Electrical engineers must learn to navigate industry codes and standards while designing battery energy storage systems (BESS)

The Coordinaide protection and coordination assistant software lets you quickly and easily select the optimal protective device (e.g., fuses, VacuFuse® II Self-Resetting Interrupters, TripSaver II Cutout-Mounted Reclosers, Vista® Underground Distribution Switchgear, or IntelliRupter® PulseCloser® Fault Interrupters) to:

• Protect transformers against damaging overcurrents and coordinate with primary- and secondary-side protective devices.  See how S&C's novel Transformer Protection Index (TPI) can be used to determine if the primary fuse will protect against certain types of secondary-side faults, including arcing phase-to-ground secondary-side faults.
• Protect capacitor units against case rupture.
  Protect underground cables from insulation damage due to excessive temperatures.
• Protect overhead conductors from damage due to annealing.
• Confirm the proper operation of protective devices against incident-arc energy curves for various Personal Protective Equipment (PPE) levels.
• Selectively coordinate two or more devices in series to minimize service interruptions.

PowerOutage.us is an ongoing project created to track, record, and aggregate power outages across the United States.
Find out about us on our About page.
Click on a state to see more detailed info.
Data is updated site wide approximately every ten minutes.

Combining a reliable and customizable design with a remote-control display screen featuring a LED bar, the Eaton Ferrups FX UPS provides rugged, IIoT-ready protection for your industrial power infrastructure. The Ferrups FX UPS supports extended runtime applications and can be deployed in harsh power environments where traditional uninterruptible power supply models are susceptible to power surge events. This industrial UPS is a completely updated and revitalized edition that builds upon the decades of proven performance of the legacy Eaton FERRUPS UPS.

Formerly Powerware FERRUPS Tower UPS

The EATON FERRUPS new FX Model delivers proven, ferroresonant battery backup power and scalable runtimes for 911 centers, global military installations, marine vessels and other critical applications. Highly configurable with a wide range of voltages, frequencies, runtimes, power cords and receptacles, the Eaton FERRUPS continually regulates voltage and eliminates harmful harmonic currents.

Calculates the short circuit fault current level of a 3-phase, core type transformer with a Dyn winding connection.

These handy electrical formulas and electronics formulas (AC Ohm's law formulas on front, DC Ohm's law formulas on back) also give you very useful formulas for apparent power, 3-phase apparent power, power factor, reactance, motor sync. generator frequency, 3-phase WYE, 3-phase delta, sine wave values and more!

As you can see on the Ohm's law charts, there's a wide variety of colors encircling the diagram. These colors serve a purpose. You can easily identify resistor band colors by looking at the chart. For instance the color brown in the 1:00 position represents the value of one...and so forth, up to the silver in the 10 minutes to position which represents 10% tolerance - the gold in the 5 minutes to position represents 5% tolerance.

In accordance with the 2015 Electricity Law of Liberia (ELL), LERC is empowered under Section 3.3 to issue Regulations designed to implement the law. Therefore, the Commission prescribed these Regulations:

Electricity Licensing Handbook.pdf - 1166kb

The Electricity Sector of Liberia has been characterized by monopoly of generation, transmission, and distribution services, and there has also been a fusion of roles, where policy, regulation and operation were combined.

Regulatory functions of the energy sector were relegated to the Ministry of Lands, Mines and Energy (MLME), Ministry of Commerce and Industry (MoCI), Liberia Electricity Corporation (LEC), Rural and Renewable Energy Agency (RREA), Liberia Petroleum Refining Company (LPRC), National Oil Company of Liberia (NOCAL), and the Environmental Protection Agency (EPA). State-owned operators including the LEC and micro-utilities have been self-regulating. The result has been high electricity cost and inadequate services, which are major constraints to Liberia’s economic growth and poverty reduction.

To address the situation, the National Energy Policy (NEP) of Liberia was approved in 2009. It provides among others, liberalization of the sector and separation of policy, regulation, and operation.

The National Energy Policy led to the enactment of the 2015 Electricity Law of Liberia (ELL) on October 26, 2015. The ELL provides the legal basis for the establishment of the Liberia Electricity Regulatory Commission (LERC) as the National Regulator. LERC is an independent agency with respect to its budget, management, staffing and the exercise of its duties and authorities as prescribed in Section 13.3 of the Law.

LERC’s function, as regulator, is to issue licenses, approve tariffs, ensure liberalization of the sector, improve service delivery, protect consumers and create a vibrant electricity sector.

Square D OEM QED-2 I-Line Switchboard Components
Single row and double row I-Line interior products
Engineered to help you create high quality, custom switchboard layouts to meet your customers’ unique business needs.

President Joe Biden’s climate agenda is likely to deliver blackouts for millions, according to a North Dakota state assessment of new rules finalized by the Environmental Protection Agency (EPA).

In May, the North Dakota Transmission Authority published a report with the firm Always On Energy Research examining implications of the EPA’s greenhouse gas regulations on the state’s power grid.

The EPA’s strict emissions standards, researchers reported, “is not technologically feasible for lignite-based power generation facilities.” State investigators say the EPA’s Greenhouse Gas Rule, finalized this spring, will force the premature retirement of reliable coal plants so they can be replaced by intermittent, weather-dependent sources such as wind and solar. //

“We determined the closure of lignite-fired powered plants,” they added, “would increase the severity of projected future capacity shortfalls, i.e. rolling blackouts.”

Larry Behrens, the communications director for the energy non-profit Power the Future, called less power and higher energy prices “two guarantees of Joe Biden’s energy failures.”

“Sadly, the threat of blackouts is the logical result of efforts to destroy reliable energy sources in favor of intermittent wind and solar,” Behrens told The Federalist.

The North Dakota state findings corroborate warnings issued by the North American Electric Reliability Corporation’s (NERC) 2024 Summer Reliability Assessment published last month. The Atlanta-based non-profit cautioned that the power grid will face extreme stress under higher-than-average temperatures expected this summer. //

Alex Epstein @AlexEpstein
·
Replying to @AlexEpstein
To function at its potential, AI requires massive amounts of power. E.g., state-of-the-art data centers can require as much electricity as a large nuclear reactor. ["several gigawatts"]
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Alex Epstein @AlexEpstein
·
Electricity demand from US data centers already doubled between 2014 and 2023. Now with the fast growth of energy-hungry AI, demand from data centers could triple from 2.5% to 7.5% of our electricity use by 2030, according to Boston Consulting Group.
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3:17 PM · May 23, 2024

Cross reference between NEMA and IEC schematic diagram symbols

Mecheri, Yacine and Nedjar, Mohamed and Lamure, Alain and Aufray, Maëlenn and Drouet, Christophe Influence of Moisture on the Electrical Properties of XLPE Insulation. (2010) 2010 Annual Report Conference on Electrical Insulation and Dielectric Phenomena (CEIDP) . pp. 1-4. ISSN 0084-9162 //

. The goal of this paper was to investigate the eventual degradation of XLPE insulation under humidity effect by characterization techniques. For this purpose, measurements of dielectric losses factor, relative permittivity, volume resistivity and dielectric strength were performed.

(ii) Preimmersing XLPE insulation in tap water prior to electrical aging at room temperature results in a reduction of more than 50% in the breakdown voltage. The preimmersion increases the moisture content, particularly liquid water at room temperature, resulting in increased degradation. (iii) Preimmersion does not have any effect on the breakdown voltage of cables electrically aged at 70°C or 90°C. (iv) For some aging conditions, the short term breakdown voltages of aged cables give no indication of the number of and times to breakdown of the cables during the electrical aging. (v) Direct voltage is quite sensitive to degradation of XLPE by the combined action of moisture and electric stress. Care must be exercised when dc testing aged cables in service.

We all know that water in an electrical system is bad news. And we do our best to keep it out by specifying waterproof cable and connectors, and following industry best practices for installation and maintenance.

So, what if water does get into a coaxial radio frequency (RF) network? Unfortunately, its presence is not always obvious and its impact can be elusive and difficult to manage. Here are some tips to help you trouble-shoot a persistent moisture problem: //

The presence of direct current (DC) voltage on the line also speeds up the corrosion process if a steady supply of moisture is available. A copper-clad steel center conductor can completely dissolve in less than a day when submerged in water while voltage is applied.

jcdpk
22 posts · Joined 2011

#65 · Sep 10, 2013

Commonly used DC test voltages for AC equipment are:
AC equipment rating DC test voltage
Up to 100 VAC 100 and 250 VDC
440 to 550 VAC 500 and 1000 VDC
2400 VAC 1000 to 2500 VDC
4160 VAC and above 1000 to 5000 VDC (or higher)

So, what is “good” insulation? Since we know that insulation has a high resistance to current flow, “good” insulation must be able to provide a high resistance to current flow and be able to maintain that high resistance over a long period of time. In order to evaluate the quality of the insulation certain standard tests have been developed which provide a reliable indicator to determine what comprises “good” insulation.

There are two tests that the production technician can easily perform using a battery powered megger like the one shown in Figure 29. The first test is the short time or spot reading test and the second test is the one minute test.

The spot reading test
In the spot reading test you simply connect the “earth” lead of the megger to a good ground and the “line” lead to the conductor and operate the megger for a short time, say for 30 seconds or so. If the apparatus you are testing has a very small capacitance, such as a short run of cable, the spot reading is all that is necessary. However most equipment (like electric motors and long runs of electrical cable) is capacitive, so the very first spot reading can be only a rough guide as to how good or how bad the insulation is.
Bear in mind that the temperature and humidity will affect the readings and electrical circuits do not have to read infinity (perfect insulation on the megger scale) for the circuit to be serviceable. The NEMA standard for minimal insulation resistance is: 1 megohm per rated KV plus 1 megohm. What that means is that if you have a 1000 volt circuit, you should have a minimum of 2 megohms to ground for the circuit to be considered safe to energize and operate. If you have a 4000 volt circuit, you need (5 megohms) and if you have a 460 volt circuit, you should have (1-1/2 megohms), and so on. Insulation that is in good condition will normally have 40 - 50 megohms, or more, to ground.

The one minute reading test
The other test is the one minute reading. This method is fairly independent of the influence of temperature. It is based on the current absorption of good insulation compared to the current absorption of moist or contaminated insulation. A characteristic of good insulation is that it will show a continual increase in resistance (which means less leakage current is flowing) over a period of time. The initial test current (called the absorption current) is absorbed by the capacitance of the equipment being tested and then after that, any current flowing is the leakage through the insulation. If the insulation contains much moisture or other contaminants, the absorption current is masked by a high leakage current which stays at a fairly constant value, keeping the resistance low.
The value of the one minute test is that it can give you a better idea as to the condition of the insulation and alert you to a problem even when the spot reading indicates that everything is OK.
For example, let’s say a spot reading on a 460 volt induction motor was 10 megohms, which at first glance is well above the minimum requirement. Now lets assume that the one minute test showed the resistance quickly climbing to 10 megohms and then from there, holding steady for the rest of the 60 seconds. This means that there may be dirt or moisture on the windings. On the other hand, if the reading gradually increases between the 30 and 60 second time interval, then you can be reasonably certain that the windings are in good condition.
The comparison of the 30 second reading to the 60 second reading is called the dielectric absorption ratio (or D.A.R.). The way the ratio is calculated is to divide the 60 second reading by the 30 second reading. Using that method, the chart in Figure 30 will give you an idea of how to determine if the insulation is good.

Insulation

condition

60/30 second

ratio

Poor

Less than 1

Questionable

1.0 - 1.25

Good

1.4 – 1.6

Excellent

Above 1.6*​

*In some cases, with motors, values approximately 20% higher than shown here indicate a dry, brittle winding which will fail under shock conditions or during starts. For preventive maintenance, the motor winding should be cleaned, treated and dried to restore winding flexibility.

Dielectric absorption ratio chart
There is another megger test called the “Ten minute test” which is similar to the one minute test. Because this test requires ten minutes to perform, it is better accomplished by line operated (120 volt) equipment. Essentially the test is performed for ten minutes, the ten minute reading is divided by the one minute reading and the resulting ratio is called the Polarization Index. This test is mostly used on larger equipment that has large capacitance and requires longer time to stabilize the absorption test current. The conclusions drawn from the test are the same as those drawn from the dielectric absorption ratio but the actual ratio values of the polarization index are not the same as for the dielectric absorption chart in Figure 30.
Using the some of the symptoms listed in the “Problem” column of the troubleshooting chart, let’s go through the process that should be followed to perform the tests and develop the solution
Breaker trips free when motor start is attempted.

If the circuit breaker trips free (or trips during normal motor operation) it should not be re-closed and another motor start attempted before testing the motor and the power cables for an insulation failure. If there is a problem, additional starts will just cause further damage.
The symptom of the circuit breaker tripping is always caused by overcurrent; either a phase to phase short circuit or a phase to ground short circuit.

Insulation appears as a bunch of capacitors. Good insulation appears almost constant with voltage. Deteriorated or contaminated insulation megger readings drop as voltage increases. The standard measurement is the dielectric absorption ratio which is the 10 minute divided by the 1 minute reading. Typically a good number is 3-5. Megger tests need a constant (NOT hand cranked) voltage source and take readings after one minute to be valid. And you need to ground (short) for 3 times that time if you've already taken readings once. The DAR test gives hint why. Repeatedly meggering shows an increase no matter what the voltage (even at the same voltage) if the system isn't grounded for 3 times the test interval in between tests.

A lot of guys just stick the megger on there and take less than a 10 second reading. That's not a valid reading but hey all I'm looking for is over 5 megaohms org 100 megaohms as per the current IEEE standard temperature corrected after 1 minute but if in 10 seconds I've already got 20+, I don't need to continue the test. So I do it too but the closer I get to 5 or 100 megaohms the more I start watching the test time to get a by-the-book reading if the test is marginal. So if what I'm doing gets passed on the next guy might think A 10 second reading is valid when it's not...it's just close enough for spot check. As I megger longer the reading will climb, fast at first then slowly eventually. If there is moisture or contamination it will be very erratic. With very accurate readings you can see stair steps as the cracks charge up one at a time. Watching the readings or graphing them can be just as useful as the number.

And you can't "increment" it except for tip up (step bvoltage) tests where DAR is a better test anyways so step voltage tests are unnecessary except by customer request. And ever try measuring each of the three leads on a 6 or 9 lead motor nd wonder why the readings "go up"? I've seen that done too. It also happens when I megger an open frame breaker but again...I'm doing pass fail. Precise readings aren't needed. Hand cranked is OK for that but not for accuracy. Not only that but at one time and cranked megger were $500 and digital battery powered ones were $5000. Now you can get a decent Amprobe (a division of Fluke) or Extech (a division of Flir) for under $200 new and the AEMCs nd Biddle/Megger brands falling in the range of around $300-500 so there is no justification for hand cranked anymore.

As to what is valid, IEEE 43 gives 500 V for everything under 1000 V. Up to 12.5 kV, 1000 V is plenty. So you can just use one of the cheap common meggers to test everything until you get out of motors nd generators and out deep into distribution voltage territory. Up to 600 V, all insulation by ICEA/NEMA/UL is actually tested (megger) to some crazy value like 3 times the rating plus some more so even 150 V insulation (the lowest quality rating that has to be special ordered) is still rated higher than what a megger puts out so there is no reason for true test to use 100 or 250 V, again using a 1 minute reading. Use either a built in timer or your phone to time it.

The exception is VFDs. Following the manufacturer instructions you inside before meggering. But knowing it has blocking in the forward nd reverse voltage directions I sometimes drop to 250 V on a 460 V motor or 100 V on a 230 V motor just so that I can save time on a spot check and megger without unwiring. If the drive/motor fails (shorted) I know I have a bad motor/cable/drive anyway and step two is unwiring it all and running diode tests on the DC and AC busses to test the antiparallel diodes for shorts. So I am not only cheating but directly ignoring manufacturers instructions that tell you that you will destroy a drive by meggering it. There is a voltage that is really close to the AC peak voltage where particularly with SCRs self commutation occurs. Even without voltage on the gates, a high enough voltage on a power semiconductor will cause it to start conducting nd once it starts with some of them, they won't stop until they re damaged or power is removed. Damage with a battery powered megger is probably impossible but it leaves the possibility open and shows a smart customer you don't know what you are doing.

So yeah I'm not surprised at all. First unless you have a special case there is no reason for a 100 or 250 V test. Second if you didn't discharge fully...and I mean shorting it with a ground clamp for 5 minutes or more between tests, you're just seeing residual charges building up as your test gradually looks more like the 10 minute result. I'll bet if you went down in voltage or started over you would continue to see increases. The way a high end meter tests for this is that it measures residual voltage and grounds the leads until it goes away. And you get just ground a little...it takes much longer to drain a capacitor at a very low voltage compared to charging it at a very high voltage where the voltage difference helps speed the process up. //

Active power, P

Active power is expressed in watt (W). Sometimes this power is also called “real power.” This is the power you are actually consuming.

Reactive power, Q

Reactive power is expressed in volt-ampere reactive (var)
This power is stored in components, then released again back to the source through the AC cycle. Capacitors and inductors do this.

Apparent power, S

Apparent power is expressed in volt-ampere (VA)
(RMS voltage times the RMS current). A power supply must be capable to output the full apparent power delivered to a circuit, not just the active power.

When looking at a typical phasor diagram on a meter, it is assumed the current phasors are rotating counter clockwise, with the voltage phasors stationary at their pre-determined locations. For demonstration purposes, Figure 1 is a 4 wire wye configured system, with ABC rotation.  Phase A voltage, or Va, lays on the primary “x” axis at 0° phase shift.  Ia is laying on top of the voltage phasor at 0° as well, indicating unity power factor, or a power factor of 1.  Phase B and C voltages and current pairs are separated by 120 degrees.

When a phase shift between the voltage and current occurs, this is due to reactance on the load, typically in the form of inductance.  This creates a lagging power factor.  When something is referenced as leading or lagging, this is a means of relating the phase relationship of the current waveform to the voltage waveform, and is always with reference to what the current is doing.  ///

quadrants

Wednesday, March 10, 2010
Power

Over the past three weeks ELWA has been hosting a group of people from the US that have been helping to make upgrades to the power system. The team consists of former missionaries, former missionary kids from ELWA, electricians, contractors and even a Liberian who used to work at ELWA but now lives in Philadelphia. In total 9 people traveled out from the US to work with ELWA's 5 electricians and an extra 8-10 ELWA services staff that helped out.

The project consisted of replacing all the transformers on campus so the voltage could be dropped from 7,200 volts to 2,400 on the primary transmission lines. The change was recommended a couple years ago after an electrical engineer analyzed ELWA's system and recommended the voltage be dropped to reduce the high voltage leaking to ground and jumping around insulators. We also installed some new transmission lines and changed our output voltage that the generators produce.