Saving time with SCADA
In an effort to minimize the number of sustained power outages resulting from storm-triggered temporary faults, Jersey Central Power & Light (JCP&L) installed an adaptive-relay scheme. The scheme improved the utility's system average interruption duration index (SAIDI) reliability metric by reducing the number of time-consuming fuse replacements.
JCP&L was previously limited by installed electromechanical relays equipped with timing options that were selectable locally at substations. JCP&L engineers proposed a series of adaptive relays tied into the utility's supervisory control and data acquisition (SCADA) system. JCP&L needed to find an adaptive relay that had field-tested reliability, complied with the SCADA system and existing electromechanical and microprocessor-based relays, operated at 48 or 125 V direct current, and controlled more than one breaker installation
Electroswitch , Weymouth, Mass., provided JCP&L with a variation of its two-position, Series 31 tagging relay (TR). Electroswitch installed the TRs at 275 locations, comprising all 1,100 circuits in JCP&L's 13 districts. Each district now has one substation outfitted with SCADA-interfaced equipment that measures wind speed and detects lighting.
When the wind speed exceeds 25 mph, or lighting is detected, the pertinent regional dispatch office (RDO) can reset the protecting-timing scheme of its substations, either individually or by group. Actuation of the Electroswitch TR changes a substation's relay timing from fuse-sacrifice mode to fuse-saving mode.
In fuse-saving mode, a feeder circuit breaker is set to operate instantaneously—faster than lateral tap fuses. Since 70% of storm faults are temporary, opening the circuit first and then closing back on a time-delayed setting allows most of these faults to clear themselves. If the fault is still present after the breaker closes, the fuse on the affected lateral will blow, which requires a line crew to replace it.
At the selected substation, the TR latches in its red mode tag, which indicates that the facility is in fuse-saving mode. After the storm, the RDO sends another SCADA command to return the substation to fuse-sacrifice mode, and the TR's tag changes to green.
In 2008, JCP&L experienced 884 breaker operations in response to the line disturbances. The system's control of the instantaneous timing response of the electromechanical protective relays saved 22.4 SAIDI minutes, while maintaining the integrity of the installed line fuses.
Information provided by Jersey Central Power & Light.
AT A GLANCE
Jersey Central Power & Light (JCP&L) installed an adaptive-relay scheme to minimize the number of sustained power outages resulting from strom-triggered faults.
JCP&L needed to find an adaptive relay that featured field-tested reliability, compatibility with the SCADA system, controlled more than one breaker installation, and operated at 48 or 125-V direct current.
Electroswitch provided JCP&L with a solution by implementing:
A variation of its two-position, Series 31 tagging relay.
SCADA-integrated equipment on one substation at each JCP&L district.
An adaptive relay system, which saved 22.4 SAIDI minutes after 884 breaker operations in response to line disturbances.
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