Areva MiCOM P921 - Page 122

P92x/EN FT/E11 Technical Guide
User Guide
Page 44/110 MiCOM P921-P922-P923
10.3 Zero sequence overvoltage (neutral displacement) protection
The zero sequence overvoltage element functions according to the VT configuration.
· VT configuration = 3V
pn
+ V
r
, then the [59N] will operate based on the residual
voltage (due to the summation of the 3 phase voltages), measured on relay
terminals (49-50).
· VT configuration = 3V
pn
, then [59N] will operate based on the zero sequence
voltage U
0
=
(Ua + Ub + Uc)
3
calculated internally.
The inverse characteristic (only for the 1
st
stage) is given by the following formula :
t = K / (1 – M)
Where, K = Time Multiplier Setting
t = operating time in seconds
M = Applied input voltage / Relay setting voltage (Vs)
To gain access to the “RESIDUAL O/V” sub-menu from the default display, press 2
once, 6 4 times, 2 once and 6 twice.
[59N] RESIDUAL O/V
Heading of the “RESIDUAL O/V” menu
[59N] V0>=
NO
Description : configuration of the 1
st
residual overvoltage stage
Range : YES/NO
Note : if disabled (« NO » selected), all the following messages
are invisible, until « V0>> » message.
[59N] V0>=
5.0 V
Description : setting of the 1
st
residual overvoltage stage
Range : range 57-130V : 0.5-130V, step = 0.1V
range 220-480V : 2-480V, step = 0.5V
[59N] DELAY TYPE =
DMT
Description : selection of the time delay characteristic
Range : definite time (DMT) / inverse definite time (IDMT)
[59N] TMS=
1.0
Description : time multiplier setting.
Range : 0.5 – 100, step = 0.5
Note : this message only seen if “IDMT” time delay selected
[59N] tRESET V0>=
10 ms
Description : reset time for the first residual overvoltage stage
Range : 0 – 100s, step = 0,01s
Note : this message only seen if “IDMT” time delay selected
[59N] tV0>=
40 ms
Description : time delay setting for a definite time curve.
Range : 0 – 599s, step = 0.01s
Note : this message only seen if “DMT” time delay selected
[59N] V0>>=
NO
Description : configuration of the 2
nd
residual overvoltage stage
Range : NO / AND / OR
Note : if disabled (« NO » selected), all the following messages
are invisible, until « V0>>> » message.
[59N] V0>>=
5.0 V
Description : setting of the 2
nd
residual overvoltage stage
Range : range 57-130V : 0.5 – 130V, step =0,1V
range 220-480V : 2 – 480V, step = 0,5V