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MicroOhmmeters are devices used to measure junction resistance of joined conductors.The resistance of the junction can tell you the internal condition of the joined metals. But how does junction resistance tell you the condition of metal joints? The gaps in joined conductors may accumulate contaminants like moisture, dirt and grease. These contaminants have a higher resistance compared to the conductors. Since they accumulate in between the joined metals, they introduce resistance. Some electrical components that are prone to junction failures are circuit breaker contacts, distribution transformer terminals, switch gears and relays. The conductors in these components carry high current and corrosion or contaminants can severely affect their current carrying capacity.

In selecting a DLRO or microOhmmeter, you must get one that provides ample current to be able to test very low resistance. It should also have various protective measures for safe operation. If you are undecided on what to get, you might want to check out Vanguard microOhmmeters. Some of the popular models are the Vanguard Auto Ohm and Vanguard DMOM. Here is a comparison of the two models to help you decide which tester is suitable for your needs.

Vanguard Auto Ohm 100 Amperes MicroOhmmeter

The Auto Ohm offers basic microOhmmeter functionality which is suitable for most low resistance measurement applications. It can measure the resistance of bus bars, welded joints and other joined metal conductors that do not need a pure DC test current. It also automates testing which saves you time and effort in getting the right testing range. Other features include:

• Can measure resistance from 1 μΩ to 300 mΩ
• Variable output current of 10 Amperes to 100 Amperes
• Stores the last three results in its memory
• Simple to use front panel interface
• Controlled rise and fall of test current
• Comes with the following accessories
  • Potential current assemblies
  • Power cord
  • Ground Cable
  • Carrying Case
  • Manual

Vanguard DMOM-200 200 Amperes True DC MicroOhmmeter

The DMOM-200 is a suitable meter if you are looking for a device for testing sensitive devices like bus differential relay schemes. This tester has an ultra pure DC output which reduces the generation of magnetic transients induced into the circuit breaker's current transformer. The reduction of magnetic transients reduces accidental tripping of the circuit breaker. This tester is also ideal for applications that need a controlled rise and fall rate of the output current. 

• Can measure resistance from 1 μΩ to 5 Ω
• Microprocessor controlled for exceptional accuracy
• Variable output test current or 10 Amperes to 200 Amperes in 1 Ampere increments
• Variable test current rise and fall rate of 5 seconds to 10 seconds
• Automated testing using a sense cable
• Dual Ground option which lets you measure contact resistance with both bushing being grounded.
• Back-lit 128 x 64 pixels LCD screen
• QWERTY Keypad on front panel
• Internal memory than can store 64 readings and 999 test records on an external flash drive
• Built-in thermal printer
• Can be controlled through a PC through an RS232 port for advanced analysis
• Can export test results to a computer in Excel, PDF and XML formats
• Comes with the following accessories:
  • 30-feet test cable set with welding type clamps
  • Case
  • Handspike set

Whether for basic low resistance measurement or for high-powered critical applications, you'll find a Vanguard microOhmmeter suitable for the job. If you want to evaluate the features of the testers first-hand, consider test equipment rental. This way you can determine if the testers operate as expected in real-world applications. This also helps you get a tester that gives the best value for your money. You do not have to waste money buying a meter and later realize that it doesn't meet your needs.

Protec Equipment Resources offers affordable rentals and leasing of test equipment. Aside from microOhmmeters, we also carry various low and high voltage testers to cater to your needs. Some of the brands that we carry include Vanguard, Raytech, ABB, Megger, Doble, Metrel, Fluke and more. Please call us at 1-866-352-5550 for more information about our services and for a rental quote.

If you think about inspecting cable insulation, it would take too much time and effort especially on long installations. To test cable insulation quick and easy, an insulation resistance tester is used. A good insulator should have a very high resistance to current. Exposure to temperature fluctuations, electrical and mechanical stress and weathering can cause the development of microscopic cracks. These crevices can cause contaminants  to seep through the insulator. When this happens, the reliability of insulators decreases which may cause problems like power losses, short circuits, accidental electrocution of personnel and electrical system failure.

If you are looking for a good insulation tester, check out Megger's MIT series. The devices in this product line are the MIT515, MIT525 and the MIT1025. These testers can conduct various tests on insulators like in cables, transformers and motors. They are lightweight, compact and portable which makes them ideal for field testing. They also feature a double case design for extra user protection. These meters are rated CATIV 600 Volts on all terminals and an Ingress Protection 65. Here is a comparison of features of the MIT515, MIT525 and the MIT1025.

Megger MIT515

If you need basic insulation testing, this Megger meter is suitable. It has a variable voltage of 50 Volts to 5 kiloVolts which allows it to measure resistance from 10 kΩ to 10 TΩ. Other features of the MIT515 include:

• Analog and Digital display
• Operation through batteries or through AC mains
• Variable voltage from 50 Volts to 1 kiloVolts at 10 Volts increments
• Variable voltage from 1 kiloVolts to 5 kiloVolts at 25 volts increments
• Measurement of voltage, capacitance, time constant and leakage current
• Automatic insulation resistance, Polarization Index and Dielectric Absorption Ratio testing
• Built-in timer control and display
• 3 milliAmpere test current
• Alarm limit mode
• 3 milliAmpere noise rejection
• 2 percent error guarding 500 kΩ leakage with a 100 MΩ
• Included accessories:
  • Manual CD
  • Power lead
  • 3-meter leadset with medium insulated clips

Megger MIT525

This Megger insulation meter is similar to the MIT515 but with additional features. The MIT525 can conduct automatic Step Voltage, Ramp and Dielectric Discharge tests. It also features a real time clock and PC connectivity through USB and RS232 ports. The PC connectivity allows advanced results analysis using the PowerDB Lite software.

Features:

• Analog and Digital display
• Operation through batteries or through AC mains
• Variable voltage from 50 Volts to 1 kiloVolts at 10 Volts increments
• Variable voltage from 1 kiloVolts to 5 kiloVolts at 25 volts increments
• Measurement of voltage, capacitance, time constant and leakage current
• Automatic Insulation Resistance, Polarization Index, Ramp, Step Voltage, Dielectric Discharge  and Dielectric Absorption Ratio testing
• Built-in timer control and display
• 3 milliAmpere test current
• Measurement of resistance from 10 kΩ to 10 TΩ
• USB and RS232 ports
• Real time clock
• Alarm limit mode
• 3 milliAmpere noise rejection
• 2 percent error guarding 500 kΩ leakage with a 100 MΩ
• Included accessories:
  • Manual CD
  • Power lead
  • 3-meter leadset with medium insulated clips
  • USB cable
  • PowerDB Lite Software

Megger MIT1025

The MIT1025 is like the MIT525 when it comes to features but has a higher test voltage output and a wider range of  resistance measurement.

Features:

• Analog and Digital display
• Operation through batteries or through AC mains
• Variable voltage from 100 Volts to 2.5 kiloVolts at 10 Volts increments
• Variable voltage from 2.5 kiloVolts to 10 kiloVolts at 25 volts increments
• Measurement of voltage, capacitance, time constant and leakage current
• Automatic Insulation Resistance, Polarization Index, Ramp, Step Voltage, Dielectric Discharge  and Dielectric Absorption Ratio testing
• Built-in timer control and display
• 3 milliAmpere test current
• Measurement of resistance from 10 kΩ to 20 TΩ
• USB and RS232 ports
• Real time clock
• Alarm limit mode
• 3 milliAmpere noise rejection
• 2 percent error guarding 500 kΩ leakage with a 100 MΩ
• Included accessories:
  • Manual CD
  • Power lead
  • 3-meter leadset with medium insulated clips
  • 3-meter leadset with large insulated clips
  • USB cable
  • PowerDB Lite Software

This comparison can help you determine the most suitable meter for your testing needs. Choosing the right meter will help you get tasks done easily and also give you the best value for your money.

For your test equipment needs, consider Protec Equipment Resources. You have several options to choose from for equipment acquisition. Rent, lease or buy equipment depending on your needs. Call us today at 1-866-352-5550 for more details.

One of the best methods of testing the current carrying efficiency of conductor junctions is by measuring the junction resistance. Circuit breaker or relay contacts, bus bars and switchgears constantly carry high currents. If the junctions deteriorate, the current carrying efficiency may be reduced and cause several problems like welding of contacts, localized Ohmic heating and eventual component failure.

Winding resistance of transformers is a good indicator of transformer condition. Developing defects like corroded terminal connections, inter coil shorts and core to coil shorts can affect the resistance of the windings. However, you can't just use any Ohmmeter to measure coil resistance of distribution transformers. You must use a device that has enough current to pass through the thick windings and has protective measures to reduce the incidence of inductive kickbacks.

If you are looking for a winding resistance test set, you might want to check out the testers from Raytech. Raytech's WR series are testers that offer accurate measurements and reliable operation. Some of the popular models are the WR50, WR50-2 and WR5012. These testers have almost similar functions and only vary in their measurement range capabilities. Here is a comparison of features of the Raytech WR testers.

Raytech WR50

• Touch screen interface
• Core demagnetization
• Built-in printer
• 3 temperature channels
• Can charge inductive loads up to 1500 Henry
• Emergency discharge stop button
• Visual and audio indicators for discharge status
• Variable output current from 5 A to 50 A at 50 Volts
• Weighs 16.8 kg
• Internal storage that can store 2000 measurements
• Can measure resistance from 0.1 μΩ up to 100 Ω
• Fast discharge
• Can be used with the Micro-Jr or Micro-Jr 2
• Comes with the following accessories:
  • 10-meter current leads
  • 10-meter potential leads
  • 10-meter safety ground
  • Micro-Jr connection

Raytech WR50-2

• 2 Channel winding resistance meter
• Touch screen interface
• Core demagnetization
• Built-in printer
• 3 temperature channels
• Can charge inductive loads up to 1500 Henry
• Emergency discharge stop button
• Visual and audio indicators for discharge status
• Variable output current from 1 mA to 50 A at 50 Volts
• Weighs 18.8 kg
• Internal storage that can store 10,000 measurements
• Can measure resistance from 0.00 μΩ up to 100 kΩ
• Fast discharge
• Comes with the following accessories:
  • 10-meter current leads
  • 10-meter potential leads
  • 10-meter safety ground
  • USB Cable
  • RS232 Cable

Raytech WR50-12

• 2 Channel winding resistance meter
• Touch screen interface
• Core demagnetization
• Built-in printer
• 3 temperature channels
• Can charge inductive loads up to 1500 Henry
• Emergency discharge stop button
• Visual and audio indicators for discharge status
• Variable output current from 1 mA to 50 A at 50 Volts
• Weighs 18.3 kg
• Large internal storage that can store almost unlimited measurements
• Can measure resistance from 0.05 μΩ up to 100 kΩ
• Comes with the following accessories:
  • 10-meter current leads
  • 10-meter potential leads
  • 10-meter safety ground lead
  • External 1 GB USB drive
  • Stylus

Choosing the right tester depends on the application. For basic winding resistance measurement of up to 100 Ω, choose the Raytech WR50. If you need a winding resistance tester that allows easy PC connectivity through USB or RS232 and can measure resistance up to 100 kΩ, the Raytech WR50-2 is the perfect choice. If you want a lighter device than the WR50-2 and a larger internal storage, get the Raytech WR50-12 model.

Protec Equipment Resources offers various electrical test equipment acquisition options to cater to your needs. You have the option to rent, lease or purchase equipment. We carry a wide range trusted brands like Raytech, Megger, Doble Test Equipment and more. Please do not hesitate to contact one of our specialists today for assistance.

Conductors must have extremely low resistance to efficiently carry current. Conductors especially the junctions are prone to degradation because of the constant exposure to the elements and stress. It is important to carry out tests regularly to ensure that the conductor junctions are in good condition. Corrosion, moisture and mechanical weakening can increase the junction resistance and cause problems like localized heating, power loss and eventual failure. To help measure the resistance of conductors, a DLRO or MicroOhmmeter is used. It measures resistance in a different way compared to your ordinary Ohmmeter. This device has a special Kelvin Bridge input that allows accurate measurement of extremely low resistance without the lead resistance affecting the results. 

Raytech offers a line of MicroOhmmeters that are accurate and lightweight. These are the Micro Jr and Micro Jr II. These DLROs can put out 10 Amperes which allows them to measure resistance from 0.1 μΩ up to 400 kΩ. Here are the other features of these MicroOhmmeters.

Raytech Micro Jr

• Selectable current ranges:
  • 0.001 Ampere
  • 0.01 Ampere
  • 0.1 Ampere
  • 1 Ampere
  • 10 Amperes
• Rugged construction
• Back-lit LCD display
• Microprocessor controlled for automated and accurate operation
• Operates on rechargeable batteries
• Automatic measurement and saving of results
• Continuous measurement mode
• Can calibrate itself
• Internal storage that can store 2,000 results
• Onboard thermal printer
• Auto polarity reversal
• RS232 port
• Parallel port for printer connection
• Optional external attachment to increase output to 100 Amperes
• 4 digits resolution with an accuracy of ±0.1% Rdg
• Device comes with the following accessories:
  • Kelvin probes
  • Power supply cord
  • Lead bag
  • Manual

Raytech Micro Jr II

• Selectable current ranges:
  • 0.001 Ampere
  • 0.01 Ampere
  • 0.1 Ampere
  • 1 Ampere
  • 10 Amperes
• Rugged construction
• Back-lit LCD display
• Microprocessor controlled for automated and accurate operation
• Operates on rechargeable batteries
• Automatic measurement and saving of results
• Continuous measurement mode
• Can calibrate itself
• Internal storage that can store 2,000 results
• Onboard thermal printer
• Auto polarity reversal
• RS232 port
• Optional external attachment to increase output to 100 Amperes
• 5 digits resolution with an accuracy of ±0.1% Rdg
• Device comes with the following accessories:
  • Kelvin probes
  • Ground cable
  • Paper rolls
  • Power Supply
  • Power supply cord
  • Lead bag
  • Manual

Raytech offers MicroOhmmeters that are suitable for field and industrial applications. These meters are lightweight, compact and durable enough to tolerate harsh conditions. Knowing the differences of the features will allow you to choose the best tester for the intended application. If you are looking for basic DLRO functionality, consider getting the Raytech Micro Jr. However, if you need a more precise meter with added safety, consider getting the Raytech Micro Jr II. 

For your electrical test equipment needs, consider getting tools from Protec Equipment Resources. You have the option to rent, lease or buy equipment depending on your needs. Our inventory offers equipment ranging from low power multimeters to high voltage testers. We carry a wide selection of equipment from trusted brands like Raytech, GE, ABB, Fluke and Metrel Test Equipment. Please call us at 1-866-352-5550 for assistance in choosing the best equipment acquisition option and for a rental quote. 

Do you want to learn even more about electrical test equipment rental or purchase? Have a question about the rental you just received from us and how to use it? Want direct access and contact with us at all times? Now you can! Follow us on Twitter and now you’ll get it all!

By simply finding us on Twitter (@ProtecEquip) you can ask us any questions you have about your Megger meter, Doble testing device, or any other testing device you have, just send us a tweet. We’ll answer it quickly so that you can get back to the testing, and back to the important project at hand as soon as you can.

But it’s not all just on you, either. When you follow us, you’ll get all the hints and tips that we tweet on a regular basis so that you can get even more out of your testing equipment and devices. No one should go into electrical work alone, especially if you’re not a professional who does it on a daily basis; and now you don’t have to. Whether you’re an electrician looking to expand your network, or a homeowner that just wants to learn more about testing equipment rentals, connect with us on Twitter and we’ll help you keep your electrical connections in line.
 

A faulty current transformer can cause erroneous readings in metering equipment and also cause protective relays not to trip during an electrical fault. These problems can be a hassle and may result in expensive repairs. Technicians often run various diagnostic tests to determine if the ratio and other transformer parameters are within normal rating.

The Megger CTER-91 1000V CT Test Set is a lightweight and popular diagnostic tester used to test CT parameters. It can perform tests to measure polarity, ratio and saturation on single or multi-tap CT's mounted in transformers and switchgears. It has a variable voltage with a maximum output of 1000 Volts. This Megger meter also gives you the option to freeze the measured readings. It has an integrated Voltmeter that lets you measure external voltages up to 600 Volts AC. It also features a zero-start interlock switch that reduces accidental energizing of the current transformer. This CT test set is housed in a durable molded case for extra protection.

When it comes to reliable equipment rental services, consider Protec Equipment Resources. Our inventory includes a wide selection of electrical test equipment to cater to your needs. Contact a Protec specialist today for more details.

A lot of problems can arise if the power line is plagued with harmonics. Harmonics are often generated by non-linear loads connected to the power line. Some of the common sources are SMPS, ballasts and rectifiers. Correcting power line distortion can be difficult especially if the technician doesn't have an idea of how much distortion and what type is present in the electrical line. That's why technicians use power quality analyzers to measure the type, amount and frequency of distortion in the electrical line. The gathered information allows technicians to plan for an effective electrical line conditioning.

One of the most popular devices used for power quality analysis is the Dranetz PX5. This power quality recorder can measure distortion in three phase power systems. It has 8 channels, four of which are for voltage and the rest for current.  It has a high resolution sampling rate of 256 samples per cycle and can measure THD and TID up to the 63rd harmonic. You have the option to power the device using AC power of through batteries. 

The Dranetz PowerXplorer 5 can be rented from Protec. Do not hesitate to call us at 1-866-352-5550 to request for a rental quote.

Businesses especially some SMEs that have a limited budget often try to find ways to reduce electrical maintenance costs. Keeping the electrical facility in good working condition is very important because the electrical line powers business operations. Whether it's high powered machinery or a simple computer, these devices won't work without electricity. If you are looking for the best way to reduce costs on maintenance, you might want to consider renting electrical test equipment.

Many business owners have discovered the advantage of renting test equipment instead of buying. Since preventive maintenance is done every month or quarter, renting can be significantly cheaper. With the price of one test equipment, you can rent various test equipment for preventive maintenance.

Aside from lower costs, you do not have to worry about where to store the tools after using them or maintaining and calibrating the test equipment. After using the tools, you can pack and ship them back to the test equipment rental provider. 

Protec Equipment Resources is a trusted rental provider. Feel free to contact us for more details about our services and for a rental quotation of the tools you need or leave a comment with any questions you might have for us.

In the past years, cable troubleshooting took a lot of time and effort. This resulted in longer down times, customer inconvenience and loss of revenue. With the advancement of technology, you can now find cable faults in just minutes with the use of a time domain reflectometer. This device works like a radar where it sends out a pulse and measures the time for the echo to return back to the source. 

One of the popular testers technicians use is the Hipotronics TDR1130A Time Domain Reflectometer. This fault locator can be used together with an arc reflection tester to pre-locate and burn-proof cable defects. This cable fault locator allows you to adjust the pulse width from 100 nanoseconds to 20 microseconds. It also has an internal memory that can store 16 cable fault traces which can be retrieved for future reference or comparison. You can use this fault locator in long overhead and even buried cables.

Protec Equipment Resources offers rental, leasing and sales of various electrical test equipment. We stock a wide selection of tools from trusted brands like Hipotronics, Megger, ABB and more. Please contact one of our Protec experts for assistance.

Bad power quality not only reduces the efficiency of the electrical line but also accelerates the deterioration of the equipment attached. Motors, transformers and sensitive electronic equipment are put under severe electrical stress. If the power quality is not corrected, the electrical system and equipment may eventually fail.

Power quality analyzers can help in measuring the type and amount of distortion present in the electrical system. The results are then used to formulate for the optimal conditioning of the power line. One of the popular analyzers today is the Fluke 435 Power Quality Analyzer. This device can measure dips, swells, unbalance, inrush, flicker, harmonics and other forms of power distortion in single and three phase electrical systems. It can simultaneously measure three phases at 200 kS/s on each channel. It lets you use zoom, cursor and other tools for in-depth analysis of test results and trends. It also features Fluke's Unified Power Measurement for calculating the fiscal cost of energy loss due to power quality problems.

Protec Equipment Resources has a wide selection of electrical test equipment to choose from. You can rent, lease of buy tools from us. Contact our Protec experts today for more details.

High current circuit breakers should be checked regularly for contact corrosion, mechanical and coil issues. Due to the high current the contacts carry, the circuit breaker undergoes a lot of electrical stress. If the circuit breaker fails to trip during an electrical fault, you'll be facing a lot of headaches.

One of the popular circuit breaker testers today is the ETI PI-5000 Circuit Breaker Test Set. It is composed of two parts, the PI2500 and AUX-5000 auxiliary unit. These devices can test low-voltage, metal-clad, direct acting, molded case and high power breakers up to 4000 Ampere ratings from various brands. This circuit breaker tester employs silicon controlled rectifiers to switch the test current. This eliminates closing time errors, contact maintenance and precise triggering at zero crossover point. This circuit breaker test set has a serial port for printing or storing test results and an RJ-12 jack for remote control.

If you need electrical test equipment, consider getting them from Protec Equipment Resources. We offer rental services, leasing and equipment sales. Our large selection of tools ensures that you find the equipment you need. Contact us today to learn more about our services.

The electrical system is part of the core of any business. It powers the equipment and machinery that drives the business. If the electrical system unexpectedly fails, you can lose a lot of money and time. This is the importance of regular electrical system maintenance. You can anticipate repairs and prevent unexpected failures. If you spot a defect, you can easily repair it and reduce electrical system down time.

With the expensive price tag of electrical test equipment, a lot of businesses cannot afford to acquire tools for maintenance. This can result in deterioration of the electrical system and higher operation costs. To reduce the cost on maintenance without sacrificing the quality of equipment, you might want to consider test equipment rental. With the price of one tool, you can already have several pieces of test equipment for thorough diagnostics. You also do not need to worry about where to keep them after usage, maintenance and calibration.

Protec is one of the trusted service providers of equipment rental. Browse our wide selection of equipment to find the tools you need. Aside from rental, we also offer equipment sales from popular brands like Megger, High Voltage and more. Contact us for more information.

Transformer faults may not show obvious symptoms until they totally fail. This can result in unexpected service interruptions, high labor costs in repairs and equipment replacement. Technicians often conduct regular testing to find faults that are just starting to develop. It would be easier and would be less expensive to correct a minor defect than repairing equipment that has totally failed.

To help you diagnose internal transformer problems, you might want to check out the Megger FRAX-101 Sweep Frequency Analyzer. This Megger meter analyzes the transformer "fingerprint" and compares it with the baseline data. Any geometrical changes in the transformer like shorted turns, open windings, loose clamps, winding deformation, core issues and faulty grounding causes a change in the transformer "fingerprint". This makes transformer troubleshooting easier because you do not need to untank the core components. This Megger tester helps you save time, money and effort in preventive maintenance of transformers.

Protec Equipment Resources is ready to provide you with the equipment you need for transformer diagnostics. You can opt to rent, lease or purchase equipment depending on your needs. Do not hesitate to contact our specialists today for a quote and for assistance.

Buried utilities like power cables, telecommunication lines and water pipes can be difficult to trace without using the right tools. Exploratory digging can take too much time and a lot of manpower to complete. If you would like a fast and easy way of tracing buried cables and pipes, consider getting the Amprobe AT-3000 Underground Cable Fault Locator.

For engineers who are planning to install new underground installations like cables or pipes, the Amprobe AT-3000 can definitely help. This tester can help in setting the proper distance of the new installation to the existing ones. Accidental hitting of an installation due to digging can result in loss of service, unexpected expenses and delays. 

The Amprobe AT-3000 can measure buried cables and pipes at a depth of 10 feet. Whether the cables are energized or deenergized, this locator can still find them. It also has visual and audio indicators and a sensitivity control. It also has a weatherproof polyethylene case to withstand rough handling.

You can get the AT-3000 and other cable testing equipment at Protec Equipment Resources. You have the option to rent, lease or buy test equipment. Check out our inventory for available test equipment or contact us for assistance.

Renting equipment has helped a lot of businesses reduce the cost of electrical preventive maintenance. How is that possible? Instead of spending several thousands of dollars on a single tool, you can rent electrical test equipment at a fraction of the cost. Test equipment rental also helps reduce the hassle and of owning equipment.

When you rent test equipment, you do not need to worry where to store them after use. You just ship the equipment back to the service provider. Renting also frees you from the headache of maintaining and calibrating the electrical test equipment. All of these are taken care by the service provider.

Protec Equipment Resources is one of the reliable service providers of equipment rental. We have distribution centers that are strategically located to ensure the tools are delivered on time no matter which state you're in. Our inventory also carries a wide selection of tools ranging from multimeters to high voltage hipot testers. The tools are from popular brands like Megger, GE, ABB, Doble, Vanguard and more. 

If you are looking for the best rental plan for your needs, do not hesitate to contact us. Our specialists are ready to assist you in choosing the best option.

When power quality deteriorates, a lot of problems may arise. Some of the common problems are erratic equipment operation, transformer and motor overheating, interference and poor power efficiency. If these problems continue, the electrical system may eventually fail. It is a good idea to regularly measure the power quality of the system to maximize power efficiency and prolong equipment life.

Bad power quality can be corrected by conditioning the electrical facility. A combination of inductors and capacitors are used to suppress the power line distortion. However, the LC combination must be tuned precisely so that it suppresses a certain brand of harmonics. To determine the type and amount of distortion in the electrical line, power quality analyzers are used. One of the popular devices today is the Fluke 1750 Power Quality Analyzer. It lets you measure distortion in three phase systems and automatically records every power quality parameter. You even have the option to store the results in its internal 1 GB storage.

Protec is a trusted source of Fluke Power Test Equipment. Call us today at 1-866-352-5550 for a consultation. Our specialists are ready to assist you in choosing the best test equipment rental option.

Clamp-on/Stakeless Method

This measurement method is innovative and quite unique.  It offers the ability to measure the earth resistance without disconnecting the ground rod under test from the grounding system.  This type of measurement also offers the advantage of including the bonding to ground and the overall grounding connection resistance.

Illustration 1 shows a simplified ground distribution system.  The equivalent circuit is shown in Figure A.  If R₁, R₂, R₃, ... R_n are simplified to R_e, then only R_g and R_eq are left in the circuit (refer to Figure B).  If a constant voltage is applied to the circuit, the following equation is true.

Where

If R_g and R₁, R₂, ... R_n are similar values, and n is a large number (such as 200), then R_eq will be much less than R_g and approaches zero.

R_g>>R_eq (R_eg → 0)

Example:

If R_g and R₁, R₂, ... R_n are all 10 ohms, respectively and n = 200.  Then R_eq by calculation equals

In this example, we can see that as long as the number of multiple electrodes is large enough, the equivalent resistance is negligible with respect to the ground resistance to be measured.

Illustration 1

Since current must flow through the ground, at least two ground rods must be in the circuit.  Caution should also be taken on the placement of the tester.  If ground resistance is to be measured, connections are typically made under the bond point.  In many situations connections above the bond point introduces another wire carrying the measurement current rather than through ground.  Connection above the bond point is useful for measuring bond integrity.  Refer to the illustration 2.

Illustration 2

In certain applications it will be necessary to connect the clamp-on tester above the bond point.  This is common when testing utility pole grounds.  As the illustration shows there may be both a butt plate under the pole and a ground rod.  In this type of circuit, the tester must be placed above the bond so that both grounds are included in the test.

Illustration 3

Protec Equipment Resources both rents and sells clamp-on earth resistance test sets from premier manufacturers like Megger and AEMC.  As always our experienced staff is ready to answer questions and set you up with the right tools for your next job.

Direct Method

When using a four- terminal earth tester, the P1 and C1 terminals connect to the ground rod under test; the P2 and C2 terminals connect to an all-metallic water-pipe system.  If you are using a three-terminal test set, connect the X terminal to the ground rod under test; P and C terminals to the pipe system.  If the water system is extensive (covering a large area), its resistance should only be a fraction of an ohm and will not influence the test results. You can then take the instrument reading as being the resistance of the ground rod under test.

The direct method is the simplest way to make an earth resistance test. With this method, resistance of two electrodes in series is measured – the driven rod and the water system. But there are three important limitations:

1. The water pipe system must be extensive enough to have a negligible resistance.

2. The water pipe system must be metallic throughout, without any insulating couplings or flanges.

3. The earth electrode under test must be far enough away from the water-pipe system to be outside its sphere of influence.

When you need to conduct earth resistance tests, let Protec Equipment Resources assist. We can either rent or sell you a quality test sets from Megger or AEMC.  Our experienced staff will always set you up with the right tools. Do not hesitate to call us at 1-866-352-5550 for assistance.

Fall-of-Potential Method Continued …

Effects of Different Reference Probe Locations

Now, if you read “Earth Resistance Testing – Techniques Part I,” you may ask: if the right location for probe P is always 62 percent of the distance between the ground rod under test and probe C, why bother with all the tests at other locations for probe P? Why not just drive P in at the 62 percent distance and assume that the measured resistance is the correct earth resistance? The following should help answer these questions.

Minimum Distance for Probe C

Consider Illustration 1, which shows earth shells around the ground rod under test and reference probe C. Probe C is so close to the ground rod under test that the earth shells seriously overlap one another.  When these field or shells overlap you don’t get the leveling off of measured resistance as P is moved away from the ground rod under test; the shells of C add to the shells of the ground rod under test so the resistance keeps increasing.

Note:  To obtain an ideal earth resistance curve at least 10 readings should be taken at equally spaced intervals.  True resistance will be obtained where the curve flattens out (typically 62% distance).  Taking readings over greater distances or in different directions from rod 1 will help to confirm results.  If the curve does not flatten the measurements should be retaken using more distance for the C probe placement.

In Illustration 2, C is placed farther away.  Then the measured resistance levels off enough and at the 62 percent distance it is very close to the actual earth resistance. The reason for having C farther away is to get assurance that the 62 percent value is “in line” with other values on the curve. The value could only be wrong (assuming there are no measuring mistakes) if the soil conditions at the 62 percent point vary from conditions at other points, causing changes in earth resistivity. Graded soil around construction sites or buried objects such as pipes can cause such localized deviations. Therefore, you want to get some degree of flatness or leveling off of your curve to make such a variation easily noticeable. At the same time, remember that the resistance will rise again in the electrical field of the current probe, so measurements in this area are to be avoided.

If you need to conduct earth resistance tests, consider renting equipment from Protec Equipment Resources. We carry power quality test sets from Megger and AEMC.  Our experienced staff can set you up with the right tools. Do not hesitate to call us at 1-866-352-5550 for assistance.