Areva MiCOM P921 - Page 55

Technical Guide P92x/EN TD/E11
Technical Data
MiCOM P921-P922-P923 Page 9/30
3. PROTECTION SETTING RANGES
All the following functions can be activated or deactivated independently.
3.1 Undervoltage (ANSI code 27)
3.1.1 Threshold settings (secondary values)
- Nominal voltage range : 57 – 130V
Setting Range Step size
V<= Voltage Set 5 – 130V 0.1V
V<<= Voltage Set 5 – 130V 0.1V
V<<<= Voltage Set 5 – 130V 0.1V
- Nominal voltage range : 220 – 480V
Setting Range Step size
V<= Voltage Set 20 – 480V 0.5V
V<<= Voltage Set 20 – 480V 0.5V
V<<<= Voltage Set 20 – 480V 0.5V
3.1.2 Time delay settings
Each voltage element is associated to an independent time delay.
Each measuring element time delay can be blocked by the operation of a user
defined logic (optical isolated) input (see “Blocking logic1” or “Blocking logic2”
functions).
Element Time delay type
1
st
stage Definite Time (DT) or IDMT
2
nd
stage DT
3
rd
stage DT
3.1.3 Inverse Time Delay Characteristic
The inverse characteristic is defined by the following formula :
÷
÷
÷
÷
ø
ö
ç
ç
ç
ç
è
æ
-
=
1
Vs
V
TMS
t
where :
t = operating time in seconds
TMS = time Multiplier Setting
V = applied input voltage
Vs = relay setting voltage
NOTE : this equation is only valid for
V
s
V
ratio< than 0.95