The Ingress Protection (IP) rating: Why it matters

Working in electrical environments is dangerous. To help mitigate those dangers, safety equipment such as clothing, gloves, boots, etc. is used to help protect electrical workers from potential accidents. A less obvious safety precaution is the design of the test equipment that is 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, as well as for instruments. One key aspect of this standard is protection from fluids and solid objects. Foreign deposits on insulation parts can lead to a hazard, and accumulations of foreign objects can potentially cause the spread of fire.

Most portable electrical test instruments are used outside of clean room environments and, as such, the environmental conditions where testing occurs are often challenging. Moisture, dust, and temperature extremes plague testing. This paper examines the Pollution Degree and the Ingress Protection (IP) ratings and why they are critical to instrument design and user selection.

Pollution Degree

As previously noted, IEC 61010 specifies protection against both fluids and solid objects. Water is the most common fluid and dust the most common solid object, although other items such as wires, fingers, tools, etc. are also considered. IEC classifies these external elements as “pollution” and has established a rating system to qualify the level of pollution in the environment where testing will occur.

The IEC 60947-1 standard describes the level of pollution or contamination that can be expected in an environment. Pollution Degree is defined as the degree of contamination by dust, conductive particles or other substances that can accumulate in the test environment and affect performance or safety. In addition to dust and other contaminants, humidity and temperature impact the number; the higher the number, the greater the level of conductive pollution.

For those wanting a more complex description of Pollution Degree, the following is extracted from the standard:

“Amount of conductive or hygroscopic dust, ionised gas or salt and on the relative humidity and its frequency of occurrence, resulting in hygroscopic absorption or condensation of moisture leading to reduction in dielectric strength and/or surface resistivity."

Pollution Degree impacts creepage and clearance distances. Safety standards bodies, such as Underwriters Laboratories and IEC, categorise the degree levels as follows:

Pollution Degree 1: No pollution or only dry, nonconductive pollution occurs. The pollution has no effect. A clean room environment.

Pollution Degree 2: Normally only nonconductive pollution occurs. Temporary conductivity caused by condensation is to be expected. Laboratory or office environment.

Pollution Degree 3: Conductive pollution or dry nonconductive pollution that becomes conductive due to condensation occurs. Harsh industrial environments.

Pollution Degree 4: The pollution generates persistent conductivity caused by conductive dust, rain, or snow. Outdoor environments with excessive humidity and/or dust.

The environment where testing will take place has a significant impact on safe instrument design. This leads us to the IP rating.

Ingress Protection (IP) rating

Electrical problems tend to occur when weather is bad. Testing in the rain with splashing water is not an uncommon occurrence. Testing is also done in dirty, dusty environments. Instruments are often stored in equally poor environments and sometimes get left outside, exposed to all types of weather.

The IP rating shows the effectiveness of electrical enclosures in blocking foreign matter (dust, moisture, liquids). It tells you if the instrument is safe for the environment where it will be used. The IP rating system has been established by the IEC in their Standard 529. It is comprised of two digits, each signifying a separate characteristic. The first number indicates the protection from hazardous parts (like wires or tools) and solid foreign objects (like dust). The second number indicates the protection from moisture. The higher the number(s), the better the degree of protection.

The following tables show the level of protection based on the IP rating:

       
Protection against access to hazardous parts (first digit)

Protection against ingress of solid foreign objects (first digit)

         
Protection against ingress of liquids (second digit)

   
As an example, let’s look at a rating of IP54. Remember that each digit relates to a separate rating. A level of “5” indicates “dust protected” as well as protected from invasion with a wire down to 1.0 mm. There is only one higher category: “dust tight.” The second digit refers to moisture. A rating of “4” means resistance to “splashing water, any direction.”

Alternatively, an instrument with a rating of IP40 may have adequate dust protection, but it has no protection against water and should not be used outside or in damp indoor environments. Some instruments have multiple ratings, one with the lid open and a higher rating with the lid closed (for storage). It is good practice to confirm both the “lid open” and “lid closed” ratings.

Instrument manufacturers should publish the IP ratings for their instruments. Compare the rating to the environment where testing will take place.

Conclusion

Electrical test instruments tend to be used in challenging environments. Understanding the nature of the environment and the Pollution Degree is critical to selecting an instrument that will survive the environment and keep you safe. Imagine working in a quarry or cement plant. Conductive dust is in the air everywhere. What about a pulp and paper plant where the moisture level is high? The same goes for different parts of the world that may have high humidity or other weather-related conditions.

The IP rating is your guide to test environment compatibility. Know your environment and then determine the minimum IP rating required to protect the instrument and yourself. An instrument that exceeds the minimum is a plus. Avoid any instrument that has an IP rating below your minimum.