7-4 Maintenance and Testing Date Code 20000421
SEL-251, -2, -3 Instruction Manual
We recommend testing the SEL-251 Relay with a latching relay to simulate line breaker auxiliary
contact action. This ensures proper assertion and deassertion of the circuit breaker status
function assigned to an input on the back panel.
INITIAL CHECKOUT
The initial checkout procedure should familiarize you with the relay and ensure that all functions
are operational. Study Functional Specification and Description in Section 2: Specifications,
Command Descriptions in Section 3: Communications, and Section 4: Event Reporting for a
complete understanding of the relay capabilities.
Equipment Required
The following equipment is necessary for initial checkout.
1. Terminal with EIA-232 serial interface
2. Interconnecting cable between terminal and relay
3. Source of control power
4. Source of three-phase voltages and currents
5. Ohmmeter or contact opening/closing sensing device
6. Plug-in mating connectors/wiring harness (Plug-In Connector model only)
Checkout Procedure
In the procedure below, you will use several relay commands. Section 3: Communications
provides a full explanation of all commands. The following information should allow you to
complete the checkout without referring to the detailed descriptions.
Note: In this manual, commands to type appear in bold/upper case: OTTER. Keys to press
appear in bold/upper case/brackets: <ENTER>.
Relay output appears in the following format:
Example 21.6 kV distribution feeder Date: 04/01/93 Time: 01:01:01
♦ ♦ Step 1
Purpose: Be sure you received the relay in satisfactory condition.
Method: Inspect the instrument for physical damage such as dents or rattles.
♦ ♦ Step 2
Purpose: Verify the requirements for the relay logic inputs, control power voltage level, and
voltage and current inputs.
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