ALMS Systems – AccuLoss®

  • 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
Model # Voltage Type Current Bushing Type
ALMS 2058 58 kV L – G 2000 A Horizontal
ALMS 4058 58 kV L – G 4000 A Horizontal
ALMS 2100 100 kV L – G 2000 A Vertical
ALMS 4100 100 kV L – G 4000 A Vertical
ALMS 2200 200 kV L – G 2000 A Vertical
ALMS 4200 200 kV L – G 4000 A Vertical
ALMS 4300 300 kV L – G 4000 A Vertical

ALMS Systems Horizontal Horizontal Bushing System


ALMS 2200 & 4058Vertical Bushing System


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.

The AccuLoss® system 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 for systems at and 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 wave form 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 the power generator, which is not part of the loss measurement system, 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.


Current Comparator Technology: The AccuLoss® system Model 2500A High Voltage Dividers use a current-comparator to automatically correct for any drifts or offsets in magnitude and phase. The Two-Stage-Current Transformer in the High Voltage Current Transformer is passive and their accuracy is not affected by age.

Software: The AccuLoss® system utilizes globally recognized and accepted LabVIEW software running on Windows XP. Software can be modified and adapted to fit specific measurement requirements. 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 on each voltage and current channel which is displayed on the measurement menu screens. 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.


Measuring Accuracy: Measuring accuracies are better than any system available on the market today with power measurements accuracies < 0.13 % at power factor of 0.05 and 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 by our highly qualified service personnel as part of the system installation and commissioning.

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 of these two devices is three years.

System Measurements


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. The output of the voltage divider is connected to the input of the wattmeter where the voltage (input/range) is displayed. System input voltage is displayed on the controller screen as RMS or AVG value.

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 years.

For in house calibration, the dividers can be calibrated using the MIL Model 7010A or 7010B High Voltage Capacitance Bridge, two Low Voltage 1000 pF Standard Capacitors and two of the High Voltage Standard Capacitors. Both the High Voltage Standard Capacitors and Voltage Dividers can be calibrated over the full range. Voltage Divider Error -15 -10 -5 0 5 10 15 1 2 5 10 20 50 10.


A current divider consisting of three (3) Model 7020H precision two-stage-compensated-current transformers mounted on horizontal bushings are supplied as part of the current measurement system in each phase. The output and compensation of the Model 7020H is connected to the current input of the Instrument Rack and then directly to the current and compensation input of the Model 2010A Wattmeter.

The ratio of the Model 7020H is 1000:1 for the ALMS 1058 and 2000:1 for the ALMS 2058 and ALMS 4058. The linearity of the 7020H is less than 10 ppm, so measurements as low as one ampere (1 A) can be made with ease. Subsequent current ranging is provided on the Wattmeter 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 7020H’s accuracy is not affected by age. As a result, annual calibration is not necessary. Recommended calibration for the 7020H is every three to 5 years.

The Model 2010A wattmeter 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 wattmeter and the control screen. The two-stage compensated current transformer within the wattmeter reduces the error of the High Voltage Current Transformer by effectively unloading its burden to a < 20 ppm in magnitude and phase.

Power Measurement

Power: The Model 2010A Wattmeters display the power of all three phases at the input to the wattmeter. The sum of the three phases is calculated and displayed on the 17” controller screen. Automatic ranging of the Model 2500A High Voltage Dividers and the Model 2010A Wattmeter 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 Page 4 of 8 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.


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 2010A Wattmeter’s, Line-to-Line Buffer and Industrial Grade CPU Controller are housed in the cabinet.

All connections are made at the rear of the control cabinet. Channels include the three current channels and the three voltage channels. The inputs to the wattmeters are updated every one (1) second. The Controller reads each wattmeter and displays the input voltage and current and calculates the real power, the apparent power and the power factor.

PC/Controller: The AccuLoss® system is controlled and monitored by an industrial grade PC/Controller. The PC comes equipped with a Pentium D CPU with a 2.8 GHz clock speed, 80 GB hard disk, multiple expansion slots and USB ports and a DVD/CD-RW, IDE drive with read/write capability. The keyboard and monitor are external to the control rack where they can be easily placed near the generator control.

Cable Leads: Interconnection cables between the Current Transformer, High Voltage Capacitor and the electronic rack are included. Systems have been installed with cable lead lengths up to 50 meters.

Software Software:

Software for the AccuLoss® Series of loss measurement systems utilizes the globally recognized LabVIEW interface from National Instruments. The software runs in a Windows XP 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 voltage and 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. Software can be modified to meet the specific needs of the User prior to shipment of the system.

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.


Voltage and Current Uncertainty (Vertical Bushings)

Model ALMS 2058 ALMS 4058
Applied Voltage 100 V to 100 kV Line to Line 100 V to 100 kV Line to Line
Accuracy 0.05 % 0.05 %
Ranges 1 kV, 2 kV, 5 kV, 10 kV,
20 kV, 50 kV, 100 kV
1 kV, 2 kV, 5 kV, 10 kV, 20 kV, 50 kV, 100 kV
Applied Current 1 A to 2000 A
(1000:1 ratio)
1 A to 4000 A
(2000:1 ratio)
Accuracy 0.05 % 0.05 %
Ranges ALMS 1058 10 A, 20 A, 40 A, 100 A, 200 A, 400 A, 1000 A 10 A, 20 A, 40 A, 100 A, 200 A, 400 A, 1000 A,
2000 A, 4000  A
Ranges ALMS 2058 10 A, 20 A, 40 A, 100 A, 200 A, 400 A, 1000 A,
2000 A
Safety Clearances
To Adjacent Walls 1 meter 2 meters
Between Phase 1 meter 2 meters
Power Supply
Voltage 100, 120, 220, 240
± 10 %
100, 120, 220, 240
± 10 %
Frequency 50/60 Hz 50/60 Hz
Power 1200 VA 1200 VA
Environmental Conditions
Operating Temperature Control Cabinet: 15° to 30 °C, Bushings and Capacitors: -10° to 40 °C
Storage Temperature -20 to 50 °C
Relative Humidity 30 to 90 % (non condensing)
Statement of Standard Deviation 2 Sigma
(1) 10 to 110 % range utilization, includes uncertainty of calibration
(2) Current measurement has 5 0% over range capability, minimum current is 100 mA with 100 mA option

Voltage(1) Line to Ground

Capacitor                               100 pF, 100 kV                         50 pF, 200 kV

Applied Voltage                   100 V to 100 kV                              200 V to 200 kV

Accuracy                                0.05 %                                              0.05 %

Ranges                                   1 kV to 100 kV                                  2 kV to 200 kv


(1) 10 to 110% range utilization, includes uncertainty of calibration


(1) 10 to 110 % range utilization, includes uncertainty of calibration

Power Uncertainty

Power Factor      Range       Accuracy (2o)*

cos ϕ = 1.000 ≥ 100 V, ≥ 1 A 0.05 %

cos ϕ = 0.100 ≥ 100 V, ≥ 1 A 0.08 %

cos ϕ = 0.050 ≥ 100 V, ≥ 1 A 0.13 %

cos ϕ = 0.020 ≥ 100 V, ≥ 1 A 0.35 %

cos ϕ = 0.010 ≥ 100 V, ≥ 1 A 0.7 %

cos ϕ = 0.008 ≥ 100 V, ≥ 1 A 0.75 %

* Accuracy specifications are calculated for an ambient temperature of 25 °C, }15 °C. Accuracies can
be improved by asking for an accredited calibration. Ask for details.

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