IEC 60524:1975

FOREWORD
PREFACE
Clause
 1 Scope
 2 Terms and definitions
   2.1 D.C. resistive volt ratio box (hereinafter
        designated 'VRB')
   2.2 Rated voltage(s)
   2.3 Nominal voltage ratio
   2.4 True voltage ratio
   2.5 Circuit installation voltage (nominal circuit
        voltage)
   2.6 Auxiliary equipment
   2.7 Leakage current screen (circuit)
   2.8 Electrostatic screen
   2.9 Ripple content
   2.10 Common mode voltage
   2.11 Influence quantity
   2.12 Variation with influence quantity
   2.13 Reference conditions
   2.14 Reference value
   2.15 Reference range
   2.16 Nominal range of use
   2.17 Limiting values of an influence quantity
   2.18 Fiducial value
   2.19 Error
   2.20 Error expressed as a proportion of the fiducial
         value
   2.21 Intrinsic error
   2.22 Accuracy
   2.23 Accuracy class
   2.24 Class index
   2.25 Parasitic voltage
 3 Classification
 4 Limits of intrinsic error
   4.1 Permissible limits of intrinsic error
   4.2 Multiple ratio VRBs
   4.3 D.C. parasitic voltages
 5 Conditions for the determination of intrinsic errors
 6 Permissible variations
   6.1 Limits of variation
   6.2 Conditions for the determination of variations
   6.3 Variation due to common mode voltage (see Appendix A)
 7 Additional electrical and mechanical requirements
   7.1 Effect of self-heating
   7.2 Voltage tests and other safety requirements
   7.3 Insulation test resistance
   7.4 Limiting temperature for storage, transport and use
 8 Information, markings and symbols
   8.1 Information
   8.2 Markings, symbols and their locations
   8.3 Documentation
   8.4 Examples of the marking of a VRB
 Appendix A - Determination of the effect of common
              mode voltage (see Figure 2)

Applicable to d.c. resistive volt ratio boxes with fixed ratios having a ratio input voltage up to 1.5 kV and a class index of 0.1 or better, as well as to all equipment which is built-in or supplied by the manufacturer (or responsible supplier) as an essential part of the volt ratio box. Classification system. Permissible errors for each accuracy class. Conditions for determination of errors. Markings. Information supplied by the manufacturer.