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This section of the Express Installation Guide provides step-by-step instructions for a typical application of the SEL-787
Transformer Protection Relay. For more information on the setting procedures, please refer to the SEL-787 manual, or con-
tact your local SEL representative. For more information on relay setting using ACSELERATOR QuickSet SEL-5030 Soft-
ware as shown in this example, refer to Section 3 in the SEL-787 manual.
Transformer applications of the SEL-787 will require the configuration of the relay to match the transformer winding con-
struction, as well as current and voltage transformer ratios and configurations. The relay is equipped with a wide selection
of protection and logic elements. Section 4 in the SEL-787 manual, describes all the protection and logic functions of the
relay, together with all the necessary settings.
Design the specific protection, logic, and communications system for your transformer application. Use the Settings Sheets
provided in Section 6 of the manual to record the relay settings, or connect the relay to a personal computer (PC) and use
ACSELERATOR QuickSet to enter the settings. Follow the steps below to set the relay.
Step 1. Connect to the SEL-787 via ACSELERATOR QuickSet.
a. Connect the relay to a PC by using a SEL-C234A serial or SEL-C662 USB cable.
b. Apply power to the relay.
c. Start the ACSELERATOR QuickSet software program and establish communication with the relay.
d. Click on the Read Settings From Device icon to download the current settings from the relay.
e. Save the downloaded setting file into your ACSELERATOR QuickSet database.
Step 2. Gather transformer nameplate information. Typical information should include the following:
➤Transformer MVA ratings
➤Transformer winding voltages
➤Transformer winding configurations
➤Transformer impedances
Additionally, verify the connection method used for
the current transformers that will be monitoring the
transformer windings. Current transformers will be
connected in a wye or delta configuration. Record the
current transformer ratios.
Record the information you gathered in this step for
use in the following steps.
Step 3. Edit the ACSELERATOR QuickSet relay settings file.
Group 1 Settings
a. Open and edit the Group Configuration settings.
Typically, the transformer configuration
information will be the same for all protection
settings groups used in the SEL-787.
b. Set the transformer CT connections, W1CT and
W2CT, to DELTA or WYE as dictated by the
recorded CT connection information from Step 1.
c. Set the CT ratio settings CTR1 and CTR2.
d. Set the transformer winding rated voltages
VWDG1 and VWDG2.
e. Set the transformer capacity setting MVA. Setting
MVA should be set to the maximum MVA rating
of the transformer.
Relay Settings
