Description
The REB670 IED (Intelligent Electronic Device) is designed for the protection and monitoring of busbars, T-connections, and meshed corners from medium to extra high voltage levels in up to six zones. Due to its extensive I/O capability, REB670 protects single, double, and triple busbar with or without transfer bus, double-circuit breaker, or one-and-half circuit breaker arrangements. It provides selective, reliable, and fast fault clearance for all types of internal phase-to-phase and phase-to-earth faults in solidly earthed or low-impedance earthed power systems. It can also handle all internal multi-phase faults in isolated or high-impedance earthed power systems. Relion – Complete confidence Busbar protection REB670 IED belongs to the Relion protection and control product family. The Relion product family offers the widest range of products for the protection, control, measurement, and supervision of power systems. To ensure interoperable and future-proof solutions, Relion products have been designed to implement the core values of the IEC 61850 standard. With Hitachi Energy's leading-edge technology, global application knowledge, and experienced support network, you can be completely confident that your system performs reliably – in any situation.
Application SEMOD121007-5 v7The IED is designed for the selective, reliable and fastdifferential protection of busbars, T-connections andmeshed corners. It can be used for protection of singleand double busbar with or without transfer bus, doublecircuit breaker or one-and-half circuit breaker stations.The IED is applicable for the protection of mediumvoltage (MV), high voltage (HV) and extra high voltage(EHV) installations at a power system frequency of 50Hzor 60Hz. It can detect all types of internal phase-tophase and phase-to-earth faults in solidly earthed or lowimpedance earthed power systems, as well as all internalmulti-phase faults in isolated or high-impedanceearthed power systems. Ordering of VT inputs inside of the busbar protectionIED will allow integration of voltage related functionalitylike under-voltage release, residual over-voltage, powerfunctions, metering and voltage recording during thefaults. However attention shall be given to the fact thatinclusion of VT inputs will reduce number of available CTinputs (in total 24 analogue inputs are the productlimit). Consequently when VT inputs are ordered thebusbar protection IED will be applicable for buses with afewer number of bays. Practically the number ofavailable CT inputs will limit the size of the stationwhich can be protected.
The IED has very low requirements on the main currenttransformers (that is, CTs) and no interposing currenttransformers are necessary. For all applications, it ispossible to include and mix main CTs with 1A and 5Arated secondary current within the same protectionzone. Typically, CTs with up to 10:1 ratio difference canbe used within the same differential protection zone.Adjustment for different main CT ratios is achievednumerically by a parameter setting.
The numerical, low-impedance differential protectionfunction is designed for fast and selective protection forfaults within protected zone. All connected CT inputs areprovided with a restraint feature. The minimum pick-upvalue for the differential current is set to give a suitablesensitivity for all internal faults. The pick-up setting forthe fault current must be less than 80% of the lowestfault current that can occur on the protected bus bars. Ifthe minimum fault current is high enough, the set valueshould be set higher than the maximum load current..This setting is made directly in primary amperes. Theoperating slope for the differential operatingcharacteristic is fixed to 53% in the algorithm.
The fast tripping time (shortest trip time is 5ms) of thelow-impedance differential protection function isespecially advantageous for power system networkswith high fault levels or where fast fault clearance isrequired for power system stability.
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