Librairie technique Megger

One of the simplest and most common electrical tests performed by electricians and test technicians today is the continuity test. This test option is featured on most multi-meters and insulation testers. The continuity test is simple to perform – connect two leads across opposite ends of the item under test (IUT), press the test button, and the instrument quickly provides a resistance reading. A low reading is considered good and a high reading bad. In fact, this test is so simple that it is often used for applications that actually require a more demanding performance from the test instrument. In this note we’ll look at some of these applications and the resulting requirements that highlight the differences between a low resistance ohmmeter (DLRO) and a digital multi-meter (DMM) – and the importance of using a DLRO to find issues that a DMM cannot.

Winding resistance measurements are conducted for detecting various faults in transformers – including shorted turns, loose connections, broken strands, and malfunctioning tap changer mechanisms. Winding resistance test sets such as the MTO106 are also capable of testing electric rotating machinery – motors and generators. Winding resistance measurements detect problems in a motor that other tests may not find. These problems include partial or fully shorted coils, poor crimps/connections, imbalance between phases (improper turns on a phase), and incorrect coil (phasing) connections. 

Effective earthing is essential for the safe operation of wind farms, but accurately measuring earth resistance at these locations presents multiple challenges. Ahmed El-Rasheed from Megger, explains how Megger and SSE are working together to address these.

A battery string consists of more than just batteries. There are also inter-cell connections, intertier connections and a charger that needs to be tested. There is also the connection between the charger and the battery string that needs to be tested. This is now required in the USA by North American Electric Reliability Corporation (NERC). A new feature has been added to the BITE2 receiver that allows for this measurement. 

   

 

  

Rate Of Change Of Frequency (ROCOF) protection is used in distributed or embedded generation schemes, where a local generator is connected directly to the distribution network, as specified in national standards such as Ansi 81R or G59/3

Check trip on relay with ABB supervision relay

The impedance measurement schemes are widely used for protection of different assets within electric power systems. Relay protection devices utilizing such schemes are benefiting from continuous monitoring of both voltage and current quantities within the protected circuit and the calculated impedance value is employed to determine whether the circuit is operating in a normal condition or not.