ABB COQ Памятка по эксплуатации - Страница 3
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Input
Condition
Phase Rating Amps Rating Amps 5 Amps At 5 Amps
Three
A
Phase
B
C
Phase
A-B
To
B-C
Phase
C-A
Phase
A-N
To
B-N
Neutral
C-N
setting of "4" the relay will close its contacts in 30
seconds with the above tap currents applied to the
relay.
As shown by the curves of Figure 5, the relay's char-
acteristic is defined by a generator characteristic
2
I2
T = K. The relay characteristic is such that it coin-
cides with the generator characteristic at 1 per unit
negative sequence current but at higher values of
negative sequence current, the relay characteristic is
substantially parallel and slightly less than the gener-
ator characteristic. In this manner, a suitable margin
of safety is obtained between the two characteristics.
Figure 5 defines the relay characteristics for two gen-
erators – one with a permissible constant of "30" and
the other with a constant of "90". The time dial set-
tings for these constants are "4" and "11" respec-
tively. Similar protection for other generators with
2
I2
T constants between "30" and "90" is obtained by
settings of the time dial. Figure 4 shows the neces-
sary time dial settings for various I2
referring to this figure, the time dial can be set so the
relay protects different generators whose I2
stants range from "30" to "90".
Figure 6 demonstrates the use of a tap setting lower
than the full load current of the machine to accommo-
2
date I2
T limits from 5 to 10 while still providing wide
TABLE 1
Typical Overcurrent Unit Burden And Thermal Rating
Continuous
One Second Watts at Volt Amps
5
100
5
100
5
100
PHASE-TO-PHASE FAULT CONDITION
5
100
5
100
5
100
PHASE-TO-NEUTRAL FAULT CONDITION
5
100
5
100
5
100
2
T constants. By
2
T con-
Z ∠θ
0.33 ∠0°
8.3
8.3
0.15 ∠110°
1.3
3.8
0.19 ∠52°
2.9
4.7
0.26 ∠−161.7° (-0.24-j 0.08)
6.1
6.5
0.32 ∠65°
3.4
8.0
0.46 ∠−152°
10.2
11.5
0.21 ∠8.70°
5.1
5.2
0.51 ∠24.3°
3.5
3.8
0.22 ∠29.0°
4.8
5.5
contact spacing. For this figure a tap setting of 3 is
used with a machine full load current of 4.
Typical time-current curves of the relay are shown in
Figure 7. Minimum pickup is approximately 0.6 of the
tap value current. See Table 1 for burdens and termi-
nal ratings.
3.2. Trip Circuit
The main contacts will safely close 30 amperes at
250 volts dc and the seal-in contacts of the indicating
contactor switch will safely carry this current long
enough to trip a circuit breaker.
The indicating contactor switch has two taps that pro-
vide a pickup setting of 0.2 or 2 amperes. To change
taps requires connecting the lead located in front of
the tap block to the desired settings by means of a
screw connection.
3.3. Indicating Contactor Switch (ICS)
0.2 ampere tap 6.5 ohms dc resistance
2.0 ampere tap 0.15 ohms dc resistance
4.
SETTING CALCULATIONS
Determine from the machine manufacturer the per-
2
missible I2
T constant. From Figure 4, find the
required time dial setting.
I.L. 41-161J
Circuit Impedance
(R+jX)
(0.33+j 0.00)
(-0.05+j 0.14)
(0.11+j 0.15)
(0.13+j 0.29)
(-0.41-j 0.22)
(0.20+j 0.03)
(0.14+j 0.06)
(0.19+j 0.11)
3