Jan
04

5 things to watch in energy in 2018

There will be no shortage of stories to follow in the energy sector in the coming year

An important year in the energy sector lies ahead, with pipeline disputes, OPEC trying to keep a grip on oil prices and a lot of U.S. natural gas about to flood the market. While many stories will be unfolding in the coming months, here are five that are sure to be making headlines.

Fuel prices

producer prices
Consumers can expect to pay more to fill up in 2018. Rising gasoline prices will be one of the energy sector stories making headlines next year.

Consumers can expect to pay more to fill up in 2018, according to Dan McTeague, senior petroleum analyst at GasBuddy.com.

McTeague anticipates gasoline prices will rise in the second half of the year as the U.S. economy strengthens and demand spikes. It's likely, he says, Canadians will see, on average, about a five-cent-per-litre increase in 2018 versus averages in 2017.

Higher gasoline prices push U.S. inflation rate up to 0.4% in November
National clean fuels strategy will affect all forms of fuels in Canada

"The whole issue of demand in the United States continues to drive prices up for Canadians, whether we like it or not," he says. "We are price takers, not price makers."

A strengthening U.S. dollar and provincial carbon taxes may also add to the pump price.

Pipelines

transcanada keystone decision 20171120
Pipelines will continue to be a lightning rod for protesters in 2018.

Don't expect an end to the pipeline drama as three major energy infrastructure projects remain in the spotlight in 2018: Trans Mountain, Keystone XL and Line 3.

Pipeline supporters, including Alberta's NDP government, believe the multibillion-dollar projects are needed to ease a transportation squeeze resulting from growing production and limited shipping options. It's one factor in why Canadian heavy oil sells at a discount to U.S. crude. New pipe would help.
TransCanada Keystone Decision 20171120

Pipelines will continue to be a lightning rod for protesters in 2018. (Nati Harnik/Canadian Press)

But opponents — whether they are jurisdictions, environmentalists or indigenous groups — remain determined to stop the pipelines. Their concerns are often both intensely local, like the direct impact on the landscape, and also part of the broader climate change issue.

Despite controversy, observers expect progress on Line 3 and Trans Mountain in the coming year. TransCanada expects to secure final federal U.S. permits for Keystone XL in early 2018.

Meanwhile, Canadian natural gas producers will be watching what happens next year when new pipelines start to move a lot more Appalachian gas out of Pennsylvania, West Virginia and Ohio and into the continental market.

Nebraska regulators reject Keystone XL route reconsideration
Pipeline bottlenecks push Canadian oil price to deepest discount in 4 years

"So it's just a question as to how quickly some of that gas will come on, and what it will do to gas prices," said Samir Kayande, director at industry research firm RS Energy Group in Calgary.

"It is just a tremendous success story from a productivity standpoint — and it's frankly a disaster from a gas market standpoint, because it's a lot of cheap gas that's hitting the market," he said.

OPEC

austria opec
OPEC agreed to extend production cuts through 2018, but the cartel will evaluate market conditions at its June 2018 meeting.

OPEC and its non-OPEC allies, including Russia, surprised observers last year when they agreed to oil production cuts — and then stuck to them. With time running out on the pact, they agreed in the fall to maintain the cuts for all of 2018.
AUSTRIA OPEC

OPEC agreed to extend production cuts through 2018, but the cartel will evaluate market conditions at its June 2018 meeting. (Akos Stiller/Bloomberg)

The agreement is aimed at drawing down the surplus oil inventories that have dampened crude prices.

"We have seen very good compliance numbers from the OPEC members as well as Russia," said Dinara Millington, vice-president of research at the Canadian Energy Research Institute. "Whether that will hold or not remains to be seen."

OPEC agrees to extend oil production cut into next year
OPEC says winning battle to end oil glut

The cartel will reassess target production levels according to market conditions at their June 2018 meeting. In the meantime, OPEC and others will be watching to see if their efforts will be undermined by oil production increases from U.S. shale.

U.S. shale

usa shale permian
One of the big questions in 2018 is how much shale oil will the U.S. produce.

What will U.S. shale producers do in 2018? The answer is critical, and even the most informed prognosticators at OPEC and the International Energy Agency (IEA) can't agree on what will happen.
USA-SHALE/PERMIAN

One of the big questions in 2018 is how much shale oil will the U.S. produce. (Ernest Scheyder/Reuters)

Prolific shale production has reshaped the energy landscape in recent years. It's also a vital component of U.S. President Donald Trump's "America First" energy plan, with the potential to turn the world's largest oil-consuming nation into a net exporter of oil by the middle of the next decade.

But the more pressing issue is whether there's a big wave of shale production coming next year.

West Texas oil boom threatens recovery in Canadian oilpatch​​
Don't write oil's 'obituary,' IEA says in long-term demand forecast

OPEC doesn't think it will be big enough to harm the cartel's efforts to erase the oil glut. The IEA, meanwhile, thinks U.S. crude production will be strong and keep the overhang in place.

"The big macro question in this industry right now, on the liquids side, is which one of those is the right one," said Ian Nieboer, also of RS Energy Group. "Both can't be [right]."

Renewable energy

solar panels
Experts expect more advances in solar panel development in 2018.

No discussion about energy in 2018 can ignore the role of renewables.
solar panels

Experts expect more advances in solar panel development in 2018. (Robert Jones/CBC)

"This is a sector that's growing faster than any of the other energy sectors out there," says Warren Mabee, Canada research chair in renewable energy development and implementation at Queen`s University in Kingston, Ont.

"It's going to continue moving forward."

Decisions made this year will ring into 2018, including fallout from B.C.'s decision to proceed with the Site C hydroelectric dam, and Alberta's aggressive plan to build 600 megawatts of new wind generation by 2019.

Canada must reduce emissions from oilsands to meet climate goals: OECD report
Record cheap electricity is transforming world energy markets as Canada struggles to keep up

But Mabee is also looking for 2018 to provide key advances in solar panel development as the industry inches closer to grid parity — the point at which it might be cheaper for people to generate electrons on their roof than to buy electrons from a utility.

"It might not happen next year, but we're moving closer and closer," he said. "That's going to be a hugely disruptive moment in the Canadian power industry."

 

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See the origial article at: http://www.cbc.ca/news/business/energy-year-lookahead-1.4456819

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Dec
26

The Best of the Worst: 2017’s Most Interesting What’s Wrong Here Photos

It's that time again — when some of the most popular and bizarre Code violations are presented. Thanks to NEC Consultant Russ LeBlanc, who continues to amaze us with a seemingly unlimited supply of electrical blunders from the field, we present (in no particular order) the "best of the worst" What's Wrong Here photos from 2017.

1 2017WWHBWBelow1 0

Look Out Below!

These unsuspecting pedestrians have no idea they’re walking over some temporary feeder cables installed to provide power for the street fair. For the most part, these cables are protected by the mats that have been placed over them, which helps minimize tripping hazards and provide some degree of separation from unqualified people. Unfortunately, the installers did not stagger the matt connectors. The result is the exposure of unguarded cables. This is a violation of Sec. 525.20(E). Laying these single conductor cables on the ground may seem like a violation of Sec. 590.4(J), which prohibits temporary feeder cables or cords from being installed in this manner. However, because this wiring is for a fair, Sec. 525.3(A) clarifies that where the Code rules for other Articles differ from the rules in Art. 525, the requirements found in Art. 525 shall apply to portable wiring. For the most part, these accessible cables comply with Sec. 525.20(G) since the protective matting does not constitute a greater tripping hazard than the cables themselves. The exposed connectors do need to be addressed though.

2 2017WWHBWCampground2

Campground Chaos

These UF cables are providing 120V power for receptacles and lights at several tent sites in this campground. While Sec. 340.10(3) permits UF cable to be used outside in wet locations, and Sec. 340.12(10) allows UF to be used where exposed to the direct rays of the sun if the cable is identified as being sunlight resistant, Sec. 225.26 specifically prohibits trees from being used for supporting overhead conductor spans. The swaying and movement of the trees can cause the cables to be damaged, resulting in shock or fire hazards. UF cable is not permitted to be used as overhead cable except where installed as messenger-supported wiring in accordance with Sec. 340.12(11). Another violation you may be able to spot in the photo relates to the splices made in the UF cable without the use of any box or enclosure. Section 300.15 requires splices to be placed in a box or enclosure. However, a box is not required when the UF is spliced underground in accordance with Sec. 300.15(G).

3 2017WWHBWDock2 0

Help Support Our Cause

Looking closely, you may notice that there is only one clip for this vertical PVC conduit run, and it’s broken. The lack of a secure supporting means has caused the conduit to slip down and out of the luminaire mounted at the top of the post. This resulted in the individual conductors being exposed. According to Sec. 352.30, ¾-in. PVC is required to be secured within 3 ft of each conduit termination and supported again every 3 ft. The exposed conductors are a violation of Sec. 300.3(A), since they are no longer installed in a Chapter 3 wiring method as required. It also appears as though there is no box installed for the luminaire. The installer simply secured the fixture canopy directly to a piece of plywood screwed to the wooden post. Not installing a box for the conductor splices is a violation of Sec. 300.15.

4 2017WWHBWConduit2

Conduit Calamity

Believe it or not, this isn’t a flexible cord or cable. This is a group of PVC runs that have “self-destructed” due to the lack of proper supports and failure to use expansion fittings. Table 352.30 establishes the maximum spacing between PVC conduit supports. For sizes ½ in. through 1 in., conduit supports must be spaced no farther than 3 ft apart. For sizes 1¼ in. through 2 in., conduit supports must be spaced no farther than 5 ft apart — so on and so forth. However, even if the conduit supports are spaced correctly, failure to install an expansion fitting as required by Sec. 352.44 can result in bending and warping of the conduit and eventual failure. That appears to have been the case for this installation. The extra strain on the conduit supports from the pipe warping and bending can cause one clip to come loose or break. Over time, another clip fails, and then another and another until the pipe eventually looks like the one in this picture.

5 2017WWHBWExtension5

A New Class of Extension Cords

Is that an extension cord made of PVC and EMT? It appears as though this installer could not figure out a way to get the wiring inside the wall or to put an extension box on the double-duplex receptacle enclosure. There are a few Code violations here including the improper supporting of the switch box. According to Sec. 352.12(B), PVC cannot be used to support boxes. The specific requirements for supporting boxes found in Sec. 314.23(F) will reaffirm the fact that this box installation is incorrect. Using the attachment plug to support the box is not a recognized use for this device, and it violates the requirements of Sec. 110.3(B). Can you imagine how the installer connected the attachment plug into the wiring inside the box and raceway? Is the metal box connected to the equipment ground wire? Based on the workmanship that is visible, it probably isn’t. Metal boxes are required to be grounded and bonded in accordance with Sec. 314.4.

6 2017WWHBWFan2

I’m Not a Member of This Fan Club

Sec. 352.30(A), which requires this PVC conduit to be securely fastened within 3 ft of each outlet or junction box and at 3-ft intervals thereafter. The fan is being used as a junction box here, and I am sure connecting a PVC conduit to it in this manner would violate Sec. 110.3(B) since it is definitely not designed for this purpose. Lastly, I strongly doubt the receptacle installed at the end of the PVC was provided with GFCI protection as required by Sec. 210.8(B)(2).

7 2017WWHBWKneeBend2

This Gives New Meaning to Deep Knee Bends

There are definitely some concerns with the bending methods used on this PVC conduit. Section 352.24 requires field-made bends in PVC conduit to be made with identified bending equipment, such as heating blankets, heater boxes, and other equipment specifically made for the purpose. This PVC looks as though the installer tried to bend the conduit by simply folding it around his knee. The conduit is now kinked and damaged, and its internal diameter has most likely been reduced. A closer look reveals that the conduit has no connector, and it is not even secured to the box. It is partially pushed into the threaded box hole but not secured to the box, as required by Sec. 314.17(B). It may be tough to tell from this angle, but there was no gasket between the weatherproof box and the cover. For this outdoor wet location, Sec. 314.15 requires boxes to be placed or equipped to prevent moisture from entering them. With the gasket missing, moisture may be able to enter the box and damage any splices or connections inside.

8 2017WWHBWSqueeze2

Squeeze Play

At one point in time, this UF cable was buried. Unfortunately, a seed landed at the concrete base of this light pole and over time it grew into a tree, which eventually swallowed the cable and pulled it right out of the ground. Since that time, this cable has gotten stepped on and damaged to the point where it shorted out and tripped the breaker. Thankfully, the breaker did its job. Otherwise this damaged cable would have continued to present a real shock hazard. Column 1 of Table 300.5 in the 2017 NEC requires UF cable to be buried with at least 24 in. of cover for this location. Sec. 340.12(10) prohibits this UF cable from being used in areas where subject to physical damage. It’s obvious from the photo that this cable has suffered some severe physical damage. I was able to cut the cable away from this tree base and use some listed underground splice kits — in accordance with Sec. 110.14(B) — to extend and re-route this cable away from this pole to a safe and properly buried location.

9 2017WWHBWParkingLot2

Parking Lot Panelboard Problems

The panelboard is certainly not very weatherproof with the cover wide open and flapping in the breeze. This open cover defeats the requirements outlined in Sec. 312.2, which states that surface-type enclosures in wet locations must be placed or equipped to prevent water and moisture from entering and accumulating in the cabinet. Enclosures in wet locations are required to be weatherproof. That won’t happen with the cover wide open. In addition, a couple of circuit breaker blanks are missing from the internal cover, exposing energized bus bars and breaker terminals. This is a violation of Sec. 408.7, which requires these unused openings to be closed up using identified closures or other approved means. The missing breaker blanks could also be considered a violation of Sec. 110.27 because the live parts are exposed and are no longer effectively guarded against accidental contact. Small fingers like those of a child could easily reach inside the panelboard and receive a dangerous shock. On another note, the rusted metal raceways coming up out of the ground may be in need of some additional approved corrosion protection as specified in Sec. 300.6(A)(3).

10 2017WWHBWTap2

A Terrible Tap

This was a terrible attempt to tap power from this 800A circuit breaker. The installer simply took a 12 AWG wire and shoved it into the same terminal with the 350kcmil conductor. This created a very poor connection, which resulted in some arcing and sparking. The heat from this arcing ultimately damaged this 800A breaker to the point where it needed to be replaced because the terminals were so badly damaged. The conductors were also damaged. Thankfully, this did not start a fire. Jamming two conductors into a terminal designed for only one is a violation of Sec. 110.14(A) and can result in damaged equipment, or even worse. There is one open terminal remaining for each pole of the breaker, but the terminal is much too big to accommodate the 12 AWG wire. If this installer was trying to make a feeder tap, there are splicing devices that could have been used to make a connection directly onto the conductors instead of jamming wires into the terminals. Of course, the installer could have put the 12 AWG wires on their own breaker too.

P3 strives to bring you quality relevant industry related news.

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http://www.ecmweb.com/whats-wrong-here/best-worst-2017-s-most-interesting-what-s-wrong-here-photos

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Dec
18

OSHA’s Top 10 Violations of 2017

OSHA announced its preliminary Top 10 list of most cited violations for fiscal year 2017 at the National Safety Council (NSC) Congress and Expo in September. The announcement was made by Patrick Kapust, deputy director of OSHA's Directorate of Enforcement Programs.

Although this annual list of the most frequently cited violations almost always features the same hazard categories, the individual rankings do shift in their ranking a bit. This year, six of the 10 categories held the same position as last year. The three categories that switched positions were Ladders (No. 6), Powered Industrial Trucks (No. 7), and Electrical Wiring Methods (No. 10). Fall Protection – Training Requirements (No. 9) is new to the list this year. The General Electrical Requirements category dropped out of the top 10 this year.

In reviewing this year’s data, it’s interesting to note the total number of violations for all 10 categories (28,774) was far lower than last year’s total (35,019) number of violations.

OSHA2017No1

No. 1 Violation: Fall Protection

Fall Protection retains its No. 1 position on this important list. These violations are associated with the Fall Protection rules of OSHA 1926.501, which sets forth requirements for employers to provide fall protection systems for its employees. The good news is this category posted 834 fewer incidents than last year. There were a total of 6,072 violations issued in this category.

OSHA2017No2

No. 2 Violation: Hazard Communication

Hazard Communication remained in the No. 2 position. The purpose of this group of rules is to ensure the hazards of all chemicals produced or imported are classified — and that information concerning the classified hazards is properly transmitted to employers and employees. The requirements of 1910.1200 are consistent with the provisions of the United Nations Globally Harmonized System of Classification and Labeling of Chemicals (GHS), Revision 3. Fortunately, this category posted 1,479 fewer incidents than last year. There were a total of 4,176 violations issued in this category.

OSHA2017No3

No. 3 Violation: Scaffolding

Violations related to Scaffolding use are still widespread across many industries. It’s important to note that the rules of 1926.451 do not apply to aerial lifts — the criteria for which are set out exclusively in 1926.453. The good news here is that this year's total number of violations was 612 less than last year. There were a total of 3,288 violations issued in this category.

OSHA2017No4

No. 4 Violation: Respiratory Protection

The rules of 1910.134, which focus on Respiratory Protection, apply to General Industry (part 1910), Shipyards (part 1915), Marine Terminals (part 1917), Longshoring (part 1918), and Construction (part 1926). Violations associated with respiratory protection requirements apply to many different trades in the construction industry as well as plant/facility workers. There were 476 fewer violations issued in this category this year, as compared to last year's listing. Overall, there were 3,097 violations issued in this category.

OSHA2017No5

No. 5 Violation: Lockout/Tagout

Lockout/Tagout rules are vitally important for many different types of employees. Standard 1910.147 establishes minimum performance requirements for the control of such hazardous energy. This standard covers the servicing and maintenance of machines and equipment in which the unexpected energization or startup of the machines or equipment — or release of stored energy — could harm employees. There were 529 fewer incidents reported in this category as compared to last year. There were a total of 2,877 violations issued in this category.

OSHA2017No6

No. 6 Violation: Ladders

Section 1926.1053 applies to all Ladders, including job-made ladders. These rules apply to many different plants/facilities as well as all types of construction sites. This category moved up one place on the ranking from last year. However, there were 384 fewer violations issued in this category this year, as compared to last year's listing. There were a total of 2,241 violations issued in this category.

OSHA2017No7

No. 7 Violation: Powered Industrial Trucks

Although violations associated with Powered Industrial Trucks don’t often come to mind when thinking about electrical work, OSHA issues a lot of citations in this area. Section 1910.178 contains safety requirements relating to fire protection, design, maintenance, and use of fork trucks, tractors, platform lift trucks, motorized hand trucks, and other specialized industrial trucks powered by electric motors or internal combustion engines. The number of violations in this category decreased by 693 over last year and it dropped to number seven on the ranking list. There were a total of 2,162 violations issued in this category.

OSHA2017No8

No. 8 Violation: Machine Guarding

As noted in 1910.212, one or more methods of Machine Guarding shall be provided to protect the operator and other employees in the machine area from hazards such as those created by point of operation, ingoing nip points, rotating parts, flying chips and sparks. Examples of guarding methods include barrier guards, two-hand tripping devices, and electronic safety devices. This category saw a decrease of 515 violations this year. There were a total of 1,933 violations issued in this category.

OSHA2017No9

No. 9 Violation: Fall Protection – Training Requirements

This violation category is new to the top 10 list this year. Section 1926.503 focuses on Fall Protection – Training Requirements. The employer shall provide a training program for each employee who might be exposed to fall hazards. The program shall enable each employee to recognize the hazards of falling and shall train each employee in the procedures to be followed in order to minimize these hazards. There were a total of 1,523 violations issued in this category.

OSHA2017No10

No. 10 Violation: Electrical Wiring Methods

The good news here is that this “electrically focused” category dropped to last place on this list. Section 1910.305 focuses on Electrical Wiring Methods, components, and equipment for general use. It does not, however, apply to conductors that are an integral part of factory-assembled equipment. This category saw 532 fewer violations this year as compared to last year's listing. There were a total of 1,405 violations issued in this category.

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Dec
04

6 wiring and grounding problems that lead to low power quality

Wiring and grounding problems

In this technical article, typical wiring and grounding problems, as related to power quality, are presented. Possible solutions are given for these problems as well as the possible causes for the problems being observed on the grounding system. (See Table 2 at the bottom of article)

wiring grounding problems 1

6 wiring and grounding problems that lead to low power quality

The following list is just a sample of problems that can occur on the grounding system.

  1. Isolated grounds
  2. Ground loops
  3. Missing safety ground
  4. Multiple neutral-to-ground bonds
  5. Additional ground rods
  6. Insufficient neutral conductors

1. Insulated grounds

Insulated grounds in themselves are not a grounding problem. However, improperly used insulated grounds can be a problem. Insulated grounds are used to control noise on the grounding system. This is accomplished by using insulated ground receptacles, which are indicated by a “∆” on the face of the outlet.

Insulated ground receptacles are often orange in color. Figure 1 illustrates a properly wired insulated ground circuit.
Properly wired isolated ground circuit

2properly wired isolated ground circuit 768x404
Figure 1 – Properly wired isolated ground circuit

The NEC has this to say about insulated grounds.

NEC 250-74 Connecting receptacle grounding terminal to box

An equipment bonding jumper shall be used to connect the grounding terminal of a grounding-type receptacle to a grounded box.

Exception No. 4. Where required for the reduction of electrical noise (electromagnetic interference) on the grounding circuit, a receptacle in which the grounding terminal is purposely insulated from the receptacle mounting means shall be permitted. The receptacle grounding terminal shall be grounded by an insulated equipment grounding conductor run with the circuit conductors. This grounding conductor shall be permitted to pass through one or more panelboards without connection to the panelboard grounding terminal as permitted in Section 384-20, Exception so as to terminate within the same building or structure directly at an equipment grounding conductor terminal of the applicable derived system or source.

(FPN): Use of an isolated equipment grounding conductor does not relieve the requirement for grounding the raceway system and outlet box.

 

NEC 517-16 Receptacles with insulated grounding terminals

Receptacles with insulated grounding terminals, as permitted in Section 250-74, Exception No. 4, shall be identified. Such identification shall be visible after installation.

(FPN): Caution is important in specifying such a system with receptacles having insulated grounding terminals, since the grounding impedance is controlled only by the grounding conductors and does not benefit functionally from any parallel grounding paths.

 

The following is a list of pitfalls that should be avoided when installing insulated ground circuits:

  • Running an insulated ground circuit to a regular receptacle.
  • Sharing the conduit of an insulated ground circuit with another circuit.
  • Installing an insulated ground receptacle in a two-gang box with another circuit.
  • Not running the insulated ground circuit in a metal cable armor or conduit.
  • Do not assume that an insulated ground receptacle has a truly insulated ground.

 

2. Ground loops

Ground loops can occur for several reasons. One is when two or more pieces of equipment share a common circuit like a communication circuit, but have separate grounding systems (Figure 2).

3circuit with ground loop
Figure 2 – Circuit with a ground loop

To avoid this problem, only one ground should be used for grounding systems in a building. More than one grounding electrode can be used, but they must be tied together (NEC 250-81, 250-83, and 250-84) as illustrated in Figure 3 below.
4grounding electrodes bonded together
Figure 3 – Grounding electrodes must be bonded together

 

3. Missing safety ground

A missing safety ground poses a serious problem. Missing safety grounds usually occur because the safety ground has been bypassed. This is typical in buildings where the 120-volt outlets only have two conductors.

 

Modern equipment is typically equipped with a plug that has three prongs, one of which is a ground prong. When using this equipment on a two-prong outlet, a grounding plug adapter or “cheater plug” can be employed provided there is an equipment ground present in the outlet box.

 

This device allows the use of a three-prong device in a two-prong outlet. When properly connected, the safety ground remains intact. Figure 4 illustrates the proper use of the cheater plug.

5grounding plug adapter

Figure 4 – Proper use of a grounding plug adapter or “cheater plug”

If an equipment ground is not present in the outlet box, then the grounding plug adapter should not be used. If the equipment grounding conductor is present, the preferred method for solving the missing safety ground problem is to install a new three-prong outlet in the outlet box.

This method insures that the grounding conductor will not be bypassed. The NEC discusses equipment grounding conductors in detail in Section 250 — Grounding.

 

4. Multiple neutral to ground bonds

Another misconception when grounding equipment is that the neutral must be tied to the grounding conductor. Only one neutral-to-ground bond is permitted in a system or sub-system. This typically occurs at the service entrance to a facility unless there is a separately derived system.
A separately derived system is defined as a system that receives its power from the windings of a transformer, generator, or some type of converter. Separately derived systems must be grounded in accordance with NEC 250-26.

 

The neutral should be kept separate from the grounding conductor in all panels and junction boxes that are downline from the service entrance. Extra neutral-to-ground bonds in a power system will cause neutral currents to flow on the ground system.

 

This flow of current on the ground system occurs because of the parallel paths. Figures 5 and 6 illustrate this effect.

6neutral current flow
Figure 5 – Neutral current flow with one neutral-to-ground bond

neutral current flow extra neutral to ground bond
Figure 6 – Neutral current flow with and extra neutral-to-ground bond

As seen in Figure 6, neutral current can find its way onto the ground system due to the extra neutral-to-ground bond in the secondary panel board. Notice that not only will current flow in the ground wire for the power system, but currents can flow in the shield wire for the communication cable between the two PCs.

If the neutral-to-ground bond needs to be reestablished (high neutral-to-ground voltages), this can be accomplished by creating a separately derived system as defined above. Figure 7 illustrates a separately derived system.
7separately derived system
Figure 7 – Example of the use of a separately derived system

 

5. Additional ground rods

Additional ground rods are another common problem in grounding systems. Ground rods for a facility or building should be part of the grounding system. The ground rods should be connected where all the building grounding electrodes are bonded together.

Isolated grounds can be used as described in the NEC’s Isolated Ground section, but should not be confused with isolated ground rods, which are not permitted.

 

The main problem with additional ground rods is that they create secondary paths for transient currents, such as lightning strikes, to flow. When a facility incorporates the use of one ground rod, any currents caused by lightning will enter the building ground system at one point.The ground potential of the entire facility will rise and fall together.

 

However, if there is more than one ground rod for the facility, the transient current enters the facility’s grounding system at more than one location and a portion of the transient current will flow on the grounding system causing the ground potential of equipment to rise at different levels.

This, in turn, can cause severe transient voltage problems and possible conductor overload conditions!

 

6. Insufficient neutral conductor

With the increased use of electronic equipment in commercial buildings, there is a growing concern for the increased current imposed on the grounded conductor (neutral conductor). With a typical three-phase load that is balanced, there is theoretically no current flowing in the neutral conductor, as illustrated in Figure 8.

8balanced three phase system 768x534
Figure 8 – A balanced three-phase system

However, PCs, laser printers, and other pieces of electronic office equipment all use the same basic technology for receiving the power that they need to operate. Figure 9 illustrates the typical power supply of a PC. The input power is generally 120 volts AC, single phase.

The internal electronic parts require various levels of DC voltage (e.g., ± 5, 12 volts DC) to operate.
9one line smps 768x328
Figure 9 – The basic one-line for a SMPS

This DC voltage is obtained by converting the AC voltage through some type of rectifier circuit as shown. The capacitor is used for filtering and smoothing the rectified AC signal. These types of power supplies are referred to as switch mode power supplies (SMPS).

The concern with devices that incorporate the use of SMPS is that they introduce triplen harmonics into the power system.

Triplen harmonics are those that are odd multiples of the fundamental frequency component (h = 3, 9, 15, 21, …). For a system that has balanced single-phase loads as illustrated in Figure 10, fundamental and third harmonic components are present.

Applying Kirchoff’s current law at node N shows that the fundamental current component in the neutral must be zero. But when loads are balanced, the third harmonic components in each phase coincide. Therefore, the magnitude of third harmonic current in the neutral must be three times the third harmonic phase current.
10balanced single phase loads 768x533

This becomes a problem in office buildings when multiple single-phase loads are supplied from a three-phase system. Separate neutral wires are run with each circuit, therefore the neutral current will be equivalent to the line current.

However, when the multiple neutral currents are returned to the panel or transformer serving the loads, the triplen currents will add in the common neutral for the panel and this can cause over heating and eventually even cause failure of the neutral conductor!

If office partitions are used, the same, often undersized neutral conductor is run in the partition with three-phase conductors. Each receptacle is fed from a separate phase in order to balance the load current.

NOTE! However, a single neutral is usually shared by all three phases. This can lead to disastrous results if the partition electrical receptacles are used to supply nonlinear loads rich in triplen harmonics. Under the worst conditions, the neutral current will never exceed 173% of the phase current.


Figure 10 illustrates a case where a three-phase panel is used to serve multiple single-phase SMPS PCs.

 

Summary

As discussed above, the three main reasons for grounding in electrical systems are:

  1. Personal safety
  2. Proper protective device operation
  3. Noise control

By following the guidelines found below, the objectives for grounding can be accomplished:

  • All equipment should have a safety ground. A safety ground conductor
  • Avoid load currents on the grounding system.
  • Place all equipment in a system on the same equipotential reference.

Table 1 summarizes typical wiring and grounding issues.

Table 1 – Summary of wiring and grounding issues

Good power quality and noise control practices do not conflict with safety requirements.
Wiring and grounding problems cause a majority of equipment interference problems.
Make an effort to put sensitive equipment on dedicated circuits.
The grounded conductor, neutral conductor, should be bonded to the ground at the transformer or main panel, but not at other panel down line except as allowed by separately derived systems.

Table 2 – Typical wiring and grounding problems and causes

Wiring Condition or Problem Observed 

Possible Cause

Impulse, voltage drop out Loose connections
Impulse, voltage drop out Faulty breaker
Ground currents Extra neutral-to-ground bond
Ground currents Neutral-to-ground reversal
Extreme voltage fluctuations High impedance in neutral circuit
Voltage fluctuations High impedance neutral-to-ground bonds
High neutral to ground voltage High impedance ground
Burnt smell at the panel, junction box, or load Faulted conductor, bad connection, arcing, or overloaded wiring
Panel or junction box is warm to the touch Faulty circuit breaker or bad connection
Buzzing sound Arcing
Scorched insulation Overloaded wiring, faulted conductor, or bad connection
Scorched panel or junction box Bad connection, faulted conductor
No voltage at load equipment Tripped breaker, bad connection, or faulted conductor
Intermittent voltage at the load equipment Bad connection or arcing


 

P3 strives to bring you quality relevant industry related news.

See the origial article at:  http://electrical-engineering-portal.com/6-wiring-grounding-problems



 

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