Commissioning substation busbars
The commissioning procedure of substation busbars for differential protection and other busbar protection schemes involves a large number of input and output circuits that require a verification check in both the primary and secondary circuits.
This large amount of data adds up to electrical parameter measurements which are related to polarity, the transformation ratio, and the identification of the CTs connected to these protections.
It is a necessary and complex task, which requires technical expertise, along with high current injection equipment that provides an accurate and stable output. This test is one of the most time-consuming tasks in the substation testing and commissioning procedure (normally days) and it is essential that test is executed and reported correctly.
This document describes new ways and methods on how this test can be achieved, by using a combination of modern electronically controlled three-phase primary injection equipment, with an accurate and stable output, along with digital three phase relay, that have reading and recording capability.
This document will explain how to save a huge amount of time and completely eliminate the possibility of errors, giving a true and accurate report of the state of busbars.
Three phase testing and commissioning
The three phase testing and commissioning of the secondary protection circuits in Substation busbars is a must to achieve maximum security and insure that all is working correctly before energizing the substation. In many countries this is even a mandatory regulation.
These tests are intended to verify the following:
• Provide the correct correlation between the secondary windings of the CT connection, and the phase identification CT # 1 phase A, which corresponds to phase A in the relay), thus ensuring the correct polarity connection of the secondary protection circuit and the correct angle between phases.
• It verifies that the CT ratio and the ratio introduced in the relay are correct.
This, at the first glance does not seem to be such an issue, but the verification check becomes more complicated when there are a number of single phase or three phase relays connected to each circuit. It is not uncommon to have up to four or six circuits, and in some cases there are up to 10 circuits shared in the same bus bar.
Obviously, there are more tests that should be made, such as, the transition logic sensitivity of the busbar, in each of the CT groups. This has been, up till now, achieved with secondary injection in which the first verification was made using secondary injection equipment and the final verification with primary injection equipment.
Now this can be done with a new three phase testing system as mentioned in this technical article.