This setting is used to uniquely identify the element.
This setting is used to select the parameter or set of parameters to be monitored.
For simple elements, this setting is used to program the level of the measured parameter above or below which the pickup
state is established. In more complex elements, a set of settings may be provided to define the range of the measured
parameters which will cause the element to pickup.
PICKUP DELAY Setting
This setting sets a time-delay-on-pickup, or on-delay, for the duration between the Pickup and Operate output states.
RESET DELAY Setting
This setting is used to set a time-delay-on-dropout, or off-delay, for the duration between the Operate output state and the
return to logic 0 after the input transits outside the defined pickup range.
The default output operand state of all comparators is a logic 0 or "flag not set". The comparator remains in this default
state until a logic 1 is asserted at the RUN input, allowing the test to be performed. If the RUN input changes to logic 0 at
any time, the comparator returns to the default state. The RUN input is used to supervise the comparator. The BLOCK input
is used as one of the inputs to RUN control.
This setting is used to define the operation of an element target message. When set to Disabled, no target message or illu-
mination of a faceplate LED indicator is issued upon operation of the element. When set to Self-Reset, the target message
and LED indication follow the Operate state of the element, and self-resets once the operate element condition clears.
When set to Latched, the target message and LED indication will remain visible after the element output returns to logic 0 -
until a RESET command is received by the relay.
This setting is used to control whether the Pickup, Dropout or Operate states are recorded by the event recorder. When set
to Disabled, element pickup, dropout or operate are not recorded as events.
When set to Enabled, an event is created for:
(Element) PKP (pickup)
(Element) DPO (dropout)
(Element) OP (operate)
The DPO event is created when the measure and decide comparator output transits from the pickup state (logic 1) to the
dropout state (logic 0). This could happen when the element is in the operate state if the reset delay time is not '0'.
The L90 may be used on systems with breaker-and-a-half or ring bus configurations. In these applications, each of the two
three-phase sets of individual phase currents (one associated with each breaker) can be used as an input to a breaker fail-
ure element. The sum of both breaker phase currents and 3I_0 residual currents may be required for the circuit relaying
and metering functions. For a three-winding transformer application, it may be required to calculate watts and vars for each
of three windings, using voltage from different sets of VTs. All these requirements can be satisfied with a single UR relay,
equipped with sufficient CT and VT input channels, by selecting the parameter to be measured. A mechanism is provided
to specify the AC parameter (or group of parameters) used as the input to protection/control comparators and some meter-
Selection of the parameter(s) to be measured is partially performed by the design of a measuring element or protection/
control comparator, by identifying the type of parameter (fundamental frequency phasor, harmonic phasor, symmetrical
component, total waveform RMS magnitude, phase-phase or phase-ground voltage, etc.) to be measured. The user com-
pletes the selection process by selecting the instrument transformer input channels to be used and some of the parameters
L90 Line Differential Relay
5.1.3 INTRODUCTION TO AC SOURCES
GE Power Management