Section 4
1MAC050144-MB C
Protection functions
244
615 series ANSI
Technical Manual
4.2.4.9
Technical data
Table 248: 47 Technical data
4.2.5
Positive-sequence undervoltage protection 27PS
4.2.5.1
Identification
4.2.5.2
Function block
Figure 115:
Function block
4.2.5.3
Functionality
The positive-sequence undervoltage protection 27PS is used to detect positive-sequence
undervoltage conditions. 27PS is used for the protection of small power generation plants.
The function helps in isolating an embedded plant from a fault line when the fault current
fed by the plant is too low to cause an overcurrent function to pickup but high enough to
maintain the arc. Fast isolation of all the fault current sources is necessary for a successful
autoreclosure from the network-end circuit breaker.
The function picks up when the positive-sequence voltage drops below the set limit. 27PS
operates with the definite time (DT) characteristics.
Characteristic
Value
Pickup accuracy
Depending on the frequency of the voltage
measured: fn ±2Hz
±1.5% of the set value or ±0.002 × V
n
Pickup time
12
1. Negative-sequence voltage before fault = 0.0 × V
n
, f
n
= 60 Hz, negative-sequence overvoltage with nominal
frequency injected from random phase angle, results based on statistical distribution of 1000 measurements
2. Includes the delay of the signal output contact
Minimum
Typical
Maximum
V
Fault
= 1.1 × set
Pickup
value
V
Fault
= 2.0 × set
Pickup
value
33 ms
24 ms
35 ms
26 ms
37 ms
28 ms
Reset time
< 40 ms
Reset ratio
Typical 0.96
Retardation time
< 35 ms
Operate time accuracy in definite time mode
±1.0% of the set value or ±20 ms
Suppression of harmonics
DFT: -50 dB at f = n × f
n
, where n = 2, 3, 4, 5,…
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Positive sequence undervoltage protection
function
PSPTUV
U1
27PS
1
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