With the increasing emergence of green energy from wind and solar power, the center of gravity within the transformer industry has been slowly shifting from large power transformers to distribution transformers. Simultaneously regulatory bodies, such as the Department of Energy, have introduced new minimum level performance requirements so that design changes are enacted to increase efficiency ratings. “Greener” energy generation will also require “greener” energy distribution. More information on efficiency regulations and the importance of high accuracy loss measurements can be found here.
The demands for higher efficiency designs for distribution transformers means that the testing capabilities need to keep up. Transformer manufacturers require highly accurate loss measurement testing capability, while also allowing a fast throughput for production quality control testing. This includes induced voltage testing, applied voltage testing, partial discharge testing, and winding resistance, turns ratio, and insulation resistance testing.
The solution? ⇒ DTTS – Distribution Transformer Test System
The DTTS allows for a high testing throughput in conformity with IEEE C57.12.90, without compromising quality. This system has been designed to allow fast automated test procedures with minimal manual intervention, avoiding human errors.
DTTS – Distribution Transformer Test System Models:
All models of the DTTS – Distribution Transformer Test System are 3-phase models, capable of testing both dry-type and oil-filled distribution transformers up to 500, 2500, or 5000 kVA. The optional extended lower current and voltage range makes the measurement system ideal for loss measurement testing the new generation of high-efficiency transformers.
- HV: 6 to 36 kV
- LV: 100 V to 2.1 kV, with the option of introducing an intermediary step-up transformer for higher LV voltages up to 9.6 kV
- Typical transformer impedance 2 – 7%
- Standard voltage range: 100 V / √3 to 4200 V / √3
- Extended low voltage range: 5 V / √3 to 100 V / √3
- Standard current range 0.5 to 500 A
- Extended low current range: 0.05 to 0.5 A
DTTS – Main Features & Benefits:
Frequency Converter (Electronic Power Supply)
A state-of-the-art frequency converter front end allows the DTTS – Distribution Transformer Test System to be smaller, quieter, more flexible, and maintenance free compared to a traditional motor generated based system. Testing at any frequency between 50/60 – 200 Hz is possible for induced testing and partial discharge testing using the DDX 9161. The low noise generated by the electronic power supply makes it ideal for highly sensitive PD measurements.
High Accuracy Loss Measurement System
The DTTS – Distribution Transformer Test System is fitted with the TMS 560 loss measurement system. This is based on the TMS 580 Loss Measurement System, known worldwide for its high accuracy loss measurement capability, guaranteeing the most accurate results at low power factor. Highly accurate current transformers and potential transformers, coupled with the use of Yokogawa wattmeters allows for the highest overall power loss measurement accuracy on the market.
- Using the standard WT330 wattmeter, the overall system accuracy can achieve ±0.3% at a power factor of 1, and ±3% at a power factor of 0.01.
- An upgrade to the WT5000 wattmeter provides an overall system accuracy ±0.1% at a power factor of 1, and ±1% at a power factor of 0.05, as well as the capability to accurately measure low current from 0.05 to 0.5 A
- The optional TMS 564 allows for highly accurate loss measurements to be conducted at low voltage range 5 V / √3 to 100 V / √3
It is very important to note that regulatory standards do not qualify power loss measurement based on any single measurement component but require total measurement system uncertainty of less than 3%. The total system uncertainty certification requires the error of all components, including the CTs and PTs, to be taken into consideration. This is what separates the DTTS – Distribution Transformer Test System from other transformer test equipment: a sophisticated system calibration encompassing all components in compliance with regulatory standards. The Haefely High Accuracy Loss Measurement System meets or exceeds even the most demanding applications.
Testing Speed and Efficiency
Time is valuable; once a transformer is ready for final quality testing, the goal is to ship it as soon as possible. This puts focus on the test area efficiency. The target is to test the transformers as quickly as possible. Haefely DTTS systems are fast and easy to use. The DTTS software actively helps the operator to stay on task with the help of pop-up messages and guides. The DTTS inverter-based implementation allows rapid testing and switching between test modes is near instantaneous. Resulting in the shortest testing times in the industry. The continuous duty cycle allows around the clock testing without the need to worry about test equipment cool-down times. The full power rating is always available for load loss and heat run testing. This raises operator confidence and maximizes throughput.
Real Time Regulation of Total Harmonic Distortion (THD) and Symmetry (Phase Balance)
Active harmonic compensation is a specialized control loop between the electronic power supply and the TMS that minimizes Total Harmonic Distortion (THD) while also phase-balancing the output voltages and currents. This advanced feature generates near-distortionless output waveforms—even when testing under highly non-linear load conditions, such as those presented by transformers.
Both domestic and international standards require waveform distortion levels below 5% for compliant measurements. Excessively distorted current waveforms and unbalanced phases can significantly impact loss measurement accuracy, often resulting in artificially high core loss values. The DTTS system’s unique real-time active harmonic compensation corrects for non-linear loads as they occur, delivering optimal waveforms and the most accurate, repeatable loss measurement results.
Semi-Automated Heat Run with Cooling Curve
Performing heat run tests and cooling curve becomes simple when using the Haefely DTTS with the optional Tettex 2293 winding analyzer. Please note that the 2293 is available as part of the mobile test trolley or as a standalone instrument. The integration between the two instruments makes a tedious task simple and automated. All calculations are performed automatically and the data is available for test report inclusion. No more separate spreadsheets, manual data collection, and cooling curve calculations.
Sequence Testing
Another standard feature is automated sequence testing. The DTTS software has the build in sequence testing capability. The software will guide the operator through the step-by-step testing process to determine the zero sequence. No other system on the market is this automated and integrated.
Remote Diagnostics
Over the lifetime on any test equipment service issues will arise. Haefely DTTS system by their design are rugged, redundant and long lasting. In the rare event that a service issue occurs the build remote diagnostic function allows Haefely engineering to quickly diagnose most issues that occur with the system. Downtime is minimized by remote diagnostics.
Low Maintenance Cost
Maintenance is essential for the proper operation of any equipment. It is an ongoing cost over the life of the test equipment. Maintenance requires down time and trained personal to perform. Ideally, these non-productive costs are minimized. The use of an electronic power supply makes the DTTS system virtually maintenance free. Haefely delivers the lowest cost of ownership in the industry!
Intuitive, All-in-One Control Unit and Application Software
Completely automated test sequences can be run from a single computer with all results reported in a single document.
All routine tests are supported by the APSW application software, including:
- Turns ratio
- Winding resistance
- No-load (iron) loss
- Load (copper) loss
- Induced voltage
- Applied voltage
- Heat run
- Partial discharge
Upgradeable to Meet Future Requirements
The DTTS – Distribution Transformer Test System is designed to use minimal footprint on your factory test floor with all equipment being housed in a 9 ft container. If needs change in the future and higher testing capability is required, an upgrade can be conducted by adding the HV compensation container to the top of the existing system, preserving precious test floor space.
DTTS Low Power Test Equipment
Compact, trolley-based system allowing winding resistance, transformer turns ratio, and insulation resistance tests. The WA 2293 Winding Analyzer built into the trolley also allows for the optional heat run test to be conducted. The included laptop with control software allows for easy operation of the tests and sends all data via WIFI to the DTTS Master PC for the generation of automated reports.
Highly Sensitive Partial Discharge Measurements
The low system noise of the frequency converter and active, real-time THD and symmetry control allows the DTTS – Distribution Transformer Test System also to be used for highly sensitive PD measurements, using the DDX 9161 Digital Partial Discharge Detector. Equipped with appropriate low and high-voltage filters and coupling capacitors, sensitive 3-phase PD measurements can be conducted with a system noise level ≤ 5 pC. The DDX 9161 is also capable of measuring Radio Interference Voltage (RIV) according to the latest standards of NEMA and CISPR.
Fully Turnkey Distribution Transformer Test System
The DTTS—Distribution Transformer Test System is highly configurable to allow for maximum testing throughput for all routine tests in a production environment. Depending on the customer’s testing needs, the system can be configured into multiple individual test bays, with centralized controlling and reporting into one single test report. This significantly reduces testing times to a few minutes per distribution transformer.
1 Test Bay with DTTS
Container solution capable of the following tests:
- Induced voltage
- No-load and Load loss measurements
- Partial discharge
- Heat run
2 Test Bays
A) DTTS with applied voltage testing capability and Low Power Test Bay
An independent AC dielectric test set, controlled by the DTTS Master PC, would be used for single phase applied voltage testing and configured next to the DTTS.
The independent Low Power Test Bay would be used for winding resistance, transformer turns ratio, and insulation resistance tests. The included laptop would control all low-power tests and submit the data via WIFI to the DTTS Master PC.
B) DTTS (without applied voltage testing) and Low Power Test Bay
3 Test Bays
Individual test bays with dedicated testing capabilities according to the DTTS Test Bay, Applied Voltage Test Bay, and Low Power Test Bay. All test sequences and data from the Applied Voltage Test Bay and Low Power Test Bay would be transmitted to the DTTS Master PC via WIFI to consolidate ALL TESTS into one single report.