GE Multilin L90 Line Differential Relay 9-79 APPLICATION OF SETTINGS 9.2 CURRENT DIFFERENTIAL (87L) SETTINGS99.2.8 DISTRIBUTED BUS PROTECTIONIn some cases, buses of the same substation are located quite far from each other or even separated by the line. In thesecases, it is challenging to apply conventional bus protection because of the CT cable length. In other cases, there are noCTs available on the line side of the line to be protected. Taking full advantage of L90 capability to support up to 4 directly-connected CTs, the relay can be applied to protect both line and buses as shown below. Proper CT/VT modules must beordered for such applications. The varying CT ratios at the breakers can be compensated locally by using the sourcesmechanism and with the CT TAP settings between remote relays. If more than 4 but less than 8 CTs are to be connected tothe L90 at one bus, the 3-terminal system can be applied, provided the user does not exceed a total of 12 CTs.Figure 9ñ2: DISTRIBUTED BUS PROTECTION
