GE STD15C User manual

INSTRUCTIONS 37
WITH
GEK
-
45307
TRANSFORMER
DIFFERENTIAL
RELAYS
PERCENTAGE
AND
HARMONIC
RESTRAINT
TYPES
STD
15
C
AND
STD
16
C
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PHILADELPHIA
.
PA
.
POWER
SYSTEMS
MANAGEMENT
DEPARTMENT
ELECTRIC
GENERAL
Courtesy of NationalSwitchgear.com

GEK-45307
CONTENTS
PAGE
..
....................................................
DESCRIPTION .....................................................
APPLICATION .....................................................
CALCULATION OF SETTINGS .........................................
METHOD ....................................................
CURRENT TRANSFORMER CONNECTIONS ...........................
DETERMINATION OF CT TURNS AND TYPE RELAY TAP SETTING . .
CURRENT TRANSFORMER RATIO ERROR ...........................
PERCENT SLOPE SETTING....................?
..............
I DETERMINATION OF CT TURNS AND RELAY TAP SETTING
.....
11 PERCENT RATIO ERROR ....................................
IA REPEAT-CT TURNS AND RELAY TAP SETTING ..................
IIA REPEAT PERCENT RATIO ERROR ..........................
III PERCENT SLOPE SETTING .................................
RATINGS
.........................................................
AND ..............................
AUXILIARY RELAY CONTROL CIRCUIT ...........................
CHARACTERISTICS ..................................................
PICKUP AND OPERATING TIME .................................
OVERCURRENT UNIT PICKUP ...................................
PERCE N T AGE CHARACTERISTICS
...................
HARMONIC RESTRAINT CHARACTERISTICS ........................
BURDENS .........................................................
CONSTRUCTION. ...................................................
CURRENT TRANSFORMERS ............................................
THROUGH CURRENT RESTRAINT CIRCUIT .........................
DIFFERENTIAL CURRENT CIRCUIT ............................
OVERCURRENT UNIT ..........................................
OPERATING UNIT
.......................................
TARGET AND SEAL-IN UNIT ...................................
CASE
............................................................
RECEIVING, HANDLING, AND STORAGE ................................
ACCEPTANCE TESTS ................................................
VISUAL INSPECTION .........................................
MECHANICAL INSPECTION .....................................
ELECTRICAL TESTS ..........................................
TEST FACILITIES ...........................................
INSTALLATION PROCEDURE...................~ .....................
TESTS .....................................................
PICKUP ....................................................
HARMONIC CURRENT RESTRAINT ................................
THROUGH CURRENT RESTRAINT .................................
INSTANTANEOUS OVERCURRENT UNIT ............................
DROPOUT OF MAIN UNIT ......................................
LOCATION ........................................................
MOUNTING.
.......................................................
.....................................................
ADJUSTMENTS .....................................................
RATIO MATCHING ADJUSTMENT .................................
UNBALANCE CURRENT MEASUREMENT .............................
PERCENT SLOPE SETTING .....................................
OPERATION. ......................................................
TARGETS ...................................................
DISABLING OF TYPE RELAY ...............................
MAINTENANCE .....................................................
CONTACT CLEANING ..........................................
PERIODIC TESTS ..................................................
PICKUP ....................................................
HARMONIC CURRENT RESTRAINT ................................
THROUGH CURRENT RESTRAINT .................................
RENEUAL PARTS ....................................................
15
15
15
15
16
16
16
17
17
17
17
18
i
3
INTRODUCTION
3
3
4
4
4
4
STD
5
6
6
STD
7
7
7
8
8
8
MODELS
12
STD
15
B
12
STD
16
B
8
8
8
9
9
DIFFERENTIAL
9
10
10
10
11
11
11
11
MAIN
12
12
12
12
12
12
13
13
13
13
13
14
14
15
.
15
CONNECTIONS
15
16
16
STD
17
17
2
Courtesy of NationalSwitchgear.com

GEK-45307
TRANSFORMER DIFFERENTIAL RELAYS
PERCENTAGE AND HARMONIC RESTRAINT
AND
INTRODUCTION
Relays of the STD type are transformer differential relays provided with the features of percentage
restraint.
A static decision unit controls a small telephone type relay the
Percentage restraint permits accurate discrimination between internal and external faults high
while harmonic restraint enables the relay to distinguish, by the between
current caused by an internal fault.
and that of transformer Inrush.
DESCRIPTION
Each Type STD relay is a single phase unit. The Type is designed to be used for the
of two-winding power transformers and has two through-current restraint and One
current circuit.
The Type relay is designed for use with three-winding power and has three through
ent restraint circuits and one differential current circuit. It may also be used for four
protection (see Figure 9) when only three circuits require through current restraint, while the
th circuit. being the weakest, needs no through-circuit
APPLICATION
The current transformer ratios and relay taps should be selected to obtain the sensitivity
out
overload of the relay or current or the Of
efor
transformer in the various windings of the power transformer should be
the points in mind:
1.
The lower the relay tap and the lower the CT
the higher will be the sensitivity.
the lowest CT ratio and the lowest relay tap may not be compatible with of the
following restrictions. a choice is available of increasing either the CT Or the
it is desirable to increase the CT ratio in preference to the
Since the relay burden is likely to be small compared to the lead burden. increasing the
ratio tends to improve the relative CT's as a result Of the
secondary fault current and increasing the accuracy of the
The CT should not exceed the continuous thermal rating Of the CT
3. The relay current corresponding to KVA (on a forced cooled should not
twice tap value, the thermal rating of the relay.
4. The CT ratios should be high enough that the secondary currents will not the relay under
internal fault conditions (refer to RATINGS).
5. The relay current corresponding
rated KVA of the power (On Self cooled basis)
should not exceed the relay tap value selected (magnetizing inrush might operate the instantaneous
avercurrent unit). If the transformer under consideration does
not have a
the transformer manufacturer should be consulted for the "equivalent self-cooled rating that is
the rating of a self-cooled transformer that would have the
same magnetizing inrush
as the transformer being considered.
3
WITH
STDI
6
C
STD
15
C
which
provides
larmonic
ict
output
.
at
difference
in
waveform
,
magnetizing
•
*
nt
,
-
inferential
STD
15
C
relay
circuits
action
,
arential
transformers
STD
16
C
circuit
sformer
restraint
.
maximum
possibility
'
misoperation
.
selected
transformer
,
'
‘
•
'
king
thermal
:
vrr
*
nt
iollowing
ratios
ratio
selected
,
some
ratio
However
,
Where
relay
tap
.
relay
tap
,
CT
maximum
reducing
performance
of
the
CT
'
s
.
secondary
secondary
’
current
2
.
winding
.
basis
)
exceed
maximum
damage
maximum
transformer
to
self
-
cooled
rating
,
it
.
x
.
i
character
-
istics
Tht
-
irt
ructions
do
not
purport
to
COVT
oil
d
.
toih
or
variohon
.
Voquip
^
n
^
or
f
to
tho
Gantro
/
Eloctric
Cotnpony
.
Courtesy of NationalSwitchgear.com

100% Transformer KVA
(Line KY)
Actually this calculation does not mean that all windings will necessarily carry these
load currents continuously. This is only convenient of calculating the currents in
other windings In proportion to their voltage ratings. This is the requirement for selecting
the relay tap setting so that the relay will not operate for any external fault.
3. Select CT ratios so that the secondary current corresponding to maximum does not exceed
secondary thermal rating amperes). In the case where a transformer is connected to ring
bus. for example. the CT ratio should be selected so that the CT thermal rating will not be ex-
ceeded by the maximum load current in either breaker. Also select CT ratios so that the relay
currents can be properly matched by of the relay taps. (Highest current not more than 3
times lowest current).
For Wye connected CT's
Tap Current
N
For Delta connected CT's
Tap Current 100%
N
Where N is the number of CT secondary turns.
4. Check the matching of relay currents to relay taps to keep the mismatch error as as possible.
Calculate the percent of mismatch as follows: on two winding transformers, determine the ratio of
the two relay currents and the tap values
The differences these ratios, divided
by the smaller ii the percent of mismatched. The mismatch normally should not exceed 5:.
For transformers, the percent of mismatch error should be checked for all combin-
ations of currents or taps.
If taps cannot be selected to this percentage error within allowable limits, it will be
necessary to choose a different CT ratio on one more lines to obtain better match between
relay currents and relay taps.
Check to see that the sum of the relay currents that be applied to the relay for a fault at
the terminals of'the power transfoner is less 220 amperes for 1 second.
If the period
during which a fault current flows in the relay can be definitely limited to shorter time,
hiqher current can be in accordance with the relation:
(Amperes)' seconds
Also check that the sum of the multiples of tap current on an internal or fault do
exceed
CURRENT TRANSFORMER RATIO ERROR
.
CT ratio error be less than 20 percent 8 times relay rated tap Current. This
the instantaneous unit being set at its normal setting which is times tap rating. If the instantaneous
pickup is raised above this value, the 20 percent figure must be reduced as described under the
heading CHARACTERISTICS.
The calculations listed below are for the worst fault condition, as far as CT is concerned
which is an internal ground fault between the CT and the transfoner winding with none of the fault Current
through the neutral of the protected
S
GEK
-
45307
10
«
I
*
P
JT
maximum
the
a
way
the
CT
!
P
(
5
a
means
,
100
%
Ip
IpV
3
low
selected
.
between
ratio
,
three
-
wind
inq
IceeD
a
or
will
5
.
RMS
than
a
accommodated
a
*
48
,
400
x
external
not
150
.
is based
on
The
at
must
8
unit
performance
transformer
.
ipplied
Courtesy of NationalSwitchgear.com

i
,
I
i
Determine burden on each CT. using the following expressions:
a. connected CT's
2R
b. For delta CT'S
relay total burden (sea Table
N number of turns in bushing CT
bushing CT resistance per turn,
(at maximum
CT resistance per lead. (at temperature)
R control cable lead (at expected temperature)
CT current for 8 times tap setting.
8 relay tap rating
(NOTE: For the location of fault assumed. a
11
the fault currant Is by one CT. so that
and relay current are the same, regardless of whether the are connected in or
.
Determine secondary CT voltage required 8 times tap setting.
excitation curve of particular tap of current transformer determine excitation
current. this secondary
the percent error In each CT by the expression:
error
should not 20 percent on set of If it does. be to
choose a higher tap on that set of and repeat the calculations on selection of relay
mismatch error, and percent ratio error.
PERCENT SLOPE SETTING
proper percent slope is determined by the sum Of: .
a. The maximum range of manual taps and the load-ratio-control,
or tap means.
in percent.
b. The percent of mismatch of the relay taps.
The percentage slope tap should greater than the ratio Of error
smaller of the through currents. In general, if the total error current does 20 Percent.
the 25 percent tap is used.
If it 20 percent, but not 35 percent. the
the lead is used (as in for example) the percent should be about
SEK
-
45307
1
.
the
c
For
Wye
Z
-
B
Ne
+
2
f
(
EQ
.
1
)
Ohms
1000
connected
Ne
+
2
f
+
2
R
Ohms
(
EQ
.
2
)
Z
-
2
B
1000
I
)
Where
B
-
STD
expected
temperature
)
mllHohms
e
*
maximum
expected
mllHohms
f
*
bushing
maximum
resistance
*
one
-
way
c
.
Determine
secondary
x
STD
S
supplied
CT
'
s
CT
current
delta
.
)
wye
3
.
at
E
I
.
Z
s
sec
being
used
,
4
.
From
l
£
.
corresponding
to
voltage
,
E
sec
*
5
.
Determine
*
h
x
100
t
17
s
It
will
necessary
CT
'
s
.
exceed
This
any
CT
'
s
,
taps
,
required
The
changing
automatic
maximum
maximum
:
total
not
exceed
40
percent
tap
Is
used
.
current
selected
be
to
exceeds
s
1
°
Pe
tap
chosen
movable
twice
as
since
F
'
iQure
9
r
-
rpftrc
^
nt
.
If
6
Courtesy of NationalSwitchgear.com

REFER TO FIG.
I DETERMINATION OF C.T. TURNS AN0 RELAY TAP
1. Transformer and Line
2. Ip = (line
3 (line
turns
5. Max. I secondary (less than
6. 100% I secondary
CT connections
Relay Current for 1002 I Sec.
20
1.37
20
2 47
1.98
125
60
2.62
3.60
Select a relay tap for one of the line currents and calculate what the currents in other lines would
be they were increased In the ratio.
If any current is greater than root three times any other,
the 6.7 tap should be chosen for it and ideal relay taps calculated for the other lines.
9. Ideal Relay Taps (Set C = 8.7)
10. Try Relay Taps
11. Check Mismatch Error
3.31 4.70 a.7
3.24.6
Ratio of Taps on Lines B-A = 1.43 of Sec. Lines Currents
1.98
-=
1.37
1.
a.7
Ratio of Taps on Lines C-6 = 1.89 Ratio of Sec. Line Currents = 1.62
Mismatch = 3.6%
1.62
Ratio of Taps on Lines C-A = 2.72 Ratio of S C . Currents 2.63
=
(All are less than therefore. error la not
12. Check the sum of the maximum relay currents is less than amps for one and
therefore. short-time rating of relay is not exceeded.
PERCENT RATIO ERROR
ASSUME (all measured at their expected
One-way CONTROL CABLE RESISTANCE
=
CT;
c
Bushing resistance per lead
18.6
.
1.
BURDENS ON CT's
USING 1
OR 2 from page 5.
a. A. Z
2 l
(2.0
000
0.312 0.205 l 1.085
l
+ 0.0% l 0.136 + 0.60
c. Line C. Z = 2 (0.046) +
100 +
= 0.0% l 0.180 0.568
= 0.833
GEK
-
45307
EXAMPLE
17
SETTINGS STD
A
C
B
19.7
3750
/
VIT
3
.
100
%
Ip
«
3000
/
V
.
4
.
Assume
CT
1
?
7
KV
)
49.5
Max
.
KV
)
15.7
39.6
(
N
)
0.98
»
»
5
a
)
0.79
1.58
2.08
v
•
r
^
Delta
Delta
Wye
7
.
8
.
1
f
same
new
8.7
4.6
1.44
Ratio
377
1.44
1.43
,
0.7
%
Mismatch
43
4.6
1.89
-
1.82
8.7
Line
n
2.72
-
2.63
3.4
%
Mismatch
excessive
)
mismatch
5
%
;
220
second
,
that
II
temperatures
)
maximum
(
R
)
.
284
ohms
4
mllHohms
resistance
per
turn
(
e
)
»
;
e
)
-
2.5
"
e
)
-
2.3
"
f
)
-
75
"
f
)
-
52.5
"
(
f
)
*
Bushing
A
H
D
B
<
4
A
CT
B
"
4
!
C
“
EQ
.
EQ
.
•
(
0.156
)
x
75
)
(
20
x
*
,
)
Line
+
2
(
.
284
)
1
0.568
-
(
2.1
x
52.51
(
20
x
2.51
©
.
sea
k
.
UlT
*
2
*
©
-
'
1
S
5
IDDO
0.568
*
(
60
x
2.3
)
+
(
2
x
18.6
)
0.568
00
7
Courtesy of NationalSwitchgear.com

2. 1.085 0.8 0.833
3. a 36.8 69.6
ES CT required
27.8 29.b 58.0
required, excitation
curve
1.00
50
Ratio Error
3.4% 136%
Exciting current on line is high;
should try higher tap on CT to improve CT
IA REPEAT CT TURNS AND RELAY TAP SETTING
1.
Try CT turns (necessary to change C
also for proper matching)
3. I secondary
Relay Current.
Ideal Relay (SET C 8.7)
6. Use Taps
7.
Mismatch error is less than
Total Burden for 60 Cycle Relays
15.7 39.6 125
0.79
1.37
4.40
4.6
40 80
0.99 1.56
0.99 2.70
TABLE I
IIA REPEAT PERCENT RATIO ERROR
1. Burden on CT's
Line A. Z 0.192 0.205 0.965
Line 0.156 + 0.568 0.912
Line Cm Z 0.096 + 0.226 0.890
2. Impedance.
3.
8 Times Tap, Amperes 36.8 25.6
CT voltage required 35.6 23.4
5. required, from excitation curve
1.1 0.25
6.
of Ratio Error
3.1%
1 .
Percent Error is less than 20%. so CT taps and Relay taps are satisfactory.
69.6
61.9
0.17
0.3%
III PERCENT SLOPE SETTING
1. Assume load ratio. control maximum range
2. Relay Tap mismatch, IA above (Lines
10.0:
4.6:
Use 25% tdp.
RATINGS
14.6%
---
Continuous rating The through current transformer differential transformer Will stand
twice value for any of taps or they will stand twice tdp value if all but one of
carry zero current the full restraint current. equal to twice tap
the current transformer.
GE
<
-
45337
A
B
C
ohms
Impedance
,
T
imec
anoeres
25
.
*
?
*
a
n
(
12
)
4
.
voltage
from
IE
.
5
.
0.5
6
.
0.8
%
*
B
too
performance
.
1002
Ip
2
.
20
100
?
4
.
Taps
5
.
3.19
8.7
a
3.2
8.7
5
S
MIN
.
P
.
U
.
AMPS
i
BURDEN
OHMS
(
B
)
8
X
TAP
AMPS
STD
TAPS
AMPS
!
0.87
0.180
0.156
0.140
0.120
0.112
0.096
0.088
0.048
23.2
2.9
0.96
25.6
>
.
2
1.05
28.0
3.5
1.14
30.4
3.8
1.26
33.6
4.2
1.38
36.8
4.6
1.50
40.0
5.0
2.61
69.6
8.7
0.568
*
s
0.188
+
B
,
Z
*
S
0.568
=
S
Ohms
.
965
.
912
.
890
(
I Z
)
E
$
ec
«
4
.
IE
0
%
l
A
-
B
)
from
MODELS
12
STD
15
C
AND
12
STD
16
C
and
Current
comfcinati
on
tap
tfie
,
res
-
value
,
flows
through
traint
windinqs
differential
and
8
Courtesy of NationalSwitchgear.com

amperes for second measured in the primary Of any
nigher may be applied for shorter lengths of time in accordance the
1%
where:
I current amperes
t time in seconds
Short Time (electrical)
For the and the Of the multiples Of tap fed
to the relay from the several sets of current transformers should not exceed 150. These multiples should
be calculated on the basis of fault current.
This limitation is a result of the voltage
of the rectifiers in the through current restraint
Note that in Fig. 9 external fault
current can flow through circuit breakers and 52-2 without being limited by the Impedance.
TABLE II
2.0
0.6 ,
0.2
Tap
Tap
Tap
D-C Resistance 0.13
0.6 Ohm
7
Carry Continuously
0.5 Amps
1.5 Amps 0.25
carry for 4 0.5
----
Carry 10 Amps for 30
4
0.2
AUXILIARY RELAY CONTROL CIRCUIT
The and relays are available for use with 48. 125, and 250 d-c voltage. A
with small links located on the front of the relay enables
the selection of one of these voltages.
The relay is provided with two open contacts connected to a output circuit. The current
closing rating of the contact is 30 amps for voltages not exceeding 250 volts. If more than one
break& is to be tripped or if the tripping current exceeds 30 amperes. an auxiliary relay must be used
with the relay. the breaker trips. it is necessary that the tripping circuit of these
be de-energized by an auxiliary switch on the circuit breaker by other
reset relay is and normally used.
CHARACTERISTICS
PICKUP AN0 OPERATING TIME
The operating characteristic Is shown in Fig. 1.
The curve for various percentage the
percent slope versus the through current flowing in the
The percentage slope is a figure
given to a particular slope tap setting and indicates an approximate pickup at
zero restraint is 30 percent of tap value (see Table III). The dropout time the
operating current is reduced from any value above pickup to zero is less than 25
of the operating time of the main unit and of the instantaneous unit are shown in Fig.
plotted against differential current. The main operating time includes auxiliary unit operating time.
OVERCURRENT UNIT PICKUP
The unit is adjusted to pickup when the differential
‘8 times the ampere produced by rated tap current flowing in that For example:
only one supplies current. and the tap plug for the CT is in the ampere tap, 40
amperes are required for pickup.
This pickup value is on the A-C Of current
only, since the differential current transformer in the relay a half
cycle of any d-c present.
GEK
-
45307
*
transformer
z
*
with
Short
Time
Rating
(
theflW
?
che
type
STD
relay
,
following
equation
:
•
•
48.400
220
1
i
-
currents
s
=
1
current
STD
15
C
STD
16
C
both
sum
RMS
symmetrical
circuit
.
rating
transformer
52
-
1
TARGET
AND
SEAL
-
IN
UNIT
Amp
Amp
Amp
Ohms
Ohms
Amps
Secs
.
Secs
.
30
Amps
Secs
.
Secs
.
Secs
.
control
STD
15
C
STD
16
C
>
»
iate
STD
common
circuit
relays
automatic
provisions
.
A
manual
STD
After
or
recommended
slopes
shows
transformer
.
slope
characteristic
.
when
milliseconds
.
approximately
2
,
Curves
unit
current
transformer
ampere
-
turns
are
tap
.
overcurrent
turns
5
CT
When
trans
-
based
component
produces
only
former
output
(
offset
)
component
9
Courtesy of NationalSwitchgear.com

It should be recognized that pickup current flows not only through current transformer
but also through one of the primary windings of the through current restraint.
However, compared to the operating energy, this quantity of restraint is so small it may assumed
to be zero.
CURRENT RESTRAINT CIRCUIT
A full wave rectifier receives the output of the secondary of each through current restraint
transformer. In the relay. the d-c output of all three units are connected in The total
output is directed to the percent slope rheostat located on the front of the relay. By means of'
adjusting the rheostat, the percent slope may be varied 15 to 40 percent. The is put through
an isolatinq transformer, rectified and to the solid state amplifier which the
telephone tyoe relay.
DIFFERENTIAL CURRENT CIRCUIT
The differential current secondary supplies the instantaneous unit the
operating signal to the solid state amplifier through a series tuned circuit; and the harmonic restraint
isolating transformer through a parallel resonant filter. The operating and restraint currents are each
rectified by a full wave bridge prior to being supplied to the sensitive amplifier.
The series resonant circuit is made up of a microfarad
capacitor (Cl) and a reactor
which are tuned to pass currents of the fundamental system frequency and to offer high impedance to
Currents of other frequencies.
Resistor is connected in the a-c side of operate
and can be to give the desired amount of operate current.
The output of the is applied
the operating of the sense amplifier.
The parallel resonant trap is made of a 15 microfarad
l Pyranol capacitor and a reactor
which are tuned to block fundamental frequency currents while allowing currents of
to pass with relatively little impedance. Resistor R2 is connected in parallel on the a-c side of the
harmonic restraint rectifier, and can be adjusted to give the desired amont of harmonic restraint. The
output of the rectifier is paralleled with the through current restraint currents and applied to
restraint of the sense amplifier.
It will evident that if the differential current applied to the relay is sinusoidal and of system
will flow mostly in the operating circuit and hence cause the relay to yield an output.
if. however. the differential circuit contains than a certain percentage of the relay will
be restrained from by the harmonic currents flowing in the restraint
A resistor connected across the secondary of the differential limits
any momentary high voltage peaks which may thus protecting the rectifiers and capacitors damage
without materially affecting the characteristics of the relay.
OVERCURRENT UNIT
The instantaneous unit is a hinged armature relay with a self contained target indicator. On
heavy internal fault currents.
this unit will pick up and the trip circuit. The
unit target will be exposed, to indicate that tripping was through the instantaneous unit.
Because of saturation of the CT's and relay transformers at high fault currents, it is impossible that
less operating currents will be provided from the differential-current than the percentage
slope tap imply, and harmonic restraint will be provided than the actual harmonic content of the
would supply.
As a result, conditions of a high internal fault current, the unit
may be falsely restrained. Tripping is assured, however, by the overcurrent unit operation. Pickup
set above the level of differential current produced by maximum magnetizing inrush current. Figure 2
the relative levels of pickup and speed of operation of the unit and the overcurrent unit.
l Trade-Mark of the General Electric Company
GEK
-
45307
differential
transformer
producing
some
that
be
THROUGH
brldae
STD
16
C
parallel
.
(
«
3
)
from
sensitive
output
controls
directed
directly
;
transformer
5
*
Pyranol
parallel
on
(
LI
)
R
1
rectifier
tne
adjusted
rectifier
to
circuit
(
C
2
)
{
12
)
.
harmonic
frequencies
the
circuit
be
freouency
,
it
harmonics
,
circuit
.
more
operating
current
transformer
Thyrite
from
occur
,
ex
-
instan
-
complete
tremely
taneous
transformer
would
'
fault
current
more
under
mam
is
shows
main
Registered
\
2
Courtesy of NationalSwitchgear.com

OPERATING UNIT
The primary functioning of the relay is a state amplifier whose controls a
simple telephone relay.
The sense ampllfler is shown In Fig. 10 and as a large rectangle. The amplifier
consists of many electronic components mounted on a printed circuit card in the top half of the relay.
This printed card is installed in an eight-prong printed card design base. This
Is adjusted prior the factory and should require no further attention. A schematic of this
card is shown in Fiq. The telephone-type relay is mounted vertically in the mid-section of the relay.
It too has been carefully adjusted at the factory and should require no further attention.
If this small
relay has been disturbed, refer to the section under adjustment.
TARGET AND SEAL-IN
a target and seal-in unit mounted on the top left of the relay. This has Its coil in
series and its contacts in parallel with the main contacts of the telephone-type relay. the
type relay contacts close, the seal-in unit operates; raising its target into vision and sealing around
the telephone type contacts. The target of this unit will remain exposed until released by pushing a
button beneath the lower left corner of the cover of the relay case.
The case suitable for surface or semi-flush panel mounting, and an assortment of hardware is pro-
vided for method. The cover attaches to the case, and carries the target reset mechanism for the
indicator and instantaneous unit. Each cover screw has provision for a sealing
The case has studs or screw connections at the bottom for the external connections. The
connections between the relay unit and the case studs are made through spring backed contact finger mounted
in stationary molded inner and outer blocks between which rests a removable connecting plug which completes
circuit. The outer block, attached to the case, holds the studs for the external connection, and the
block has terminals for the internal connections.
The relay mechanism is mounted in a steel framework called the cradle and is a unit with all
leads terminating at the inner block. This cradle held in the case with a latch at the top and
a guide pin at the back of the case.
The case and cradle are so constructed that the relay
cannot be inserted in the case upside down.
The connecting plug. besides the connection
between the blocks of the cradle and case, also locks the latch In place. The cover. which fastened to
the case by thumbscrews. holds the connecting plug in place.
To draw out the relay unit, the cover is removed and the plug is drawn out. Shorting are provided
in the case to short the current circuits (see Fig. 6). The latches are then released and the
relay can be easily drawn out.
A separate testing plug can be inserted in place of the connecting plug to rest the relay in On
the panel either from its own source of current, or from other sources. Or, the relay unit can be drawn
out and replaced by another which has been tested in the laboratory.
RECEIVING, HANDLING OR STORAGE
These relays, when included as a part of a control panel will shipped In cartons designed
protect them against damage;
upon receipt of a relay, examine It for any damage in
transit.
If injury or damage resulting from rough handling is evident. file a damage claim at once with
the and promptly notify the nearest General Electric Apparatus
Reasonable care should be exercised in unpacking the relay in order that none of the parts are
or the adjustments disturbed.
If the relays are not to be installed they should be stored in original cartons in
a place that is free from moisture, dust and metallic chips. Foreign matter collected on the outside of
case may find its way inside when the cover is removed and cause trouble in the operation of the relay.
GEK
-
J
5307
iIN
sol Id
unit
STD
output
11
component
circuit
to
leaving
18
.
UNIT
unit
There
is
telephone
-
When
CASE
1
s
either
wire
.
trip
electrical
ner
complete
firmly
is
bottom
and
.
by
electrical
making
1
s
bars
transformer
unit
place
to
be
not
sustained
Immediately
Sales
Office
.
transportation
company
injured
their
immediately
,
the
13
Courtesy of NationalSwitchgear.com

ACCEPTANCE TESTS
the relay an inspection and acceptance test be to insure that
the relay has not been in and that the relay calibrations are unchanged.
VISUAL INSPECTION
Check the nameplate stamping insure that the model number. rating and calibration range of
relay received agree with the
molded Remove the relay from its case and chock by visual Inspection that there are no broken cracked
parts or other signs of physical damage and that all screws are tight.
INSPECTION
that
Check the of the telephone type relay and instantaneous overcurrent unit manually to see
they operate smoothly without noticeable friction or binds. Check the contact gap and of these
units which should agree with values given under the section on
It is that the electrical tests be upon receipt of relay.
1. Minimum pickup of main operating unit.
2. Minimum pickup of the Instantaneous overcurrent unit.
3. A single check on the restraint characteristic.
4.
A single check point on the slope characteristic curve for slope to be used.
TEST FACILITIES
In order to facilitate tests, the following test is
1. Two load boxes for regulating the test currents.
2. Three (2 A.C. and O.C.) for measuring the test currents.
3. A test rectifier for checking the relays response to the second harmonic.
4. One indicating lamp.
5. single pole double switch selector.
6. A double pole single throw line
Chock the unit connections shwn In Fig. 12.
this test. the selector
switches and are open and current passes through the differential circuit only. For example, with
a relay with a 25 percent slope and at the 2.9 ampere ratio matching taps, the main unit should pick
at of tap rating plus or minus 10 percent, or the pickup should be between 0.78 and 0.96
amperes. To check that the main unit has picked up a source of DC pwer at rated voltage should
connected shown Fig. 12, and the Indicating lamp will provide a signal showing that the main unit
has operated.
For an additional pickup test, the pickup should be 1.5 amperes with current flowing terminals 5
and 6 and the tap plugs in the 5 ampere tap, and the 25 percent slope tap position. If the pickup is
between 1.35 and 1.65 amperes, no adjustment should be made.
The pickup of the relay-has wider
variations than most protective relays, but due to the relay design and application, the relay accuracy
is entirely adeuqate under all conditions even during transformer magnetizing inrush or severe fault
a
the selector switch, in the A position,
the section on INSTALLATION PROCEDURE.
check the
current restraint described
The instantaneous unit should be chocked by passing a high current through the 5-6
The pickup should be about 8 times tap rating.
Check through current restraint as described under section on INSTALLATION PROCEDURE.
14
6
EK
-
45307
Immediately
upon
recelptof
damaged
shipment
should
made
to
the
requisition
.
or
MECHANICAL
ooeratlon
wipe
SERVICING
.
followlng
recormiended
made
Immediately
the
point
harmonic
approximate
expected
equipment
recommended
:
1
aimeters
.
Two
throw
switch
.
pickup
of
the
main
During
(
S
2
S
4
)
set
up
30
percent
be
as
in
in
permissable
conditions
.
With
S
2
harmonic
as
under
overcurrent
terminals
.
Courtesy of NationalSwitchgear.com

This curve represents the relay characteristic. of a voltage across studs 8 and 9
which is 75: or less of the value given on the curve does not necessarily indicate that
operate at higher through current This is especially true where very high through may
cause CT saturation.
Small rectifier-type AC voltmeters are suitable for the measurement of unbalance. voltmeter
should not be left permanently connected since the shunt current it draws reduces the
PERCENT SLOPE SETTING
Scribe marks for 15. 25 and 40 percent slope settings are provided In both the and
relays.
It practice to use the 25 percent setting unless special connections make It advisable
to use one of the others. See the corresponding heading under CALCULATIONS for further details.
TARGETS
Targets are provided for both the seal-in unit the unit. In
event of an internal fault. one or both of these units will operate depending upon the fault magnitude.
This will produce a target of the unit which operates. After a fault Is cleared.
the target should be reset by the reset slide located at the lower left hand corner the
DISABLING OF TYPE STD RELAY
When by-passing a breaker for maintenance, will be necessary to disable the relay to prevent
tripping. If the disabling of the relay is done by a remote switch rather than by the relay
connection plug, the following precautions should be taken:
1.
The relay may be disabled by short-circuitino studs 8 and 9 of the relay or by opening the
circuit at stud 1.
2. If the CT secondaries are short-circuited as part of the disabling procedure, the trip circuit
should be opened at stud 1 and studs 8 and 9 should be short circuited first.
It is not to rely
on short circuitingthe CT secondaries alone, because any difference in time of shorting them
false tripping.
CONTACT CLEANING
For contacts. a flexible burnishing tool should be used. This consists of a flexible
strip of metal with an etched roughened surface , resembling in effect a superfine file. The polishing
action is so delicate that no scratches are left. yet corroded material will be removed rapidly and thoroughly.
The flexibility of the tool insures the cleaning of the actual points of contact.
Contacts should not be cleaned with knives.
files or abrasive paper or cloth. Knives or files
leave scratches which Increase arcing and deterioration of the contacts. Abrasive paper or cloth
leave minute particles of insulating abrasive material in the contacts and thus prevent closing.
The burnishing tool described in the standard relay tool kit obtainable the factory.
PERIODIC TESTS
An operation test and Inspection of the relay and its connections should be made at every
six months.
Tests may be performed as described under INSTALLATION TESTS if desired. they MY be
on the service taps as described in this section.
Inserting or withdrawing a test plug with U-shaped through jumpers to complete the trip circuit
through the test plug, similar through jumpers should also be used on studs 8 and 9 to maintain the
connections the relay to the case. If this is not done,
there is a risk of false tripping upon in-
serting or withdrawing the plug.
SCK
-
45307
Measurement
STD
the
relay
will
faults
values
.
The
relay
sensitivity
.
STD
15
STF
16
is
common
OPERATION
instantaneous
overcurrent
the
and
indication
particular
relay
.
of
false
it
removing
trip
sufficient
may
cause
MAINTENANCE
cleaning
may
may
is
included
from
least
once
or
,
made
When
from
18
Courtesy of NationalSwitchgear.com

CKUP
The pickup is as described under the heading INSTALLATION of
current be different depending upon the UDG Pickup value be determined as
0.30 1 Tap
IO percent variation Still
course, when pickup on a particular service the
the acceptable as found values being
II 0.30 YDG Tap to 1.10 0.30 UDG I
Example UDG 1 Tap
0.90 x 0.30 3.5 to 1.10 0.30 3.5
0.94 to 1.16 amperes
CURRENT RESTRAINT
The for harmonic restraint Is as described the heading TESTS
the test current values must be modified follows:
12 (DC) 0.80 x UDG 1 Tap
UDG I Tap to 1.10 x 1
In event a suitable DC meter available.
I2 (AC) 2.25 (DC). (Theoretically
be 2.22 if the rectifier back resistance
UDG 1 lap
0.80 x 3.5 2.8 amperes
0.90 x 3.5 to 1.10 3.5
3.15 to 3.85 amperes
If DC meter is not available, (AC) 2.25 x 2.8
RESTRAINT
order to check the
the current values indicated in Table IV must
to take into account any difference the circuit in
of is connected to the stud to the tap
I4 the lead from 13 to the test Plug is to the stud
setting.
For any combination of taps,
percent slope is given by the
Slope
where
smaller tap setting
higher tap setting
differential current
smaller of the two through currents
GEK
-
4530
?
TESTS
except
,
course
.
method
for
checking
1
service
tap
.
will
ckup
Hows
:
may
x
WDG
II
*
tap
,
checking
expected
Of
i
.
plies
.
Tap
•
0.90
x
1
x
X
X
*
3.5
A
II
*
x
X
X
II
"
1
RM
0
NIC
INSTALLATION
under
checking
procedure
<
cept
as
M
WOG
Tap
Ij
*
0.90
x
this
1
s
not
$
T
•
>
were
Infinite
)
.
the
*
anverslon
factor
would
-
3.5
A
imple
I
2
(
DC
)
*
s
h
=
X
n
-
6.30
amperes
12
"
HROUGH
CURRENT
service
tap
slope
setting
,
test
'
in
tap
settings
.
corresponding
In
shown
5
e
modified
f
1
g
.
-
.
must
be
set
up
such
that
Ihe
conmon
lead
^
Furthermore
,
test
connected
winding
Wftn
the
higher
foTlowing
equation
:
setting
.
ammeter
course
,
the
'
T
1
(
I
1
x
100
-
1
+
1
X
3
Tl
"
T
2
*
h
-
h
"
19
Courtesy of NationalSwitchgear.com

. .
FIG. 1 LOW CURRENT OF THE RELAY
GEK
-
45307
80
r
NOTE
:
FOR
TWO
WINDING
TRANSFORMER
RELAYS
"
THROUGH
CURRENT
"
IS
TAKEN
AS
THE
SMALLER
OF
THE
TWO
CURRENTS
.
FOR
THREE
WINDING
TRANSFORMERS
,
IT
IS
TAKEN
AS
THE
SUM
OF
THE
INCOMING
OR
OUTGOING
CURRENTS
,
WHICH
-
EVER
IS
SMALLER
.
(
EACH
CURRENT
TO
BE
EXPRESSED
AS
A
MULTIPLE
OF
TAP
.
)
701
50
,
40
*
4
£
S
CO
S
30
ae
25
*
4
£
I
i
20
15
%
.
*
-
0
16
14
12
10
8
6
2
4
0
THROUGH
CURRENT
IB
MULTIPLES
OF
TAP
STD
SLOPE
CHARACTERISTICS
(
0378
A
588
-
3
)
22
Courtesy of NationalSwitchgear.com

INSTALLATION PROCEDURE
TESTS
Before placing the relays I"
, check the relay calibration to be used in its final location
to insure that It Is correct. The following test procedure is outlined for this purpose.
CAUTION: RELAY CALIBRATION IS ACCOMPLISHED BY ADJUSTING RESISTORS R
IN ME
.
IN ANY ONE THESE RESISTORS WILL AFFECT THE OTHER TWO SETTINGS. IS CHANGED.
PICKUP, RESTRAINT, AND CURRENT RESTRAINT ADJUSTMENT PROCEDURES SHOULD BE REPEATED
UNTIL FURTHER DEVIATION FROM PROPER CALIBRATION IS NOTED. BEST RESULTS CAN BE OBTAINED IF THE
CURRENT ADJUSTMENT IS MADE ONLY AFTER THE OTHER TWO SETTINGS ARE CORRECT.
The-test circuit for pickup is shown in Fig. 14 with open. Pickup should be 1.5 amperes with
current flowing in terminals 5 and 6. and the tap plugs in the 5 ampere position. and 25 percent slope
tap setting.. The pickup operation should be repeated several times until two successive readings agree
ampere and the total pickup current being interrupted between successive checks. pickup
is found to be from 1.35 1.65. the setting should not
be disturbed.
With d-c control voltage to the proper terminals of the relay. the pickup of the telephone
type relay can be used as an indication of operation of the amplifier. This voltage may be applied as
in Fig. 14 and the indicating lamp will verify that the has produced an output signal.
Before adjusted for pickup. put a D.C. voltmeter (1 volt scale) on pin 2 and pin
of the sense card.
The pins are counted from right to left when viewed from the card socket
connections. Apply pickup current and adjust for a voltage input to the sense amplifier card
of 5.430 to 0.470 volts. If the pickup is not in with this setting then adjust on the sense
amplifier card to obtain the proper pickup value.
CURRENT RESTRAINT
. .
The restraint adjusted by means of a Test Rectifier used in conjunction with
and load boxes. The test circuit is as shown in Fig. 14 with to position A. Tests
should made on the 5.0 ampere and 25% slope taps.
analysis of a single phase half wave rectified current shows the presence of percentages of
and second harmonic components as well as
percentages of all higher even
harmonics.
This closely appmximates a typical inrush current as seen as the relay
in as much as its principal components are d-c.
fundamental, and second harmonic. Although the percent
second is fixed, the overall
percentage may be varied by providing a path for a
of by-passed current of frequency.
The by-passed current is added in phase with fundamental
component of the half wave rectified current and thus provides a means of varying the ratio of second
harmonic current to fundamental current.
The following expression shows the relationship between the percent second harmonic. the d-c component.
and the by-pass current.
Second 0.212
100
+ 0.5
Figure 15 is derived fmm the above expression. It shows the percent second corresponding
to various values of by-pass current (II) for a constant d-c set at 4.0 amperes.
The relay calibrated with a composite current of two time tap value. properly set the
will restraint with greater than twenty percent second harmonic but will operate with second
harmonic equal to twenty percent or lower.
With the d-c (I ) at 4.0 amperes, the
should just begin to close its contacts gradually
increa
by-pass current (I at a value
4.5-5.5 amperes.
This corresponds to percent second harmonic (see
a two
percent tolerance at the set point to compensate for normal fluctuations in pickup. It should be noted
that the current nangitude in the rectifier branch (I ) is slightly influenced by the Of by-
pass current and should be checked to insure it maintained at its proper value.
15
SEK
-
45307
service
CHANGES
MADE
THE
SETTING
OF
EVE
HARMC
'
N
IC
THROUGH
THE
THROUGH
NO
RESTRAINT
PICKUP
S
2
If
within
O
.
Ol
applied
amplifier
shown
(
-
)
amplified
8
(
)
limits
wiring
pi
HARMONIC
harmonic
1
s
suitaole
S
2
closed
ammeters
be
The
fixed
negligible
d
-
c
,
fundamental
,
terminals
transformer
harmonic
controlled
amoant
fondamental
I
Harmonic
*
X
d
-
c
x
0.451
I
1
d
-
c
harmonic
When
is
RMS
relay
*
elay
auxiliary
set
ammeter
^
1
ng
with
Fig
.
15
)
providing
application
if
19
-
21
?
;
(
i
,
)
i
Courtesy of NationalSwitchgear.com

If harmonic restraint is found to be of adjustment. it be corrected by adjusting Rheostat
THROUGH CURRENT
The through current restraint. which gives the relay the percentage differential or percent slope
characteristics are in Fig. 1.
It may be checked and adjusted using the circuit illustrated in Fig.
with closed to II reads the differential current
and I3 reads the smaller of
the two through currents. In testing relays,
the setting should be checked with the switch first
in one position and then the other,
thus checking all the restraint coils. Uith the current
ampere position and the percent slope tap plug in the percent position, the relay should Just
up for values of the I and 13 currents indicated in Table IV. Repeat with the percent slope tap plug
in the 25 percent and 5 percent position.
If any one of these Set points is found to be the other than as
prescribed. the adjustment may be made by adjusting It should be noted that the current magnitude in
the through current branch (13) is slightly influenced by the application of differential current (II) and
should be checked to insure that it maintained as its proper value.
Any in to give the desired slope will have small effect minimum pickup and harmonic
restraint. However! after the slope setting has once any adjustment of minimum pickup will change
the slope
The slope set points must then be rechecked to insure that they are in
accordance with Table III.
NOTE: These currents should be permitted to flow for only a few seconds at a time cooling
between tests; otherwise. the coils will be overheated.
NOTE: The percent slope tolerance is 10 percent of nominal. all in the plus direction. This is to
the slope characteristic never falls below tap value.
TABLE IV
PERCENT POSITION AMPERES TRUE SLOPE
SLOPE TAP'
ON RHEOSTAT II
Middle
Left
INSTANTANEOUS OVERCURRENT UNIT
This unit is at the upper right-hand of the relay. Its setting may by passing
a high current of rated through and 6.
The unit should pick up at times the tap
rating as described under CHARACTERISTICS. If the setting is incorrect. it may be adjusted by loosening
the lock-nut at the top of the unit and turning the cap screw until the proper pickup is obtained. In
this adjustment. the current should not be allowed to flow for more than approximately one second
iime.
DROPOUT OF UNIT
After the other tests are complete, check the dropout of the main as described under ACCEPTANCE
TEST section.
LOCATION
The location should clean and dry. free dust and excessive and to
facilitate inspection and testing.
MOUNTING
The relay should be mounted on a vertical surface. The outline and panel drilling are
in Figure 5.
SEK
-
45307
out
may
RESTRAINT
shown
position
B
.
Anmeter
14
S
2
S
4
ST
016
C
tap
plugs
in
pick
40
'
5.0
1
R
3
-
is
change
R
3
upon
been
.
set
,
characteristics
.
periods
with
Insure
that
Oi
/
13
*
100
)
13
40.0
-
44.0
25.0
-
27.5
15.0
-
16.5
12.0
-
13.2
7.5
-
8.3
4.5
-
5.0
30
40
Right
30
25
30
15
be
checked
located
side
8
terminals
5
frequency
makinq
at
a
MAIN
unit
well
lighted
vibration
.
be
from
dimensions
hown
16
Courtesy of NationalSwitchgear.com

CONNECTIONS
Internal connection diagrams are shown in Figs. 10 and 11.
Figs. 7. 8 and g for differential applications. Typical wiring diagrams are given in
Of course, any through current winding may used for any
provided the taps are properly chosen.
the relay is mounted on an insulating panel, one of the supporting studs should be
cntly grounded by a conductor not less than No. 12 AUG gage copper wire its quivalent.
Every circuit in the case has an auxiliary brush.
the connecting plug should engage first. This is the shorter brush in the case which
On every current circuit or other circuit witn shorting bars,
make sure the auxiliary brushes are bent high enough to engage the connecting plug or test plug before the
main brushes; otherwise. the CT secondary circuit may be opened where one brush touches the shorting
before the circuit is the plug to the other main brush.
ADJUSTMENTS
, RATIO
TAP PLUG POSITIONING
To obtain unbalance current in the'differential circuit. means in the relay
to compensate for unavoidable differences in current transformer ratios. Taps on the relay
primary are rated 8.7, 5.0. 4.6. 3.8. 3.5, 3.2 and 2.9 amperes for each line current
The tap plugs should be to the locations which most nearly match the expected CT currents for the
same KVA assumed in each of power transformer windings.
method outlined under CALCULATIONS. The selection of should be guided by the
The connections plug must be removed the relay before changing
tap positions in order to prevent open-circuiting a CT secondary. A check should be made after changing
to insure that only one plug is left in any horizontal row of tap holes.
Inaccurate calibration
overheating may result if more than one plug is connected to any one uinding.
UNBALANCE CURRENT
Unbalance current is useful in checking the best tap setting when matching current
former ratios in the field.
It is also useful in detecting errors or faults in the transformer
winding, or small faults within the power transformer itself where the fault current is too low to operate
the relay.
The type STD relays have a special arrangement for the unbalance current flowing in the
differential circuit without disturbing the relay connection. Provision is made for temporarily connecting
a 5 volt high-resistance A.C. voltmeter (1000 or more per volt) across the secondary of the
current
and 11).
This may be done by connecting the meter across 8 and g (see Figs. 10
a perfect match of relay currents is obtained by the ratio matching taps, the voltmeter
will read zero. indicating no unbalance. If the voltmeter reads 1.5 volts or less. the unbalance current
entering or leaving a given tap approximately 0.03 times the voltmeter reading times the tap
For higher voltmeter readings, the approximate unbalance current may be calculated the
voltage reading tap rating into the following equation:
(Unbalance) 0.2) Tap'
The unbalance percentage 100 times the unbalance current divided by the measured tap
For a three winding bank. this checked with load on at least two pairs of In order to
insure that the connections are correct.
The curves in Fig. 16 show the approximate voltage across terminals 8 and g to operate the
ielay for various percent slope tap settings and through currents expressed as percentage of tap. To
insure a margin of safety against false operation, the unbalance voltage should not exceed 75 percent of
that required to operate the relay for any given through current and percent slope tap setting. This
of unbalance may result the relatively high error currents of low ratio bushing CT's at low
of tap current.
GEK
-
45307
transformer
be
power
transformer
winding
When
steel
perman
-
or
drawout
bar
completed
from
MATCHING
ADJUSTMENT
a
minimum
are
provided
STD
transformer
transformer
.
windings
moved
the
taps
from
’
ps
.
d
MEASUREMENT
trans
-
measurment
current
measuring
differen
-
ohms
t
1
al
transformer
.
terminals
When
equals
rating
.
by
substituting
and
I
«
(
0.16
V
-
x
equals
must
be
current
.
windings
required
•
xtent
from
1
tiples
17
Courtesy of NationalSwitchgear.com

This curve represents the relay characteristic.
of voltage across studs 8 and g
which or' less of the value given on the curve does not necessarily indicate that will
operate at higher through current values.
This is especially true where very high through faults My
cause CT saturation.
Small rectifier-type AC voltmeters are suitable for the measurement Of unbalance. The
should not be left permanently connected since the shunt current it draws reduces the relay
PERCENT SLOPE SETTING
Scribe marks for 15. 25 and 40 percent slope settings are provided in both the ST015 and STF16
It is practice to use the 25 percent setting unless special connections make it advisable
to use one of the others. See the corresponding heading under CALCULATIONS for further details.
OPERATION
TARGETS
Targets are provided for the seal-in unit the instantaneous unit. In
event of an internal fault. one or both of these units will operate depending Won the fault magnitude.
This will produce a target indication of the unit which operates. After a fault is cleared.
the target should be reset by the reset slide located at the lower left hand corner of the relay.
DISABLING OF TYPE STD RELAY
by-passing a breaker for maintenance. it will be necessary to the relay to prevent false
tripping.
If the the relay is done by a remote switch rather than by removing the relay
plug, the following precautions should be taken:
1.
The relay may be disabled by short-circuiting studs 8 and g of the relay or by Opening the
circuit at stud
2. If the CT secondaries are short-circuited as part of the disablfng procedure, the circuit
should be opened at stud 1 and studs 8 and g should be short circuited first. It is not to rely
on short circuitingthe CT secondaries alone. because any difference in time of shorting them may cause
false tripping.
MAINTENANCE
CONTACT CLEANING
For cleaning contacts, a flexible burnishing tool should be used. This consists of a flexible
strip of metal with an etched roughened surface,
resembling in effect a superfine file. The
action is so delicate that no scratches are left, yet corroded material will be removed rapidly and thoroughly.
The flexibility of the tool insures the cleaning of the actual points of contact.
Contacts should not be cleaned with knives,
files or abrasive paper or cloth. Knives or files may
leave scratches which increase arcing and deterioration of the contacts. Abrasive paper or cloth may
leave minute particles of insulating abrasive material in the contacts and thus prevent closing.
The burnishing tool described is'included in the standard relay tool kit obtainable the
PERIODIC TESTS
An operation test and inspection of the relay and its connections should be made at once every
six months. Tests may be performed as described under INSTALLATION TESTS or. if desired, they may be
made on the service taps as described in this section.
When or withdrawing a test plug with U-shaped through jumpers to the trip circuit
through the test plug, similar through jumpers should also be used on studs 8 and g to maintain the
connections the relay to the case. If this is not done, there is a risk of false tripping upon
serting or withdrawing the plug.
&
K
-
45307
STD
Measurement
a
the
relay
is
75
S
voltmeter
sensitivity
.
relays
.
common
overcurrent
the
and
both
particular
disable
When
disabling
of
connection
trip
1
.
trip
sufficient
polishing
factory
.
from
least
comp
!
ete
Inserting
1
n
-
frcm
18
Courtesy of NationalSwitchgear.com

method checking pickup is as described under the heading INSTALLATION of
current will be different depending upon the 1
Pickup value may be determined as
11 0.30 1 Tap
when a particular service tap, the percent
the as found values being
0.90 0.30 1 Tap to 1.10 0.30 1 Tap
Example
UDG
1
Tap
0.30 3.5 to 1.10 0.30 3.5
0.94 to 1.16 amperes
CURRENT RESTRAINT
restraint is as described the
the test current values must be modified as follows:
12 (DC) 0.80 WOG 1
Tap to 1.10 UDG L
In the event a suitable DC meter not available.
I2 ( A C) 2.25 (Theoretically this
be 2.22 if the rectifier back
0.80 3.5 2.8
amperes
IL
0.90 3.5 to 1.10 3.5
3.15 to 3.85 amperes
available, (AC) 2.25 2.8 6.30
CURRENT RESTRAINT
order to check the service tap setting. the test current indicated in Table IV
modified to take into account any difference the test
the lead from 13 to Plug is to stud
connected to the stud to the with
setting .
For combination of taps,
percent slope is given by the
l
where
smaller tap setting
higher tap setting
I1
differential current
smaller of the two through
19
GEK
-
45307
CKUP
TESTS
except
,
course
,
for
The
WDG
service
tap
.
ckup
Hows
:
x
WDG
expected
variation
still
+
10
'
•
-
heckina
pickup
on
Of
course
,
acceptable
plies
,
xWOG
x
UDG
II
-
x
X
11
*
Sl
5
A
90
x
X
X
X
II
“
WMONIC
heading
INSTALLATION
TESTS
under
The
procedure
for
checking
harmonic
<
cept
Tap
x
Tap
Ij
-
0.90
x
UDG
1
x
-
xI
?
T
(
0
Cl
.
resistance
were
Infinite
)
.
is
.
inversion
factor
would
jmple
WDG
1
Tap
=
3.5
A
^
I
2
(
DC
)
«
‘
X
X
3
X
II
3
amperes
12
If
DC
meter
1
snot
*
X
UROUGH
must
values
in
tap
settings
.
Furthermore
,
ammeter
slope
In
circuit
shown
in
je
setting
.
connected
the
winding
the
higher
tap
following
equation
:
the
test
corresponding
r
1
gJ
4
.
mustf
.
be
set
up
such
that
The
common
lead
,
of
course
,
is
the
any
1
1
x
100
-
1
1
l
Slope
=
*
1
r
2
Tl
“
T
2
'
currents
i
3
-
Courtesy of NationalSwitchgear.com

IIIII I II
FIG. 1 CURRENT SLOPE CHARACTERISTICS OF THE RELAY
22
GEK
-
45307
80
r
NOTE
:
FOR
TWO
WINDING
TRANSFORMER
RELAYS
"
THROUGH
CURRENT
"
IS
TAKEN
AS
THE
SMALLER
OF
THE
TWO
CURRENTS
.
FOR
THREE
WINDING
TRANSFORMERS
,
IT
IS
TAKEN
AS
THE
SUM
OF
THE
INCOMING
OR
OUTGOING
CURRENTS
,
WHICH
-
EVER
IS
SMALLER
.
(
EACH
CURRENT
TO
BE
EXPRESSED
AS
A
MULTIPLE
OF
TAP
.
)
70
4
40
*
3
<
/
5
S
30
QC
25
*
4
£
1
|
20
15
SJ
.
0
16
14
4
6
8
10
12
THROUGH
CURRENT
IB
MULTIPLES
OF
TAP
0
2
STO
(
0378
A
538
-
3
)
LOW
Courtesy of NationalSwitchgear.com