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State of Nebraska

2017 NEC codebook

On May 10, 2017 Governor Pete Ricketts signed Legislative Bill 455 directing the states electrical board to adopt the 2017 NEC with an effective date of August 1, 2017. Governor Ricketts along with the electrical board should be applauded for their continued dedication to electrical safety.

Additional information for Bill 455 Click Here>.

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See the origial article at: http://www.nema.org/Technical/Code-Alerts/Pages/17-May-Nebraska.aspx?NL=ECM-01&Issue=ECM-01_20170518_ECM-01_536&sfvc4enews=42&cl=article_8

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Safety means more than just selecting the correct equipment. NFPA 70E, Art. 130 tells you when an electrically safe work condition must be established [130.1(1)] and then covers the electrical safety-related work practices for when that condition cannot be established [130.1(2)].

Although it’s not split into two parts, Art. 130 logically can be. The second part [130.7] provides the requirements for personal protective equipment (PPE) and other protective equipment. The first part [130.1 through 130.6, plus 130.8, 9, and 10] provides the requirements for such things as work permits, approach boundaries, and precautions for personnel activities. This first part is what we’ll cover here.

Working hot

You don’t perform energized work simply because your boss wants you to, it’s quicker, or you “know what you’re doing.” You can perform energized work only if one (or more) of three conditions applies [130.2(A)]:

  1. The employer can demonstrate that de-energizing introduces additional hazards or increased risk.
  2. The employer can demonstrate it’s infeasible to perform the work in a de-energized state due to equipment design or operational limitations.
  3. The circuits operate at less than 50V. This is contingent upon the capacity of the source and any overcurrent protection between the source and the worker; there must be a determination that there will be no increased exposure to electrical burns or explosion due to electric arcs.

The Informational Notes below these conditions provide examples to help illustrate what’s meant.

Normal operation

Understanding the concept of “normal operation” is critical to correctly applying the requirements of Art. 130. Actually verifying normal operation may require some serious sleuthing. If you’re a contractor, don’t just ask about the maintenance of the equipment — insist on seeing the maintenance records.

All five of the following conditions must be met, or you must consider the equipment to be operating abnormally [130.2(A)(4)]. The equipment:

  • Is properly installed.
  • Is properly maintained.
  • Doors are closed and secured.
  • Covers are in place and secured.
  • Shows no evidence of impending failure.

The Informational Note following this list explains what’s meant by properly installed and properly maintained. In essence, both activities were performed per industry standards. The Informational Note also provides some explanation of what “evidence of impending failure” means.

Don’t assume the short paragraph that constitutes this Informational Note tells you everything you need to know. Use it as a starting point. Ask more questions, such as:

  • What equipment anomalies indicate failure?
  • What standards are used for maintenance, and do the maintenance procedures align with those?
  • Is the “qualified worker” standard strictly enforced, or do inadequately trained people perform maintenance work?

Energized electrical work permit

A qualified person doesn’t need an electrical work permit to do any of the following [130.2(B)(3)]:

  • Perform tests and/or measurements.
  • Conduct thermography.
  • Enter/exit area with energized equipment, if not performing electrical work in that area and not crossing the restricted approach boundary.
  • Conduct general housekeeping and/or miscellaneous non-electrical tasks (and not crossing the restricted approach boundary).

Most people view a work permit as something that gives them permission to do the work. Instead, think of a work permit in the opposite way. You aren’t filling out the permit to get permission; you are filling it to give permission.

With this perspective, you will look for dangers rather than see what you can get by with. Someone else may sign the official approval, but you are the one who will pay the real price if something happens. Put yourself in charge of ensuring the conditions of that permit are properly met.

An electrical work permit has, at a minimum, the eight elements enumerated in 130.2(B)(2)(1) through (8). Consider number 7, which is “Evidence of completion of a job briefing, including a discussion of any job-specific hazards.” If you weren’t in charge of the permit (traditional viewpoint), you might seek some quick “check the box” way of satisfying this requirement so you can get on with the job.

But since you are in charge of the permit, that’s not what you want. Is that briefing sufficient if it’s just a quick summary with a sign-off sheet? No, you want to understand the job and its hazards. You want to be able to not only outline the major steps, but also identify how to protect against every known hazard any of those steps might bring.

If you take ownership of each element of that permit, are you going to have a happy boss or an unhappy boss? Let’s see. You are taking personal responsibility to ensure something extremely bad doesn’t happen. What competent boss would not be thrilled with this?

If you view the permit as an obstacle, then your boss is tasked with trying to make sure you comply. That’s just more work for your boss, and it leaves you at a higher level of risk.

Approach boundaries

How close can you get to the energized equipment? The answer to this question is only as close as your shock protection boundary allows. There are two kinds of shock protection boundary: limited and restricted [130.4(B)]. In either case, the distances must be established using Table 130.4(D)(a) for AC voltages or Table 130.4(D)(b) for DC voltages.

The limited approach boundary applies to unqualified personnel. There is some confusion on what this means. It’s not just a matter of expertise; you are also unqualified if you don’t need to be there. Generally, if you don’t have specific assignments on the other side of that boundary then don’t cross that boundary.

Circumstances do arise where an unqualified person needs to cross that boundary. That person probably hasn’t had the job briefing and so would be unfamiliar with the hazards. This in itself creates a dangerous situation.

The solution in NFPA 70E is that a qualified person advises the unqualified person of the possible hazards and escorts that person at all times [130.4(C)(3)]. That unqualified person cannot, however, cross the restricted approach boundary regardless of “need.”

The privilege of crossing the restricted boundary is restricted to qualified people. But even they must work under restrictions after having crossed that boundary. They can’t approach (or take any conductive object) closer to exposed energized conductors (50V or more) than the distance(s) set forth by Table 130.4(D)(a) or (b), unless the following conditions are met:

  • The person is insulated from or guarded from the energized conductors.
  • The person is insulated from any other conductive object.
  • The energized conductors are insulated from any other conductive object that’s at a different potential.

Arc flash

Another boundary on the job is the arc flash boundary. An arc flash study must be conducted to determine where this boundary is [130.5(1).b]. As a result of this study, which is documented, workers will know what PPE and work practices are required for them to be able to cross that boundary.

Determining the arc flash boundary is complicated. Informative Annex D, which runs nine pages, explains how to do this.

Let it shine

Electrical testing firms and electrical service firms have long considered rental of lights and generator a normal part of switchgear work. In most facilities, the lights for the switchgear are supplied by that switchgear instead of by another source. The logic of this has escaped explanation.

Where lighting is present, it’s typically inadequate for working inside the cabinets. It’s just ambient lighting and not intended to facilitate work — no logical explanation for that, either.

If a poor lighting situation exists, it must be corrected (e.g., with portable lights) before work may be performed. In fact, employees cannot even enter spaces where electrical hazards exist unless there is sufficient illumination to perform the work safely [130.6(C)(1)].

Having a helper stand there with a D-cell flashlight doesn’t count as providing illumination. The area should be lit up with work lamps. And you’ll have to light around obstructions so there aren’t shadows creating optical illusions or other visual difficulties. Typically, this will mean running several cords across the floor. Cord management is a safety issue; therefore, tape those cords down, and use cord protectors so that people don’t trip.

Other precautions

You’ll find other precautions listed in 130.6, such as:

  • Be alert at all times when within the limited approach boundary. Note that you can’t be alert if you’re fatigued. It’s better to call it a day than to make this your last day.
  • Don’t reach blindly into cabinets or other places that might contain energized conductors or circuits.
  • Don’t wear conductive items such as jewelry.
  • Where there is evidence that electrical equipment could fail, shut it down unless the employer can demonstrate that de-energization poses a greater hazard.

While Art. 130 provides a good basis for working safely around electrical hazards, it is by no means a substitute for diligently analyzing every work situation. Never take anything for granted, and never accept “that’s good enough” as a substitute for properly implementing safety principles.

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See the origial article at: http://ecmweb.com/nec/energized-work-what-s-required-beyond-ppe

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Even though a 2-cycle power outage can damage electronic equipment, sometimes a 3-cycle outage causes no problems.

To many of us, the utility power grid is a vast system of unknowns. Its performance can make unprotected electronic equipment useless. Why? Because grid voltage values, higher or lower than guaranteed nominal values, have an effect on electronic intelligence processing equipment. Incoming grid power “sees” the equipment's DC power supply, which bears the brunt of any AC grid voltage variation.

811ecmIPQpic1
Damaged computer equipment could be caused by poor quality power supplies.

The impact of voltage sag

We can hardly assume our electronic hardware operates from a distribution network with zero internal impedance, receives a pure undistorted sine wave, and never sees line voltage variations of 55% from nominal. Yet that's exactly what many electronic system manufacturers think when designing their power supplies.

The combination of utility- and locally generated disturbances results in no such modest limits. Most utilities are permitted line voltage reductions (brownouts) to cope with seasonal demands. In addition, large motors accelerating high inertia loads, spot welding, and other loads act to further drop the voltage level delivered to our power supplies.

Computer shutdowns and sag-induced logic errors aren't the only problems. Damage to the DC power supply is a greater danger. Reduced input voltage can cause excessive power supply heat dissipation, resulting in short equipment life. What's behind this overheating? While trying to maintain constant DC output as the line voltage declines, the DC-to-DC converter circuit has to draw from the reservoir capacitor. With line voltage reduced, this capacitor experiences deep discharges between the twice-per-cycle charging periods.

Now, electrolytic capacitors aren't designed for deep discharge — and they're not designed for the resulting large terminal variations. So, the excessive capacitor charge and discharge currents cause internal heat dissipation, which produces dielectric stress. This condition results in reduced mean time between failures (MTBF). In addition, rectifiers and DC-to-DC converter switching transistors draw high-peak currents, which raise their junction temperatures. These temperature excursions take a toll on semiconductor longevity.

The impact of overvoltage, surges, RFI, and harmonics

Short-term voltage surges (10% beyond nominal) aren't usually harmful. However, higher input voltages can overwhelm the voltage regulating ability. The result is damaging voltage levels fed to the electronic circuits.

High input voltage can also puncture a power supply's rectifier and switching transistor junctions, causing MTBF reduction and eventual breakdown. High-voltage transients lasting microseconds can permanently wreck the power supply and its electronic equipment load.

Digital logic circuits that define zeros by voltages in the 0V to 0.5V range and ones by 4.5V to 5V levels are highly susceptible to inductive “kicks” directly impressed on their 5VDC power supply. The power supply's reservoir capacitors don't absorb transient energy, because their wiring inductance (negligible at 60 Hz) introduces isolating impedance at the MHz-equivalent frequencies of fast-rise transients. As a result, transient energy follows the line of least resistance, which is to the power supply's output terminal.

Line-borne noise (RFI and low-voltage transients created by high-current logic circuits) will not likely damage a power supply. However, relatively few power supply designs have careful component shielding and placement. Therefore, line noise can couple (by stray capacitance) to the DC output, where it can disrupt communications and computer circuits. Because this noise may be intermittent and beyond the frequency range of many measuring instruments, you may have trouble diagnosing the source of the malfunction.

Harmonic voltages of the 60-Hz line frequency impressed on the AC power line are also unlikely to damage a power supply. However, higher harmonics of the 60-Hz power supply can fool control circuits. The more numerous zero crossings of higher harmonic frequencies can falsely trigger timing operations the sine wave's zero crossings initiate.

Sidebar: The DC Power Supply: How and Why It Works

PQ1

Shown is a typical switch-mode power supply wiring schematic. Here, the DC-to-DC converter normally switches at 100 kHz to 1 MHz. The PWM circuit regulates the DC output voltage by adjusting the ON/OFF durations of switching transistor Q.

A typical DC power supply (also called a switch-mode power supply or SMPS) is a sophisticated assembly of electronic components. Its basic function is to deliver stabilized low-voltage DC to the digital logic circuit it feeds. Based on a fast-switching DC-to-DC converter, the device converts rectified 60 Hz into the low-voltage DC (typically 5VDC) required by computer logic.

The power supply's pulse-width modulating (PWM) circuit compares the supplied 5VDC output to an accurate 5V reference so that an error-correcting feedback signal develops. This signal adjusts the relative ON and OFF durations of the DC-to-DC converter, holding the output at the required 5V.

An SMPS can bridge a total power outage for periods of up to three complete cycles. However, there's a key requirement for this maximum immunity to happen: The filter capacitor (denoted as “C1” in the Figure) must be fully charged to its design voltage. Basically, this capacitor acts like a short-term battery. During a power outage, this capacitor provides current to the power supply's DC-to-DC converter to keep it running.

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A power monitor can provide the data to determine when a transient event occurred and how long it lasted.

By definition, transient voltage events don’t last long. But a single event, if of sufficient magnitude, can destroy a motor. So can events of smaller magnitude that go unnoticed as they cause winding insulation to deteriorate.

We call a voltage event a transient when it lasts only momentarily. The voltage event may be a spike or a dip. A spike can do things like cause overheating or simply punch a hole in the insulation of conductors or motor windings. A voltage dip also can cause overheating, because the motor is going to demand more current when that dip occurs.

Suppose someone asks you if a given motor has been experiencing transient voltage events. How would you know? If lightning struck the building yesterday, you could probably say “yes” with reasonable confidence. But without instrumentation, you really have no way of knowing if that motor got hit by transients or not.

TransientVoltageWaveform

These random transient voltages (i.e., waveform notching) were recorded at a 480V service entrance with a power monitor.

You can’t hook up a digital multimeter (DMM) and have it look backward in time to measure an event that already happened. The only way to know if an event happened is to look at measurements that have been recorded. You want to do this with something more than the high-low recording feature on a DMM. For one thing, that DMM can’t tell you how many transient events it saw (if, indeed, it was fast enough to capture any).

You need something that is fast enough to capture each transient event, and you need something that will tell you when each occurred and how long it lasted. It would be nice to know not only the magnitude of each transient but also what its waveform looked like.

A power monitor fits the bill. It’s unlikely you can have it watch all of your motors, but you can have it watch your critical motor feeders.

If you have any large motors that start across the line but you haven’t been able to get management to spring for a soft starter, a report generated from the power monitor data will show what those motors are doing to the rest of your equipment via the power distribution system.

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See the origial article at: http://ecmweb.com/site-files/ecmweb.com/files/uploads/2017/03/13/TransientVoltageWaveform.jpg

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Do you have an adequate electrical preventive maintenance (EPM) program in place at your facility? If so, then you will be very familiar with NFPA 70B, Recommended Practice for Electrical Equipment Maintenance. Many of the chapters in NFPA 70B relate to different types of electrical equipment and call for a defined periodic “visual inspection” as part of the recommended maintenance.

If your EPM program does not include a recommended periodic visual inspection component, then you need to view these photo gallery slides, which include a sampling from the Hartford Steam Boiler Inspection and Insurance Company’s Thermographic Services group. Many of the photos show correctable conditions found by simple visual inspections. You will be surprised to see what can be going on inside your critical electrical equipment if you’re not paying close attention to it.

In an Internet of Things (IoT) world, sensors can be used creatively to monitor just about every negative condition that can happen to your equipment. As you flip through the slides, think about sensors that could detect and annunciate some of these deleterious conditions. If you can’t envision a sensor for some applications, then you will quickly realize the importance of the periodic visual inspection process defined in NFPA 70B.

If you’re not constantly looking for trouble, these photos represent a few ways trouble will find you first — and cost you a lot of money and business disruption in the process!

Electrical Trouble 2017 1

The Clock is Ticking to a Major Electrical Outage

This is a common occurrence with many types of electrical equipment — long-term exposure to excessive moisture or active leaks. The source of water could be roof leaks, chilled water lines condensing on the equipment, plumbing supply or drain line leaks. In this case, water has been leaking on the top of this busway and busway switch for a very long time. Once the corrosion penetrates the top enclosure steel, water will run directly onto the busway splices and cause phase-to-phase and phase-to-ground arcing. These failures usually result in arcing ground faults that destroy several 10-foot sections of the busway. Fires and fire-sprinkler water damage also commonly occur and can cause significant business interruptions.

Electrical Trouble 2017 2

Damage Is Occurring Where You Least Expect It

Visual inspections should include checking panelboard connections where the breakers spring-clamp onto the panelboard busbars. The integrity of these connections can be checked using periodic infrared thermography. These damaged busbars were discovered while working on other nearby failed electrical components. Unchecked failures of this type usually advance to a catastrophic panelboard loss due to phase-to-phase and phase-to-ground arcing faults that melt sections of all three of the busbars. Melting of the steel enclosure typically occurs before the overcurrent protection opens the circuit. Although the arcing initially starts at one phase, the initial ionized air and arc plasma quickly conducts to all of the other phases and ground.

Electrical Trouble 2017 3

Improper Field Modifications = No Motor Overload Protection

Visual inspections should always include checking that the motor overload protection is set properly based on the motor nameplate amps and the manufacturer’s setting instructions supplied with the overload relay. Originally, the two IEC motor starters and overload relays in this panel were identical. One of the motor controls was replaced with a different unit that does not have a settable range to protect the connected motor. Motor overload relays that have an adjustable range of amp settings can easily be set to a value that will provide no overload protection for the motor. NEMA type motor overload relays with one overload heater element per phase cannot be changed without physically replacing the three heater elements. These are less likely to be accidentally set to the wrong amp values.

Electrical Trouble 2017 4

An Obvious but Critical Mistake

Periodic visual inspections of busway include paying close attention to the bolted compression splice clamps. Many manufacturers of busway use a double-headed bolt whereby the outer head snaps off with a wrench at the initial installation. The outer bolt head is designed to snap off at the proper applied torque to avoid needing a torque wrench. The two red washers seen on the bolt heads in this photo indicate that the bolts have never been tightened. The red washers are designed to fall away after the heads are snapped off. This busway has been energized for many years with both splice bolts loose. A visual inspection found this mistake and initiated corrective actions before a potential major arcing event could occur.

Electrical Trouble 2017 5

Maintaining Environmental Barriers

Sometimes your own processes can invade the electrical enclosures. This can happen from improper NEMA type enclosure selection or from failing to properly secure the enclosure doors or knockout closures. The combustible dust collection in this fused switch can insulate the conductors and affect the conductor heat dissipation. High moisture in the dust can make the contaminants electrically conductive, causing short circuits, arcing, and equipment damage.

Electrical Trouble 2017 6

No Moving Parts but Still Requires Maintenance

In some cases, the outside environment tries to invade the electrical equipment. In this case, the electrical equipment is invading the surrounding building environment. Fluid leaking from these transformer bushings is getting out of the electrical equipment and contaminating the concrete floor. A quick visual inspection of this installation is all that it takes to establish a corrective action-plan. Without a formal electrical preventive maintenance program, what would compel someone to enter these often forgotten spaces? What damage could result from a low oil condition? What is the cost to repair these leaks now compared to a fire, catastrophic failure, and collateral damage in this space?

Electrical Trouble 2017 7

“It’s Always Been Like That”

Some improper electrical installations are very obvious. High-tech equipment or IoT sensors are not needed to pick up on this installation issue. Vertical busway installations are vulnerable to failures due to joint damage from leaks penetrating the enclosure and contaminating the closely spaced busbars. The NEC requires curbs around busways where they penetrate floors. Although spring mounts are used in this installation, it looks like hard cementitious material abuts the busway enclosure. Will the busway spring mount function properly when the busway is bonded to the floor? Will this stack of blocks move up and down with the spring mounts?

Electrical Trouble 2017 8

Not a Natural Habitat

This problem would be hard to find until it is too late without having an effective electrical preventive maintenance program in place. Periodic internal inspections would catch this condition before the conductors and the enclosures were damaged from rodents gnawing, corrosive excrement, or shorting of terminal from nesting materials. This enclosure invasion can be cleaned up, but it is equally important to seal off all penetration points to prevent a recurrence. One missing knockout closure may be all that is needed to allow rodents to access the internal electrical components.

Electrical Trouble 2017 9

“Define Qualified…”

Some electrical problems are from self-inflicted wounds. Who is allowed to do electrical work at your facility? Are they electrically “qualified” per the NFPA 70E definition?” Would a truly qualified electrician install a copper wire in place of a proper fuse? If unqualified personnel are performing electrical work in your facility, they are exposed to serious danger. In addition, their unsafe acts may cause injury to others who work nearby or are affected by their improper electrical installations. Regardless of how this installation occurred, routine and periodic inspections can discover problems and allow corrective actions to be taken before a fire, injury, or equipment damage occurs.

Electrical Trouble 2017 10

Monday Morning Production

Some electrical problems are not immediately recognizable during a visual-only inspection. This problem was discovered after using infrared thermography to view the connections while under load. When one of three conductors was observed to be “cold” on a 3-phase balanced load, the system was deenergized and looked at more closely. This new cooling tower, variable-frequency drive (VFD) came from the factory with one conductor terminated onto the conductor insulation that was never stripped.

Electrical Trouble 2017 11

You Can’t Judge A Switch by Its Cover

Sometimes electrical equipment looks perfectly fine from the outside. You might assume that if the outside is clean, then everything inside must be okay too. In reality, this is a perfect example of why periodic visual inspections are so critical to the reliability of electrical equipment. Spiders can get into enclosures through holes in enclosures that are small and normally do not present any unwanted access problems. When dirt and moisture collect on these spider webs that bridge phases and provide paths to ground, conditions are ideal for flashovers and arcing ground fault damage. Arcing ground faults and products of combustion can contaminate adjacent switchgear sections. Long lead times for new switchgear can create unrecoverable business losses.

Electrical Trouble 2017 12

An Electrical Industry Concern

The white conductor insulation on this 2-pole breaker shows signs of overheating. The insulation is black and burned at the breaker screw terminal. This damage can be seen during a close visual inspection. If thermographic inspections had been used as part of the periodic EPM, this failing breaker or termination would have been seen much sooner before the insulation became heat damaged. This panel is a Federal Pacific Electric (FPE) Stab-Lok panel that should be scheduled for replacement due to potential electrical and fire safety issues. Read “Old Circuit Breaker Panels Pose Danger” for more information about FPE Stab-Lok panels.

 

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See the origial article at: http://ecmweb.com/ops-maintenance/12-reasons-why-electricians-should-always-be-looking-trouble?PK=UM_Top517&elqTrackId=15eefc87eca043f8b58d029732d7a7fb&elq=cc9fc3dff6224d4c8d40d1a7d0b9e33a&elqaid=13472&elqat=1&elqCampaignId=11370&utm_rid=CPG04000000918978&utm_campaign=13472&utm_medium=email&elq2=cc9fc3dff6224d4c8d40d1a7d0b9e33a#slide-0-field_images-146711

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