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Electrical Specifier Link
Issue V
Dielectric Fluids For Transformer Cooling Dielectric Fluids For Transformer Cooling
History and Types

Gain insight into the role of dielectric fluids, the appropriate selection of them and their application in transformer cooling. This article will also provide an historical perspective and overview of the various types of fluids available by manufacturers of liquid filled transformers.

Aluminum vs. Copper in Electrical Equipment

The debate on the use of aluminum conductors in electrical equipment has gone on for many years. While there is much information on the subject, there is also a lot of miss-information. . Many changes in the use of aluminum as a conductor in electrical equipment have taken place over the last 30 years. However, many of the current beliefs and practices are still based on characteristics of aluminum conductors and their application from past years. Improvements in aluminum alloys offer performances equal to copper.

There are many factors that must be considered when comparing aluminum versus copper conductors as used in electrical equipment. The standard copper conductor has a conductivity of 98% while the aluminum conductor commonly used has 56% conductivity. Even though a greater physical volume of the aluminum must be used to carry the same electrical current as copper, the weight of the aluminum conductors will be less than the equivalent copper conductors. Another fact is that with the current commodity prices, equipment built with aluminum conductors will be less expensive than the equivalent equipment assembled with copper conductors.

Electrical equipment manufacturers must design and build the equipment to meet the applicable standards from UL, NEMA, and ANSI/IEEE. These standards dictate specific temperature rises over set ambients that the equipment must meet. Current standards for transformers also dictate the minimum efficiencies for all general purpose transformers. The requirements of these standards dictate performance and not conductor materials. Therefore the equipment manufacturer must take into account the different characteristics of aluminum or copper conductors when designing the apparatus so that the performance is the same regardless of conductor material.

One of the myths about aluminum conductors in electrical equipment is that aluminum conductor equipment is always larger than copper equipped assemblies. But with most equipment types that are available with aluminum conductors, the physical size is identical to that of the same equipment equipped with copper conductors. Another myth is that aluminum bus connections require special hardware and increased maintenance, but modern plated alloyed aluminum bus is very similar to copper bus. Where previous aluminum cable used compression connectors, modern 8000 series alloy conductors in plated mechanical lugs give excellent reliability.

These issues along with plating and environmental applications are discussed in depth in the white paper on this subject, which is attached. This paper explains the difference between the conductor materials and demonstrates that aluminum equipped equipment will perform the same as copper equipped equipment when designed to the applicable industry standards.

Zig-Zag Transformers

When considering updating a 480-volt ungrounded transformer system, a Wye grounded system could provide an advantage with its ground fault protection.

Grounding transformers are a cost-effective way to obtain a system neutral and come in three commonly used types: Zig-Zag; the Wye-Delta; and the Scott-T style.

Read this article to learn more specifically about the Zig-Zag transformer.

Design For Safety

Part 1 of our ongoing series focuses on safety tips and suggestions for electrical engineers designing electrical distribution systems. The article outlines the numerous items that can be specified and designs that can be implemented to address increasing worker safety concerns.

Arc Flash & Low Voltage
Over-Current Protective Devices (OCPDs)

Read this overview of the importance of conducting Arc Flash studies and how to interpret the results. You'll also learn about the different types of over-current protective devices and their role in mitigating the Arc Flash Hazard or reducing the Hazard Risk Category (HRC)

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