Eaton Magnum DS Technical Data Manual

Also see for Magnum DS: Instruction leaflet Instruction booklet Instructions Instructional Leaflet

Technical Data Effective: May 1998Page 12TD.44A.01.T.ECutler-Hammer(M) (T) (M)Magnum DSMetal-EnclosedLow-Voltage SwitchgearApplicationTypes of SystemsA. Simple Radialn Simplest and least costlyn Easy to coordinateB. Primary Selective RadialSimilar to simple radial, with addedadvantage of spare primary incomingcable circuit. By switching to sparecircuit, duration of outage from cablefailure is limited.C. Secondary SelectiveNormally operates as two electricallyindependent unit substations, withbus tie breaker (T) open, and withapproximately half of total load oneach bus. In case of failure of eitherprimary incoming circuit, only one busis affected, and opening main breaker(M) on dead bus and closing tiebreaker (T) can promptly restore ser-vice. This operation can be made auto-matic, with duration of outage oneither bus limited to a few seconds.Since the transformers are not con-tinuously paralleled, secondary faultcurrents and breaker applicationare similar to those on radial unitsubstations.If required, and equipped with theappropriate relaying, either trans-former can be removed from serviceand isolated with no interruption ofservice on either bus, by first closingthe tie breaker and then opening theassociated main breaker.Service continuity and substationcapacity can be further improved bysubstituting selector type primaryswitches, shown above in B.D. Spot NetworkThe transformers are paralleledthrough network protectors. In case ofprimary voltage failure, the associatedprotector automatically opens. Theother protector remains closed, andthere is no “dead time” on the bus,even momentarily. When primary volt-age is restored, the protector automati-cally checks for synchronism andrecloses.n Secondary voltage regulation isimproved by paralleled transformersn Secondary fault capability isincreased by paralleled transformers,and the feeder breakers and busbracing must be selected accordinglyn Primary switches are usually selectoror duplex type, so that transformerscan be transferred to alternate livesources, thus shortening duration ofoverloadswww . ElectricalPartManuals . com