System protection
Protective Relay Testing
Testing, calibration, and functional verification of protective relay systems — ensuring that your power system protection operates correctly when a fault occurs.
Protection That Works When You Need It
Protective relays are the intelligence of a power system's protection scheme. They monitor electrical quantities — current, voltage, frequency, and impedance — and initiate circuit breaker operation when abnormal conditions indicate a fault or system disturbance. A relay that fails to operate, operates too slowly, or operates incorrectly can allow a fault to escalate into catastrophic equipment damage, extended outages, or personnel injury.
J. Wesley Services Group performs protective relay testing and calibration in accordance with NETA ATS and MTS standards, IEEE C37 guidelines, and manufacturer specifications. We test both electromechanical and modern digital (microprocessor-based) relay systems, working in close coordination with utility operations and facility maintenance personnel under strict safety protocols.
Testing Services We Perform
Functional Testing and Calibration
Verification that each relay element operates at its specified pickup value and within the required time-delay curve. We apply test currents and voltages using precision relay test equipment and confirm operation against the relay's coordination study settings.
Overcurrent Relay Testing
Testing of phase and ground overcurrent elements including pickup, time-delay curves (inverse, very inverse, extremely inverse), and instantaneous elements. Overcurrent relays are the most common protection element in distribution systems.
Differential Relay Testing
Functional testing of transformer, bus, and generator differential relays including slope characteristics, restraint, and harmonic restraint elements. Differential protection is the primary protection for large transformers and generators.
Distance (Impedance) Relay Testing
Testing of distance relay zones, directional elements, and load encroachment settings for transmission and sub-transmission line protection. Distance relays require precise calibration to ensure correct zone reach and coordination.
Voltage and Frequency Relay Testing
Testing of overvoltage, undervoltage, overfrequency, and underfrequency relay elements used for generator protection, load shedding, and system stability applications.
End-to-End and Scheme Testing
Functional testing of complete protection schemes including communications-assisted tripping (POTT, PUTT, DCB), breaker failure, and automatic reclosing schemes. Verifies that all elements of the protection system work together correctly.
Relay Types We Test
- Electromechanical relays (induction disc, plunger, balanced beam)
- Solid-state (static) relays
- Microprocessor-based (digital) protective relays
- Multi-function digital relays (SEL, GE, ABB, Schweitzer, Beckwith)
- Generator protection relays
- Motor protection relays