P12x/EN AP/A96
Application Guide
Page 48/80
MiCOM P120/P121/P122/P123
As a consequence, for an open circuit in a particular part of the system, I2/I1 can be
determined from the ratio between the zero sequence and the negative sequence
impedance. It must be noted however, that this ratio may vary depending on the location of
the fault. It is therefore desirable to apply a setting that is as sensitive as possible.
Practically, the levels of standing negative phase sequence current present on the system
guide the choice of this minimum setting. A system study, or the use of measurement data of
the relay during commissioning stage are two ways to determine this minimum setting. If the
latter method is chosen, it is important to take measurements during maximum load
conditions, to be sure that all single phase loads are taken into account.
When sensitive settings are used, it is probable that the element will operate for any
unbalance condition occurring on the system (for example, during a single pole autoreclose
cycle). Therefore, a long time delay is necessary to ensure co-ordination with other
protective devices. It is common to set the time delay to 60 seconds.
The setting range of the Broken Conductor feature is described in the following table:
SETTING RANGE
MENU
DEFAULT
SETTING
MIN
MAX
IN STEPS
OF
AUTOMAT. CTRL
Brkn Cond.?
NO
NO
YES
tBC
1
1 s
14 400 s
1 s
RATIO I2/I1
20 %
20 %
100 %
1 %
21.1 Example
of
Setting
The following information comes from a the relay commissioning report;
I
full load
= 500A
I
2
= 50A
Then:
I
2
/I
1
= 50/500 = 0.1
To tolerate some margin and load variations, it is typical to set this value at 200% above this
value: Therefore,
RATIO I2/I1
= 20%
Set
tBC
at 60s to allow short circuits to be cleared by time delayed protections.
Summary of Contents for MiCom P120
Page 1: ...MiCOM P120 P121 P122 P123 Overcurrent Relays Version 11 Technical Guide P12X EN T A96...
Page 2: ......
Page 4: ...P12x EN T A96 Technical Guide Contents Page 2 2 MiCOM P120 P121 P122 P123 BLANK PAGE...
Page 13: ...Introduction P12x EN IT A96 MiCOM P120 P121 P122 P123 INTRODUCTION...
Page 14: ......
Page 16: ...P12x EN IT A96 Introduction Page 2 8 MiCOM P120 P121 P122 P123 BLANK PAGE...
Page 22: ...P12x EN IT A96 Introduction Page 8 8 MiCOM P120 P121 P122 P123 BLANK PAGE...
Page 24: ......
Page 35: ...User Guide P12x EN FT A96 MiCOM P120 P121 P122 P123 USER GUIDE...
Page 36: ......
Page 40: ...P12x EN FT A96 User Guide Page 4 72 MiCOM P120 P121 P122 P123 BLANK PAGE...
Page 108: ...P12x EN FT A96 User Guide Page 72 72 MiCOM P120 P121 P122 P123 BLANK PAGE...
Page 109: ...Menu Content Tables P12x EN HI A96 MiCOM P120 P121 P122 P123 MENU CONTENT TABLES...
Page 110: ......
Page 112: ...P12x EN HI A96 Menu Content Tables Page 2 68 MiCOM P120 P121 P122 P123 BLANK PAGE...
Page 180: ......
Page 221: ...Application Guide P12x EN AP A96 MiCOM P120 P121 P122 P123 APPLICATION GUIDE...
Page 222: ......
Page 226: ...P12x EN AP A96 Application Guide Page 4 80 MiCOM P120 P121 P122 P123 BLANK PAGE...
Page 302: ...P12x EN AP A96 Application Guide Page 80 80 MiCOM P120 P121 P122 P123 BLANK PAGE...
Page 304: ......
Page 306: ......
Page 368: ......
Page 370: ...P12x EN CT A96 Communications COURIER DATABASE Page 2 248 MiCOM P120 P121 P122 P123 BLANK PAGE...
Page 514: ...P12x EN CT A96 Communications COURIER DATABASE Page 146 248 MiCOM P120 P121 P122 P123...
Page 516: ......
Page 518: ...P12x EN CT A96 Communications IIEC 60870 5 103 Page 2 248 MiCOM P120 P121 P122 P123 BLANK PAGE...
Page 536: ...P12x EN CT A96 Communications IEC 60870 5 103 Page 20 248 MiCOM P120 P121 P122 P123...
Page 538: ......
Page 540: ...P12x EN CT A96 Communications DNP 3 0 Database Page 2 248 MiCOM P120 P121 P122 P123 BLANK PAGE...
Page 554: ......
Page 573: ...Connection Diagrams P12x EN CO A96 MiCOM P120 P121 P122 P123 CONNECTION DIAGRAMS...
Page 574: ......
Page 580: ......
Page 582: ...P12x EN RS A96 Commissioning Test Record Sheets Page 2 60 MiCOM P120 P121 P122 P123 BLANK PAGE...
Page 642: ......
Page 667: ......