Concerning PRC_024-02, we work with those who offer Reactive Following Seminars concerning ride through technologies, and how an interlocked-combine-breaker grounding switch (VDH/GSMI) with a “Reactive Following Program” may provide the functionality required by PRC-024-02 for SPP and WPP.
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The Grounding Breaker Provides Internal/External Fault Discrimination
Here is why we think or project this can work, the grounding breaker, provides discrimination and quickly signals via “the phase conductors on the affected collector circuit”, the generators when the fault is inside or outside the solar plant; where the VDH/GSMI opens and clears and then closes to ground the home run cable of the affected collection circuit, causing the voltage to drop below 15%.
Should the fault appear outside the plant for nine cycles near or at zero volts, at full power, PSCAD simulations show for the same conditions with near full active power that the voltage measured at the generators should be higher when there is zero voltage at the point of interconnection (POI) than when the VDH/GSMI opens and then grounds the collection circuit, thus providing a level of discrimination for protection and trip as measured at the terminals of each individual generator within the solar power plant or wind power plant. If the power is less than 100% for the wind plant the voltages would be certainly lower, however,
We believe PRC-024-02 specifically specifies “full power” as a test condition.
With the above in mind, generators shut down quickly; or if they island, they island into a three-phase bolted ground, and they can wait for the remote trip signal without creating over voltage and other damage. Therefore, with a grounding breaker we know we may support quick discrimination of internal and external faults within Solar Power Plant (SPP) or Wind Power Plant (WPP); where PRC-024-02 requires that the plant does not need to ride through internal faults, and therefore, the grounding breaker handles many islanding conditions.
Reactive Following Program
A reactive following program involves engineers and technicians in the field. This is a big part of the job. The work includes but not limited to many expensive man hours to figure out the condition of the “as configured” along with the “operating conditions” of a WPP or SPP. The work may include high side remediation of the WPP or SPP; where work may either include the addition of a high side cap bank, with switch on zero-cross breaker, or STATCOM located on the high side with a separate transformer other than the Main Plant Transformer, and not connected directly to the 34.5 kV bus.
The National Electric Reliability Corporation (NERC) that acts as an electric reliability organization (ERO) requires relay settings and wind power plants to operate down to zero volts for nine cycles as shown in PRC-024-02. We find if the plant has an OLTC and it is “out of position”, the WPP or SPP may not ridethrough the fault as required by PRC-024-02. Reactive Following can help WPP or SPP designers and engineers provide the functionality required by NERC as specified in PRC-024-02. We believe each OEM provided their customers with dynamic reactive capability with ridethrough technology. With that in mind, each individual generator within a SPP or WPP is expected to provide Dynamic Reactive Power, and can provide Dynamic Reactive Power during a fault on the Transmission-Provider’s transmission system.
A “Reactive Following Program” provides for the “constraint assessment” needed within the plant. We find that with existing technology a WPP or SPP may provide the capability of its existing assets along with other technology to support the “Transmission-Providers” transmission system with combined dynamic reactive power and ridethrough during the fault in accordance with PRC-024-02.
Dynamic Reactive Power with Ride Through Technologies
At Lake Benton Minnesota in the year 2000 with the Zond Z750, Type 3 wind turbine generator, together we developed high voltage ride through and low voltage ride through technologies that had dynamic reactive support during a “ridethrough” event, since then many have joined in to evolve and provide improvements on such technologies. Together we invite those folks at your company to come and learn about what we are doing and promote and teach such novel and useful technologies.
Copyright Thomas Wilkins et al. 2017 All Rights Reserved