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What Exactly is a Doble Test?

The Doble test is basically a power factor test performed on transformers to ensure they are functioning correctly. This dissipation testing can also be performed on MV cables and motors.

Some techs use the term as a catchall phrase for a breaker’s timing test using a shunt trip. Doble is actually an 85 year old diagnostic testing equipment manufacturer whose name has become synonymous with this form of testing. The company’s goal is to assist those in the electrical power industry streamline operational improvements and increase performance of electrical equipment.


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Conducting a Doble test is no longer specific to the company name. Another large manufacturer of diagnostic test equipment is Megger. Their line also includes the power factor set.

Doble M4000 M4100 Power Factor Insulation Analyzer

Doble M4000 M4100 Power Factor Insulation Analyzer – high voltage test equipment using sine wave technology for reliability. 

Megger Delta-2000 Power Factor Test Set – offers complete diagnostics in AC insulation for transformers, bushings, breakers and more.  

Related products available for rent from Protec:

Doble F6150 Relay Testing System

Omicron CPC 100 Multi-Functional Primary Test System

Megger CB-100 28V Power Factor Test Set

This electrical test equipment is available for rent, lease, or purchase from Protec Equipment Resources. We are here to help you with your testing equipment needs.

Protec’s Calibration Lab offers accurate and affordable calibration services for all makes and models of electrical test and measurement equipment. Contact us today for a quote.


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