Page 619 - Industrial Power Engineering and Applications Handbook

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cables. For an assessment of the possible magnitudes and Where this is not necessary, it can be assessed by
durations of the TOVs and the prospective amplitudes and the equipment’s exposure to such TOVs and surges and
steepnesses of the lightning or switching surges, particularly thus determine the appropriate level of BIL. IEC 6007 1 -
at critical installations such as a generating station or a 2 provides guidelines for the most appropriate surge
large switchyard, it isessential tocarry out system transient protection scheme and is discussed in Section 18.6.
analysis (TNA) as noted later.

Relevant Standards

IEC Title IS BS
60060-1/1989 High voltage test techniques. General definitions and 207 1 - l/1993 BS 923-1/1990
test requirements
60071- MY93 Insulation coordination - Definition, principles and 2165- M99 I, BS EN 60071-1/1996
rules 21 65-2/1991
6007 1 -2/1996 Insulation coordination - Application guide 37 16/ I 99 I, BS EN 60071-2/1997
60470/1974 High voltage a.c. contactors 9046/1992 BS 77~19n4
60947-4- 1/1990 Contactors and motor starters. Electromechanical 13947-4- 1/1993 BS EN 60947-4-
contactors and motor starters 111992
61024- 1/1990 Protection of stmctures against lightning - General 2309/ I989 BS 6651/1992,
principles DD ENV 61024-111995
- Capacitors for surge protection for systems 0.65 kV to
33 kV

Relevant US Standards ANSVNEMA and IEEE
IEEE.4/1995 Standard techniques for HV testing
ANWIEEE Insulation Coordination, Definitions, Principles and Rules
131 3.1/1996

Notes
1 In the tables of Relevant Standards in this book while the latest editions of the standards are provided, it is possible that revised editions
have become available. With the advances of technology and/or its application, the updating of standards is a continuous process by
different standards organizations. It is therefore advisable that for more authentic references, readers should consult the relevant
organizations for the latest version of a standard.
2 Some of the BS or IS standards mentioned against IEC may not be identical
3 The year noted against each standard may also refer to the year of its last amendment and not necessarily the year of publication.

List of formulae used Surge energy

Vt’
Rate of rise of recovery voltage W = - x 10’ kW-s or kJ (17.3)
x
t
zc
r.r.r.v. = - kV/ps W = energy released in kW-s or kJ
vt
t, V, = prospective crest of the surge in kV
V, = peak value of the voltage surge in kV Z, = surge impedance of the power system and the
t, = rise time in ps terminal equipment in
t = duration for which it exists (in seconds)
(17.1)
f, = surge frequency in Hz Velocity of propagation
L = leakage inductance of the circuit ‘in henry (H)
C = lumped leakage capacitance of the circuit in U = ~ (1 7.4)
farad (F)

Surge impedance U = velocity of propagation in kds
Lo = line or conductor mutual inductance in Hkm
zs = J$n (17.2) Co = leakage capacitance of the same medium in
F/km