publications with their corresponding European
publications