Areva MiCOM P921 - Page 107

Technical Guide P92x/EN FT/E11
User Guide
MiCOM P921-P922-P923 Page 29/110
7.7 "FREQ. and df/dt CONFIG" submenu
Additional menu for MiCOM P923 only.
This menu allows the user to select the number of cycle to be involved in the
calculation of the rate of change of frequency elements, and the number of
confirmation of calculation for positionning the protection.
In fact, the instantaneous element is positionned after exceeding the threshold for a
programmable number of df/dt function calculation.
This number of confirmation is 2 or 4.
In addition, it allows the configuration of the undervoltage blocking element.
When the input voltage value is unsufficient this will lead to irregular behavior and it
is imaginable that the frequency elements could mal operate.
This is important during line energization, de-energization or a generator
acceleration where significant distortion can be experienced. To prevent the mal
operation, all the frequency elements and related thresholds are blocked by mean of
an adjustable U/V blocking function.
To gain access to this menu from the default display, press 2 once, 6 once,2 once
and 6 4 times.
7.7.1 HMI description
FREQ. and df/dt
CONFIG
Heading of "FREQ. and df/dt CONFIG" submenu.
df/dt : CYCLE NB =
1
Description : define the total number of fintegration time
involved for calculation of the rate of change of frequency
Range : 1 – 200 step of 1
df/dt : VALIDAT.
NB = 4
Description : validation number for protection operation
Range : 2 or 4
PROTECTION
BLOCK = 20.0 V
Description : U/V threshold for blocking frequency elements
Range : 5V to 130V, step of 0.1V (for the "57-130V" model)
20V to 240V, step of 0.1V (for the "220-480V"
model)
NOTE : This threshold is independent of the undervoltage threshold in
the "PROTECTION MENUS". It uses the analogic input voltages
delivered for the calculation and measurement of the frequency.
It never uses the line to line voltage.