P.3.280
SEL-411L Relay Protection Manual Date Code 20151029
Protection Functions
87L Enable and Blocking Logic
87L Enable and Blocking Logic
Set up the 87L function by configuring the general 87L application, enabling
the 87L function, and enabling individual sequence differential elements.
The E87CH setting configures the 87L communication scheme by specifying
the number of relay terminals (2, 3, or 4), the type of communications
channels (serial or Ethernet), and the master/outstation role, if applicable. If
the E87CH is set to N, the scheme cannot operate (see Figure 3.193).
The E87L group setting enables the 87L function as a protection element. The
87L element must be enabled in each of the relays to fully configure the 87L
scheme. Setting E87L to Y makes all three sequence differential elements
(phase, negative-sequence, and zero-sequence) available. However, further
control of each of these elements is possible through the use of their pickup
settings (87LPP, 87LQP, and 87LGP) for phase, negative-sequence, and
ground differential, respectively.
Setting the pickup threshold setting (87LPP, 87LQP, 87LGP) to OFF disables
a given element, even if E87L is set to Y.
Note that the values of the E87L, E87CH, 87LPP, 87LQP, and 87LGP settings
are not distributed within the 87L scheme; the settings remain local to a given
relay. As a result, you must enter these settings individually in each relay
within a given 87L scheme. Typically, you would apply the same settings
values in all relays, with the exception of the E87CH setting. This setting can
differ in three-terminal applications (3SM master versus 3SS outstation
configuration).
In the outstation relays, the E87L must be enabled and the E87CH setting
configured properly to initiate transmission of data to the relay master as well
as reception of 87DTT transfer tripping from the relay master. The 87LPP,
87LQP, and 87LGP settings are irrelevant in the outstation relays, because the
outstation relays do not use currents to run the 87L function.
Table 3.146 87L Enable and Blocking Settings
Setting Description Range Default
E87CH Application configuration for 87L
function
N, 2SS, 2SD, 3SM,
3SS, 2E, 3E, 4E
N
E87L Enable 87L function N, Y N
87LPP Pickup threshold of the phase
differential element in the normal
security mode (pu)
OFF, 0.1–2 1.2
87LQP Pickup threshold of the negative-
sequence differential element in the
normal security mode (pu)
OFF, 0.1–2 0.25
87LGP Pickup threshold of the zero-
sequence differential element in the
normal security mode (pu)
OFF, 0.1–2 0.25
87BLOCK Block condition for the 87L function SEL
OGIC control
equation
Not
PLT01
NOTE: To enable the overall 87L line
current differential protection, be sure
to set all of the following:
1) Set Port 87 setting E87CH to the
appropriate setting (2SS, 2SD, 3SS,
3SM, 2E, 3E, or 4E).
2) Group setting E87L = Y.
3) Push front-panel pushbutton
87L Enable.
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