BECKWITH ELECTRIC M-3520, Instruction Book

Page: 174 / 217

Testing – 6
6–41
81R Rate of Change of Frequency (#1, #2)
VOLTAGE INPUTS: V1
CURRENT INPUTS: None
TEST SETTINGS: Pickup P Hz/s (0.10 to 20.00)
Delay D Cycles (1 to 8160)
Negative Sequence
Voltage Inhibit
N % (0 to 99)
Programmed Outputs Z Output (1 to 8)
Function 59 Disable
Functions 79, 81 See Below
■
NOTE : Testing of the 81R function requires a 3-phase voltage source capable of smoothly sweep-
ing the frequency of all voltages at a variable rate, continuously.
1. Disable functions as shown. Refer to Section 3.2, Configure Relay Data, for procedure.
2. Confirm settings to be tested.
3. Connect inputs in Configuration V1 designated previously. Refer to Section 6.4, Input Configurations
for configuration.
4. It is recommended that the 81 function be used to establish a window of operation for the 81R
function which is smaller than the actual sweep range of the frequncy applied. This is accomplished
by enabling 81#1 to pickup at a frequency 1 Hz higher than the minimum frequency of the ramp, and
assign a unique output. Set 81#2 to pickup 1 Hz lower than the maximum frequency of the ramp, and
assign a unique output (see figure below). The frequencies given are suggested for testing rates
below 10 Hz/S. Higher rates will require consideration of the capabilities of the test equipment
involved. Conncet both of these outputs to an input with jumpers, and set the 81R function to block
on this input. Set the time delays and seal-in times of the 81 functions to minimum. This will result in
an operational window that is free of erroneous Hz/S measurements when the voltage source begins
or ends the sweep.
F81#1 Block
81R Active Region
F81#2 Block
56.5 Hz
57.5 Hz 60 Hz 62.5 Hz 63.5 Hz
Using this setup, it is important to remember that the 81 elements being used will be operating in the
81R blocking regions, and the 81R contact operation must be distinguished from the 81 contacts.
5. Pickup Test: Apply Nominal Voltage to all three phases. Calculate the time for the pickup setting
and apply a sweep rate 25% less than the pickup ( P ) to all three phases.
Hold the TARGET RESET button in and slowly decrease the sweep time until the RATE OF CHG
FREQ 81R LED lights, or the pickup indicator operates on the computer target screen. The level
should be equal to P
&
0.05 Hz/S or
&
5 %. Release the TARGET RESET button, and increase the
sweep time, and the OUTPUT LED will go out.
6. Negative Sequence Voltage Inhibit Test : Reset targets and apply Nominal Voltage to all three
phases at a sweep rate 25% above P . Verify that the RATE OF CHG FREQ 81R LED lights, or the
pickup indicator operates on the computer target screen. Swing the phase angle of a phase voltage
and monitor the positive and negative sequence voltage levels. The
81R OUTPUT should reset when
the negative sequence voltage is N %
&
0.5% of the positive sequence voltage.