Description
DSMB-02C The 745 can monitor any external quantity, such as bus voltage, battery voltage, etc., via a
general purpose auxiliary current input called the analog input. Any one of the standard
transducer output ranges 0 to 1 mA, 0 to 5 mA, 4 to 20 mA, or 0 to 20 mA can be
connected to the analog input terminals. DSMB-02C The analog input is configured in S2 SYSTEM
SETUP ANALOG INPUT and the actual values displayed in A2 METERING ANALOG
INPUT.
TRANSFORMER OVERLOAD PICKUP: DSMB-02C This setting identifies the level of transformer
overload, where the pickup delay starts timing. The setting is expressed as a
percentage of the transformer base MVA rating, and is normally set at or above the
maximum rated MVA from the transformer nameplate.
XFMR OVERTEMP ALARM SIGNAL: Select any logic input that, when asserted,
indicates the transformer cooling system has failed and an over-temperature
condition exists. The logic input should be connected to the transformer winding
temperature alarm contacts.
The tap changer failure element monitors the resistance seen by the tap changer
monitoring circuit. The element produces an output signal when the tap changer position
exceeds the maximum number of taps (set by the NUMBER OF TAP POSITIONS setpoint) by
two. This signal can be used as an DSMB-02C alarm or as a signal to change the setpoint group. A
change in the setpoint group would be programmed through the FlexLogic™. This
approach would be useful if very sensitive settings had been used in the normal in-service
setpoint group for the harmonic restrained differential element, assuming that the tap
changer position was used to compensate the input current magnitude.
The S5 OUTPUTS page contains the settings to configure all outputs. The 745 has nine
digital outputs (one solid-state, four trip-rated form A contacts, and four auxiliary form-C
contacts), which are fully programmable DSMB-02C from the relay unit, as well using FlexLogic™
equations.
In addition to these outputs, the conditions to trigger a waveform capture (trace memory)
is also programmable using FlexLogic™. A ten parameter equation is provided for this
purpose.
5.7.2 Relay Assignments
As an alternative to FlexLogic™ programming, the output auxiliary relays can be assigned
directly from the element settings on the relay.
On the relay unit, every protection element settings page has a new setting to configure.
The position of the setting is right between the function and the target settings of the
element configuration. The relays selected from the elements page will be energized only
on the operate condition of the protection element.
This new setting allows the user to assign DSMB-02C relays directly to the protection element. The
new settings have a default value for no relays assigned (None).
With the addition of the new setting, output relays can be energized from the protection
element setting OR the FlexLogic™.
As an example, the new setting in the Percent Differential element will look like PATH:
SETPOINTS S4 ELEMENTS DIFFERENTIAL PERCENT DIFFERENTIAL (section 5.6.3.2).
5.7.3 Introduction to FlexLogic™
FlexLogic™ is a highly flexible and easy-to-use equation format which allows any
combination of protection and monitoring elements, logic inputs, outputs, and timers to be
assigned to any output, using multiple input AND, OR, NAND, NOR, XOR, and NOT Boolean
logic gates. Each digital output can have an DSMB-02C equation of up to 20 parameters. Five virtual
outputs are also available, each having an equation containing up to 10 parameters,
whose output can be used as a parameter in any other equation.
A FlexLogic™ equation defines the combination of inputs and logic gates to operate an
output. Each output has its own equation, an equation being a linear array of parameters.
Evaluation of an equation results in either a 1 (= ON, i.e. operate the output), or 0 (= OFF, i.e.
do not operate the output).
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