AS/NZS 60255.27:2025
Measuring relays and protection equipment – Part 27: Product safety requirements (IEC 60255-27:2023 (ED. 3.0) MOD)
Standard specifies the product safety requirements for measuring relays and protection equipment having a rated AC voltage up to 1 000 V, or a rated DC voltage up to 1 500 V. Above these limits, IEC 60664‑1 is applicable for the determination of clearance, creepage distance and withstand test voltage.
This document specifies essential safety requirements to minimize the risk of fire and hazards caused by electric shock or injury to the user and property.
This document is an adoption with national modifications, and has been reproduced from IEC 60255‑27:2023 Measuring relays and protection equipment – Part 27: Product safety requirements.
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AS/NZS 60255.27:2025 Measuring relays and protection equipment Product safety requirements (IEC 60255-27:2023 (ED. 3.0) MOD)
Preface
Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Protection against electric shock
4.1 Protection from contact with hazardous-live-parts
4.1.1 General
4.1.2 Insulation
4.1.3 Equipment enclosure and barriers
4.1.4 Hazardous live terminations using stranded wire
4.2 Protective impedance
4.3 Accessible parts
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
4.4.1 General
4.4.2 Insulation between live parts and accessible conductive parts
4.4.3 Protective bonding
4.5 Functional earthed circuits
4.6 Protective conductor connection
4.7 High leakage current
4.8 Solid insulation
4.8.1 General
4.8.2 Requirements
4.9 Clearances and creepage distances
4.9.1 General
4.9.2 Clearances
4.9.3 Creepage distances
4.10 Single fault conditions
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
5.1 Protection against mechanical hazards
5.1.1 Stability
5.1.2 Moving parts
5.1.3 Edges and corners
5.2 Mechanical requirements
5.3 Mechanical security of terminations
6 Flammability and resistance to fire
6.1 General
6.2 Requirements for protection against the spread of fire
6.3 General hazards from overheating and fire
6.3.1 Surface temperature limits for protection against burns
6.3.2 Hazardous gases and chemicals
6.4 Minimization of fire risk
6.4.1 General
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
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
6.8.1 Parts requiring a fire enclosure
6.8.2 Parts not requiring a fire enclosure
6.9 Fire enclosures and flame barriers
6.9.1 General
6.9.2 Fire enclosures and flame barrier requirements
6.10 Assessment of the fire risk due to a single fault condition
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
6.11 Limited-energy circuit
7 General and fundamental design requirements for safety
7.1 Climatic conditions for safety
7.2 Electrical connections
7.3 Components
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
7.6.1 General
7.6.2 Components at risk of explosion
8 Marking, documentation and packaging
8.1 Marking
8.1.1 General
8.1.2 Identification
8.1.3 Auxiliary supplies, measurands, inputs and outputs
8.1.4 Fuses
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
8.1.9 Test voltage marking
8.1.10 Warning markings
8.1.11 Marking durability
8.2 Documentation
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
9.1 General
9.2 Safety type tests
9.3 Routine testing
9.4 Conditions for testing
9.5 Verification procedure
9.6 Tests
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
9.6.5 Electrical environment and flammability
9.6.6 Reverse polarity and slow ramp test
9.6.7 Resistance to mechanical stress
Annex A (normative) Isolation class requirements and example diagrams
Annex B (normative) Rated impulse voltages
Annex C (normative) Guidance for the determination of clearance, creepage distance and withstand voltages
Annex D (informative) Components
Annex E (normative) External wiring terminations
Annex F (informative) Examples of battery protection
Annex G (informative) Risk assessment
Bibliography
Figure 1 — Flow chart showing requirements for protection against the spread of fire
Figure 2 — Baffle
Figure 3 — Location and extent of a flame barrier
Figure 4 — Voltage ramp test
Figure 5 — Impact test with sphere
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)
Figure C.1 — Guidance for determination of clearances, creepage distances and withstand voltages
Figure F.1 — Non-rechargeable battery protection
Figure F.2 — Rechargeable battery protection
Figure G.1 — Iterative process of risk assessment and risk reduction
Figure G.2 — Risk reduction
Table 1 — Equipment enclosure requirements for protection against electric shock
Table 2 — Current levels under normal use
Table 3 — Charge or energy of capacitance levels under normal use
Table 4 — Altitude multiplication factor
Table 5 — Current levels in single fault condition
Table 6 — Maximum temperature under normal use and at an ambient temperature of 40 °C
Table 7 — Acceptable perforation in the bottom of an equipment case
Table 8 — Insulation material of windings
Table 9 — Limits of maximum available current
Table 10 — Overcurrent protective device
Table 11 — Fuse types
Table 12 — Symbols
Table 13 — Symbols for marking of test voltage(s)
Table 14 — Overview of tests
Table 15 — Impulse generator characteristics
Table 16 — Guidance for routine dielectric voltage testing for safety
Table 17 — Limiting dynamic values
Table 18 — Impact energy levels, test height and corresponding IK codes
Table A.1 — Circuit isolation class for product circuits and/or groups
Table A.2 — Insulation requirement between any two circuits
Table B.1 — Rated impulse voltages (waveform: 1,2/50 µs)
Table C.1 — Comparative tracking index (CTI)
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
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
Table G.1 — Severity of harm
Table G.2 — Probability of harm
Table G.3 — Risk category
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AS/NZS 60255.27:2025 Measuring relays and protection equipment Product safety requirements (IEC 60255-27:2023 (ED. 3.0) MOD)
Preface
Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Protection against electric shock
4.1 Protection from contact with hazardous-live-parts
4.1.1 General
4.1.2 Insulation
4.1.3 Equipment enclosure and barriers
4.1.4 Hazardous live terminations using stranded wire
4.2 Protective impedance
4.3 Accessible parts
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
4.4.1 General
4.4.2 Insulation between live parts and accessible conductive parts
4.4.3 Protective bonding
4.5 Functional earthed circuits
4.6 Protective conductor connection
4.7 High leakage current
4.8 Solid insulation
4.8.1 General
4.8.2 Requirements
4.9 Clearances and creepage distances
4.9.1 General
4.9.2 Clearances
4.9.3 Creepage distances
4.10 Single fault conditions
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
5.1 Protection against mechanical hazards
5.1.1 Stability
5.1.2 Moving parts
5.1.3 Edges and corners
5.2 Mechanical requirements
5.3 Mechanical security of terminations
6 Flammability and resistance to fire
6.1 General
6.2 Requirements for protection against the spread of fire
6.3 General hazards from overheating and fire
6.3.1 Surface temperature limits for protection against burns
6.3.2 Hazardous gases and chemicals
6.4 Minimization of fire risk
6.4.1 General
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
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
6.8.1 Parts requiring a fire enclosure
6.8.2 Parts not requiring a fire enclosure
6.9 Fire enclosures and flame barriers
6.9.1 General
6.9.2 Fire enclosures and flame barrier requirements
6.10 Assessment of the fire risk due to a single fault condition
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
6.11 Limited-energy circuit
7 General and fundamental design requirements for safety
7.1 Climatic conditions for safety
7.2 Electrical connections
7.3 Components
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
7.6.1 General
7.6.2 Components at risk of explosion
8 Marking, documentation and packaging
8.1 Marking
8.1.1 General
8.1.2 Identification
8.1.3 Auxiliary supplies, measurands, inputs and outputs
8.1.4 Fuses
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
8.1.9 Test voltage marking
8.1.10 Warning markings
8.1.11 Marking durability
8.2 Documentation
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
9.1 General
9.2 Safety type tests
9.3 Routine testing
9.4 Conditions for testing
9.5 Verification procedure
9.6 Tests
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
9.6.5 Electrical environment and flammability
9.6.6 Reverse polarity and slow ramp test
9.6.7 Resistance to mechanical stress
Annex A (normative) Isolation class requirements and example diagrams
Annex B (normative) Rated impulse voltages
Annex C (normative) Guidance for the determination of clearance, creepage distance and withstand voltages
Annex D (informative) Components
Annex E (normative) External wiring terminations
Annex F (informative) Examples of battery protection
Annex G (informative) Risk assessment
Bibliography
Figure 1 — Flow chart showing requirements for protection against the spread of fire
Figure 2 — Baffle
Figure 3 — Location and extent of a flame barrier
Figure 4 — Voltage ramp test
Figure 5 — Impact test with sphere
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)
Figure C.1 — Guidance for determination of clearances, creepage distances and withstand voltages
Figure F.1 — Non-rechargeable battery protection
Figure F.2 — Rechargeable battery protection
Figure G.1 — Iterative process of risk assessment and risk reduction
Figure G.2 — Risk reduction
Table 1 — Equipment enclosure requirements for protection against electric shock
Table 2 — Current levels under normal use
Table 3 — Charge or energy of capacitance levels under normal use
Table 4 — Altitude multiplication factor
Table 5 — Current levels in single fault condition
Table 6 — Maximum temperature under normal use and at an ambient temperature of 40 °C
Table 7 — Acceptable perforation in the bottom of an equipment case
Table 8 — Insulation material of windings
Table 9 — Limits of maximum available current
Table 10 — Overcurrent protective device
Table 11 — Fuse types
Table 12 — Symbols
Table 13 — Symbols for marking of test voltage(s)
Table 14 — Overview of tests
Table 15 — Impulse generator characteristics
Table 16 — Guidance for routine dielectric voltage testing for safety
Table 17 — Limiting dynamic values
Table 18 — Impact energy levels, test height and corresponding IK codes
Table A.1 — Circuit isolation class for product circuits and/or groups
Table A.2 — Insulation requirement between any two circuits
Table B.1 — Rated impulse voltages (waveform: 1,2/50 µs)
Table C.1 — Comparative tracking index (CTI)
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
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
Table G.1 — Severity of harm
Table G.2 — Probability of harm
Table G.3 — Risk category
AS/NZS 60255.27:2025
Online Library subscription information
Online library subscriptions provide a cost-effective solution for organisations of any size to access the latest standards, offering 24/7 access to a personalised catalogue. The service ensures subscribers have have the most up-to-date version of selected standards, incluing automatic updates for any amendments or versions. Pricing is dependent on the chosen standards and the number of concurrent users, with discounts applied from the standards PDF price. For customised subscriptions or further inquiries, contact the Online Library team.