Basler BE1-CDS220, Instruction Manual

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8-2 Application BE1-CDS220
When the 87 protection element is applied to other than transformer protection, set the pickup thresholds
for the 2
nd
, 5
th
, and 87UT units to 0 (setting disabled).
Basic Differential Protection Logic Scheme
This logic scheme (BASIC-87) provides three-phase, percent-restrained differential protection, with high-
speed unrestrained instantaneous differential protection for motor, generator, bus, and transformer
applications. A single zone of time overcurrent phase, neutral, and negative-sequence protection (51P, N,
and Q) is also included for backup protection.
Basic Transformer Logic Scheme
This logic scheme (BASIC-TX) provides three-phase, percent-restrained differential protection with high-
speed unrestrained instantaneous differential protection. The differential protection also includes 2
nd
and
5
th
harmonic restraint to improve security for transformer inrush. Time overcurrent phase, neutral, and
negative sequence protection are included on the high side (151P, N, and Q) and low side (251P, N, and
Q) of the transformer to provide time delay backup protection for the transformer and low-side zones. A
separate 51N fed from an optional ground CT (
I
G
) input is also included in this scheme and provides
sensitive, time overcurrent ground fault backup protection for the transformer low-side winding, the bus,
and the feeders.
Basic Transformer with Control Logic Scheme
This logic scheme (TX-W-CTL) provides the same differential and overcurrent protection elements as the
basic transformer logic scheme but with different outputs and the addition of virtual control switch logic
that can be operated locally or remotely (SCADA). The virtual 101-control switch is applied for tripping and
closing the low-side breaker, while 43 and 143 control switch elements are applied for tripping and closing
the high-side breaker. Virtual control switch 243 is used to turn off the differential protection element, and
virtual control switch 343 allows for automatic or manual selection of the active setting group.
Transformer Differential with Backup Logic Scheme
This logic (TX-W-BU) incorporates nearly all the protection elements available in the BE1-CDS220. These
include the differential functions with harmonic restraint as well as 51 phase, neutral, and negative-
sequence backup protection as seen from the transformer high side. Also included is a separate 51N fed
from an optional ground CT (
I
G
), 50P, N, and Q definite time bus protection as seen from the transformer
low-side breaker, and low-side breaker BF (breaker failure) protection with fast current reset. A current
supervised, external breaker failure initiate (BFI), 50/62, and a contact supervised BFI, 62, are also
included. The 101 virtual control switch is used to trip and close the low-side breaker while the virtual 43
switch is used to turn off the 87 function. Both virtual functions can be operated locally or remotely
(SCADA).
Bus Protection with Backup Logic Scheme
This logic scheme (BUS-W-BU) provides a primary zone of high-speed, low impedance, bus differential
protection and a backup zone of high-speed instantaneous overcurrent (bus interlocking) protection.
Feeder circuit backup protection and overall backup protection from the bus main to the first down-line
interrupting device for each feeder circuit are also provided.
The percent-restrained differential protection function is the only function of the 87 protection element
required for this application. Set the pickup of the 2
nd
, 5
th
, and 87 unrestrained functions to 0 (setting
disabled). The 87 unrestrained function has a setting only when the 2
nd
and 5
th
harmonic restraint functions
are set for transformer applications (refer to the discussion in Overview of Preprogrammed Logic
Schemes).
The 87 restrained element provides conventional high speed, low impedance, bus differential protection.
On feeder circuits using the 851 or 951 distribution feeder protection relays, the 50T, P, and Q elements
from the BE1-CDS220 are hard wired to the feeder protection package, providing a high-speed backup,
bus interlocked, zone of bus protection. When the BE1-CDS220 detects a feeder relay out of service, the
BE1-CDS220 50/51P, N, and Q protection elements and outputs are automatically reconfigured to provide
feeder protection. The 150/151P, N, and Q protection elements of the BE1-CDS220 are time coordinated
with the bus and feeder circuit protection, providing overall backup protection from the transformer side of
the bus main breaker through the first down-line interrupting device on the distribution circuit.