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GEK-2 6423
GROUND DISTANCE RELAY
CEYG51A RELAY
INTRODUCTION
The CEYGSIA is a three phase, high speed, single zone, inho type, directional distance ground relay.
It
consists of three single-phase units in one L2—D case with facilities for testing one unit at a time.
One
target and seal-in unit provides indication of operation for all three distance units.
The transient over
reach characteristic of the CEYG51A relay has not been limited to the point where it is suitable for use as
a first-zone relay.
The relay was specifically designed for use as an overreaching device in directional
comparison and transferred tripping schemes.
Figure 3 shows the internal connections.
APPLICAT ION
The CEYGS1A ground mho relay is applied as the primary ground relay in directional comparison and per
missive overreaching transferred tripping schemes, employing separate primary and separate backup protec
tion.
The ground rnho units of the CEYG51A relay are specifically designed to detect single phase to ground
faults.
To this end they are supplied with quadrature voltage polarization.
Thus, the polarizing voltage
will be quite high and the relay will have a high operating torque level even on very close in line to
ground faults.
For this reason, these units are not provided with memory action.
These ground mho units
will also respond to three phase faults.
If this is objectionable, the relay can be made unresponsive to
any faults not involving ground simply by adding a non-directional zero sequence fault detector.
The ground mho units are provided with separate current circuits for zero sequence current compensa
tion.
A tapped auxiliary current transformer is used to obtain the proper ratio of compensation.
When
zero sequence current compensation is used, the ground niho unit has essentially the same reach on single
phase to ground faults as on three phase faults.
If zero sequence compensation is NOT used, the ground
mho
unit roach is considerably foreshortened on single phase to ground faults.
See Appendix I for the
minimum permissible reach settings under both conditions.
In directional comparison schemes, two CEYG51A relays connected back—to-back are required at each
terminal.
These relays operate in conjunction with a carrier channel to provide high speed protection
against all single phase to ground faults in the protected line section.
One relay acts to stop carrier
and trip for internal faults while the other initiates carrier blocking on external faults.
If zero
sequence current compensation is used on the carrier stopping and tripping units, it should also be used
on the carrier starting units.
This will facilitate the unit settings and insure that both units that
must coordinate will be operating on the same torque level.
In any event, the carrier starting unit
should be set as sensitively as possible.
This will tend to increase security since the presence of a
carrier signal will block tripping.
In permissive overreaching transferred tripping schemes, one CEYG5IA relay is required at each ter
minal.
It acts as a combined transferred trip initiating and a permissive relay for ground faults in the
protected line section.
The choice of whether or not to use sequence current compensation depends upon the protected line
length and system conditions.
When zero sequence current compensation is NOT used, the ground mho unit
reach required may be about 2 to
3 times the positive sequence impedance of the line in order to provide
the proper coverage.
This then tends to make the ground niho unit more sensitive to operation on load con
ditions or on power swings.
The use of zero sequence current compensation reduces the necessary ground
mho unit reach setting to approximately 1.2S times the positive sequence impedance of the line and,
thus,
minimizes its response to load or power swings.
This is true provided there is little or no mutual im
pedance present from a parallel line.
These
h?structlons
do
not
purport
to cover all
details or variations in equipment nor to provide for
evero
pass:nle
contingency
to
be met
an
connection
with installation, operation or maintenance.
Should
fartn-r ;nformation be desired or shouM particular problerrm arise which are not covcrci suffic;enLlq for
tni
purchaser's
r'Jrposes,
the matter should be referred to the General Electric Company.
To the extenL reaured the ;roducL-s described herein meet applicable 7'IS1, IEEE and
.VEM.4
standards;
ut not sicn assurance s 7iven w th respect to local codes and ordnan:esj,ecaue
ti?C5
car
greatly.
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