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• I • <br /> ( �� ��Sin� �., � _ � . <br /> t.� _ : <br /> , <br /> ��v :, � ,.�.�; �OFFMAN <br /> : ;: �. � • t-;�. .,: <br /> November i l, 1992 • � w,�,.m <br /> BE&C En�inaers �`""" <br /> Everea Divuuon Mail Sap OF-76 �� <br /> P. O. Boz 3707 �� <br /> SeatUe,WA 981242207 <br /> Attendon: Ma. Sharon Culbenson,Project Engineer �� <br /> wme. <br /> Subjoct: ��pon se W Paa Revicw of Medium Voltage Design � <br /> Fuel Dock Eapaneion F4/FS <br /> Bceing Projact No.EYCs 91245 <br /> BCAd No.911326 j <br /> Dear Sharon: <br /> 7Le following commentn ue Coffmun Engineer's responsc to the pcer review pedortned <br /> by C�uune Eogincering, Inc., of our medium voltage design for the Bceing, Everett, Fu^.1 <br /> Dock Eacpansion, Posidona F4 & FS. A copy of Casne Engineering's rev�e�v comments <br /> ue atuchod for rofaena. <br /> Puagraph 6 on Page 1 of Coane Enginaering's letter dated October l9, 1992, <br /> rofers to SpeciCcaUon 16310, "Secondary Unit Substadons", paragraph 2.11 Dry <br /> Type Two Winding Transformera: <br /> Ilcm d. Casne Recommended 60 kV Basic Impulse I.evel. CEl Response: <br /> Per long-standing Bceing rcquirementa for a 12.47 kV <br /> transfortner, the B.I.L. should be 95 kV. Thia correcdon has <br /> bxn made with the trans[ormer submittal from the menufacwrer. <br /> Item N. Casne Recommended 15 kV Surge Arrestcra.• CEI Reaponae: <br /> 'Ihe transfortner manufacturer ia fumishing: (3) 12 kV nominal <br /> voltege, 10.2 kV MCOV arteclers,w protoct Ihe tranafom►er. 'Ihe <br /> arrostcr's temporory overvoltage capability ia used while <br /> protecting the transformer. The minimum MCOV (maaimum <br /> condnuous operating voltage) for ungrounded circuita is <br /> detertnined by dividing the system voltagc by a 1.23 factor. 'Ilius, <br /> the MCOV for a 12.47 kV syatem would be 10 kV fex� normal � <br /> Juty(line-to-ground Cuult up to 30 minJ For severe duty(line-to- <br /> ground fault up to 20W hours) the MCOV would be detcrtnined <br /> by dividing the system voltagc by a 1.11 fnctor. The aevere <br /> service MCOY would be 11.23 kV. 'I1ie severe dury nting of a <br /> nominal 12 kV armster is 12.7 kV. Thc advuntage of using a 12 <br /> kV arrester instead of a 15 kV urrester from the tranaformer <br /> manufacwrer's standpoint is that the kV crost voltage is � <br /> approaimatcly 1696 less, which relat�s to longer insulation life. � <br /> We therefore concur with the manofacwrer's recommended surge ; <br /> errcster ruting; then:foro, the nominul 12 kV anesters ahould � <br /> remain ns designed. � <br /> � <br /> - --— teu,�,iy�+�«t i..rw�nd tfo w M.,n i��w+..��reo � <br /> ua ime���R t.u+ao i��e«µ�,w�,moi � <br /> Mnh.NSdryw+M01�MA M1711 MN lu NI III SN1 I <br /> rwninnw�«mim <br /> I <br /> � I <br />