Basler BE1-CDS220, Instruction Manual

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BE1-CDS220 Application 8-1
SECTION 8
•
APPLICATION
INTRODUCTION
This section discusses application of the BE1-CDS220 Current Differential Protection System using
preprogrammed logic schemes. The paragraphs on Details of Preprogrammed Logic Schemes describe
the characteristics of each logic scheme and how they combine to create a differential protection scheme
for transformers, generators, motors, and buses. A detailed description of preprogrammed schemes is
also provided. This section concludes with tips on programming custom logic schemes to meet specific
user applications.
The preprogrammed logic schemes are designed to accommodate the most common differential
protection applications. The protection engineer can choose a logic scheme that closely meets his
application and adapt it by changing the protection and control elements and settings. In most cases, this
eliminates the need to create a custom logic scheme from scratch.
Please note that each preprogrammed logic scheme also illustrates typical ways of using or controlling
various functions. The user may choose to create a custom logic scheme by mixing the logic from several
of the preprogrammed schemes. The logic also can be modified to incorporate some of the features
described in the Application Tips provided at the end of this section. The flexibility of BESTlogic allows the
engineer to create a protection and control scheme that meets the exact requirements of his application.
EXPLANATION OF TERMS
Understanding the following terms and definitions will help to clarify the application discussions that follow.
Function Element
Stand-alone protection or control function that is equivalent to the discrete component counterpart.
Virtual Switches
Virtual switches are logic switches that emulate traditional protection and control panel switches such as
the breaker control switch (101) and on/off, selector switches (43). Virtual switches may be operated via
the ASCII command interface or the front panel HMI. Operation of these switches can be password
protected or disabled if the user chooses not to use them. You might do this when using a preprogrammed
logic scheme without changing the preprogrammed logic.
OVERVIEW OF PREPROGRAMMED LOGIC SCHEMES
The BE1-CDS220 has six preprogrammed logic schemes. Three of the logic schemes are intended for
use on transformers. One of the schemes is for motor protection with a speed sensing input, one is for bus
protection with backup, and one is a basic 87 function designed for multiple applications including
transformer, motor, bus, or generator protection.
The 87 function as applied to transformer protection is fundamentally different from the application of the
87 function to motors, generators, and buses. That is, the 2
nd
and 5
th
harmonic restraint elements are
required on transformer applications to prevent false tripping resulting from magnetizing inrush currents.
However, waveform distortion resulting from heavy current transformer (CT) saturation can cause the
harmonic restraint units to block restrained differential tripping (87RT) for internal faults. Therefore, a high-
speed, unrestrained instantaneous differential element (87UT) is also required for transformer
applications.
CAUTION
If "NONE" logic is selected, the protection elements are not connected to the
virtual outputs or output relays, and fault recording features including targets are
not enabled. The user will have to program and enable these features and
functions as part of building a custom logic scheme.