Application - GE IBCG51M A Series Instructions Manual

. . . .
, ,
*
Relay
The Type
IBCG
ground fault detectors in a transmission line protective relaying scheme.
The relays contain a time overcurrent unit that is torque controlled by an
instantaneous directional overcurrent unit.
a source of potential, or current, or both sources may be used to dual polarize the
unit.
It is advantageous to use dual polarization because changing system conditions
may cause current polarization to be favored at some times whereas voltage polarization
* might be favored at others.
as compared to polarization from a source of voltage or current alone.
The differences between the various models covered by this instruction book are shown
in Table I.
Inverse
flowing through a given relay is influenced largely by the system generating capacity
at the time of the fault.
used in cases where the fault current magnitude is dependent mainly upon the location
of the fault in relation to the relay, and only slightly or not at all upon the system
generating setup.
maximum fault current flowing.
becomes greater as the current is decreased.
capacity, together with variation in short-circuit-current with fault position, the
operating time with minimum fault current may
time relays and even longer with extremely inverse time relays. For such cases, the
inverse time relay is more applicable.
The operating time of the time overcurrent unit for any given value of current and
tap setting is determined by the time dial setting.
* proportional to the current magnitude as illustrated by the time curves in Figs. 15, 16
and 17. Note that the current values on these curves are given as multiples of the tap
setting.
That is, for a given time dial setting, the time will be the same for 80
amperes on the eight ampere tap as for 50 amperes on the five ampere tap, since in both
cases, the current is ten times setting.
*Indicates Revision
EXTENDED RANGE
Time
Characteristic
Inverse
Inverse
Inverse
Very
Inverse
Very
Inverse
Very Inverse
Extremely Inverse No
Extremely Inverse No
relays are ground directional overcurrent relays that may be used as
Fig. 13 illustrates the effect of using dual polarization
time relays should be used on systems where the fault current
Very inverse time and extremely inverse time relays should be
The reason for this is that relays must be set to be selective with
For fault currents below this value, the operating time
GEK-49822
RELAYS
IBCG
Pickup Range
Inst
Unit Inst.
N 0 5 4
0.5-4, 2-16
Yes 6-150
No
No
Yes

APPLICATION

The directional unit may be polarized from
If there is a wide range in generating
exceedingly long with very inverse
be
The operating time is inversely
4
Int
Conn.
Time
2-16 5
Fig. 6
Fig. 5
Fig. 7
Fig. 6
1.5-12 Fig. 8
1.5-12 Fig. 26