BS 3941:1975

Co-operating organizations
Foreword
Specification
Section one. General
1 Scope
2 References
3 Definitions
4 Service conditions
Section two. Requirements for all voltage transformers
5 Rated frequency
6 Rated secondary voltages
7 Rated outputs
8 Rated transformation ratios
9 Rated voltage factors
10 Characteristics of voltage transformers with
    residual voltage windings
11 Limits of temperature rise
12 Rated insulation levels
13 Creepage distances
14 Accuracy class designations
15 Limits of error
16 Marking
17 Test requirements
18 Tests
Section three. Additional requirements for capacitor
               voltage transformers
19 General requirements
20 Additional performance requirements
21 Test requirements
22 Marking
Section four. Requirements for capacitors for use with
               capacitor voltage transformers
23 General requirements
24 Test requirements
25 Tests
26 Insulation level
27 Marking
Appendices
A Service conditions
B Guidance on the application of measuring voltage
    transformers
C Rating of voltage transformers at frequencies other
    than rated frequency
D Temperature measurements
E Guidance for installation and operation of
    capacitors
F Information required by the manufacturer
Tables
1 Rated transformation ratios
2 Standard values of rated voltage factors
3 Characteristic of voltage transformers with residual
    voltage windings
4 Limits of temperature rise of windings
5a Insulation test levels for rated highest equipment
    voltages up to and including 72.5 kV
5b Insulation test levels for rated highest equipment
    voltages of 100 kV and above
6 Limits of voltage error and phase displacement for
    measuring voltage transformers
7 Limits of voltage error and phase displacement for
    protective voltage transformers
8 High voltage winding terminal to be earthed during
    impulse voltage tests
9 Applied power frequency test voltages on primary
    windings (after erection on site)
10 Applied power frequency test high voltage tests for
    durations exceeding one minute (after erection on
    site)
11 Selection of class of accuracy of measuring voltage
    transformers
Figures
1 Single-phase voltage transformer having one or two
    secondary windings without tappings
2 Single-phase voltage transformer having one or two
    secondary windings with tappings
3 Single-phase or 3-phase voltage transformer with one
    residual voltage winding
4 3-phase voltage transformer with one or two
    secondary windings without tappings
5 3-phase voltage transformer with one secondary
    winding with tappings
6 Circuit for accuracy test on a transformer having a
    rated voltage factor of 1.5
7 Circuit for accuracy test on a transformer having a
    rated voltage factor of 1.9
8 Circuit for accuracy test on the residual voltage
    winding of a transformer having a rated voltage
    factor not exceeding 1.5
9 Circuit for accuracy test on the residual voltage
    winding of a transformer having a rated voltage
    factor of 1.9
10 Alternative circuit for accuracy test on the
    residual voltage winding of a transformer having a
    rated voltage factor of 1.9
11 Diagrammatic arrangement of capacitor voltage
    transformer

Performance and test requirements for electromagnetic and capacitor voltage transformers for use with measuring instruments and protective equipment. Requirements for capacitor dividers for use with capacitor voltage transformers. Guidance on application.