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eLibrary >
BS EN IEC 60255-27:2025 Measuring relays and protection equipment - Product safety requirements >
BS EN IEC 60255-27:2025 Measuring relays and protection equipment - Product safety requirements, 2025
- undefined
- European foreword
- Endorsement notice
- Annex ZA (normative) Normative references to international publications with their corresponding European publications [Go to Page]
- English [Go to Page]
- CONTENTS
- FOREWORD
- INTRODUCTION
- 1 Scope
- 2 Normative references
- 3 Terms and definitions
- 4 Protection against electric shock [Go to Page]
- 4.1 Protection from contact with hazardous-live-parts [Go to Page]
- 4.1.1 General
- 4.1.2 Insulation
- 4.1.3 Equipment enclosure and barriers
- Tables [Go to Page]
- Table 1 – Equipment enclosure requirements for protection against electric shock [Go to Page]
- 4.1.4 Hazardous live terminations using stranded wire
- 4.2 Protective impedance
- 4.3 Accessible parts [Go to Page]
- 4.3.1 General
- 4.3.2 Determination of accessible parts
- 4.3.3 Permissible limits for accessible parts
- 4.4 Earthing and protective bonding requirements [Go to Page]
- 4.4.1 General
- 4.4.2 Insulation between live parts and accessible conductive parts
- Table 2 – Current levels under normal use
- Table 3 – Charge or energy of capacitance levels under normal use [Go to Page]
- 4.4.3 Protective bonding
- 4.5 Functional earthed circuits
- 4.6 Protective conductor connection
- 4.7 High leakage current
- 4.8 Solid insulation [Go to Page]
- 4.8.1 General
- 4.8.2 Requirements
- 4.9 Clearances and creepage distances [Go to Page]
- 4.9.1 General
- 4.9.2 Clearances
- 4.9.3 Creepage distances
- Table 4 – Altitude multiplication factor
- 4.10 Single fault conditions [Go to Page]
- 4.10.1 Testing in single fault condition
- 4.10.2 Application of single fault condition
- 4.10.3 Duration of tests
- 4.10.4 Compliance
- 5 Mechanical aspects [Go to Page]
- 5.1 Protection against mechanical hazards [Go to Page]
- 5.1.1 Stability
- 5.1.2 Moving parts
- Table 5 – Current levels in single fault condition [Go to Page]
- 5.1.3 Edges and corners
- 5.2 Mechanical requirements
- 5.3 Mechanical security of terminations
- 6 Flammability and resistance to fire [Go to Page]
- 6.1 General
- 6.2 Requirements for protection against the spread of fire
- Figures [Go to Page]
- Figure 1 – Flow chart showing requirements for protection against the spread of fire
- 6.3 General hazards from overheating and fire [Go to Page]
- 6.3.1 Surface temperature limits for protection against burns
- 6.3.2 Hazardous gases and chemicals
- 6.4 Minimization of fire risk [Go to Page]
- 6.4.1 General
- Table 6 – Maximum temperature under normal use and at an ambient temperature of 40 °C [Go to Page]
- 6.4.2 Eliminating or reducing the sources of ignition within the equipment
- 6.5 Cabling and fusing
- 6.6 Flammability of materials and components [Go to Page]
- 6.6.1 General
- 6.6.2 Materials for components and other parts inside fire enclosures
- 6.6.3 Materials for fire enclosures
- 6.6.4 Materials for components and other parts outside fire enclosures
- 6.7 Fire ignition sources
- 6.8 Conditions for a fire enclosure [Go to Page]
- 6.8.1 Parts requiring a fire enclosure
- 6.8.2 Parts not requiring a fire enclosure
- 6.9 Fire enclosures and flame barriers [Go to Page]
- 6.9.1 General
- 6.9.2 Fire enclosures and flame barrier requirements
- Figure 2 – Baffle
- Figure 3 – Location and extent of a flame barrier
- Table 7 – Acceptable perforation in the bottom of an equipment case
- 6.10 Assessment of the fire risk due to a single fault condition [Go to Page]
- 6.10.1 Guidelines for maximum acceptable temperatures when subjecting a circuit or component to a single fault condition
- 6.10.2 Temperature of windings under normal use or a single fault condition
- 6.10.3 Conformity of equipment with requirements for protection against the spread of fire
- Table 8 – Insulation material of windings
- 6.11 Limited-energy circuit
- Table 9 – Limits of maximum available current
- Table 10 – Overcurrent protective device
- 7 General and fundamental design requirements for safety [Go to Page]
- 7.1 Climatic conditions for safety
- 7.2 Electrical connections
- 7.3 Components [Go to Page]
- 7.3.1 General
- 7.3.2 High-integrity part or component
- 7.4 Connection to other equipment
- 7.5 High-intensity light sources
- 7.6 Explosion [Go to Page]
- 7.6.1 General
- 7.6.2 Components at risk of explosion
- 8 Marking, documentation and packaging [Go to Page]
- 8.1 Marking [Go to Page]
- 8.1.1 General
- 8.1.2 Identification
- 8.1.3 Auxiliary supplies, measurands, inputs and outputs
- 8.1.4 Fuses
- Table 11 – Fuse types [Go to Page]
- 8.1.5 Measuring circuit terminals
- 8.1.6 Terminals and operating devices
- 8.1.7 Equipment protected by double or reinforced insulation
- 8.1.8 Batteries
- Table 12 – Symbols [Go to Page]
- 8.1.9 Test voltage marking
- 8.1.10 Warning markings
- Table 13 – Symbols for marking of test voltage(s) [Go to Page]
- 8.1.11 Marking durability
- 8.2 Documentation [Go to Page]
- 8.2.1 General
- 8.2.2 Equipment ratings
- 8.2.3 Equipment installation
- 8.2.4 Equipment commissioning and maintenance
- 8.2.5 Equipment operation
- 8.3 Packaging
- 9 Type tests and routine tests [Go to Page]
- 9.1 General
- Table 14 – Overview of tests
- 9.2 Safety type tests
- 9.3 Routine testing
- 9.4 Conditions for testing
- 9.5 Verification procedure
- 9.6 Tests [Go to Page]
- 9.6.1 Climatic environmental tests
- 9.6.2 Mechanical tests
- 9.6.3 Clearances and creepage distances
- 9.6.4 Safety-related electrical tests
- Table 15 – Impulse generator characteristics
- Table 16 – Guidance for routine dielectric voltage testing for safety [Go to Page]
- 9.6.5 Electrical environment and flammability
- Table 17 – Limiting dynamic values [Go to Page]
- 9.6.6 Reverse polarity and slow ramp test
- Figure 4 – Voltage ramp test [Go to Page]
- 9.6.7 Resistance to mechanical stress
- Figure 5 – Impact test with sphere
- Table 18 – Impact energy levels, test height and corresponding IK codes
- Annexes [Go to Page]
- Annex A (normative) Isolation class requirements and example diagrams [Go to Page]
- A.1 General
- A.2 Hazardous live voltage (HLV)
- Table A.1 – Circuit isolation class for product circuits and/or groups [Go to Page]
- A.3 Symbols
- Table A.2 – Insulation requirement between any two circuits [Go to Page]
- A.4 Typical insulation examples complying with the requirements of Table A.2
- Figure A.1 – Equipment with SELV input and/or output (I/O)
- Figure A.2 – Equipment with PELV input and/or output (I/O)
- Figure A.3 – Equipment with PEB input and/or output (I/O)
- Figure A.4 – Equipment with ELV input and/or output (I/O)
- Annex B (normative) Rated impulse voltages
- Table B.1 – Rated impulse voltages (waveform: 1,2/50 µs)
- Annex C (normative) Guidance for the determination of clearance, creepage distance and withstand voltages [Go to Page]
- C.1 General [Go to Page]
- C.1.1 Introductory remark
- C.1.2 Rated insulation voltages
- C.1.3 Determination of rated insulation voltage
- C.1.4 Determination of rated impulse voltage
- C.1.5 Switching overvoltages generated by equipment
- C.1.6 lnsulation material
- C.1.7 Overvoltage categories
- Table C.1 – Comparative tracking index (CTI) [Go to Page]
- C.2 Determination of clearances, creepage distances and withstand voltages [Go to Page]
- C.2.1 Guidance for determination of clearances, creepage distances and withstand voltages
- Figure C.1 – Guidance for determination of clearances, creepage distances and withstand voltages [Go to Page]
- [Go to Page]
- C.2.2 Determination of clearances, creepage distances and withstand voltages
- Table C.2 – Functional insulation, pollution degree 1, overvoltage category I
- Table C.3 – Functional insulation, pollution degree 2, overvoltage category I
- Table C.4 – Functional, basic or supplementary insulation, pollution degree 1, overvoltage category II
- Table C.5 – Functional, basic or supplementary insulation, pollution degree 2, overvoltage category II
- Table C.6 – Functional, basic or supplementary insulation, pollution degree 1, overvoltage category III
- Table C.7 – Functional, basic or supplementary insulation, pollution degree 2, overvoltage category III
- Table C.8 – Double or reinforced insulation, pollution degree 1, overvoltage category II
- Table C.9 – Double or reinforced insulation, pollution degree 2, overvoltage category II
- Table C.10 – Double or reinforced insulation, pollution degree 1, overvoltage category III
- Table C.11 – Double or reinforced insulation, pollution degree 2, overvoltage category III
- Table C.12 – Test site correction factor for proving the clearance in air
- Table C.13 – Reduction of the pollution degree of internal environment through the use of additional protection within the equipment
- Annex D (informative) Components [Go to Page]
- D.1 General
- D.2 Introductory remark
- D.3 Transformers
- D.4 Equipment primary circuit capacitors
- D.5 Coil devices – transformers, instrument transformers and transducers, reactors, and operating coils of relays and contactors with multiple windings and/or screen [Go to Page]
- D.5.1 Coil windings
- D.5.2 Insulating foil
- D.5.3 Interposing protective screen
- D.5.4 Safety isolation transformers
- D.6 Electromechanical components
- D.7 Semiconductor components and semiconductor configurations
- D.8 Connectors and terminal blocks
- D.9 Voltage dependent resistors (VDRs)
- D.10 Intentional radio transmitters
- Annex E (normative) External wiring terminations [Go to Page]
- E.1 General
- E.2 Permanently connected equipment
- E.3 Conductors
- E.4 Terminals
- Table E.1 – Range of conductor sizes to be accepted by terminals
- Table E.2 – Sizes of terminal studs or screws directly securing supply conductors
- Annex F (informative) Examples of battery protection
- Figure F.1 – Non-rechargeable battery protection
- Figure F.2 – Rechargeable battery protection
- Annex G (informative) Risk assessment [Go to Page]
- G.1 General
- G.2 Risk assessment procedure
- Figure G.1 – Iterative process of risk assessment and risk reduction [Go to Page]
- G.3 Achieving tolerable risk
- Figure G.2 – Risk reduction [Go to Page]
- G.4 An application of risk assessment procedures
- Table G.1 – Severity of harm
- Table G.2 – Probability of harm
- Table G.3 – Risk category
- Bibliography [Go to Page]
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