Industry — Renewable Energy
Collector and interconnection switchgear for inverter-based generation plants
Utility-scale solar and wind plants gather hundreds of inverters or turbines onto a medium-voltage collector system and deliver power to the grid through a substation the utility will scrutinize closely. Apex engineers the collector switchgear, interconnection protection and controls, and integrates plant SCADA so operators and the utility see the same picture of the plant.
Operating realities
What makes renewable energy distribution its own discipline
Collector system design at 34.5 kV
Collector feeders at 34.5 kV aggregate inverter blocks or turbine strings across large sites, and the switchgear at the collector substation has to handle their continuous current, fault duty and switching frequency. Feeder count, cable sizing, grounding transformer placement and reactive compensation are traded against cost and losses. Collector switchgear is often outdoors and far from staffed facilities, which shapes enclosure and maintenance choices.
Fault current from inverters and turbines
Inverter-based generation contributes limited fault current with characteristics that depend on the control firmware, and Type 3 and Type 4 wind turbines behave differently again. Feeder protection has to detect faults with contribution from both the grid and the plant, and ground-fault detection depends on how the collector system is grounded. Manufacturer short-circuit models are required inputs to the protection study.
Interconnection studies and utility requirements
The transmission or distribution provider's interconnection study defines protection at the point of interconnection, ride-through and reactive power requirements, metering and telemetry. The plant's protection and control design has to satisfy those requirements and pass the utility's review and witness testing. Study timelines and requirement changes late in the process are a common schedule driver.
Plant SCADA, curtailment and reporting
Plant controllers manage real and reactive power set points, respond to utility curtailment signals and report telemetry over DNP3 or IEC 61850 to the utility and the owner's operations center. Breaker status, relay events and meter data from the collector switchgear have to be integrated into that same system with synchronized time stamps. Communication loss to a remote collector breaker must be visible, not silent.
How Apex fits
LV, MV, automation and monitoring for renewable energy
Low-voltage equipment
Auxiliary and inverter-block distribution
Apex engineers 480 V switchboards and auxiliary power distribution for inverter skids, tracker systems, substation controls and communications equipment, including transfer between grid, auxiliary generator and, where present, storage sources. Protection accounts for bidirectional flow at inverter-block transformers.
Learn moreMedium-voltage equipment
34.5 kV collector switchgear and interconnection breakers
Metal-clad switchgear at 38 kV class with vacuum circuit breakers forms the collector bus and feeder breakers, with relaying, grounding transformer connections and capacitor or reactor feeders as the plant design requires. Walk-in outdoor enclosures and arc-resistant construction are evaluated for remote sites.
Learn moreAutomation & controls
Plant controller and utility interface
Plant control systems coordinate inverter or turbine set points, interconnection breaker supervision and curtailment response with the utility's telemetry and control requirements. Protective functions remain with the relays, and switching follows the approved plant operating procedures.
Learn moreMonitoring & analytics
Collector switchgear health and event records
Relay event reports, breaker operation counts, feeder metering and enclosure environmental data are collected into plant SCADA and the historian over DNP3 or IEC 61850 where applicable. Condition indicators help schedule maintenance trips to remote collector substations; the analytics recommend, and the operator acts.
Learn moreTypical equipment
What a renewable energy one-line usually contains
- 38 kV class metal-clad collector switchgear with 1,200 A to 3,000 A vacuum circuit breakers
- Collector feeder protection relays with directional and voltage-supervised overcurrent elements
- Grounding transformers and neutral grounding equipment for collector systems
- Capacitor bank and reactor feeder breakers for reactive compensation
- Interconnection protection panels with 27, 59, 81, 32 and 87 functions per the utility study
- Walk-in outdoor switchgear enclosures for collector substations
- 480 V switchboards and auxiliary power transfer for inverter skids and substation controls
- Plant SCADA gateways and RTUs (DNP3, IEC 61850 where applicable)
Codes and standards that commonly apply
Specifications govern
- Interconnection of inverter-based generation commonly references IEEE 1547 for distribution-connected plants and IEEE 2800 for transmission-connected plants, together with the interconnecting utility's own requirements; the utility's interconnection study and agreement govern.
- Metal-clad collector switchgear generally follows IEEE C37.20.2, with vacuum circuit breakers rated to IEEE C37.04 and C37.06; arc-resistant designs are tested per IEEE C37.20.7 where the specification requires them; the project specification governs.
- Installation of photovoltaic and wind systems commonly follows NEC Articles 690 and 694 for portions under NEC jurisdiction, while utility-side substation work often follows the National Electrical Safety Code; the engineer of record and the jurisdiction govern which applies.
Questions we hear
Frequently asked
+Why is the collector system usually 34.5 kV?
It is a practical balance between cable cost, losses over long collector runs and the availability of switchgear, transformers and cable at 38 kV class ratings. Lower voltages increase losses and cable count on large sites, while higher collector voltages bring equipment that is harder to source and site. Most inverter-block and turbine transformers are readily available with 34.5 kV secondaries.
+How does inverter fault behavior change collector feeder protection?
Inverters contribute roughly rated current during a fault, and the contribution can drop quickly as controls react, so a collector feeder fault may look like a modest overload from the plant side while the grid side supplies most of the fault current. Directional elements, voltage-supervised overcurrent and careful ground-fault design based on the collector grounding method are the usual answers. The study uses the manufacturer's short-circuit models rather than a generic source assumption.
+Can Apex support a plant that has already been built by others?
Yes, for modernization and integration scopes such as relay upgrades, SCADA integration, monitoring additions or collector switchgear replacement. Apex has engineering and integration experience across ABB, Eaton and Schneider Electric power platforms, and the work begins with the existing drawings, settings and interconnection agreement so that any change stays consistent with the utility's requirements.
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Apex Power Distribution · ApexPower.ai
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