5-428
L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
TESTING
CHAPTER 5: SETTINGS
5
The minimum and maximum positive-sequence voltages to be monitored are:
Eq. 5-58
The base unit for voltage (see the FlexElements section in this chapter for additional details) is:
Eq. 5-59
The minimum and maximum voltage values to be monitored (in pu) are:
Eq. 5-60
The following settings are entered:
DCMA OUTPUT H3 SOURCE
: “SRC 2 V_1 mag”
DCMA OUTPUT H3 RANGE
: “0 to 1 mA”
DCMA OUTPUT H3 MIN VAL
: “0.404 pu”
DCMA OUTPUT H3 MAX VAL
: “0.635 pu”
The limit settings differ from the expected 0.7 pu and 1.1 pu because the relay calculates the positive-sequence quantities
scaled to the phase-to-ground voltages, even if the VTs are connected in “Delta” (see the Metering Conventions section in
chapter 6), while at the same time the VT nominal voltage is 1 pu for the settings. Consequently the settings required in this
example differ from naturally expected by the factor of
.
The worst-case error for this application could be calculated by superimposing the following two sources of error:
•
±0.5% of the full scale for the analog output module, or ± 0.005 x (1-0) x 254.03 kV = ±1.27 kV
•
±0.5% of reading
For example, under nominal conditions, the positive-sequence reads 230.94 kV and the worst-case error is
0.005
×
230.94 kV + 1.27 kV = 2.42 kV.
5.11 Testing
5.11.1 Test mode function
SETTINGS
TESTING
TEST MODE FUNCTION
The L90 provides a test facility to verify the functionality of contact inputs and outputs, some communication functions
and the phasor measurement unit (where applicable), using simulated conditions.
The test mode can be in any of three states: Disabled, Isolated, or Forcible.
The Disabled mode is intended for normal in service operation; relay protection, control and communication function is
normal. Test features are disabled, except channel tests and phasor measurement unit tests remain usable when
provided.
The Isolated mode is intended to allow the relay to be quickly placed in a state where the relay cannot negatively impact
the power system or other parts of the substation automation system. This is to allow changing settings, loading new
firmware, changing hardware modules, and changing communication connections. As far as practical all relay output
signals are blocked. Contact outputs are de-energized, latching outputs are frozen. Commands to bricks are blocked.
GOOSE transmissions have their "simulation" flag (also known as "test" flag) set, which results in the messages not being
accepted by compliant receiving devices that do not have a "Sim" data attribute set. The quality attribute of values that
can be output via 61850 MMS services are set to "invalid," which results in the values not being used for operational
purposes by compliant receiving devices. Direct I/O channel tests and PMU tests are usable on applicable models.
TESTING
TEST MODE
FUNCTION: Disabled
Range: Disabled, Isolated, Forcible
