Current transformer cabinets and terminal boxes (also known as junction box) are integral to many electrical distribution systems for their ability to provide an isolated enclosure, whether for metering purposes (CT cabinet) or acting as protection to important connections (junction box) in a wired loop.
Like terminal enclosures, current transformer cabinets also act as a physical barrier against electric shocks, too, by essentially separating an operator from the live parts of an electrical system. In addition, it also serves as a kind of shield as well against environmental elements which results to either significant damage or deterioration of the system hardware.
Current Transformer (CT) Cabinets and Terminal Enclosures
Governing Bodies for Safety Standards
For something that play essential role in upholding the security of the operator and good maintenance of an ongoing electrical distribution system, the best current transformer cabinets—at least, in the United States—are designed based on the established standards of two overseeing bodies:
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Underwriters Laboratories (UL)
A global certification and safety consulting company, based in Northbrook, Illinois.
•
National Electrical Manufacturers Association (NEMA)
The biggest conglomeration of electrical equipment manufacturers, which is based in Rosslyn, Virginia.
In the United States, therefore, each electrical equipment manufacturer must at least live up to the standard set by any of the two aforementioned governing bodies. In particular, current transformer cabinets must meet either Underwriters Laboratories Type 1 standard or National Electrical Manufacturers Association Type 3R.
Alternatively, terminal boxes are mostly designed to follow National Electrical Manufacturers Association’s four different standards— Type 1 , Type 3R , Type 4X , and Type 12 .
Conversely, failing to meet any of these adhered standards by the two agencies would render a current transformer cabinet and junction boxes subpar to the ideal hardware build.
UL Type 1 and NEMA Type 3R, what are the differences?
The Underwriters Laboratories Type 1 standard is primarily concerned to a design which offsets the chances of a person getting in contact with a live electrical component. Mainly intended as a standard for building current transformer cabinets that are used indoors, the UL Type 1 does not concern weather-sealing which therefore could allow the entry of environmental elements if used outdoors.
The National Electrical Manufacturers Association Type 3R , on the other hand, is focused about setting a standard for CT enclosure products that can withstand the outdoor setting while at the same time considering the demands of the indoor setup.
As such, the NEMA Type 3R highlights protection from environmental elements such as water exposure due to the ingress of snow as well as light rain. In addition, the standard also emphasizes on setting a safeguard against windblown dust, but is diminished due to the design’s inherent need for ventilation. The needed passage of air in a NEMA Type 3R-adherent design is facilitated by having louvers, either in the door or on the sides of the cabinet.
The Different Kinds of Current Transformer Cabinet and Terminal Boxes
Not all current transformer cabinets and junction boxes are the same. As the adoption of both these parts has widened throughout the years, so are the need to modify their designs in order to suit varying conditions of any given setup.
For instance, as a whole, there are three types of current transformer cabinets which ranges between:
• Freestanding
• Pad-mounted
• Wall-mounted
But do not mistake the difference in how these enclosures are employed in an actual physical setup, all of these hardware functions the same.
Then, there are also other variations to the same enclosure based on a few smaller details such as:
• Hinged screw cover
• Hinged double door
• Screw cover current transformer cabinet
• Vented double-door
• Liftoff cover enclosure
Do note, however, that while certain CT enclosures are classified similarly, there may still be some nuances which makes one substantially differently-looking from its sibling. Usually the case, size is the most ostensive differentiating factor e.g. a freestanding CT cabinet with vented double-door may be bigger or smaller than another enclosure of the exact same type.
On the other hand, a terminal box can be classified primarily into one of two:
• Screw cover
• Hinged cover
What are Current Transformer Cabinets and Terminal Boxes Made Of?
Many current transformer cabinets are of metallic composition. This ranges between a carbon steel, stainless steel, or galvanized iron with thickness of either 14, 16, or 18 gauge. The purpose of this metallic envelopment is to make an isolated space without electrical potential which would otherwise be harmful to a person to get in contact with.
But more than just keeping the enclosure grounded, the cabinet is also pivotal in keeping the insides free from unwanted exposure to environmental elements such as water and dirt. Commonly, this is thanks to the cabinet’s seamless cover on the sides and drip-shield topping.
Alternatively, some manufacturers develop a current transformer cabinet with channels from the inside which allows the installation of the transformer in either horizontal or vertical position.
Junction boxes, on the other hand, are little simpler as they are either made with just either plastic or metal.
Where to get Current Transformer Cabinets and Terminal Boxes?
Buying some current transformer cabinets or junction boxes have become relatively simpler nowadays, thanks to e-commerce which facilitates online purchases. Apart from the benefit of getting the items purchased delivered to your door, another major perk of looking for any of these important hardware on the internet is the ability to see actual images of the product remotely.
That is not to say that seeing the products in actual before buying is not an advantage in itself—it is, still. However, for those who are already have much experience dealing in these kinds of hardware, the convenience of doing so without having to visit the seller is oftentimes preferred.
However, it is also worth reiterating that not all current transformer cabinets and junction boxes are made the same. For peace of mind, always know the quality of the products you are buying, particularly if its meets either Underwriters Laboratories or National Electrical Manufacturers Association’s standards.