IEC 61010: Why it matters
Electricity can shock, burn, or even kill, so working with it daily can be very hazardous. As such, safety equipment, including clothes, gloves, and boots, is critical in helping protect electrical workers from potential accidents. However, a less obvious, but equally essential safety precaution is the design of any test equipment being used to maintain the electrical system.
The International Electrotechnical Commission (IEC) 61010 standard covers safety requirements for electrical equipment for measurement, control, and laboratory use. It includes requirements for testing and measuring circuits and for instruments. At minimum, all instruments should meet the requirements of this standard. The following paper will provide an overview of key elements of the standard.
Overview
IEC 61010 was first published in 1990. The purpose of the standard is to minimise hazards to operators, the surrounding area, and equipment. The standard has different parts (-01, -02-030, -02-032, -031, etc.) that apply to test instruments. Updates and technical changes to the standard have been made over the years to keep up with changing technologies and field application experience.
Simply complying with IEC 61010 is often not enough to guarantee safety in all situations. Having a skilled and application-specific understanding of the standard is crucial to designing instruments that are ‘field safe’. The standard is not black and white; it requires judgment based on foreseeable misuse and that judgement is driven by real life application experience regarding potential sources of danger.
The environment where the instruments are intended for use is a factor in meeting the requirements of the standard. Requirements for protection against specific hazards are listed below:
- Protection against electric shock
- Protection against mechanical hazards
- Resistance to mechanical stresses
- Protection against the spread of fire
- Resistance to heat
- Protection against hazards from fluids
- Protection against radiation
- Protection against liberated gases
The safety requirements for IEC 61010 do not include:
- Reliable function, performance, or other properties of the equipment not related to safety
- Effectiveness of transport packaging
- EMC requirements
- Protective measures for explosive atmospheres
The protection requirements outlined in IEC 61010 serve as foundational guidelines that draw upon other standards influencing the safe design of instruments. Let’s look at each of the requirements.
Protection against electric shock
Protection against electric shock is maintained in normal and single fault conditions. Single fault conditions include short circuits, open circuits, ground faults, and overloads. As an example, a short circuit occurs when there is an unplanned low resistance between two points in the circuit which can cause excessive current to flow.
Two key words in shock prevention are ‘creepage’ and ‘clearance.’ Creepage is the shortest distance between two points at different electrical potential along the surface of an insulating material. Clearance is the shortest distance in the air between two conducting parts. Conductive parts at significantly different voltages must be a safe distance from one another, or an arcing failure may occur. Arcing failures cause circuit damage, overheating, and fire, as well as causing a serious electrical shock hazard for the user.
Protection against mechanical hazards
The standard prohibits equipment from containing hazards including:
- Sharp edges, which could cause cuts
- Moving parts that could crush body parts or penetrate the skin
- Unstable equipment that could fall on a person while in use or being moved
- Falling equipment, resulting from breakage of a supporting part
- Expelled parts from the testing equipment
Resistance to mechanical stresses
The equipment must be able to withstand static, impact, and drop tests carried out as outlined in the standard. Following testing, the equipment is examined to ensure the insulation and effectiveness of all other parts of the enclosure have not been affected. The equipment is also inspected to check that:
- There have been no leaks of corrosive or harmful substances
- Enclosures show no cracks which could cause a hazard
- Electrical clearances are not less than their permitted values
- The insulation of the internal wiring remains undamaged
- Protective barriers necessary for safety have not been damaged, loosened or dislodged
- No moving parts are exposed
- There has been no damage that could cause the spread of a fire
The instrument must be able to survive accidents like falling off a truck, including not cracking. Even small cracks may create a near invisible electrical path, exposing the user to danger.
Protection Against the Spread of Fire
Under normal or single fault conditions, fire cannot spread outside of the equipment. During the compliance testing process, conformity is checked three different ways:
- Testing in single fault conditions that cause the spread of fire outside the equipment.
- Verifying removal or reduction of the sources of ignition in the equipment. It is critical that the insulation and any physical electrical barriers between parts meet specified requirements.
- Verifying that if a fire occurs, it will be contained within the equipment. The equipment and enclosure must conform to constructional requirements, including connectors and insulating material having a flammability class of V-2, or better. Insulated wires and cables must prevent flame spread. The enclosure must have adequate rigidity.
With plastic cases, fire resistant additives can make the case more vulnerable to mechanical damage.
Resistance to heat
Hazards caused by severe temperatures are not uncommon. Non-metallic enclosures must be resistant to elevated temperatures. This part of the standard impacts the materials used for instrument cases.
Protection against fluids and solid objects
Equipment must be designed to give the operator protection against hazards from fluids and solid foreign objects found in normal use. Normal use is determined by application experience. It must be designed for ingress protection from foreign objects. Foreign deposits on insulation parts can lead to a hazard and accumulations of foreign objects can potentially cause the spread of fire.
Protection against radiation and sonic pressure
Electronic equipment must provide protection against the effects of internally generated ultraviolet, ionising, and microwave radiation.
Protection against liberated gases and substances
Equipment cannot leak dangerous amounts of hazardous substances. This standard includes poisonous or injurious gases in normal or single fault conditions. If hazardous substances are released, the operators cannot be directly exposed to a specified quantity of the substance.
Conclusion
IEC 61010 should be the basis for electrical instrument design if user safety is a concern. It leads to three main areas of the design process:
- Electrical design elements
- Materials
- Mechanical design elements
There are related standards and tools that further address each of these areas to ensure maximum user safety.
The standard does not exist in a vacuum. Simply designing to the standard without understanding the application and test environment is not enough. If you are a test instrument user, make sure you understand the standard and use it to ask the right questions.
