To explain VLF tan delta, we must first explain the reason it was developed and how the concept and equipment used to perform this test came about. Tan delta is still a form of high-potential (hipot) testing but utilizes the advantages of both AC and DC testing while eliminating many, but not all, of the disadvantages. The very-low-frequency (VLF) portion …
While the chemistry behind dissolved gas analysis (DGA) is complex and important for industry chemists to understand, the typical DGA review need not be as complex. Thermal or hot metal gasses are commonly known in DGA, and they are widely understood by industry experts, chemists, and many asset owners. The carbon oxide gasses — carbon dioxide and carbon monoxide — …
Bushings are the means by which electric power passes to and from different electrical devices, as they provide a point of interface for electrical voltage to be applied and current to pass to and from an electrical apparatus. The bushing’s center conductor is above ground potential and must be electrically insulated from the tank walls, which are at ground potential. …
Due to the complex temperature-driven dynamics of the exchange of water between the paper insulation and the oil and the lack of thermal equilibrium in most operating transformers, it is difficult to interpret the water content of oil or paper insulation by looking at individual dissolved-water measurements or time-series data. Furthermore, increases in water solubility due to aging of oil …
Line differential protection is one of the most popular applications used for transmission line protection. Line differential protection works on the theory of Kirchhoff’s current law, where the magnitude of the current flowing into the line should be equal to the current flowing out of the line. For line differential protection, the zone of protection is defined by the location …
All networks are susceptible to problems that affect communications. One consequence of a fiber optic system’s high bandwidth, long distance capability, and security is the extreme dependence of users on the non-stop operation of these systems. Because they can transmit large amounts of data long distances with immunity from signal degradation and extremely high reliability, these systems usually carry the …
The high level of penetration of distributed energy resources (DERs) is one of the main characteristics of the smart grid, and it requires a different approach to the protection of the grid. IEC 61850 is widely accepted around the world due to the significant benefits it provides compared with conventional hardwired solutions. However, many specialists in the industry still hesitate …
Dissolved-gas analysis started out many years ago as a quick and simple test: Someone in the substation would briefly open a valve and sniff the transformer’s head-space gas. The pungent odor of a trace of acetylene would signify a potentially serious problem. By the late 1960s, it was possible to use a gas chromatograph as a much more sensitive nose …
Partial discharge (PD) testing is becoming common in U.S. industrial systems and is gaining acceptability in U.S. utilities. Testing in the form of periodic surveys can provide valuable insight into asset condition. Beyond periodic surveys, full-time system monitoring is the state of the art in PD detection, offering additional capabilities that: Warn of rapidly evolving PD situations that might go …
Part 1 of this article, which was the cover story in the previous issue of NETA World, explored the need for high-voltage arc flash (HVAF) assessment to protect utility workers who are exposed to voltages above 15kV. It also compared various methods to calculate the incident energy from HV and MV electric arcs. Analyzing the results demonstrated that several methods …