7-8 Maintenance and Testing Date Code 20011026
SEL-321/321-1 Instruction Manual
Acceptance Testing
When: When qualifying a relay model to be used on the utility system.
Goal: a) Ensure relay meets published critical performance specifications such as
operating speed and element accuracy.
b) Ensure that the relay meets the requirements of the intended application.
c) Gain familiarity with relay settings and capabilities.
What to
test:
All protection elements and logic functions critical to the intended application.
SEL performs detailed acceptance testing on all new relay models and versions. We are certain
the relays we ship meet their published specifications. It is important for you to perform
acceptance testing on a relay if you are unfamiliar with its operating theory, protection scheme
logic, or settings. This helps ensure the accuracy and correctness of the relay settings when you
issue them.
Commissioning Testing
When: When installing a new protection system.
Goal: a) Ensure that all system ac and dc connections are correct.
b) Ensure that the relay functions as intended using your settings.
c) Ensure that all auxiliary equipment operates as intended.
What to
test:
All connected or monitored inputs and outputs; polarity and phase rotation of ac
current and voltage connections; simple check of protection elements.
SEL performs a complete functional check and calibration of each relay before it is shipped.
This helps ensure that you receive a relay that operates correctly and accurately. Commissioning
tests should verify that the relay is properly connected to the power system and all auxiliary
equipment. Verify permissive trip or blocking signal inputs and outputs. Check breaker
auxiliary inputs, SCADA control inputs and monitoring outputs. Use an ac connection check to
verify that the relay voltage and current inputs are of the proper magnitude and phase rotation.
Brief fault tests ensure that the relay settings are correct. A Zone 1 AB fault, Zone 2 CG fault,
and Zone 3 three-phase fault can verify distance and directional elements, time delays, and the
relay trip and output functions. It is not necessary to test every relay element, timer, and function
in these tests.
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