Grades of busway protection
Now and then, there may be a case where a project requires part or all of the busway line to pass through the street, in corrosive environments or where there are increased requirements for fire protection. In this case, both the user and the engineering organization must be very careful in selecting the type of bus ducts.
PitON's technical department provides detailed explanations to its contractors on the subject of protection of busway against penetration of dust, water and dirt.
PitON busways are interacting with different types of moisture and it is necessary to understand where the equipment can be immersed and where it is not allowed. At the same time, the boundaries of what is allowed must be clearly marked.
We would recommend two basic criteria to guide you:
- DEGREE OF PROTECTION (IP**)
And here to help with definitions comes the standard - GOST 14254-2015. A little clarity for a more complete understanding. This standard was prepared by the Technical Committee for Standardization TC 341 "External influences". IEC 60529:2013 "Degrees of protection by enclosures (IP code)" was taken as the basis, in fact, an authentic translation of this standard was made. GOST 14254-2015 was adopted by the Interstate Council for Standardization, Metrology and Certification (protocol of December 10, 2015 № 48-2015), and is used in Belarus, Kyrgyzstan, Russia and Tajikistan. By Order of the Federal Agency for Technical Regulation and Metrology No. 604-st of June 10, 2016, the interstate standard GOST 14254-2015 (IEC 60529:2013) was put into effect as a national standard of the Russian Federation from March 1, 2017.
So, the degree of protection describes products for information technology, electrical and instrumentation with a voltage not exceeding 72.5 kV. In other words: the degree of protection of equipment that requires an electric current, to some extent, can be explained using GOST 14254-2015 (hereinafter "GOST").
The degree of protection of the enclosure is encoded in the code of the form IP X1 X2 X3 X4, where IP are the letters of the code (International Protection), they are always fixed.
X1 is the first digit of the characteristic designating the degree of protection of the enclosure against dust penetration. A scale from 0 to 6 is used where 0 is totally unprotected and 6 is dustproof.
X2 is the second digit of the characteristic that denotes the degree of protection of the enclosure against penetration of water. Here a scale from 0 to 9 is used, where 0 is totally unprotected and 9 is protected against hot jets of water under high pressure.
and X4 are auxiliary letters describing additional conditions that are not disclosed in the numerical characteristics, and there may be no letters in the cipher. In this article, we will not consider the letters because of their specific and infrequent use.
For example, the basic degree of protection of PitON E3-Series busbar trunking system is IP55. Protection class IP55 means that the outer protection enclosure (busbar trunking enclosure) is not fully protected (the first number is 5) but the dust that gets inside does not influence the the system at all and the water (the second number 5) should not have any harmful effect. Overall, operation of E3 is ensured without any issues.
Anyway, you can specify all the values by referring to GOST, but we go on and focus on the degrees of protection IP68, IP69, IP69K.
First of all, GOST 14254-96, the predecessor of GOST 14254-2015, did not presuppose water protection degree IPX9 ("X" - symbol of the first digit), the maximum degree was IPX8 - that is protection from long-term immersion under water. IPX9 is protection against hot jets of water under high pressure. In other words, as time passed, technology changed, and with it the needs, so did the need to reflect the new degree of protection - IPX9.
Secondly, the protection degree IP69K — it's the same as IP69, only IP69K degree of protection by European standard IEC 60529:2013, it's GOST 14254-2015 in Russian version, and IP69K degree of protection by German standard DIN 40050-9, that's the difference.
For electrical equipment with a rated voltage not exceeding 72.5 kV, we have the two highest degrees of protection: IP68 and IP69. Let's examine them in detail. Both protection classes indicate that no dust particles can get into the equipment interior. Those who want to know about the enclosure protection testing can look into GOST 14254-2015 in more detail. But there is a difference in water resistance: IP68 — protection against immersion in water for a long time, IP69 (aka IP69K) — protection against hot streams of water under high pressure.
In practice, IP68 applies to equipment that is submersed in deep water (such as probes for well surveys), IP69 applies to equipment that is used for intensive cleaning with hot jets of water, like in the transport, chemical or food industries.
To make it even clearer, here is a comparison of the degree of protection of the E3 (IP67) and CR1 (IP68) busbar trunking systems. The conditions in which the equipment has to be used require a minimum protection degree of IP67 (protection against water entering the casing if immersed to a depth of 1 meter and lasting not more than 30 minutes). And CR1-series has a basic degree of protection IP68 with a maximum immersion depth of 10 meters and no time limit — a reserve guaranteed by the manufacturer. IP69 in this case is unnecessary and excessive degree of protection.
The manufacturer, who claims IP69, as well as IP69K degrees of protection, should specify the characteristics of the water flow, namely water temperature, capacity in liters per minute, as well as exposure time. Otherwise, it's just a marketing ploy with no basis whatsoever, and at best the IP68 rating is implied, or even less.
- THE ACCEPTABLE ENVIRONMENTAL TEMPERATURE
Most of the busbar trunking systems available on the market have technical specifications stipulating normal (failure-free) operation only in the range of -5 to +40 degrees Celsius ambient temperature. This is more than enough for indoor applications but not enough for outdoor applications where the temperature can vary from -40 to +50 degrees C.
Some manufacturers offer solutions for increasing the degree of protection of bus ducts of indoor usage from IP54 to IP66 by means of additional sealing of all joints. But even after all the steps to increase the degree of protection, the busbar trunking can only be used for indoor installation.
WHY?
1) Because the insulation of busbars is not designed not only for such temperature differences, but also for the condition of the humidity of the external environment.
2) Because there is a danger of condensation of water on the insulation and busbars, a particular risk has a product with jointed polyester insulation.
These are already serious enough reasons to abandon the use of the "indoor" busways for "outdoor" solutions. Also in case of any technical problems — it will be a non-warranty case.
We see only one technically adequate solution — the use of a SPECIAL outdoor conductor series CR1 (IP68).
WHAT IS SO SPECIAL ABOUT IT?
1) In the manufacture of an outdoor busbar trunking, the current-carrying busbars and joints (during installation) are covered with a special compound, which serves both as a protective enclosure and as an insulator for the busbars. There is absolutely no possibility of water and dust penetration inside the busduct (IP68).
2) Considering the outdoor conditions in which this system has to work, PitON guarantees failure-free operation in ambient temperatures ranging from -60 to +60 degrees C.