80
80
NV10P - Manual - 01 - 2015
CHARACTERISTICS
Frequency rate of change - 81R
Preface
Fast trips may be issued when positive/negative or any (module) changes in frequency are detected.
The 81R element is faster than underfrequency and overfrequency protections.
Four operation thresholds, independently adjustable with adjustable delay are provided.
Each threshold may be separately enabled or disabled.
Operation and settings
The frequency rate of change, acquired from U
L1
[1]
input voltage, is compared with the setting values
(df>, df>>, df>>>, df>>>>); a start is issued when the frequency overcomes the adjustable threshold
(START); after expiry of the associated operate time (t
df
>, t
df
>>, t
df
>>>, t
df
>>>>) a trip command is
issued; if instead the frequency rate of change drops below the threshold, the element is restored.
When the frequency value is out of the lock range, it is fi xed to the upper or lower limit
(20 Hz or 90 Hz).
All elements operate with defi nite time characteristic.
The frequency rate of change protection is enabled only when the maximum of the U
L1
input voltage
overcomes 0.2 U
n
for a tfEN adjustable time.
Setting of the tfEN value is available inside the Set \ Base menu with “level 1” session.
Each element can be enabled or disabled by setting ON or OFF the State parameter inside the Set \ Profi le
A(or B) \ Frequency rate of change-81R \ df> Element (df>> Element, df>>> Element, df>>>> Element) \ Def-
inite time menu.
For every threshold the positive/negative or module of frequency change cam be selected (typi-
cally for speedup/slowdown or any speed change of the generator; the df operating mode can be
set (Mode-df>, Mode-df>>, Mode-df>>>, Mode-df>>>>) inside the Set \ Profi le A(or B) \
Frequency rate of change-81R \ df> Element (df>> Element, df>>> Element, df>>>> Element) \ Set-
points menu.
The trip of df> element may be inhibited by the start of the second, third and/or fourth ele-
ment (df>>,
df>>>, df>>>>) by setting ON the Disable df> by start df>>, Disable df> by start
df>>>, Disable df> by start df>>>> (df>disbydf>>, df>disbydf>>>, df>disbydf>>>>)
parameters available inside the Set \ Profi le A(or B) \ Frequency rate of change-81R
\ df>> Element (df>>> Element, df>>>> Element) \ Setpoints menus.
Similarly the trip of the:
df>> element may be inhibited by start of the third and/or fourth element (df>>> and/or
df>>>>) by setting ON the Disable df>> by start df>>>, start df>>>> (df>>disbydf>>>,
df>>disbydf>>>>) parameter available inside the Set \ Profi le A(or B) \ Frequency rate of
change-81R \ df>>> Element, (df>>>> Element) \ Setpoints menus.
Note 1 For sensors inputs versions the frequency is measured on the phase voltageU
L1
, while for versions with inductive VTs inputs the frequency is
measured on-phase-to-phase voltage
U
12
On the diagrams U
L1
, U
L2
, U
L3
are the input phase voltages or phase-to-phase according to the corresponding versions
•
t-int-F81R.ai
df
t
General operation time characteristic for the frequency rate of change elements - 81R
df>>>>
def
df>>>
def
df>>
def
df>
def
dt
f
def>>
dt
f
def>>>
dt
f
def>>>>
dt
f
def>
TRIP
Timers-F81R.ai
t
dfEN
81R Enable
81R enabled81R disabled 81R disabled
0.20 U
n
U
L1
t
Frequency rate of change enable timer - 81R
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