TECHNICALLY SPEAKING:

Using Harmonic Filters to Satisfy UtilityPower Quality Regulations

by Christopher Schmidt  regional sales manager / western U.S. & Mexico

Electronic variable-speed drives have contributed greatly to the increased energy efficiency and productivity of many applications in the oil and gas industry. Unfortunately, the increased use of variable-speed drives has also contributed to the electrical pollution of utility power grids. Objectionable levels of electrical pollution caused by variable-speed drive harmonic currents have caused many utilities to enact regulations restricting the amount of harmonic distortion a customer is allowed to inject into the power grid.

Conventional variable-speed drives will not generally satisfy these tougher harmonic regulations without some additional equipment, such as a harmonic filter. The consequences of not satisfying utility requirements can be severe, as illustrated by the example regulations from the Powder River Energy Corporation (PRECorp) below. To help us understand the cause of the utility's concern, the unfiltered charts below show the power quality of a typical variable-speed drive without an input filter or reactor.

Fortunately, disruptive harmonic currents can be lowered to levels that satisfy utility regulations, as illustrated in the filtered charts below. Unico offers filters that reduce total harmonic distortion to less than 12% or 8%.

For more information on harmonic filters or for assistance in complying with utility regulations, please contact us.






PRODUCT WATCH:

Software Option Allows Use of Palm Pilots for Archiving Well Parameters

Unico's newly released Drive Archiver™ software for Palm Pilots and other handheld computers makes managing wells a breeze. With Drive Archiver™, well operators can quickly and easily capture drive settings and crucial operational information while doing their rounds in the field, then communicate that information to field managers back for analysis back at the office. Newly added enhancements include a chart-recorder-type plot that can be used to display rod-pump gearbox torque as a function of time, a circle chart commonly used for displaying motor torque in ESP applications, and an X-Y mode that can display rod-pump load and position in the familiar dynagraph format for analysis.

Drive Archiver™ interrogates the drive over a serial connection and records the values of each setup parameter. Users can create any number of archives and categorize them according to well location or other meaningful criteria. Each archive is time and date stamped. Archived setup values can easily be restored to the drive in the event of a problem, or they can be transferred to another drive to speed the commissioning process.

Drive Archiver™ becomes a powerful tool for monitoring well operation when used in conjunction with the event-logging capabilities of some pump-control programs. In addition to faults and warnings, many applications log an event whenever a pump starts, stops, goes to standby, or whenever there is bridle separation, belt slippage, or a host of other application-specific conditions. This information is continually recorded along with the date and time each event occurred. Drive Archiver™ reads and stores the event history, which can then be transferred to a personal computer for study. It's a handy way to eliminate the guesswork about what happened during the middle of the night.

Drive Archiver™ operates on any handheld running Palm OS 3.5 or later. It works only with drives running Unico's proprietary Embedded System Protocol (ESP), which includes our 2000 series and our 1000 series when used with the 40 MHz controller. Synchronization with a PC requires version 4.0 or later of the HotSync Manager for Windows.

Contact us to learn more about Drive Archiver™.


FEATURE FOCUS:

1110 Series Drives Eliminate the Single-Phase Barrier

Many well locations are served only by single-phase power, making it problematic to operate ordinary three-phase pumping equipment. One option is to have the power utility install a three-phase line, but this can be prohibitively expensive. Installation costs can amount to tens of thousands of dollars per mile. Another alternative is to use a traditional rotary mechanical phase converter. Rotary converters, however, are bulky, inefficient, and costly to maintain. Their most serious flaw, however, is that their imbalanced output leads to premature motor failures.

Imbalanced phase currents directly affect motor life. According to the Institute of Electrical Engineers, a mere 5% imbalance leads to overheating sufficient to reduce overall motor life by 25%. A 10% imbalance reduces motor life another 25%. Traditional phase converters commonly see imbalances in the range of 25% to 30%. Although special equipment can be used to balance rotary converters at a specific load, motors seldom run at constant load due to changing downhole conditions. Hence, the motor is nearly always running with imbalanced current.

Unico's 1110 series provides a superior solid-state solution that overcomes these limitations. The 1110 combines motor control and phase conversion in a single unit that operates standard, off-the-shelf three-phase AC motors up to 100 hp from existing single-phase power lines. Unlike other phase converters, the output of the 1110 is perfectly balanced at all loads and speeds. It is also compact, energy efficient, and provides dedicated variable-speed control for progressing cavity, electric submersible, and sucker-rod pumping applications—something no ordinary phase converter can do.

Contact us to learn more about how the 1110 can be your key to greater productivity.



WHAT'S COMING UP:

In Future Issues...

Look for the following articles in upcoming issues of Oil & Gas Automation Solutions:

A new benchmark for artificial lift energy efficiency
Determining rod-pump fillage without a load cell
Rod force limiting eliminates rod parts on deep wells
Rotaflex maximum pumping capacity increased 33% using novel speed control
Integral dynamic braking option included in new 1105 series drives


Unico, Inc., 3725 Nicholson Rd., P. O. Box 0505, Franksville, WI 53126-0505
262.886.5678 / 262.504.7396 fax
oilgas@unicous.com / unicous.com