‘Best practices,’ according to who?

Posted by Bruce Brandt on February 14, 2014 @ 10:54 am

While many best practices are based off of decades of experience there are many who don’t follow them for their own reasons.

In my role here at Maverick I’m often asked about best practices, and I’m expected to drive the use of them by our employees. The problem with that is the assumption that best practices are universally accepted as being truly the best, yet I’ve repeatedly run into situations where the best practice I offer up is met with either skepticism or the old “we tried that and it didn’t work here.” The former is easier to address since I can usually offer the names of contacts where it proved itself out. The latter is much harder to overcome. I spent quite a few years working in the utility power industry, which was very much a mature technology when I started. There were many best practices that had come about through decades of experiences, yet ... Continue Reading

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Understanding time current curves: Part 3

Posted by MAVERICK Leadership Team on February 13, 2014 @ 2:53 pm

The final installment of a three-part series about time current curves (TCCs) reviews the coordination of sample curves and the importance of coordination.

Continued from Part 2… Now that the basics of TCCs have been explained, a review of coordination is in order. Our sample curves to coordinate will consist of an MCC with main 800-A fuses, a 1,200-A feeder circuit breaker and the switchgear 3,200-A main circuit breaker. In the uncoordinated system there is overlap of the circuit breaker trip curves, and in some instances the main circuit breaker will trip before the feeder circuit breaker. The main fuse in the MCC is also uncoordinated. While the fuse is not required, it is included in this example because it is typical of an industrial installation. The purpose of the f... Continue Reading

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Understanding time current curves: Part 2

Posted by MAVERICK Leadership Team on January 30, 2014 @ 9:17 am

The second installment of a three-part series about time current curves (TCCs) covers short and long time settings, including their purpose and examples of such overcurrents.

Continued from Part 1 The light blue curve represents the circuit breaker settings for the feeder circuit breaker. The lower portion of the curve (below 0.05 sec or three cycles on the time axis) is the instantaneous trip function. The purpose of the instantaneous trip is to trip the circuit breaker quickly with no intentional delay (no more than a few cycles) on high magnitude fault currents. This quick trip protects electrical distribution equipment from damage and keeps arc flash hazard categories low. Clearly these type faults must be interrupted quickly and do not al... Continue Reading

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Understanding time current curves: Part 1

Posted by MAVERICK Leadership Team on January 28, 2014 @ 2:36 pm

The first installment of a three-part series about time current curves (TCCs) provides a quick overview of item identification and how to read TCC plots.

A time current curve (TCC) plots the interrupting time of an overcurrent device based on a given current level. These curves are provided by the manufacturers of electrical overcurrent interrupting devices, such as fuses and circuit breakers. These curves are part of the product acceptance testing required by Underwriters Laboratories (UL) and other rating agencies. The shape of the curves is dictated by both the physical construction of the device as well as the settings selected in the case of adjustable circuit breakers. The time current curves of a device are important for engineers to understand because they graphically show the response of the device to various levels overcurrent. The curves allow the power systems engin... Continue Reading

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Configuring control systems through wireless devices, remote I/O: With great power comes great responsibility

Posted by Bruce Brandt on January 23, 2014 @ 4:18 pm

In the new world of wireless devices and remote I/O we have the power to create control configurations that use I/O and that are not physically connected to the controller running the control loops.

In the new world of wireless devices and remote I/O we have the power to create control configurations that use I/O and that are not physically connected to the controller running the control loops. In the case of at least one distributed control system (DCS), the I/O attached to its gateway can be assigned to different controllers on a per I/O point basis. Within the confines of the configuration application there are pointers to where these live, but in the context of project documentation the world becomes a bit blurry. Wireless I/O is another story all together. Even if the technician trying to troubleshoot the loop knows which wireless gateway the device is talking to, that ... Continue Reading

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