-Bypass/Isolation Switches- Russelectric Builds Two Types: Failsafe & Maintenance

2. -Bypass/Isolation Switches- Russelectric Builds Two Types: Failsafe & Maintenance

3. Bypass switching section ATS switching section(mounted in a draw-out assembly) Benefits and main purpose of a bypass/isolation switch A Bypass/Isolation switch (switch within a switch)… • Power can be maintained to load during ATS failure • and until the ATS is repaired. • Provides a means of bypassing the ATS for maintenance • Unit can be operated as a manual transfer switch until • the automatic portion is serviced and/or repaired

4. Bypass/Isolation Functions Variations on the Theme Russelectric offers the most variations, beginning with 2 major considerations: 1. Bypass feature used mainly for maintenance of the automatic transfer switch portion of the unit (Maintenance bypass) 2. Bypass feature used mainly in emergency situations (Failsafe bypass) • ATS Portion of unit may be open transition or closed • transition, regardless of Maintenance or Failsafe bypass

5. ATS • RTB(D) - Load Break design (Break-Before-Make Bypass) NORM ISOLATE AUTO BPN BPE BPN BPE LOAD EMERGENCY NORMAL Maintenance Bypass(All manufacturers offer this type) Advantages: Disadvantages: • Cannot bypass the ATS portion of the unit to the alternate source. • Can bypass the ATS portion of the unit without disturbing the load • Design relies on both electrical and mechanical interlocking, arguably reducing reliability. (This interlocking cannot be isolated, so unit must be taken completely off line for servicing.) • Routine maintenance on ATS portion of units is • possible with by no • interruption to the load. X

6. Maintenance Bypass design Load Contacts Overlap Bypass Handle Bypass Handle Bypass Handle Load Momentarily Disconnected Load Momentarily Disconnected LOAD BYPASSED TO NORMAL Contacts are electrically interlocked to prevent bypassing to the alternate source, thus connecting normal and emergency sources together. ATS ATS NORM NORM ISOLATE NORM NORM Load Break Contacts Load Break Contacts Load Break Contacts Load Break Contacts Load Break Contacts AUTO AUTO BPN BPE Load Momentarily Disconnected BPN BPE BPN BPN BPE Bypass Handle Bypass Handle Bypass Handle Bypass Handle Bypass Handle Bypass Handle Bypass Handle Bypass Handle Emergency Power Available LOAD LOAD LOAD Switch Bypassed to Emergency LOAD BYPASSED TO NORMAL LOAD BYPASSED TO NORMAL LOAD BYPASSED TO NORMAL EMERGENCY EMERGENCY EMERGENCY NORMAL

7. X Bypass Handle Bypass Handle Bypass Handle Load Momentarily Disconnected Load Momentarily Disconnected LOAD BYPASSED TO NORMAL ATS ATS NORM NORM ISOLATE NORM NORM Load Break Contacts Load Break Contacts Load Break Contacts Load Break Contacts Load Break Contacts AUTO AUTO BPN BPE Load Momentarily Disconnected BPN BPE BPN BPN BPE Bypass Handle Bypass Handle Bypass Handle Bypass Handle Bypass Handle Bypass Handle Bypass Handle Bypass Handle Emergency Power Available LOAD LOAD LOAD Switch Bypassed to Emergency LOAD BYPASSED TO NORMAL LOAD BYPASSED TO NORMAL LOAD BYPASSED TO NORMAL EMERGENCY EMERGENCY EMERGENCY NORMAL

8. Load Contacts Failsafe Bypass Switches(Where simplicity of operation is critical during an emergency condition) Diagram showing a normal operating state.

9. Load Contacts Bypass Handle Failsafe Bypass Switches Bypass operation

10. Load Break Contacts Bypass Handle Failsafe Bypass Switches Bypassing to normal Load Momentarily Disconnected

11. ATS NORM ISOLATE AUTO BPN BPE BPN BPE LOAD EMERGENCY NORMAL Failsafe Bypass Switches Isolating the ATS Portion LOAD BYPASSED TO NORMAL

12. ATS NORM ISOLATE ATS NORM ISOLATE AUTO BPN BPE LOAD BYPASSED TO NORMAL AUTO BPN BPE BPN BPE BPN BPE LOAD EMERGENCY NORMAL LOAD EMERGENCY NORMAL Failsafe Bypass Switches Isolating the ATS Portion LOAD BYPASSED TO NORMAL

13. ATS NORM ISOLATE ATS NORM ISOLATE AUTO BPN BPE LOAD BYPASSED TO NORMAL AUTO BPN BPE BPN BPE BPN BPE LOAD EMERGENCY NORMAL LOAD EMERGENCY NORMAL Failsafe Bypass Switches If the transfer switch portion is bypassed & isolated to normal. If the normal power fails an engine start signal will initiate... LOAD BYPASSED TO NORMAL

14. ATS NORM ISOLATE ATS NORM ISOLATE AUTO BPN BPE LOAD BYPASSED TO NORMAL AUTO BPN BPE BPN BPE BPN BPE LOAD EMERGENCY NORMAL LOAD EMERGENCY NORMAL Failsafe Bypass Switches If the transfer switch portion is bypassed & isolated to normal. if the normal power fails an engine start signal will initiate... LOAD BYPASSED TO NORMAL

15. ATS NORM ISOLATE AUTO BPN BPE BPN BPE LOAD EMERGENCY NORMAL Failsafe Bypass Switches Emergency Power Available LOAD STILL BYPASSED TO NORMAL

16. ATS NORM ISOLATE AUTO BPN BPE BPN BPE LOAD EMERGENCY NORMAL Failsafe Bypass Switches Switch Bypassed to Emergency

17. Failsafe Bypass Switches Should Normal Source return switch can still be racked in…

18. Failsafe Bypass Switches ATS • RTB(D) - Load Break design (Break-Before-Make Bypass) NORM ISOLATE AUTO BPN BPE BPN BPE Should Normal Source return switch can still be racked in… LOAD EMERGENCY NORMAL