On-Site Circuit Breaker Testing

Substation assets are costly and, particularly in the case of transformers, there is often a very long lead time if a damaged asset needs to be replaced. Effective protection for these vital assets is therefore essential and this is most usually provided by circuit breakers. Modern circuit breakers are very reliable but, like any complex electromechanical device, they are not infallible. In fact, despite the best efforts of the manufacturers, circuit breakers in power applications still have a failure rate of around 0.3 major faults per 100 circuit breaker years (Cigré 2004-2007). That may not sound particularly high but it means that in a distribution system with, say, 350 circuit breakers, one major fault is likely to be experienced, on average, every year.

One of the best ways of minimising the risk of failure is by regularly testing circuit breakers so that actual and incipient problems are detected before they lead to asset damage. There is, however, a problem: circuit breaker testing, and the subsequent generation of reports, can be a complicated and time-consuming processes. This means that testing is often performed less frequently than it should be, creating an increased risk of breaker failure and asset damage. To address this issue, what’s needed is a test set that’s fast and easy to use, able to operate reliably in the electrically noisy environments that are typical of substations, and capable of producing easy-to-interpret reports with a minimum of effort.

Such a test set must be able to perform all the key measurements associated with breaker testing, including timing of main and PIR contacts, coil current, motor current and station voltage, as well as motion monitoring for the mechanism. The information provided by this battery of tests is sufficient to provide a dependable insight into the health of the circuit breaker and to reveal any areas of weakness that might require attention to ensure reliable operation in the future. The same information is also an invaluable aid for maintenance planning, ensuring that breakers are maintained as often as is necessary for reliable operation, but not more often, which would waste money and resources.


circuit breaker testing        circuit breaker testing with Megger EGIL200


A more user-friendly Circuit Breaker Tester is here

It is with these requirements for a more user-friendly test set in mind that Megger has developed its new EGIL200 mid-range circuit breaker analyser. As might be expected of a modern instrument, this incorporates a display screen for settings and results, but it adopts a new approach to set up: all parameters are based on the properties of the circuit breaker rather than on the requirements of the test set inputs, as is typically the case with other instruments.  This change of emphasis makes operation faster and more intuitive as well as minimising the risk of error.

Further benefits are that all key settings are displayed on the welcome screen, thereby eliminating the time-consuming process of hunting through menus and tabs, and that only one set of test connections to the breaker are needed for the full range of tests; no longer is there a need to make different connections for different tests.

The accuracy of results such as pre-insertion resistor contact timing and resistance value can be relied upon even when high levels of electrical noise are present, as the EGIL200 incorporates patented active interference suppression technology, the effectiveness of which has been widely demonstrated. A final aid to fast, convenient operation is one-click report generation, which produces printed results in a format that requires no further analysis and is easy to interpret.

It is, perhaps, sometimes rather tempting to put off circuit breaker testing in favour of tasks that seem less challenging and possibly more urgent.  But when the consequences of a circuit breaker failure are taken into account, it’s not hard to see that time and effort spent on testing these key assets is a very sound investment.  This is especially true with new generation test sets like Megger’s EGIL200 that have been designed from the outset to make breaker testing easier, faster, more reliable and much more convenient.


The NEW Megger EGIL200