Basler BE1-CDS220, Instruction Manual

Page: 82 / 476

4-16 Protection and Control BE1-CDS220
Table 4-7. Operating Settings for Phase Differential
Setting Range Increment Unit of Measure Default
Minimum Pickup (minpu)
0 = Disabled
0.10 to 1.00
0.01 Times tap 0
Slope (Maximum restraint)
(Average Restraint)
15 to 60
15 A to 60 A
1
1 A
% I operate vs. maximum
restraint
% I operate vs. average
restraint
45
N/A
2
nd
Harmonic Inhibit
0 = Disabled
5.0 to 75.0
0.5
% of 2
nd
vs. fundamental I
operate
18
5
th
Harmonic Inhibit
0 = Disabled
5.0 to .0
0.5
% of 5
th
vs. fundamental I
operate
35
Unrestrained output pickup
(URO)
0 = Disabled
0 to 21
1 Times tap 0
2
nd
Harmonic sharing
between phases
0 = Independent
1 = Shared
N/a N/a 1
Maximum restraint uses the maximum of two compensated input currents, and average restraint uses the
average of the two compensated input currents. For example, if maximum restraint is used (no A after the
slope percentage), the restraint current for phase A would be
I
RA
= max (I
A1 COMP,
I
A2 COMP
). If average
restraint were used (an A after the slope percentage), the restraint current for phase A would be given by
Equation 4-4.
2
) I ( ) (I
I
A2COMP A1COMP
RA
+
=
Equation 4-4. Calculate Restraint Current for Phase A
Retrieving Phase Differential Status from the Relay
The status of each logic variable can be determined from the ASCII command interface using the RG-
STAT command. See Section 6, Reporting and Alarm Functions, General Status Reporting, for more
information.
87ND - Neutral Differential Protection
When equipped with the optional independent ground input, BE1-CDS220 relays can provide sensitive
differential protection for ground faults on the grounded side of a delta/wye transformer. On impedance
grounded systems, ground fault levels may be reduced below the sensitivity of the phase differential
protection. The result is that ground faults within the protected zone have to be cleared by time delayed
backup overcurrent protection if sensitive differential protection is not available.
The function block in Figure 4-15 has two outputs: 87NDPU (pickup) and 87NDT (trip). A BLK (block)
logic input is provided to block operation of the differential protection. When this expression is TRUE, the
function is disabled. For example, this may be an input wired to a differential cutoff switch.
D2840-25
02-01-99
PERCENT
NEUTRAL
DIFF
(87ND)
BLK
87NDT
87NDPU
Mode =
0- disable
1- G vs. N1
2- G vs. N2
Figure 4-13. Neutral Differential Logic Block