4.2
SEL-787 Relay Instruction Manual Date Code 20081022
Protection and Logic Functions
Application Data
When you calculate the protection element settings, proceed through the
subsections listed earlier. Skip the RTD, voltage-based, and frequency
protection subsections if they do not apply to your specific relay model or
installation. See Section 6: Settings for the list of all settings (SEL-787
Settings Sheets) and various methods of accessing them. All current and
voltage settings in the SEL-787 are in secondary.
NOTE: The DeviceNet port
parameters can only be set at the rear
of the relay on the DeviceNet card
(see Figure G.1).
You can enter the settings by using the front-panel SET RELAY function (see
Section 8: Front-Panel Operations), the serial ports (see Section 7:
Communications), the DeviceNet port (see Appendix G: DeviceNet
Communications), or the Ethernet port (see Section 7: Communications).
Application Data
It is faster and easier for you to calculate settings for the SEL-787 if you
collect the following information before you begin:
➤ Power transformer data: MVA rating, winding configurations
and voltages, impedance, etc.
➤ Highest expected load current
➤ Current transformer primary and secondary ratings and
connections
➤ System phase rotation and nominal frequency
➤ Voltage transformer ratios and connections, if used
➤ Type and location of resistance temperature devices (RTDs), if
used
➤ Expected fault current magnitudes for ground and three-phase
faults
Group Settings (SET Command)
ID Settings
All models of the SEL-787 have the identifier settings described in Table 4.1.
The SEL-787 prints the Relay and Terminal Identifier strings at the top of the
responses to serial port commands to identify messages from individual
relays.
Enter up to 16 characters, including letters A–Z (not case sensitive), numbers
0–9, periods (.), dashes (-), and spaces. Suggested identifiers include the
location or number of the protected Transformer.
Table 4.1 Identifier Settings
Setting Prompt Setting Range
Setting Name :=
Fa c tor y D efa ult
UNIT ID LINE 1 16 Characters RID := SEL-787
UNIT ID LINE 2 16 Characters TID := TRNSFRMR RELAY
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