Month: November 2018

Choosing Circuit Breakers Over Fuses

In the past fuses were the only option when it came to protecting homes, businesses, and equipment against overloaded circuits, shorts in circuits, and other faults.  With advancements in technology, circuit breakers became a popular option over the use of fuses due to the number of advantages they are able to offer.  The use of modern-day circuit breakers creates increased safety and reliability, decreased costs, and additional support for energy management initiatives.

Benefits of Using Circuit Breakers

Performance Reliability

The performance of fuses can decrease overtime.  Age increases the instances of fault, causing fuses to open even under normal conditions.  There is no way for fuses to be tested thus the current value that causes it to become faulty can never be determined.  Circuit breakers however are tested when manufactured and can be tested throughout its lifetime to ensure peak performance.

Comprehensive Protection

Circuit breakers trip circuit, breaking the electrical connection, up to a thousand times faster than fuses.  The trip capacity of a circuit breaker is greater than the equivalent fuses.  Modern day circuit breakers provide exception fault current limitations which was once only known to occur with fuses.  This function offers reliable protection while increasing the life of equipment by decreasing the aging that occurs with frequently tripped circuits.  Unlike fuses that can experience an overload even when one of multiple fuses opens, this will never occur within a circuit breaker.  When one breaker experiences an overload, the connection will be stopped immediately.

Increased Safety and Production

Replacing fuses can be risky for untrained personnel.  Fuses have exposed conductors and therefore can be quite tricky to change out.  The connections for circuit breakers are hidden, being that it is unexposed it keeps re-connecting the circuit safer for employees.  A major cause of fires within industrial settings occurs because of fuses that were incorrectly replaced.  This could include using the wrong fuse, incorrect model and/or rating, and more.   These issues are almost inconceivable when correcting a tripped connection when using a circuit breaker. The time saved is also considerable when using circuit breakers as reclosing the breaker can occur instantly which prevents production downtime.

Savings

Although the cost of a single fuse is less than the cost of a circuit breaker overall the installation and usage is less expensive.  Consider that three-phrase circuits must have three fuses.  Also, the cost of keeping extra fuses in stock.  Overall operation costs of using fuses instead of a circuit breaker are higher.

More Functionality

Circuit breakers, unlike fuses, can offer additional functions like ground fault protection.  System coordination between breakers, cascading and selectivity cannot occur when using fuses whereas circuit breakers allow for this feature.  Newer technology allows for circuit breakers to use remote controls, have alarm features, offer measurement features, and communication within your network.

J & P Electrical Company is a full-service electrical company that supplies contractors, end users, and supply houses with new surplus, quality reconditioned, and obsolete electrical equipment. We purchase a wide range of electrical equipment such as bus plugs, bud ducts, panel switches, substations, and transformers.  More information can be found at https://www.jpelectricalcompany.com

 

 

Power System Studies

Understanding the importance of a short circuit protection and coordination study and an arc flash hazard assessment.

A typical power distribution system for a large facility or campus is comprised of multiple distribution voltages and corresponding equipment. An incoming electrical service is provided by the local utility, which may consist of one or more utility circuits, in either a split-bus arrangement (the facility load is shared between circuits) or a duty/standby arrangement (one circuit carries the entire load, under normal operating scenarios). The incoming electrical service is usually at a medium voltage, which ranges between 600V-69,000V (common voltages include: 4.16kV, 12.47kV and 13.8kV). The incoming service voltage can be stepped down to a lower medium voltage or it can be distributed around the facility to electrical service spaces. The medium voltage will subsequently stepped down to a utilization voltage – 600V or 480V for motor loads or equipment and 208/120V for receptacles and lighting. At each distribution voltage, major electrical equipment will include: switchgear/switchboards, feeders, transformers, distribution panels and lighting/receptacle panels.

Tasked with managing these electrical assets, facility managers should ask the following important questions. How will my electrical power system operate during abnormal operating conditions, such as a short-circuit event? Is equipment properly rated to prevent damage and failure during a short-circuit event? What level of personal protective equipment should operators wear, when performing routine switching operations or maintenance on electrical distribution equipment? Two important power system studies can provide answers to these questions, along with other essential information: a short-circuit protection and coordination study and an arc flash
hazard assessment.

At each voltage level in a power distribution system, protective devices, including fuses, circuit breakers and protective relays, are used to protect electrical distribution equipment and the loads served. Fundamental protection consists of protection from overload scenarios, where too many amps are drawn by loads and overheating becomes an issue, and protection from instantaneous overcurrent scenarios, where large magnitude currents can damage equipment in a fraction of a second (a short-circuit event). Protective devices have to be adequately rated for both scenarios.

In the event of a short-circuit or other abnormal event, a large magnitude fault current will flow through multiple protective devices and levels of distribution, before it reaches the point of failure. The flow of current in the faulted circuit will be interrupted by the melting of a fuse or the opening of a circuit breaker. In an ideal situation, the upstream protective device closest to the point of failure will open before a higher-level protective device opens. For example, a fault in a motor should trip the circuit breaker supplying the motor, without impacting the main breaker for the entire facility. When this occurs, protective devices are said to coordinate, power interruptions are localized and disruption to the rest of the facility is minimized.

A short-circuit protection and coordination study provides a complete evaluation of a power distribution system to ensure all protective devices are rated for the available fault level (at a particular voltage) and adequately protect downstream equipment. As part of the study, time current curves (TCC), which plot the interrupting time of an overcurrent device based on a given current level, are produced. TCC plots provide a graphical illustration of the coordination between multiple protective devices at an available fault level. In the event that devices do not coordinate, adjustable protection settings may be revised or devices may be replaced, to provide an optimal level of protection and coordination.

An arc flash hazard assessment takes information produced in a short-circuit protection and coordination study and produces a safety analysis for those who will be working on an electrical power system. The primary threat to electrical workers is the risk of an arcing ground fault and the associated blast. An arcing ground fault can cause thermal burn injuries and physical trauma, due to the force of the blast and flying projectiles, which may consist of partially melted components. Key elements to the assessment include: short-circuit levels at various points in the distribution system, the clearing time associated with upstream protective devices, the distance between the worker standing in front of the equipment to the arc source within the equipment, the incident energy available (cal/cm2) and the flash protection boundary. Once the incident energy available is calculated, the appropriate level of personal protective equipment can be identified.

The flash protection boundary will identify the minimum distance from live parts, that are uninsulated or exposed, within which a person could receive a second-degree burn. While one might expect higher short circuit levels to be associated with higher levels of incident energy, this is often not the case. Lower short circuit currents can often cause an arc to burn longer, before a protective device is tripped, resulting in a higher level of available incident energy. Time delays on protective devices may be increased to provide better levels of coordination, however this may also increase incident energy levels. Consideration should be given to both the coordination of protective devices and mitigation strategies for arc flash hazards. Temporary settings (maintenance settings) can be used to reduce incident energy levels, during routine maintenance and work on electrical systems.

Short-circuit protection and coordination studies and arc flash hazard analyses are typically performed with the use of industry standard power system software and computer modelling. A detailed model of a power system is created and information on the power system, including: the incoming utility service, equipment ratings, protective devices and settings, feeder lengths, transformer sizes and motor sizes are inputted. Information is typically collected from the facility’s electrical single line diagrams, electrical drawings with the location of equipment in plan, record shop drawings from construction and data gathering from site surveys. Software programs will have a large database of protective devices, with user-defined protective settings when adjustable. This will allow the modeler to select appropriate settings or suggest alternative protective devices, to achieve better levels of device coordination. Once a model is complete, a multitude of deliverables can be produced, such as reports, TCC plots, graphical representations of a various operating scenarios, arc flash labels and information on PPE requirements. Correct information must be inputted into the power system model, to ensure automated calculations and results are accurate.

Most new construction projects and projects that involve significant modifications to electrical equipment will include the requirements for power system studies in the project specifications. This will ensure that an electrical installation is optimized, properly integrated with any existing power distribution equipment and operators have the necessary information to operate new equipment. While new projects provide the opportunity for updated studies, many facility managers inherit complex power distribution systems, which have undergone a multitude of upgrades and modifications over the years, with minimal updates to record documentation.

Upper Canada College faced these challenges when they undertook a project to update record documentation on their power system, complete with an updated short-circuit protection and coordination study and arc flash hazard analysis.

Founded in 1829, Upper Canada College (UCC) is one of Canada’s leading independent schools and is located on a 16-hectare (40-acre) campus in midtown Toronto. The campus is home to a number of academic buildings, student and staff residences and facilities. The campus receives an incoming utility service at 13.8kV and distributes power to a number of campus buildings, via a 13.8kV distribution network. Major buildings have individual main electrical rooms, where the incoming medium voltage circuit is transformed down to 600/347V and 208/120V. Low voltage distribution systems provide power to building mechanical systems, lighting, equipment and academic facilities. Power distribution systems had been modified over the years along with campus re-development and renovations in various buildings.

Chris Martins, Senior Operations Manager, Angus Consulting Management Ltd. (UCC’s Facilities Management Group) said, “We recognized the need to update record information on electrical power systems throughout the campus and this provided an excellent opportunity to complete an updated coordination study and arc flash hazard analysis.”

C2C Enertec Inc. was selected to complete the electrical audit and provide updated power system studies. Detailed site investigation work was completed over the span of several months. As-built drawings and building records, spanning several decades, were reviewed in detail. Electrical equipment, protective devices and existing settings were reviewed on site and catalogued. Site work was completed after hours, to avoid disruption to building occupants. Updated electrical single line diagrams were created and information collected on site was used to produce a detailed power system model of UCC’s electrical power systems. A short-circuit study was completed and time current curves were produced for the power distribution system. An arc flash hazard analysis was completed and a report detailing arc flash hazard levels, along with recommended personal protective equipment, was produced.

Information was consolidated in a detailed report for UCC’s operations group, arc flash labels were installed on electrical equipment throughout the campus and updated electrical single line diagrams were mounted on walls, in main electrical rooms. The updated power system studies and electrical records provide operations staff with new insight into how their power distribution system can be expected to operate, along safety requirements when working on equipment.

Steve Thuringer, Executive Director of Facilities, UCC said, “UCC’s electrical power distribution system is an essential part of campus operations. Having updated record information will go a long way in helping our staff with future maintenance work and renovation projects.”

In today’s world of integrated systems, the requirements of a reliable power supply and the need for workplace safety are an integral part of facility management. It is recommended that every facility consider having an up to date arc flash hazard assessment and short circuit protection and coordination study, for its electrical power systems. These two important power system studies help ensure equipment is properly protected, can minimize the impact of an unexpected short-circuit event and promote operator safety when working with electrical equipment. By developing detailed requirements for technical experience and deliverables, such as compliance with industry standards and the associated methods for creating power system models, a facility manager can help ensure that their service provider produces meaningful results.

As demonstrated by the successful project at Upper Canada College, undertaking power system studies provide significant insight into an existing power distribution system, which has been modified and upgraded over time.

Original Source: https://www.mromagazine.com/features/%EF%BB%BFpower-system-studies/

Original Date: Nov 12 2018

Written By:

Fact or Fiction? What Do You Believe About Reconditioned Electrical Equipment?

There are several common myths surrounding the use of reconditioned electrical equipment and components. Is it really true that with the purchase of refurbished manufacturing equipment and parts can truly save companies time and money while also meeting environment goals?  It is our goal in this installment to debunk several myths that surround the use of reconditioned equipment and parts in the work place.

It is important to note that business decisions should always be based on facts instead of myths.  Many times, myths are just handed down stories and experiences of one user that have been embellished upon throughout the years.  In order to successfully navigate and grow your company it is crucial for companies to make decisions based on facts.  When it comes to being competitive the goal is to find a solution that meets your needs.  Purchasing high quality electrical equipment and components at a reasonable price with little to no down time should be of the highest priority.

Myth #1: Original Equipment Manufacturers Are the Only Ones That Can Properly Recondition Electrical Parts and Equipment

The biggest difference between public reconditioning companies and private OEM recondition services is the inspection process they must go through to be available for resale.  This is why it is important that you only buy from reputable product reconditioning companies like J and P Electrical Company.

At J and P, you can rest knowing that we only sell the highest quality reconditioned electrical distribution equipment available.   The standards set forth by the experts at J and P are in fact more stringent than any set-in place by OEM manufacturers.  We disassemble each part, cleaning and inspecting each one, replacing parts that need to be replaced as we go along.  They are then painted with high quality paints and acrylic enamel for durability.  Equipment is reassembled and tested until it exceeds manufacturers UL certification standards.

Myth #2: Liability Concerns are Increased with the Use of Reconditioned Electrical Equipment and Parts

When you are purchasing a part does it make you feel better to know it is fresh off the line or that it has been rigorously tested over and over again to ensure its safety?  When you purchase reconditioned parts and equipment from a company like J and P you can rest assured knowing it has been tested two times over, before and after reconditioning, each and every time.  There is less liability involved in products and equipment that have gone through arduous testing.

 

J & P Electrical Company is a full-service electrical company that supplies contractors, end users, and supply houses with new surplus, quality reconditioned, and obsolete electrical equipment. We purchase a wide range of electrical equipment such as bus plugs, bud ducts, panel switches, substations, and transformers.  More information can be found at https://www.jpelectricalcompany.com

Power Supplies and Circuit Breakers Keep Faults in Check

Sponsored by Digi-Key and Phoenix Contact: Industrial power supplies that incorporate features such as SFB circuit breakers provide a better level of protection and overall reliability.

In the last decade or so, significant advances have been made in the design of industrial power supplies and dc-dc converters, from the materials and device levels to size and weight reduction, thermal management, and package design. However, one often-overlooked category is protection of circuits and systems provided by the power supply and accompanying circuit breakers. These advances have contributed greatly to reliability and system availability while maintaining safety as well.

One of the most far-reaching is selective fuse breaking (SFB) or selective shutdown, which when enabled in both power supply and thermomagnetic, as well as other types of circuit breakers, provides significant benefits. There are two types of trip mechanisms in these thermomagnetic breakers—temperature-sensitive and magnetic—the former having a response delay and the latter almost instantaneous.

The temperature-sensing element of the circuit breaker consists of a bimetal strip with a heating coil. When current exceeds a threshold, the protective device generates heat in the coil, which causes it to bend and actuate the switch, shutting off power. The temperature-sensitive circuit is even effective when current is temporarily greater than nominal, such as when overload currents are shut down.

The magnetic trip mechanism consists of a solenoid coil and a plunger or pivoted armature. When current exceeds a specific threshold, a magnetic field is created in the coil, which attracts the armature to it and interrupts the circuit. Response time of this type is much faster than its counterpart, typically 3 to 5 ms, allowing it to respond to short-circuits and excessive overload currents.

1. Shown are the three common response curves available in thermomagnetic circuit breakers and the maximum current required to actuate them.

Thermomagnetic circuit breakers are available with one of three different characteristic response curves, M, SFB, and F and subsets of each, that suit specific operational situations. These curves are shown in Figure 1. The SFB characteristic provides the most overcurrent protection and prevents the breaker from switching off too soon, even when a very short overcurrent condition occurs, such as when the system is started. It also prevents long-lasting overload currents that would result in high equipment temperatures.

SFB-Curve Thermomagnetic Circuit Breakers

Phoenix Contact was the first to introduce thermomagnetic circuit breakers that follow the SFB curve, and are designed for use with power supplies that also are based on SFB technology. When combined, the two provide exceptionally reliable tripping, even with long cable lengths between the power supply and the devices it serves. For example, Figure 2 shows a short-circuit occurring on one of three devices connected in parallel over 25-m lengths of copper cable to a Phoenix Contact QUINT Series 20-A power supply, a control subsystem, and circuit breakers protecting each current path. In this case, a short-circuit occurred in the second-to-last device, so the power supply selectively cuts power to it while allowing the controller and the other devices to remain in operation.

2. This example shows a power supply, controller, and secondary devices, one of which experienced a short-circuit. SFB allows power to be removed from only the faulted circuit, enabling the controller and the remaining devices to continue in operation. Without this capability, the entire system would be shut down.

The power supply also delivers the large amount of power reserve required in systems like this one that have long power cable runs, in which the amount of current available for tripping the breaker is limited. In these cases, the current level is often too low to quickly trip the circuit breaker and may not trip it at all. In the interim between the event and when the breaker disconnects power, the voltage continues to flow, which can overload the controller and potentially damage or even destroy it.

By delivering a higher level of current than is normally required to trip the breaker (up to 10 times normal for 12 ms in Phoenix Contact QUINT SFB power supplies), such situations are prevented. The capability is useful for systems experiencing high start-up current peaks, too.

In addition to possibly causing equipment damage, a power supply/breaker combination without SFB would shut down the entire system, rather than electively addressing only the faulted circuit path. The power supply also provides comprehensive diagnostics that include output voltage and current monitoring of critical operating conditions, and alerts operators to critical operating states before errors occur.

Summary

Industrial power supplies are changing with requirements for higher efficiency and greater integration with the plant management systems where they’re located. They’re also increasingly incorporating features such as SFB circuit breakers that when combined with compatible power supplies are solving some basic problems, e.g., keeping equipment functioning in the event of a fault.

Without SFB, faults become a detriment to system availability, as they take an entire block of functions offline, even though only a single circuit has failed. The Phoenix Contact QUINT power supplies also complement SFB with comprehensive monitoring of key performance parameters that alert operators to potential problems before they result in a failure.

Original Source: https://www.electronicdesign.com/power/power-supplies-and-circuit-breakers-keep-faults-check

Original Date: Oct 30 2018

Written By: Barry Manz |