GE L60 Instructions Manual page 354

SYSTEM SETUP CHAPTER 5: SETTINGS
5.4.3.1 User selection of AC parameters for comparator elements
CT/VT modules automatically calculate all current and voltage parameters from the available inputs. Users must select the
specific input parameters to be measured by every element in the relevant settings menu. The internal design of the
element specifies which type of parameter to use and provides a setting for source selection. In elements where the
parameter can be either fundamental or RMS magnitude, such as phase time overcurrent, two settings are provided. One
setting specifies the source, the second setting selects between fundamental phasor and RMS.
5.4.3.2 AC input actual values
The calculated parameters associated with the configured voltage and current inputs are displayed in the current and
voltage sections of actual values. Only the phasor quantities associated with the actual AC physical input channels display
here. All parameters contained within a configured source are displayed in the sources section of the actual values.
5.4.3.3 Disturbance detectors (internal)
The disturbance detector (ANSI 50DD) element is a sensitive current disturbance detector that detects any disturbance on
the protected system. The 50DD function is used directly in some elements in the relay, for example VT Fuse Failure
detector or Fault Report. It can also be used to supervise current-based elements to prevent maloperation as a result of
the wrong settings or external CT wiring problem. A disturbance detector is provided for each source.
The 50DD function responds to the changes in magnitude of the sequence currents. The disturbance detector logic is as
follows.
Figure 5-67: Disturbance detector logic
5
The disturbance detector responds to the change in currents of twice the current cut-off level. The default cut-off threshold
is 0.02 pu; thus by default the disturbance detector responds to a change of 0.04 pu. The metering sensitivity setting
( ) controls the sensitivity of the disturbance detector
PRODUCT SETUP  DISPLAY PROPERTIES  CURRENT CUT-OFF LEVEL
accordingly.
5-146 L60 LINE PHASE COMPARISON SYSTEM – INSTRUCTION MANUAL