ABB Relion® 670 series Transformer protection RET670 Pre-configured

ABB Relion® 670 series Transformer protection RET670 Pre-configured

RET670 provides fast and selective protection, monitoring and control for two- and three-winding transformers, autotransformers, generatortransformer units and shunt reactors. The transformer IED is designed to operate correctly over a wide frequency range in order to accommodate power system frequency variations during disturbances and generator start-up and shut-down. A very fast differential protection function, with automatic CT ratio matching and vector group compensation, makes this IED the ideal solution even for the most demanding applications. Since RET670 has very low requirements on the main CTs, no interposing CTs are required.It is suitable for differential applications with multi-breaker arrangements with up to six restraint CT inputs. The differential protection function is provided with 2nd harmonic and wave-block restraint features to avoid tripping for magnetizing inrush current, and 5th harmonic restraint to avoid tripping for overexcitation. The differential function offers a high sensitivity for low-level internal faults. The unique and innovative sensitive differential protection feature of the RET670 provides the best possible coverage for winding internal turn-to-turn faults, based on wellknown theory of symmetrical components . Low impedance restricted earth-fault protection functions are available as complimentary sensitive and fast main protection against winding earth faults. This function includes a directional zerosequence current criterion for additional security. Additionally a high impedance differential function is available. It can be used as restricted earth fault or, as three functions are included, also as differential protection on autotransformers, as differential protection for a tertiary connected reactor, as T-differential protection for the transformer feeder in a mesh-corner or ring arrangement, as tertiary bus protection and so on. Tripping from Pressure relief/Buchholz and temperature devices can be done through the transformer IED where pulsing, lock-out contact output and so on, is performed. The binary inputs are heavily stabilized against disturbance to prevent incorrect operations at for example, dc system capacitive discharges or DC earth faults.

Distance protection functionality for phase-tophase and/or phase-to-earth faults is available as back-up protection for faults within the transformer and in the connected power system. Versatile phase, earth, positive and zero sequence overcurrent functions, which can optionally be made directional and/or voltage controlled, provide further alternative backup protection. Thermal overload with two timeconstants, volts per hertz, over/under voltage and over/under frequency protection functions are also available. A built-in disturbance and event recorder provides valuable data to the user about status and operation for post-fault disturbance analysis. Breaker failure protection for each transformer breaker allows high speed back-up tripping of surrounding breakers. The transformer IED can also be provided with a full control and interlocking functionality including Synchrocheck function to allow integration of the main and/or a local back-up control. Out of Step function is available to separate power system sections close to electrical centre at occurring out of step. The advanced logic capability, where user logic is prepared with a graphical tool, allows special applications such as automatic opening of disconnectors in multi-breaker arrangements, closing of breaker rings, load transfer logic and so on. The graphical configuration tool ensures simple and fast testing and commissioning. Serial data communication is via optical connections to ensure immunity against disturbances. The wide application flexibility makes this product an excellent choice for both new installations and the refurbishment of existing installations. Six packages have been defined for the following applications: 

• Transformer back-up protection (A10) 

• Voltage control (A25)