Disconnecting circuit breakers
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isconnecting Circuit Breaker laximum availability ith minimum footprint Power and productivity for a better world1

Air insulated substations with DCBs give maximum availability with minimum footprint HANS-ERIK OLOVSSON, CARL EJNAR SLVER, RICHARD THOMAS - The development of circuit breakers (CBs) has led to a change of design principle for substations. Previously the substation's design was based on the fact that CBs needed a lot of maintenance and were therefore surrounded by disconnectors (DSs) to enable maintenance without disturbing nearby circuits. With today's CBs having a maintenance interval of 15 years plus, the design principle is more focused on the maintenance of overhead lines, transformers,...

Development in circuit breaker (CB) technology has led to a significant decrease in maintenance and an increase in reli -ability. The maintenance intervals of modern SF6 CBs requir-ing the de-energising of the primary circuit is now 15 years or more. No significant improvements in maintenance require-ments and reliability have been made with open air DS, which during the same period focused on cost reductions by opti-mising production materials. The maintenance interval for the open-air DS's main contacts is in the order of two to six years, depending on user practices and pollution levels...

Design of disconnecting circuit-breakers n a DCB, the normal interrupter contacts also provide the DS function when in an open position. The contact system is similar to that of a normal CB with no extra contacts or linkage system, see Figure 3. The DCB is equipped with silicone rubber insula-tors. These insulators have hydrophobic properties, ie, any water on the surface will form droplets. As a result they have excellent performance in polluted environments and the leakage current across the poles in the open position is minimized. DCBs will significantly reduce maintenance in air...

shown in Figure 9 on page 6. The DCB solution will reduce the switchyard area by more than 40 percent. Outages for an incoming / outgoing bay, due to maintenance on the switch-gear main apparatus are shown in Figure 4 below. Assumed maintenance intervais are in accordance with manufacturera recommendations, ie, 5 years for open air DS and 15 years for CB and DCB. Introduction of the DCB thus reduces the average maintenance outage from 3.1 to 1.2 hours per year. Fault aspects Equipment and apparatus are getting more and more reliable, however faults still happen even though they occur with...

03 If 0X) a 10 aoo}60* ■n ■ i&79 2COQ C 2001 fWBTdl * CB dt CSb+ DSs Figure 7 DutftQt duraUon duo to prlmary faults In tha 400kV&wttchg aa Solution wfth tradmcnai Sb Modinad va raton by ramovhg buabar D8 8c CCD solution 77 m Figura 9 8lno-iin» and layout for132kV traditional CBs and DSa va ma 룛CBa solution

Outages for an incomlng / outgoing bay. due to faults In the swltchgear, are shown In Figure 7 on page G* Failure frequen-cy Input are taken trom Internationa] statlstics sources, such as CIGRE and CEA, which gattier Information from apparatus in service. Slnce the DCB is very simllar to a traditional CB. tailure statistics are assumed to be the same lor CB and DCB. The introduction ot the DCB thus reduces outages by 50 percent. Unplanned outages may De very problematlc and lead to loss of power supply to consumers. whlch is not acceptable "no black-outs ptease". Application of DCB DCBs can...

Example 1 - 420 kV substation in Sweden Svonska Krattnt (SvK), the transmission System operator (TSO) in Sweden. is responsible for the 420 kV and 245 kV Systems in Sweden. The Swedish 420 kV system started In the 1950s, and was real ploneering work since it was the frst system in the world at that voltage level. Today the Swedish 420 kV system consista of about 70 substations, most of whlch are coming to the end of their lire, so SvK now makes a compl௨te renewar (retroflt) of about 3 substations per yoar. Basic principle for renewal of the substations is lo make a complte exchange of ail...

Existing line towers can remain due to low space requirement of DCB. New equipment located beside old substation equipment Old main busbar reused and extended. Location of old equipment. Outage less than one week for whole renewal of S/S. Figure 11 Example of renewal of a Swedish 420 kV transmission substation ABB Circuit Breakers | Disconnecting Circuit Breakers 9

Example 2 - 132 kV substation in Norway The Grytten substation is part of the Norwegian TSO Statnett's rgional grid. The substation was originally built around 1970. The substation was designed in a traditional manner with a double busbar system (Figure 6a and 6b), and a transfer bus (Figure 6c). The large number of disconnectors in the substation, made operational switchovers complicated. Furthermore, periods with reduced service capability occurred since portions of the substation had to be taken out of service to enable the maintenance of the disconnectors. In Statnett's maintenance...

VT VT VT DS ES -^Hl. ES DS -^Hl. ES DS CB CB 132 kV A DS x 3 DS x 3 DS x 3 132 kV B 132 kV C (1>CT DS x 3 DS x 3 DS x 3 DS x 2 tu VT x 3 CB DS DS DS ES x 3 ES ES ES CT ct q> VT SA SA TR TR a. Before refurbishm ES ES 132 kV VT DCB VT DCB DCB DCB DCB DCB DCB ES ES ES ES ES ES CT CT CT (]> CT CT CT Q> VT VT K2> VT VT VT VT SA SA TR TR b. After refurbishment Figure 12 Substation Grytten before and after refurbishments ABB Circuit Breakers | Disconnecting Circuit Breakers 11

Contact us ABB AB High Voltage Products SE-771 80 LUDVIKA, SWEDEN Phone: +46 (0)240 78 20 00 Fax: +46 (0)240 78 36 50 E-Mail: circuit.breaker@se.abb.com www.abb.com www.abb.com/highvoltage Authors Hans-Erik Olovsson ABB Substations Vsters, Sweden hans-erik.olovsson@se.abb.com Carl Ejnar Sࢴlver ABB Power Products Ludvika, Sweden carl-ejnar.solver@se.abb.com ©Copyright 2010 ABB. All rights reserved NOTE! ABB is working continuously to improve the products. We therefore reserve the right to change designs, dimensions and data without prior notice. ~C C 11 "S 2 c X X X X X I Q. C E z ̣ Richard...