ABB RELION REX640 Technical Manual page 841

1MRS759142 F
4.4.4.10 Technical data
Table 768: PREVPTOC Technical data
Characteristic
Operation accuracy
1, 2
Start time I
Reset time
Reset ratio
Retardation time
Operate time accuracy in definite time mode
Suppression of harmonics
4.4.5 Negative-sequence overcurrent protection for machines
MNSPTOC (ANSI 46M)
4.4.5.1 Identification
Function description
Negative-sequence overcurrent pro-
tection for machines
4.4.5.2 Function block
Figure 476: Function block
4.4.5.3 Functionality
The negative-sequence overcurrent protection for machines function MNSPTOC
protects electric motors from phase unbalance. A small voltage unbalance can
produce a large negative-sequence current flow in the motor. For example, a 5
percent voltage unbalance produces a stator negative-sequence current of 30
percent of the full load current, which can severely heat the motor. MNSPTOC
detects the large negative-sequence current and disconnects the motor.
The function contains a blocking functionality. It is possible to block the function
outputs, timers or the function itself.
1
Negative-sequence current before = 0.0, f
1000 measurements.
2
Includes the delay of the signal output contact.
REX640
Technical Manual
Start value
= 2.0 × set
Fault
Value
Depending on the frequency of the measured current: f
±1.5% of the set value or ±0.002 × I
Minimum Typical
23 ms 25 ms
Typically 40 ms
Typically 0.96
<35 ms
±1.0% of the set value or ±20 ms
DFT: -50 dB at f = n × f
IEC 61850
identification
MNSPTOC
= 50 Hz, results based on statistical distribution of
n
Protection functions
n
Maximum
28 ms
, where n = 2, 3, 4, 5,...
n
IEC 60617 ANSI/IEEE C37.2
identification device number
I2>M 46M
±2 Hz
n
841