The following chart includes the values generated for a three-phase balanced offline-meter test into an SEL-351 relay using a Megger Test-Set or RTS.

Test-Set
Relay Magnitude Angle
Voltage Channel V1 VA 69.28V 0°
Voltage Channel V2 VB 69.28V 120°
Voltage Channel V3 VC 69.28V 240°
Current Channel I1 IA 1.000A 0°
Current Channel I2 IB 1.000A 120°
Current Channel I3 IC 1.000A 240°

The relay is connected to 300:5 CTs and 35:1 PTs. Is everything correct in the following meter test?

Here’s what we know so far:

• The metering results aren’t zero, which means the relay’s analog to digital converters are working.
• The CT and PT ratio settings in the relay are correct (notice that we don’t need to look at the actual settings to determine this). We’re injecting 1A in all three phases and the relay is reporting approximately 60A. The worst-case accuracy is -0.355% error, which is consistent with the 60:1 CT ratio. The relay is reporting approximately 2.42kV in all three-phases with a maximum percent error of -.07%, which matches the PT ratio.
  • The relay is looking in the correct direction because the currents and voltages are in-phase.
  • We are injecting A-B-C, or 1-2-3, rotation because the following pattern exists in the relay and test-set: A-Phase is 0°, B-Phase lags A-Phase by 120°, and C-Phase lags A-Phase by 240°.
  • The relay is programmed with the WRONG phase rotation because the sequence components show 0% positive sequence, 100% negative sequence, and 0% zero-sequence.

Understanding phase rotation is vital when connecting two systems together because the results can be catastrophic if someone doesn’t understand how to interpret phase rotation drawings. You would think something as important as phase rotation would have consistent terms across the entire industry. Unfortunately, you’d be wrong. //

You can’t determine phase rotation with a phasor diagram unless you know the one universal rule in the relay testing world. ALL PHASORS ROTATE COUNTER-CLOCKWISE. //

If you want to be sure you understand phase rotation correctly, put your finger anywhere on the phasor diagram and imagine that the phasors are spinning counter-clockwise. Start paying attention when your reference phasor crosses your finger. Which phasor crosses your finger next? Which is the last phasor to cross your finger?

Here are five additional reasons why generators fail

Established in in 1985, Blackstone Laboratories strives to provide an easy-to-use, understandable, fast, and accurate oil analysis program.

At the heart of our program is ICP (inductive coupled plasma) spectrometry, database averages for comparing wear, and a comments section on each report that explains — in plain English! — what your results mean.

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After over 60 years of service, the James River Power Station (JRPS) is officially being retired. The decision to retire JRPS was based on escalating costs for compliance upgrades, aging infrastructure, and the availability of reliable renewable resources.

To decommission the power station, steps will be taken to dismantle or demolish parts of the plant. This work will include some exterior components, the lakeside water intake structure, and removal of the four stacks.

The demolition process will be handled under strict safety and environmental compliance rules. The process will begin mid-September and is expected to conclude in early 2022. Usable areas of the facility, such as the building office space, electrical substation equipment, and two natural gas combustion turbines will remain.

Electrical engineers must concern themselves with power quality issues in buildings and electrical systems. Learn how to mitigate power quality issues in this webcast.

Electrical engineers should understand what power factor correction is, why engineers should correct power factor, the evolution from power factor to true power factor and various power factor correction techniques. The presenter will also examine applications that involve power factor correction in harmonic-rich networks and how it can be used to mitigate flicker. The discussion will conclude by looking at the future of power factor correction by exploring electronic VAR compensation.

When designing backup, standby and emergency power systems for mission critical facilities, there are several considerations beyond NFPA 70: National Electrical Code, NFPA 110: Standard for Emergency and Standby Power Systems and other building code requirements that must be addressed. Electrical engineers must understand the owner’s project requirements for the building’s power systems. Mission critical facilities can include data centers, hospitals, laboratories, semiconductor manufacturing, pharmaceutical and other facilities where interruption of power would have a severe impact on operations and business.

Engineers also need to be mindful of the overall new construction or existing building retrofit process and ensure equipment replacement is coordinated, temporary power strategies are identified and phasing concepts are developed.

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When selecting protection devices, consideration must be given to the prospective short-circuit current (PSC) at the location the device is to be installed in (AS/NZS 3000:2018 clause 2.5.4.1). The PSC can be determined by measurement or by calculation. Many multi-function testers are able to measure the PSC.

PSC can also be calculated by undertaking a Live Fault Loop Impedance measurement (in ohms) and dividing the voltage by this measurement.

Example

Voltage tests as 240 volts and the measured fault loop impedance between incoming line and neutral is 0.08.

Max PSC = E/R

240/0.08 = 3000 A or 3kA

Three Phase Supplies
Where there is a three phase supply, the PSC is likely to be between line conductors. In this case, the PSC can be calculated by multiplying the single phase reading by the square root of 3 or 1.73. Therefore in the example above, the PSC would be 3000 x 1.73 = 5190 A or 5.19kA.

To properly sizing the amount of capacitor (kVAR) required to correct the lagging power factor,we must have three (3) important of information below:

• kW (kilowatts)

• Existing Power Factor ( % )

• Desired Power Factor ( % )

From this information,now we can calculate the capacitor size for power factor correction.The formula to calculate the required kVAR is:

Calculation Example :

1 unit air-compressor ( 3 phase 415 VAC ) used an average of 90 kW with an existing power factor of 80%.The desired power factor is 95%. The factor value for this case is 0.421 to raise the power factor from 80% to 95% using table 1.

0.421 x 90 kW = 38 kVAR

In order to calculate power factor correction for your installation, your should follow the steps below: //

At the end of the spreadsheet you will get the calculation of the energy savings for above power factor correction.

I once watched two engineers/technicians argue for two hours about what power definitions should be displayed on a HMI interface. One of them argued that VARs were being EXPORTED during lagging conditions, so a lagging current should be shown as POSITIVE VARS and Power Factor! The other argued that VARs were IMPORTED during lagging conditions, so a lagging current should be shown as NEGATIVE VARs and Power Factor!

I was fairly new to the business and had no skin in the game, so I couldn’t contribute at the time, but I did find both arguments compelling and the whole scene was hilarious. Now that I’ve had some experience, I realize that they were both correct… from their perspectives.

Here’s an excerpt from The Relay Testing Handbook: Generator Relay Protection Testing that should help clarify how Phasor Diagrams can be interpreted differently by electrical workers with different backgrounds, and why you should NEVER plot a phasor on a Power (P-Q) Diagram:

webcast - Schneider

In this Sept. 15, 2021, webcast, several questions were left unanswered. Read the details here
BY GARY GLUCK AND JAMES ALVERS SEPTEMBER 29, 2021

There are 3 major reasons to install a fuel cooler on your tuned PD TD:

Reduced intake diesel temperatures will reduce temperatures inside the motor and consequently EGT temperatures.
There’s a fuel limiting table in the code that limits the injected diesel quantity, depending on the fuel temperature. To keep injection quantity at its maximum you need to keep the fuel under 80ºC. This may sound simple, but under spirited driving or track day situations you’ll easily get fuel temperatures in excess of the 80ºC. During the summer months, I easily see in excess of 90ºC.
Diesel at higher temperatures has less lubrification properties, when compared with cooler diesel.

The 855 Big Cam is regarded as one of the last true variable timing mechanical engines on the heavy duty side before electronics came into play with the N-14. The engine was first introduced in 1976 and mass produced up until 1985. After ’85 the engine was engine was still supplied by Cummins up until 2000, with engineering supersessions from 1988-1991. The Big Cam 855 replaced the Small Cam 855 of the 60s and in fact was the first engine designed to meet the new updated mandates of the Clean Air Act of 1976.

Old school truckers and farmers all loved the Cummins 855 Big Cam because of its simple design and reliability all the while producing some major horsepower and torque to get the job done in the field. The over the road truck application is designed to run for 700,000 before a major overhaul.

Notable aspects of the design is the demand flow cooling system which only cools parts of the engine when needed. This saved energy is this used at the crankshaft to deliver more horsepower to the task at hand. This additional horsepower is what made the engine so popular over the previous smaller cam models. A larger camshaft diameter and larger top stop injectors really pushed up the HP on these engines. Top-Stop Injectors are all mechanical but are designed to using a zero lash setting on the base circle on the cam injector lobe. This zero lash setting became known as the Inner Base Circle or “IBC” and increased fuel flow significantly over the small cam models.

Reaching 400+ HP was now attainable and stable without having to do any performance upgrades to the fuel pump. The drawback to the fuel injection system is the lower 2,200 psi it runs at which negatively affects power to the oil pump, water pump, variable timing system and valve spring pressures. In cold climates the engine can be difficult to start. However this can be remediated with block heaters or oil immersion heaters. Overall, you’re not going to have a whole lot of issues with this classic diesel engine.

Long block 855 Engines (1/2 - 3/4 Assembly) are suitable replacements for existing engines that have experienced catastrophic failure, but the ancillary components are still in good working order. If you spun a bearing, threw a rod through the block or dropped a valve a long block is more cost effective alternative to a more complete option. Check the turbo, fuel pump, manifolds, fuel lines and accessory drive components are undamaged before looking at a long block option. Metal shavings and lack of oil pressure can oftentimes leave unseen damage. Long blocks are a good option for both on-highway and off-highway industrial use. 855 NTC, NTA, NT, NH versions can be built to spec either as an extended long block or long block option to an ESN and CPL Number. Check with your sales representative for lead time and availability for custom engine orders.

This engine has gone through a complete overhaul and has been remanufactured with roughly 90% new Cummins parts 10% aftermarket.

Engine comes complete and includes starter, alternator, flywheel, flywheel housing which ship separately.

Build Sheet and Run Test Video available upon request.

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