Transformer Testing Equipment

Automatic Cap & Tan Delta Test Kit


The M4100 is the industry standard for power apparatus and insulation testing. Its unique combination of test capabilities and artificial intelligence analysis software makes it the power industry’s most trusted Power Factor/Tan-Delta instrument.
These instruments are used around the globe thanks to their comprehensive testing options, safety features and measurement accuracy.


Technical Specification

Sweep Frequency Response Analyzer


Use the Doble M5400 Sweep Frequency Response Analyzer to detect mechanical failure or movement of windings due to short circuits, mechanical stresses or transportation. Sweep Frequency Response Analysis is a proven technique, pioneered by Doble, for making accurate and repeatable measurements. The sweep approach is the industry standard and the preferred method for making frequency domain measurements.


Online Bushing Monitoring

Doble Prime IDD

The unparalleled Doble PRIME IDD Bushing Monitor detects deterioration in bushings, finding abnormalities in the insulation and issuing actionable alerts. Over almost 20 years of successful monitoring Doble has identified two distinct failure modes-rapid onset and graceful decay-and have cases of averting bushing failures in both modes. The Doble PRIME IDD Bushing Monitor provides leakage current, phase and harmonic analyses for up to 12 bushing, measuring parameters for each bushing individually and together. The intelligent device also uses an embedded expert System to provide you with notifications and alarms based on comparisons between off-line and calculated on-line data.



Transformer Turn Ratio Meter

ATRT 01 S3

The ATRT-01 S3 is Vanguard’s fourth generation, micro-processor based, single phase, automatic transformer turns-ratio tester. This portable test unit is available in two models, the ATRT-01 S3 (line power only), and the ATRT-01B S3 (rechargeable-battery powered).

The ATRT-01 S3 uses the IEEE C57.12.90 measuring method to determine the transformer turns-ratio. The transformer turns-ratio is determined by precisely measuring the voltages across the unloaded transformer windings. The ATRT-01 S3’s measuring circuitry self adjusts before each measurement to ensure turns-ratio accuracy. Two selectable test voltages, 4Vac and 40Vac, offer flexibility in testing different types of transformers.


ATRT 03 S2

The ATRT-03 S2 is Vanguard’s third generation, microprocessor-based, automatic, three phase, transformer turns-ratio tester. This lightweight and rugged portable unit is designed for transformer testing at utility power substations.

The ATRT-03 S2 determines the transformer turns-ratio using the IEEE C57.12.90 measurement method. The ATRT-03 S2 outputs an excitation test voltage to the transformer’s primary windings. The induced secondary voltage is sensed and the transformer turns-ratio is calculated. The ATRT-03 S2 can measure turns-ratios from 0.8 to 15,000. The transformer turns-ratio, excitation current, and phase-angle readings are displayed on the large backlit LCD. The built-in transformer type detection feature allows the ATRT-03 S2 to detect and test 130 transformer types defined by ANSI, CEI/IEC and Australian standards.


TRF 250

The TRF-250 is Vanguard’s fourth generation transformer turns ratio tester. This latest design provides a higher turns-ratio test voltage of 250Vac, provides a wireless Bluetooth PC interface, and features a 44-key “QWERTY”-style membrane keyboard. All these features greatly improve the accuracy of the turns ratio readings, ease of operation, and reliability.

The TRF-250 determines the turns ratio of the transformer under test using the IEEE C57.12.90 measurement method. The turns-ratio range is from 0.8 to 50,000 to 1. Transformer turns ratio, excitation current, and winding polarity are displayed on the built-in 128 x 64 pixels graphic LCD screen. The TRF-250 can be used as a standalone unit or can be computer-controlled.


Winding Resistance Meter

TRM 20/40

The TRM-20 and TRM-40 are Vanguard Instruments’ third generation transformer winding resistance meters. The TRM line is designed specifically to measure DC resistance values of transformer windings, rotating machine windings, or any dc resistance of an inductive device.

The TRM line features dual resistance-reading input channels that can measure two winding resistances simultaneously (primary and secondary windings of a

Both the TRM-20 and TRM-40 can provide a fast and stable reading of very large transformers by utilizing a 60Vdc power supply. The TRM-20 is capable of outputting a selectable test current from 1A to 20A while the TRM-40’s test current is selectable from 1A to 40A.


TRM 203/403

The TRM-203 and TRM-403 are three phase transformer winding resistance meters that allow the user to connect all test cables to the transformer bushings. The unit will then measure the transformer resistance value for each of the phases without the need to disconnect and reconnect cables for each phase.

The TRM-203/403 can provide fast and stable readings of very large transformers by utilizing a 60Vdc power supply. The TRM-203 is capable of outputting a selectable test current from 1A to 20A while the TRM-403‘s test current is selectable from 1A to 40A.

Since both units can accurately measure resistance from 1 micro-ohm to 500 Ohms (up to 2000 Ohms for the TRM-203), they can be used as micro-ohmmeters to measure EHV circuit breaker contact resistance, or for any low resistance measuring application.


Continuous on line Monitoring

Prime PD Guard

The doblePRIME PD-Guard™ continuously monitors partial discharge (PD) in equipment such as transformers, rotating machines, cables and switchgear.

The doblePRIME PD-Guard provides local alarms and will communicate data and notifications across standard interface channels and through to networked supervisory systems. It analyzes RF emissions in the HF, VHF and lower UHF ranges.

Install the doblePRIME PD-Guard on critical assets and configure using a computer, tablet or web-enabled device to monitor PD activity.

Designed to fit your monitoring program, the doblePRIME PD-Guard can operate as a standalone partial discharge monitor or as part of a doblePRIME™ Condition Monitoring Platform.



PDS 100

The Doble PDS100 Partial Discharge Surveyor is an RFI surveying tool that is
designed for use in a live substation. Without the need for outages, the PDS100 can detect partial discharge (PD) in just a few seconds, thus making it an ideal tool for a condition based maintenance program. Whole substations can be quickly surveyed and analyzed.


DFA 300

Identify and locate insulation defects with the DFA300, a surveying tool that
combines radio frequency interference (RFI) and acoustic emission (AE). It can detect and locate partial discharge (PD) in a few seconds. Designed for surveying live, high voltage apparatus, its versatility makes it the perfect, multi-purpose tool for condition-based maintenance programs.


Registered Office

114 , 24 – B Raja Bahadur Mansion 2,
Ambalal Doshi Marg, Fort,
Mumbai 400023, Maharashtra

Corporate Office

201,2nd Floor, Sahayog Complex,
Near Delux Crossroads, Nizampura,
Vadodara 390002, Gujarat


Tel: 0265 – 2575343-350