Electricity Today is a leading electrical transmission and distribution magazine distributed subscribe free of charge to North American T&D electric utility engineering, construction and maintenance personnel, and high voltage T&D consulting engineers.
In the Latest Issue
How utilities can yield significant operational benefits
BY JEFF WALZ, Siemens Smart Grid
As North American electric utilities continue to transform their existing electric delivery assets into a smarter grid, strong emphasis is placed on systems, products, and services that provide value in automating and managing the electric distribution network. Within this context, utilities are focusing on four main themes in distribution: reliability, efficiency, safety, and interoperability.
These themes relate directly to the operational objectives of distribution utilities but achieving these goals is becoming increasingly challenging. North America’s electricity grid infrastructure is aging, with many assets near or beyond their expected lifespans. Customer expectations with respect to reliability and power quality continue to grow, not only for commercial and industrial but for residential consumers as well. Moreover, the avail- ability and penetration of distributed energy resources, including renewable generation, is on the rise.
Detecting and avoiding preventable failures
BY JAY GARNETT, Doble Engineering Company
While metal clad switchgear can be very reliable, sometimes operating for over 50 years, throughout the aging process, this group of electrical disconnect switches, fuses and circuit breakers can experience issues such as moisture ingress, animal intrusion, enclosure rusting, and insulation deterioration. One efficient approach to detect incipient failures is partial discharge (PD), a leading indicator of various failure modes. Using both acoustic and electrical partial discharge techniques, sources of partial discharge can be detected and pinpointed to a source, such as a particular metal clad compartment.
PARTIAL DISCHARGE TECHNIQUES
• Acoustic methods use acoustic emission signals to detect sources of
sound within the switchgear
• Transient earth voltage (TEV) approaches look at signals developed in
grounded metalclad surfaces
• High-frequency current transformers (HFCTs) can be used to
determine local sources of partial discharge for investigation
Optimizing conservation benefits through AMI
BY MELODY TOMKOW, Aztech Associates
The conservation benefits of ‘real-time’ electricity consumption information provided by home energy monitors, also known as in-home displays, have been studied repeatedly over the past decade. Recent studies such as the NV Energy’s “2011 Annual Demand Side Management Update Report” report a household electricity consumption reduction of 3.5 percent to nine percent.
Additionally, a well-known survey of existing U.S., Canadian and Japanese studies entitled, “The Impact of Informational Feedback on Energy Consumption — A Survey of the Experimental Evidence”, published by the Brattle Group, shows an electricity usage reduction of seven percent.
However, electric utilities are still challenged to draw applicable meaning from this plethora of information. While the studies clearly demonstrate conservation benefits, the variables across studies—from the range of methodologies to the analytical models used, and the constant evolution of the Smart Grid make it nearly impossible to develop a robust synthesis of results. Importantly, there has been no review that adequately delineates the divergent conservation benefit of advanced metering infrastructure (AMI), connected in-home displays (IHDs) and non-AMI connected IHDs.
Field data management: The value and challenge of asset health insight
BY PAUL BARNETT, JOHN STEWART, Tennessee Valley Authority & PAT BROWN, Electric Power Research Institute
Intelligent management and operation of assets is of major importance to electric utilities. In an era where assets are being kept in service beyond their originally anticipated life spans, where replacement dollars are tight and where reliability expectations are increasing, insight into the health of utility assets is critical to intelligent decision-making.
ASSET HEALTH INSIGHT
Tennessee Valley Authority (TVA), similar to many transmission utilities across North America, is focusing on improving its understanding of the condition of its assets to allow it to make better repair, replace, and monitor determinations, to prioritize maintenance activities more effectively, to operate its transmission system more intelligently, and to reduce its operating costs over the long run.
Similar to other utilities, TVA’s ability to evaluate the condition of its assets accurately and continuously is hampered by the difficulty of assembling the data pertinent to determining asset health.
Enhancing protection using directional faulted circuit indicators
BY CHRISTOPHER EVANICH, Thomas & Betts
Underground electrical networks provide reliable service to end users, but create problems for utility personnel in locating faults. Electric utilities who utilize an underground network could spend several weeks trying to locate a fault or potentially not even be able to locate it until a second fault occurs.
A directional faulted circuit indicator (DFCI) is a beneficial piece of equipment in an underground network for assisting line crews in locating faults. A conventional faulted circuit indicator (FCI) is not as useful since the device does not have any directional element. The purpose of a DFCI is to detect faults on the underground network in only a specific direction. Since a fault can occur on any part of the network, directional capabilities are especially important on underground networks.
Sweep frequency response analysis: Reliable demagnetization of transformer cores
BY MARKUS PÜTTER, MICHAEL RÄDLER, BORIS UNTERER, OMICRON electronics GmbH
Whenever a power or distribution transformer is isolated from the power system, it is very probable that residual magnetism remains in the core due to the phase shift. However, residual magnetism also occurs when performing winding resistance tests.
Since manufacturers use these measurements in their routine testing and these tests are typically performed for on-site condition assessment, transformers can be regularly influenced by the effect of residual magnetism.
Residual magnetism leads to high inrush currents which put a great and unnecessary load on the transformer. Additionally, a large number of diagnostic measurements are affected by residual magnetism. As a result, a utility can have difficulties obtaining a reliable condition assessment of its transformers.
Therefore, utilities should demagnetize the transformer before re-energizing it or performing diagnostic measurements. Within the last few years, the first testing devices have been launched which allow practical demagnetization of transformers on-site.
The 2014 Transformer Report highlights the importance and the effect of residual magnetism and increases awareness of the associated risks with re-energizing transformers after an outage.
Removing hazards caused from in-vehicle computing
BY SCOTT BALL, Motion Computing
No utility company would send a worker out in a truck with a known safety defect. North American electric utilities may not realize, however, that by failing to ensure that computing devices are used safely within their vehicles, management could be putting their employees and the public at risk. Even worse, if an accident was to occur, the utility could be held liable.
Access to mobile computing is now the rule rather than the exception. The latest generation of mobile-friendly applications has made computing devices essential for connecting workers with peers, receiving and fulfilling work orders, reporting problems, and managing inventory. As electric utilities adjust their workflows to take advantage of the power of mobile computing systems, a dangerous side effect exists—a growing likelihood that workers will use their device while driving the utility vehicle.