BE1-951
Application
8-53
Figure 8-17. Under frequency Load Shed Bus Level Application
BE1-951 (single source sensing can also be used). These schemes are easily customized to meet the user’s
specific requirements.
Bus Level Application:
The following logic was designed to work with the preprogrammed BUS Logic Scheme described in Section
8,
Application.
Referring to Figure 8-17, if sensing voltage is above the inhibit setting, and system frequency below the 81
and 181T setting, UF_TRIP, VO6 will go high. This in turn forces VO3 (UFLO_TRP) high, closing Output
3 contact and tripping the user lockout(s) (86) devices and in turn, tripping the associated breakers. When
the “load condition” that caused the under frequency event has subsided, the system operator/dispatcher
will initiate a remote restoration procedure. A “restoration permissive” from the 951 verifies that the following
conditions are met prior to restoring load:
Conditions:
•
The under frequency trip (81and 181T) is no longer present.
•
The 86UF(s) is/are tripped
•
Sensing voltage is above the predetermined inhibit level.
•
System Frequency is above the predetermined restore level (281 and 381T).
The first two conditions must be met to remove REST_BLK from the 281 and 381T over frequency elements.
Then, with sensing voltage above the inhibit setting of 281 and 381T and the system frequency above the
281 and 381T setting, VO10 (REST_PER) will go high forcing VO4, UFLO_RES high, closing Output 4
contact. As long as these conditions remain unchanged the output 4 contact will remain closed. When the
last 86UF (electrical reset lockout relay) is reset, Input 1, UF_RESTORE will go low, blocking the 281 and
Содержание BE1-951
Страница 157: ...BESTlogic Programmable Logic BE1 951 7 2 Figure 7 1 BESTlogic Function Blocks Courtesy of NationalSwitchgear com...
Страница 238: ...BE1 951 Human Machine Interface 10 5 Figure 10 5 Metering Menu Branch Structure Courtesy of NationalSwitchgear com...
Страница 239: ...10 6 Human Machine Interface BE1 951 Figure 10 6 Reports Menu Branch Structure Courtesy of NationalSwitchgear com...
Страница 270: ...12 2 Installation BE1 951 Figure 12 1 BE1 951 S1 Case Dimensions Courtesy of NationalSwitchgear com...
Страница 274: ...12 6 Installation BE1 951 Figure 12 5 BE1 951 H1 Case Dimensions Courtesy of NationalSwitchgear com...
Страница 283: ...BE1 951 Installation 12 15 Figure 12 16 Typical AC Connections Courtesy of NationalSwitchgear com...
Страница 394: ...A 18 Appendix BE1 951 Figure A 14 Time Characteristic Curve B Very Inverse 99 1376 Courtesy of NationalSwitchgear com...
Страница 396: ...A 20 Appendix BE1 951 Figure A 16 Time Characteristic Curve G Long Inverse 99 1622 Courtesy of NationalSwitchgear com...
Страница 397: ...BE1 951 Appendix A 21 Figure A 17 46 Time Characteristic Curve Courtesy of NationalSwitchgear com...