ABB REX 521 Technical Reference Manual, Standard Configurations

Also see for REX 521: Operator's manual Technical Reference Manual, General Technical Reference Manual, General Operating guide Technical Reference Manual, Standard Configurations

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ABB REX 521 Technical Reference Manual, Standard Configurations Manual pdf 153 page image

1MRS 751802-MUM Protection RelayTechnical Reference Manual, Standard ConfigurationsREX 52115310.2.3.1. Overcurrent protectionThe overcurrent protection can be implemented as described in the secondapplication example (chapter 9.2.).10.2.3.2. Residual voltage protectionOn the busbar, the residual voltage can be measured with a set of voltagetransformers in an open-delta connection.In this example, the directional earth-fault functions are configured to operate asthree-stage residual voltage protection. The directional earth-fault functions includethree protection stages: a low stage Io>->, a high stage Io>>-> andan instantaneous stage Io>>>->. The protection is based on measuring the neutralcurrent Io, the residual voltage Uo and the phase angle between these. In thisapplication example the stages are set to residual protection (Uo).In an isolated network, a three-stage residual overvoltage protection can be used forthe main earth-fault protection of the busbar system and for the back-up protectionof the network. The low stage can be given a sensitive setting and have an alarmingfunction. Note that in this application example the CBFP signal has to be taken outof use for this stage. With the default settings, the CBFP is in use.The high stage can work as back-up for the network and perform trip on the outgoingfeeders. Further, the start signal from the high-set stage can be routed to an outputcontact to release the blocking for the non-directional earth-fault protection stagesof the outgoing feeders (see also application example 8.1. for the outgoing feeder).The instantaneous stage can be configured as busbar protection and provide trip tothe incoming feeder.The settings for the residual voltage protection are made in the settings for thedirectional earth-fault current functions and can be found inMain menu\Protection\Io>->\ … \Io>>>->\.In Main menu\Protection\Io>->\Setting group 1, the operationcriteria is set to “Non.dir.Uo”.10.2.4. ConnectionsAll the necessary settings for the connections and signal routings can be set via theRelay Setting Tool or the local HMI.10.2.4.1. Protection signal routingThe settings for the protection signal routing (except the settings for the earth-faultprotection) can be implemented as described in the second application example(chapter 9.2.).10.2.4.2. Indication and control connectionsThe connections for the indication and the control signals of the circuit breaker andthe disconnector for the incoming feeder can be set as described in the firstapplication example on page 117 onwards. Settings are made via the Relay SettingTool or the local HMI. The settings can be found in: