Technical library

The fault current is set to 80mA tosimulatethe high current generated at the intermittent earth fault. The zero voltage is set to 20V;theconfiguration ismade in13 states.The fault states and the first two memory states are set to 20ms. The memory states havetimesselected togetthetrip as close to set time 1,2s as possible. In generator configuration,set U4gen to aux voltage DC.Set “Advanced mode” in SVERKER configuration.

Megger has partnered with several rail customers for many decades in developing and supplying test instrumentation to suit Rail applications. We continue to grow our product portfolio to compliment the rail industry and have recently added the Balto product testing range (page 9) to increase our HV breaker testing capabilities. Whether it’s specific test applications such as transformer testing, cable fault finding or more widely used general electrical test instruments, Megger is available to support you with your testing needs.

OTS Test Standards

Gain insight into the different types of oil testing methods, including oil dielectric breakdown testing moisture content testing. This guide covers best practices for oil testing, the correct equipment to use, and the different IEEE/IEC standards to adhere to when testing.

This case study has been generously supplied by the Hitachi Energy Service group in Sweden. A 22 MVA, 10.5 kV/276 V (voltage regulation from 336 to 216 V), Diii furnace transformer, operating in heavy use for many years at a steel melting plant in Europe was subjected to a complete series of tests after a sudden failure during operation. The service contractor evaluated the electrical and dielectric condition of this transformer. During service, this type of transformer has its secondary winding connected externally in a Delta configuration through a high current bridge.

Software update for 'A' models

When unexpected results are experienced in testing the dielectric breakdown of oil samples the cause can often be traced to insufficient attention to one or more of the following key elements of vessel preparation.

A new transformer was tested in the field using Megger’s DELTA4000. This is what was found...

A 1978 vintage, 20 MVA, 69/13.09 kV, Dyn1 transformer, operating for a major North American utility, was taken out of service to repair a pump in the cooling system. The technical maintenance team completed the required repairs and conducted a complete protocol of routine commissioning tests, including a 10 kV line frequency (LF) power factor (PF) test.

Measurement of the outer limits of the operating mechanism is required by international standards such IEEE C37 and as IEC 62271, when certifying a circuit breaker (CB). Some of those tests are valuable to repeat in field tests, obviously to ensure that the CB fulfil its design specification, but those tests and some additional tests in similar spirit can also disclose potential future problems. The most common is to vary the auxiliary voltage but it could also be other energy resources for example hydraulic and pneumatic pressure. This application note will focus of the auxiliary voltage, what the standard requires, sort out the terminology and what tests that are valuable to repeat in field tests.