ABB SA-1 Manual

41-348.11C SA-1 Generator Differential Relay - Class 1E
2
2.0 CONSTRUCTION
The type SA-1 relay consists of:
•Restraint Circuit •Operating Circuit
•Sensing Circuit •Amplifier Circuit
•Trip Circuit •Indicating Circuit
•Surge Protection Circuit •External Reactors
The principal parts of the relay and their location are
shown in Figures 1 through 4 (page 5 thru page 9)
and Figure 14 (page 16).
2.1 RESTRAINT CIRCUIT
The restraint circuit of each phase consists of a cen-
ter-tapped transformer, a resistor, and a full-wave
rectifier bridge. The outputs of all the rectifiers are
connected in parallel. The parallel connection of rec-
tifiers is a maximum voltage network. Hence, the
voltage applied to the filter circuit is proportional to
the phase current with the largest magnitude.
2.2 OPERATING CIRCUIT
The operating circuit consists of a transformer, a
resistor, and a full wave rectifier bridge. The outputs
of all the rectifiers are connected in parallel. This par-
allel connection of rectifiers is a maximum voltage
network. Hence, the voltage applied to the filter cir-
cuit is proportional to the differential current with the
largest magnitude.
2.3 SENSING CIRCUIT
The sensing circuit is connected to the output of the
restraint filter circuit, the operating filter circuit and
the input to the amplifier circuit.
2.4 AMPLIFIER CIRCUIT
The amplifier circuit consists of a two-transistor
amplifier which controls the operation of a relaxation
oscillator.
The amplifier circuit is connected to the sensing cir-
cuit such that it receives the difference in output of
the restraint filter and the operating filter. Thus, the
polarity of the input voltage to the amplifier depends
upon the relative magnitude of the voltages appear-
ing on the restraint and operating filters. When the
voltage output of the operating filter is greater than
the output voltage of the restraint filter, a voltage of a
certain polarity appears across the input of the ampli-
fier. To trigger the amplifier requires that the output
voltage of the operating filter be greater than the out-
put voltage of the restraint filter.
2.5 TRIP CIRCUIT
The trip circuit consists of a thyristor which has an
anode, cathode, and a gate. The anode of the thyris-
tor is connected to the positive side of the dc supply
and the cathode of the thyristor is connected to the
negative side of the dc supply through the trip coil of
a breaker. The gate of the thyristor is connected to
the output of the amplifier circuit through a pulse
transformer.
With no gate current flowing, the thyristor acts as an
open circuit to the breaker trip coil. When a gate cur-
rent is applied to the thyristor, the thyristor connects
the breaker trip coil to the dc supply.
2.6 INDICATING CIRCUIT
The indicating circuit is triggered by a signal from the
amplifier of the relay. Under normal or non-fault con-
ditions, the indicating circuit is turned off. When a
fault is applied to the relay, the amplifier will conduct
to cause a signal to flow into the indicator circuit.
When the indicator circuit is triggered, the lamp will
turn on. This lamp will remain lit until the indicator cir-
cuit is interrupted by resetting the micro-switch.
2.7 SURGE PROTECTION CIRCUIT
The surge protection circuit consists of two capaci-
tors (C10 and C11) and a RC network which is con-
nected across the anode and cathode of the tripping
thyristor to prevent the SCR from firing by a surge
voltage on the dc supply.
2.8 EXTERNAL REACTORS
Three reactors are mounted on a metal plate with a
separate terminal strip. The reactors are of the satu-
rable type.
3.0 OPERATION
The type SA-1 relay is connected to the protected
apparatus as shown in Figure 5 (page 10). On exter-
nal faults, current flows through the primary winding
of the restraint transformers to induce a voltage on
the restraint side of the sensing circuit. If the two sets
of main current transformers have different perfor-
mances, some current will flow out of the mid-tap of
the restraint transformers to the operating transform-
ers. This will produce a voltage on the operating side
of the sensing circuit. With the relay correctly applied,
sufficient restraint voltage will exist to prevent the
operating voltage from triggering the amplifier.

SA-1 Generator Differential Relay - Class 1E 41-348.11C
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The percentage slope characteristic of the relay lim-
its the operating voltage on heavy external faults
where the performance of the two sets of current
transformers may be quite different.
On internal faults, the operating coil current is the dif-
ference of the current flowing in each of the windings
of the restraint transformer and sufficient operating
voltage is available to overcome the restraint voltage.
4.0 CHARACTERISTICS
The percentage slope curves are shown in Figures 8
and 9 (page 12 and page 13). It will be observed that
the relay operates at 5% unbalance at 5 amperes
restraint (Figure 8, page 12) to provide high sensitiv-
ity for internal faults up to full load conditions. At 60
amperes restraint, the operating current required to
trip the relay is 30 amperes or 50% unbalance (Fig-
ure 9, page 13). Thus, when 60 amperes through
fault current is flowing, the output of the main current
transformers may vary considerably without causing
incorrect operation.
The minimum pickup of the relay is 0.14 amperes.
The time curve of the relay is shown in Figure 10
(page 14).
The frequency response characteristic of the Type
SA-1 relay is shown in Figure 11 (page 15).
5.0 ENERGY REQUIREMENTS
5.1 EACH RESTRAINT CIRCUIT
Burden at 5 amperes is 0.25 VA
Continuous rating 20 amperes
1 second rating 300 amperes
5.2 OPERATING CIRCUIT
The burden imposed by the operating circuit on each
current transformer is variable because of the satu-
rating transformer. At 0.5 amperes, it is 1.48 ohms,
and at 60 amperes, it is 0.47 ohms.
Note that the neutral reactors are in series with the
operating coil circuit. They also have a saturating
characteristic, with a maximum impedance of roughly
80 ohms.
Continuous rating 10 amperes
1 second rating 200 amperes
5.3 AMPLIFIER
The dc burden on the station battery is:
6.0 SETTINGS
There are no taps on either transformer and, conse-
quently, there are no settings to be made. The
48/125 Vdc relays are normally shipped for 125 volts.
For 48 Vdc applications use the mid tap on the resis-
tor mounted at the top of the relay. The red dot on the
resistor is the common point –DO NOT REMOVE.
7.0 INSTALLATION
The relays should be mounted on switchboard pan-
els or their equivalent in a location free from mois-
ture. Mount the relay vertically by means of the four
mounting holes on the flange for semi-flush mount-
ing.
Either a mounting stud or the mounting screws may
be utilized for grounding the relay. The electrical con-
nections may be made directly to the terminals by
means of screws.
The external reactor assembly should be mounted
and wired per “Interwiring Connection Drawing”, Fig-
ure 7 (page 11).
For detailed FT case information, refer to Instruction
Leaflet 41-076.
8.0 ADJUSTMENTS AND
MAINTENANCE
The proper adjustments to insure correct operation of
this relay have been made at the factory and should
not be disturbed after receipt by the customer.
8.1 ROUTINE TEST
The following check is recommended to insure that
the relay is in proper working order. All checks can
best be performed by connecting the relay per the
test circuit of Figure 12 (page 15). Due to high imped-
ance of the external reactor, prior to saturation, the
test circuit of Figure 12 should be used to test the
relay only. The reactors can be checked by applying
Volts Milliamperes Watts
125 dc
48 dc 55 60 6.9 2.9

41-348.11C SA-1 Generator Differential Relay - Class 1E
4
0.2 amperes 60 hertz and reading the voltage drop
across the reactor with a high impedance true rms
reading voltmeter. The voltage drop will be between
20 and 26 V (true rms). For 0.4 amperes input, the
reading should be between 24 and 31 volts (true
rms).
1. Minimum Trip Current with IRset at zero
amperes, apply 0.14 ±5% amperes operating
current to each operating circuit of the relay. The
relay should operate and the indicator lamp
should light.
2. Differential Characteristic
a) Apply IRof 5 amperes and adjust the operat-
ing current until the relay operates. The relay
should operate and the indicator lamp should
light with an operating current of 0.25
±0.012 amperes. Repeat for each phase of
the relay.
b) Apply IRof 60 amperes and adjust the oper-
ating current until the relay operates. The
relay should operate and the indicator lamp
should light with an operating current of 30
±3 amperes. Repeat for each phase of the
relay.
8.2 MAINTENANCE
All relays should be checked once a year to detect
the electronic component failures which occur on a
random basis. The tantalum capacitors C1, C2, C3,
C4 and C13 may have a common mode failure char-
acteristic and should be checked visually for symp-
toms of electrolyte leakage every year and replaced
if necessary.
9.0 CALIBRATION
Use the following procedure for calibrating the relay if
the relay adjustments have been disturbed. This pro-
cedure should not be used until it is apparent the
relay is NOT in proper working order.
1. Minimum Trip Current –Connect the relay per
test circuit of Figure 12 (page 15). With switch K
open, adjust the operating resistor in the rear of
the relay until the relay operates with I0equal to
0.14 amperes. Do not make adjustments to the
resistor unless the dc is disconnected.
The indicator lamp should light when the relay
operates.
Repeat for each phase of the relay.
2. Percentage Slope Characteristic (Low Cur-
rent) –Set IRequal to 5 amperes and adjust the
restraint resistor in the rear of the relay until the
relay operates with I0= 0.25 ±0.012 amperes.
Do not adjust resistor with dc applied to relay.
The indicator lamp should light when the relay
operates.
Repeat for each phase of the relay.
Percentage Slope Characteristic (High Cur-
rent) –Set IRequal to 60 amperes for the operat-
ing current of 30 amperes. Replace the resistor
R17 if necessary. The value of R17 can be
between 0 and 100 ohms. Repeat for the other
two phases, if necessary, replacing R18 and R19
respectively.
3. Electrical Checkpoints –See Table 1 (page
page 6)
10.0 ELECTRICAL CHECKPOINTS
Connect relay per test circuit of Figure 12 (page 15).
All voltage readings should be made with a high
resistance voltmeter. Refer to Figure 4 (page 9) for
the location of checkpoints. Voltage readings are
approximate. The voltage readings “Input to Ampli-
fier”should NOT be taken with relay in service.
11.0 RENEWAL PARTS
Repair work can be done most satisfactorily at the
factory. However, interchangeable parts can be fur-
nished to customers who are equipped for doing
repair work. When ordering parts, always give the
nameplate data.

SA-1 Generator Differential Relay - Class 1E 41-348.11C
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Figure 1. Type SA-1 Generator Differential Relay without Case (Front View) Figure 2. Type SA-1 Generator Differential Relay without Case (Rear View)
LB
LM
LT
UB
UM
UT
Terminal Numbers

41-348.11C SA-1 Generator Differential Relay - Class 1E
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Table 1:
(Values in Parenthesis Represent Desensitized SA-1)
CIRCUIT PRIMARY CURRENT PHASE
CHECKPOINTS (TYPICAL VALUE)
TERMINAL VALUE FUNCTION
Operating 0.14A 1 2
3
2 - 7
3 - 6
4 - 5
2.5 ac
2.5 ac
2.5 ac
Input to operate rectifier
Input to operate rectifier
Input to operate rectifier
Sensing
(Operating)
0.14A Any Phase
+ to -
23 - 26
24 - 26
24 - 8
8 - 25
25 - 26
2.1 dc
1.85 dc
0.55 dc
0.65 dc
0.65 dc
Ref: a = b + c + d
Output to rectifier
a. Output to operating sensing circuit
b. Input to amplifier
c.
d. Output to restraint sensing circuit
30.0A Any Phase + to -
24 - 26 51.0 dc
Restraint 5.0A 1 2
3
18 - 13
17 - 14
15 - 16
6.0 ac
6.0 ac
6.0 ac
Input to restraint rectifier
Input to restraint rectifier
Input to restraint rectifier
Sensing
(Restraint)
5.0A Any
Phase + to -
25 - 26
25 - 8
8 - 24
24 - 26
2.1 dc
1.2 dc
0.6 dc
0.3 dc
Ref: a = b + c + d
a. Output to restraint sensing circuit
b.
c. Input to amplifier
d. Output to operating sensing circuit
60.0A Any Phase + to -
25 - 26 42.0 dc
Amplifier
0 + to -
27 - 8
12 - 8
10 - 8
0.7 dc
24.0 dc
24.0 dc
Minimum
Trip
Current
+5%
Any
Phase + to -
27 - 8
12 - 8
21 - 8
0.5 dc
24.0 dc
10.0 dc
NOTE: Terminal numbers refer to the printed circuit board (See Figure 4)

SA-1 Generator Differential Relay - Class 1E 41-348.11C
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Table 2:
Electrical Parts List
CIRCUIT SYMBOL REFERENCE STYLE
Resistors UT, UM, UB
Resistors LT, LM, LB
Resistors R14
Zener Z2
SCR
Reactor L1
60 Ohms, 25W
265 Ohms, 25W
1.8K, 40W
IN2986B
1875676
1725542
187A321H06
629A798H03
184A614H05
1478B98G01
SA Module Style Number 408C673G01 Sub 45
Resistor R1
Resistor R2
Resistor R3, R4, R5
Resistor R6
Resistor R7
Resistor R8
Resistor R9
Resistor R10
Resistor R11
Resistor R12
Resistor R13
Resistor R17, R18, R19
Capacitor C1, C2, C3, C13
Capacitor C4
Capacitor C5
Capacitor C6
Capacitor C7
Capacitor C8, C9
Diode D1 to D24
Diode D25, D26
Zener Z1
SCR
Transistor T1, T2
Transistor T3
Transformer TR-1
270 Ohms, 1W
2K, 5%
15K, 5%
2.7K, 5%
68K, 5%
27K, 5%
2.2K, 5%
100 Ohms, 10%
220 Ohms, 5%
680 Ohms, 5%
47K, 5%
33 Ohms, 5%
25 MFD, 125V
22 MFD, 35V
0.5 MFD, 200V
2.2 MFD, 35V
2.0 MFD, 200V
0.47 MFD, 50V
IN4821
IN645A
IN752A
K1149-13
2N3417
2N2647
629A531H18
184A763H34
184A763H55
184A763H37
184A763H71
184A763H61
184A763H35
187A643H03
184A763H11
184A763H23
184A763H67
187A290H13
184A637H01
184A661H16
187A624H11
837A241H16
187A624H05
762A680H04
188A342H16
837A692H03
186A797H12
184A640H13
848A851H02
629A435H01
629A372H02
SPK Module Style Number 1584C01G01
Resistor R15
Capacitor C10, C11
Capacitor C12
470 Ohms, 1W
0.01 MFD, 1.5KV
2.0 MFD, 200V
187A643H19
3536A32H02
3509A33H01

41-348.11C SA-1 Generator Differential Relay - Class 1E
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Figure 3. Internal Schematic of Type SA-1 Relay in Type FT-32 Case 48/125 Vdc
*Sub 9
3520A40

SA-1 Generator Differential Relay - Class 1E 41-348.11C
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Figure 4. Component Location on Printed Circuit Board Type SA-1 Relay 48/125 Vdc
3525A93
Sub 3

41-348.11C SA-1 Generator Differential Relay - Class 1E
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Figure 5. External Schematic of Type SA-1 Relay for Generator Protection
Figure 6. Reactor Outline
775B965
Sub 4
775B982
Sub 1

SA-1 Generator Differential Relay - Class 1E 41-348.11C
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Figure 7. Relay and Reactor Interconnection
775B981
*Sub5
NOTE: A - PLACE IT. 1 TO 3 IN IT. 5 FOR SHIPPING
Lead
IT. LSCREW SIZE
AB
1 3.00 .164 - 32 .164 - 32
2 4.00 .164 - 32 .190 - 32
3 3.00 .164 - 32 .190 - 32
4 13.438 .164 - 32 .190 - 32
ITEM
PART
NAME STYLE DWG. ITEM GR. NOTE CODE ENG. REF. REQ
01 LEAD 57Z0301 616 A 63-D-653 2
02 LEAD 57Z0401 622 A 63-D-655 3
03 LEAD 57Z0301 622 A 63-D-655 1
05 BAG 836A618 H04 B 27-D-5478 1
AB
L±.156

41-348.11C SA-1 Generator Differential Relay - Class 1E
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Figure 8. Percentage Slope Characteristic at Low Value of Restraint Current
3537A44
Sub 2

SA-1 Generator Differential Relay - Class 1E 41-348.11C
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Figure 9. Percentage Slope Characteristic at High Value of Restraint Current
878A742
Sub 3

41-348.11C SA-1 Generator Differential Relay - Class 1E
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Figure 10. Typical Operation Time Characteristic
471106

SA-1 Generator Differential Relay - Class 1E 41-348.11C
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Figure 11. Typical Frequency Response Curve
Figure 12. Test Diagram for Type SA-1 Relay
3537A45
Sub 2
184A864
Sub 6