4-22 Control Logic Date Code 20080110
SEL-387E Instruction Manual
The three Close variables, CL1 through CL3, are set up to define the conditions under which a
closing can take place. In our example these are set up to respond to a CLOSE n command from
a communications port or an external contact input from a SCADA RTU or other switch.
Specifically, CL1 = CC1+ /IN104, CL2 = CC2 + /IN105, and CL3 = CC3 + /IN106, where “/”
denotes detection of a “rising edge” for the input shown. Within these SEL
OGIC
control
equations, inputs IN104 to IN106 have been defined as being related to the close initiation
function for the specific breakers. The CLn variable initiates the close logic, resulting in Relay
Word bit CLSn being set to logical 1, unless the logic is disabled by an unlatch condition,
discussed below. Note that connections for the closing function are not
shown in Figure 2.19 in
Section 2: Installation.
Closing can now take place, but only if an output contact has been assigned to this function.
Returning to the Output Contact Logic setting area for our example, we set OUT105 = CLS1,
OUT106 = CLS2, and OUT107 = CLS3. These contacts must be wired to the closing circuits of
the individual breakers.
In the Close Logic setting area three variables remain. ULCL1 to ULCL3 define the conditions
for unlatching the close logic. These are set in our example to be the presence of any trip logic
output. That is, ULCL1 = TRIP1 + TRIP4, ULCL2 = TRIP2 + TRIP4, and ULCL3 = TRIP3 +
TRIP4. ULCLn will remove the seal-in of the close logic, and return Relay Word bit CLSn to
zero. A closed 52a contact or a Close Failure Detection will also unlatch the Close logic. The
output contact that follows the CLSn bit will open in response.
CFD, or Close Failure Detection time delay, is an additional miscellaneous timer setting for
close logic. CFD is an overriding timer to unlatch the close logic if the breaker has not yet
closed. The default setting is 60 cycles.
SEL
OGIC
C
ONTROL
E
QUATIONS
This manual refers throughout to settings or variables that take the form of SEL
OGIC
control
equations. These equations are convenient for customizing control logic to the relay and
enhancing relay performance for specific customer needs and practices.
While most users of SEL relays are familiar with SEL
OGIC
control equations, the capabilities of
this logic, types of operators, number of variables, and equation syntax have varied from one
relay product to another. We intend in this manual to explain how SEL
OGIC
control equations
work in general and how we implement these equations in the SEL-387E Relay.
SEL
OGIC
Control Equations Fundamental Description
Relay Word bits are the basic building blocks of SEL
OGIC
control equations. The end of this
section of the manual contains a complete list of these bits. The Relay Word bits are simple
digital quantities having a logical value of either 0 or 1. The terms “assert” or “asserted” refer to
a Relay Word bit that has a value of 1 or is changing from 0 to 1. The terms “deassert” or
“deasserted” refer to a Relay Word bit that has a value of 0 or is changing from 1 to 0. Various
relay elements cause assertion or deassertion of Relay Word bits, which the fixed internal logic
of the relay uses to make decisions, to interpret inputs, or to drive outputs. You have access to
these bits and can use them to exercise flexibility in defining inputs or outputs, specifying
To Next Page
Loading...
