Features and Benefits

The measurement of electric power and energy at high-voltages and currents at low power factors is becoming increasingly important economically as a way to reduce costs in an ever-growing industrial economy. Today the transformer purchaser subjects the transformer manufacturer to an economic penalty for losses that occur in load and no-load conditions. To keep these penalties as low as possible, it is important that the manufacturer accurately measure these losses. Failure to do so can result in the manufacturer losing important contract awards to their competitors who may be utilizing a more accurate system.

Using “State-of-the-Art” proven two-stage-current comparator technology, the AccuLoss® series of transformer loss measurement systems is designed to meet the needs of today’s transformer manufacturer by providing the most accurate power loss measurement system in the world. Designed for power frequency testing and calibration, the AccuLoss® system can be used for testing small, medium and large power transformers as well as motors and turbines up to 400 Hz. The system is also ideal for R&D facilities and can also be used to measure losses in single and three phase reactors.

The AccuLoss® series of transformer loss measurement systems has been accepted and installed by transformer manufacturers around the world and distinguished itself in the rugged transformer manufacturing environment. There are two types of bushings available for the AccuLoss® system, Vertical Loss Measurement System for systems above 58 kV L-N and Horizontal for systems below 58 kV L-N.

The AccuLoss® system includes powerful “operator friendly” software. Included are voltage and current waveform analysis, manual and fully automatic time saving range selection and overvoltage and overcurrent protection.

The AccuLoss® system controller can be directly connected to the plant LAN for transferring data to a host computer for backup and further processing including generating customer reports. As an option, AccuLoss® can be controlled remotely from a separate program running on another computer. This is very helpful in those situations when AccuLoss® has to be controlled automatically and from a different location.

The AccuLoss® system is a complete transformer loss measuring system and is in compliance with the latest standards and specifications dealing with the calibration of test systems to measure transformer losses.

Capabilities

• Performance of Load and No-Load Loss Measurements
• Heat Run Test
• Induced Voltage Test
• Zero Sequence Impedance Measurements
• Manual and Auto-ranging
• Automatic Calculation & Display of Power Measurements

AccuLoss® Features

• Calibration Cycle for CT’s and PT’s:
  In the voltage arm of AccuLoss® the model 2500A Divider uses a two-stage-compensated current comparator to correct for magnitude and phase errors within the divider. As a result, calibration does not drift from year to year. Recommended calibration for the dividers is every three to five years.
  In the current arm of AccuLoss® the model 7020H Two-Stage Current Transformer’s accuracy is not affected by age. As a result, annual calibration is not necessary. Recommended calibration for the 7020H, or 7020H current transformer is recommended every three to five years.
• Software: The AccuLoss® system utilizes globally recognized and accepted LabVIEW software running in a Windows environment. The software can be modified and adapted to fit specific measurement requirements at the time of order. Output data is supplied in an ASCII file format ready to import into an Excel spreadsheet.
• Waveform Analysis: The AccuLoss® systems features a built-in waveform analyzer for extracting harmonics for each voltage and current channel. The waveforms are displayed on the measurement menu screen. The waveform on each channel can be printed.
• Range: Full-scale accuracy can be maintained over the full range of both voltage and current.
• Shielded Control Cabinet: The control cabinet houses the electronics and is shielded against outside interference and is protected against impulse surges through the input and ground connections.
• Automatic Test Procedure: Maximizes transformer throughput with increased accuracy and minimal operator involvement.
• Communication: IEEE-488 communication interface.

Benefits

• Measuring Accuracy: Measuring accuracies are better than any system available on the market today with voltage and current measurements < 0.05 %. All accuracy specifications are stated as 2 sigma.
• ROI/Payback: High accuracy first time measurements maximize testing time and production throughput resulting in a shorter payback period, increased ROI and lower operating cost.
• Quality/Reliability: AccuLoss® system components are designed and tested to stringent quality control standards ensuring exceptional reliability and years of trouble free operation in the rugged transformer test environment.
• Operator Training: Operators can be fully trained in all aspects of the system in one to two days.
• Reduced Calibration Cost: Annual calibration of the AccuLoss® system voltage divider and current transformer components is not required reducing future calibration cost and downtime. Recommended calibration is three to five years.

System Measurements

Voltage Arm: A capacitive divider consisting of three (3) shielded gas-filled (SF6) high-voltage-standard capacitors and three model 2500A Voltage Dividers are used for measuring the phase to ground voltage in each phase. The output of the high-voltage standard capacitor is connected to the voltage input of the instrument rack and then directly into the voltage input of the model 2500A Voltage Divider.

In the ALMS 1058 (1000 A) and ALMS 2058 (2000 A) the model 7020H Precision Current Transformer has only one range of 1000:1. In the model ALMS 4058 (4000 A) the range is 2000:1. The linearity of the two-stage compensated current transformer is less than a few ppm, so measurements as low as one ampere (1 A) can be made with ease. Subsequent current ranging is provided in the power analyzer which has 10 current ranges in stages of 5, 2, 1, 0.5, 0.2, 0.1, 0.05, 0.02, 0.01 and 0.005 A.

The model 2020A Power Analyzer uses a multi tapped two stage-compensated CT to perform the switching on its input to measure the current. The current value is displayed on the power analyzer and the control screen. The two-stage compensated CT within the power analyzer reduces the error of the High-Voltage Current Transformer to a few ppm in magnitude and phase.

Power Measurement

The model 2020A Power Analyzer display the power of all three phases at the input to the power analyzer. The sum of the three phases is calculated and displayed on the controller screen. Automatic ranging of the model 2500A High-Voltage Dividers and the model 2020A Power Analyzer ensures that each component measures in the best range. The values are calculated and displayed with 5-digit numbers on the screen.

Accuracy and Uncertainty: The maximum power measurement accuracy and uncertainty of the AccuLoss® series of loss measurement systems is shown below as a function of power factor. This accuracy can further be improved by asking for a National Measurement Institute (NMI) calibration of the components. An optional system calibration is also available.

Software and Hardware

The AccuLoss® series of Loss Measurement Systems utilizes the globally recognized LabVIEW interface from National Instruments. The software runs in a Windows operating environment and is fast, easy and intuitive. Large buttons on the main screen are used to insure correct settings for the measurements. All measurement data is displayed on the measurement screen as well as waveforms for the three voltage and three current channels. Measurement data is stored to an ASCII file which can be exported over the ethernet to a main computer for analyzing and producing calibration reports.

The software can be modified to meet the specific needs of the user prior to shipment of the system.

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Main Menu Screen

Main Screen: The Main screen provides easily recognized icons for entry into the UUT Data, Test GPIB and Calibration data entry screens. Test configuration selectors are also available.

The Main Menu Screen is divided into four (4) sections:

1. UUT Data [F6]
2. Test Configurations [slide selectors]
3. Continue [F1] (move onto the Measurement screen)
4. Test GPIB [F3] (permits testing of the IEEE-488 communications interface between each of the individual components)
5. Calibrate Menu [F7]

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Measurement Screen

The Measurement Screen allows the operator to quickly review the measurement data. Included on this screen is the Hold [F6] and Save button for saving the data to an ASCII file. The Hold and Save button toggle back and forth depending on which is selected. Each phase is distinguished by different colours making the screen data easier to view and monitor. Large green displays are used to display the combined power, voltage and current. The large screens can also be used to monitor the generator voltage adjustments.

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Waveform Analyzer Screen

Scrolling down to the bottom of the screen reveals the Waveform Analyzer showing the waveforms for both current and voltage on all three phases including even and odd harmonics up to the 25th harmonic. These waveforms can also be printed at the time of measurement.

The Measurement Screen displays are updated every one second. The controller reads each power analyzer and displays the input voltage and current and calculates the real power, the apparent power and the power factor.

Hardware

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Control Cabinet: The control cabinet houses the electronics and is protected against impulse through the input and ground connections.

The model 2500A Voltage Dividers, model 2020A Power Analyzers, a Line-to-Line buffer and Industrial Grade PC Controller are housed in the cabinet. The three current transformer and three high voltage capacitor connections are made at the rear of the control cabinet. A printer, keyboard and monitor port is also available on the rear panel.