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ACCELERATING TOWARDS GREATER TESTING EFFICIENCY – A true transformer test van

Test lead management, including quality of connection and correct lead placement, is an important part of testing. Poor or incorrect connections can be the culprit for nonrepresentative results that ultimately lead to longer test times and, in some cases, wasteful investigations to diagnose transformer problems that do not exist.

The time required to perform electrical testing is mostly influenced by the time involved during test set-up and breakdown. Therefore improving test efficiency largely becomes a matter of improving lead management. Solutions are emerging that address the challenges in managing test leads and in general, advance testing efficiency.

One solution, that is perhaps least understood, is a transformer test van. The term “transformer test van” has been applied broadly to describe any van that carries transformer test equipment. From there, the variances are wide. A true test van, however, is an instrument on four wheels.

 

ELECTRICAL TESTING

A number of electrical tests may be performed on a transformer to gain information about each of the facets of its health (dielectric, mechanical, thermal, and magnetic). No single test facilitates
a comprehensive assessment of a transformer’s condition. The reason for testing a transformer and the nature of concern about a transformer’s state of health, if any, will determine which tests make sense to perform.

There are many tests in common field use, including transformer turns ratio, winding resistance, power factor and capacitance, dielectric response methods like DFR, insulation resistance, exciting current, SFRA, leakage reactance and frequency response of stray losses (FRSL). Each has a different strength – some are recommended screening methods, while others are only called upon when a problem is suspected.

 

Generally, there are three stages of testing:
Stage 1: Planning: planning/scheduling tests
Stage 2: Executing: isolating the transformer, preparing the transformer for test and performing the test(s)
Stage 3: Review and Asset Management: assessing the results, decision making and data management

Stage 2 is arguably the most time consuming part of testing. It is also one of the areas where advancements in test instruments, leads and systems is increasing efficiency and safety.

Quite a bit of time is wasted during testing set-up and breakdown. Therefore improving test efficiency largely becomes a matter ofminimizing the time required to move between tests and improving lead management.

Test lead management includes the knowhow of where to connect leads, making good test connections and the number of “touches” with test leads required to complete a test(s). It is noted that poor test lead management can influence Stage 3 of testing by increasing time required to figure out results that are typically affected by incorrect or poor connections.

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PROPER CONNECTIONS: ENSURING EFFICIENCY WITH ACCURATE TRANSFORMER AND PHASE CONNECTIVITY

TRANSFORMER CONNECTIVITY 


Electric meters are connected to secondary distribution transformers to reduce distribution high voltage to safe levels for households. There are many transformers of different capacities along distribution lines, both underground and overhead. The choice of which transformer a meter is connected to is dictated by physical proximity as well as by optimal loading of transformer capacity. This connection between an individual meter and a distribution transformer is known as transformer connectivity. 

Transformers may fail without warning because of overloading due to incorrect connectivity data on record, thus leaving all connected customers without power. Meanwhile, other transformers may be left inadvertently oversized with fewer meters than the original design specified. This causes unnecessary waste of equipment capacity and power. Theft detection strategies, based on comparing voltages of all meters connected to the same transformer, fail because knowledge of connectivity is faulty. Similarly, detecting high impedance connections – a threat to customer safety – is impaired by the lack of reliable data on connectivity.


Finally, outage detection and reporting systems rely on accurate knowledge of transformer and phase connectivity. In today’s communication networks, only a subset of the Power-Off-otifications (PONs) sent by all smart meters affected by an outage are “heard” by the head end. To accurately and quickly determine the true extent and identification of all customers affected by an outage requires precise connectivity information for each and every transformer. 

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ANALYZING THE VEGETATION PROBLEM: Getting the Most Out of Collected Data Through Advanced Analytics

As a utility, vegetation management is of the utmost importance – for ensuring transmission and distribution reliability and complying with complex North American Electric Reliability Corporation (NERC) regulations for minimum vegetation clearance distance and facility ratings. Utilities now rely on advanced remote sensing technologies to survey transmission infrastructure, then use the data collected to show compliance.

 

While utilities may rely on basic analytical tools to deliver the required NERC compliance data, they may not take full advantage of the valuable data being collected. In this article, we’ll explain
how utilities can go beyond basic descriptive analytics, using both prescriptive and predictive analytics to transform massive data sets into real-time, actionable information critical to ensuring reliability across the electric grid. And, we’ll share examples of how utilities are leveraging advanced analytics to drive greater efficiency and cost savings across their organization.

 

GOING BEYOND DATA COLLECTION

Utility vegetation management practitioners rely on a wealth of information to both optimize and streamline decision making related to budgetary needs, schedule prioritization and risk management. In our previous article, “Advanced Survey Technologies Deliver Clear View of Geologic Hazards” (ET issue Third Quarter 2016 Volume 29, No.3), we described the various technologies – such as multispectral, hyperspectral and thermal imaging as well as LiDAR – used for remote data sensing and shared how they are leveraged in applications to assess tree health, forest inventory, soil composition analysis and asset inventory.

 

Raw data collected using these technologies is prohibitively large regardless of the source. A single LiDAR collection covering a 35- mile transmission circuit can result in files exceeding 100 gigabytes. Add in corresponding imagery and the data size easily doubles or triples. This data alone – or combined with other sources – often leads to a perceived “data overload,” leaving utilities overwhelmed and unsure how the information can be used in the most effective manner. Remotely sensed data is a powerful information source that requires specialized skills and techniques to exploit its inherent advantages. Ultimately, utilities will employ advanced analytics solutions to leverage any quantity or type of remote sensing data – as well as data that comes from other sources – to extract the specific business intelligence they require.

Read the full article in our digital magazine

Fighting Heat Stress With Effective Workwear

In a perfect world, we could all work in weather-controlled environments where heat wouldn’t be a factor and comfort could be maximized. Many workplaces however, deal with very high temperatures and heat stress is a year-round risk that requires serious consideration. For many years the standards addressing the prevention of heat stress-related issues went untouched. Recently the National Institute of Occupational Safety and Health (NIOSH) released an evaluation of the available data on this subject (criteria for a recommended standard), with the goal of setting a new standard. The report; Occupational Exposure to Heat and Hot Environments, contains detailed information to aid employers, managers and workers in managing the occurrence of heat stress.

Read the full article in our digital magazine

The Role of Cable Rejuvenation in Addressing the Maintenance of Aging Underground Cables

Aging underground residential distribution (URD) cables is a growing problem in communities around the world, disrupting customers and causing business challenges for utility providers. But in most cases, the traditional remedy for URD cable failure—taking the impacted cable out of service and putting new cable in its place—has proven to be unfeasible. When cables fail, the resulting outages and the replacement work required to restore power create logistical problems that are usually unpredictable and expensive—costs that must be absorbed by the provider, the customer, or both. Meanwhile, customers often experience multiple outages as the providers install new cable, often disrupting the customers’ property and landscaping in the process.

 

CABLE REJUVENATION: THE MODERN GO-TO OPTION FOR UPGRADING URD CABLE

When rehabilitating aging URD infrastructure, many utility providers forgo cable replacement and opt for rejuvenation as the proven superior method for fixing damaged cable. With cable rejuvenation, the affected cables are left undisturbed and injected with compounds that restore each cable’s dielectric strength, effectively adding the same value as a new cable but without the burden of time, cost, environmental disruption, and consumer downtime associated with cable replacement. This method was first developed in 1986 and its use has steadily gained adoption and popularity in the 30 years since.

 

Rejuvenation technology focuses on the injection of silane-based fluid into the strands of aging medium-voltage power cables. The fluid is injected by accessing cables through transformers or other cable termination points. Technicians typically open two adjacent transformers and de-energize cables in a way that generally does not impact power to customers. Then, specialty fittings are attached to each end of the cable to allow for fluid injection. As the fluid moves through the cable, it migrates into the conductor shield and insulation. The chemistry and the physics of the insulation are modified and the result is a cable that is returned to full dielectric strength in as little as seven days.

The use of cable injection is approved for capitalization by the Federal Energy Regulatory Commission and hence does not impact tight operation and management budgets.

Read the full article in our digital magazine

ET Partner Media




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