Electric Power Generation Electrical Construction & Instrumentation: Plant Through Switchyard
The Full Electrical Scope of a Power Generation Facility
Power generation facilities require electrical construction from the generator terminals through the step-up transformer, high-voltage switchyard, and interconnection to the transmission grid. Between the generator and the grid lies a system of protection relays, metering, auxiliary power distribution, and plant control instrumentation that must be installed, tested, and commissioned as an integrated system before the unit can be synchronized to the grid.
Wikota Electrical Services delivers electrical construction and I&C for thermal, combined-cycle, and peaking power generation facilities. In-house electrical engineering through Mid-America Services supports power systems design, protective relay coordination, and arc-flash analysis from the earliest project stage through commissioning. Zero recordable incidents in company history and ISNetworld tracking meet the prequalification requirements of utility and independent power producer owners.
Generator Electrical Systems
Generator Output and Step-Up Transformer
The generator output circuit connects the generator terminals to the generator step-up transformer, which raises the generator output voltage to transmission voltage for delivery to the switchyard. This circuit, typically at medium voltage, carries the full generator output current and is among the most consequence-laden electrical installations on the project. Wikota Electrical installs isolated phase bus duct or cable connections between the generator and the GSU transformer, including the grounding transformer, potential transformers for voltage measurement, and current transformers for protection and metering. The generator neutral grounding system is installed and tested before the unit is energized.
Excitation and Voltage Regulation Systems
The generator excitation system controls the magnetic field in the generator rotor to regulate terminal voltage and reactive power output. Excitation system electrical scope covers the excitation transformer wiring, automatic voltage regulator panel installation, power potential transformer connections, and the field flashing circuit used to establish initial field current at startup. The AVR is commissioned in coordination with the equipment manufacturer’s commissioning engineer before the unit is synchronized.
Auxiliary Power Distribution
Power plant auxiliary systems, including cooling pumps, fans, fuel handling equipment, and plant service loads, require a reliable auxiliary power supply that remains available even when the main generator is offline. Auxiliary power distribution scope covers unit auxiliary transformers, station service transformers, medium-voltage motor control centers for large auxiliary motors, and low-voltage distribution to plant service loads. Emergency diesel generator installation and automatic transfer switching for critical plant loads are included in the auxiliary power scope.
Switchyard Construction and Protection Systems
High-Voltage Switchyard Electrical
The high-voltage switchyard connects the power plant to the transmission grid through circuit breakers, disconnect switches, current and potential transformers, surge arresters, and bus work at the transmission voltage level. Switchyard construction scope includes equipment foundations and structure assembly coordination, equipment setting, grounding grid installation and testing, bus work installation, and protective relay panel installation in the switchyard control building. Wikota Electrical performs switchyard electrical installation in coordination with the utility’s interconnection requirements and line energization sequence.
Protective Relay Installation and Testing
Generator protection systems defend the generator and associated electrical equipment against faults, abnormal operating conditions, and out-of-step operation. Protection scope includes differential protection, loss-of-field protection, over and under-voltage protection, frequency protection, and the generator breaker failure scheme. Wikota Electrical installs protection relay panels, CT and PT wiring, and relay communications wiring. Relay testing is performed using secondary injection methods to verify that each protection function operates at the specified setpoint before the unit is energized.
Revenue Metering and SCADA
Interconnection agreements require revenue-grade metering at the point of interconnection that measures the energy and reactive power delivered to the grid. Revenue metering scope includes metering-class CT and PT installation, revenue meter installation and sealing, and the communication interface reporting metered values to the utility’s billing system. Plant SCADA system field device installation covers the data acquisition points required for plant operations monitoring and reporting to the owner’s energy management system.
Plant Instrumentation and Control Systems
Balance of Plant I&C
Balance of plant instrumentation covers the field devices monitoring temperatures, pressures, flows, and levels throughout the plant’s cooling systems, fuel systems, and auxiliary equipment. Wikota Electrical installs field instrumentation to the instrument index and loop diagrams, performs loop checks, and commissions the BOP control system inputs and outputs before unit startup. Combustion turbine and heat recovery steam generator instrumentation is installed in coordination with the equipment manufacturer’s commissioning requirements.
Emissions Monitoring Systems
Power generation facilities are required to monitor stack emissions continuously under Title V air permits. Continuous emissions monitoring systems measure NOx, SO2, CO, CO2, and oxygen concentration in the stack gas. CEMS electrical scope covers analyzer enclosure electrical connections, sample conditioning system electrical, and the data acquisition system recording and reporting emissions data to the regulatory authority. CEMS commissioning includes relative accuracy test audits performed in coordination with the state environmental agency.
Combined-Cycle and Peaking Facility Scope
Combined-cycle power plants recover heat from combustion turbine exhaust in a heat recovery steam generator to drive a steam turbine, increasing overall plant efficiency. The electrical scope spans two generator electrical systems, two sets of protection systems, and the interconnection between the combustion turbine and steam turbine auxiliary systems. Peaking facilities are designed for rapid startup and frequent cycling. Their electrical systems must accommodate the thermal and mechanical stresses associated with frequent startups and shutdowns, which affects protective relay setpoints, auxiliary power transfer sequences, and the design of cooling system electrical controls.
| Electrical Construction | Generator output circuit, GSU transformer connections, auxiliary power distribution, switchyard electrical, bus work, grounding systems, and protective relay panel installation. |
|---|---|
| Instrumentation & Controls | Balance of plant I&C, protective relay installation and secondary injection testing, revenue metering, CEMS electrical, and plant SCADA field devices. |
| Engineering & Design | Power systems design, protective relay coordination studies, arc-flash analysis, and electrical drafting through Mid-America Services. |
| Project Delivery | Pre-construction engineering coordination, construction management, commissioning support through grid synchronization, and project visibility. |
| Safety, Quality & Compliance | Zero recordable incidents, ISNetworld tracking, NFPA 70E, high-voltage switchyard safety protocols, and QA/QC documentation for utility interconnection requirements. |
Frequently Asked Questions
AA power generation facility electrical scope begins at the generator terminals and extends through the generator step-up transformer, high-voltage switchyard, and transmission interconnection. Within the plant, the scope covers auxiliary power distribution for cooling, fuel handling, and plant service loads, emergency diesel generator installation, protective relay panels for generator and transformer protection, revenue metering at the interconnection point, balance of plant instrumentation, and emissions monitoring systems. The specific scope varies by facility type: combined-cycle plants have two generator electrical systems, and peaking plants have electrical systems designed for frequent startup cycling.
A generator step-up transformer raises the generator output voltage from the generator terminal voltage, typically in the range of 13.8 to 25 kV, to the transmission voltage level, typically 115 kV or higher. The electrical installation scope includes isolated phase bus duct or cable connections from the generator terminals to the transformer primary, grounding transformer installation, surge arrester connections at the transformer terminals, CT and PT connections for protection and metering, and the transformer secondary connections to the high-voltage switchyard bus. The transformer is commissioned with insulation resistance testing, turns ratio testing, and dissolved gas analysis before energization.ms.
Secondary injection testing verifies that a protective relay operates at the correct setpoint by applying a simulated fault current or voltage signal to the relay's current and voltage inputs from an external test set rather than from the actual CT and PT circuits. This allows the relay settings to be verified before the system is energized and without creating an actual fault on the power system. Each protection function is tested individually, and test records document the applied test values and the relay's measured pickup, dropout, and timing characteristics. Secondary injection testing is required before energization of any protection system.
A continuous emissions monitoring system measures the concentration of regulated pollutants in a facility's stack gas on a continuous basis and reports that data to the regulatory authority. The electrical scope covers power connections to the analyzer enclosure, sample conditioning system electrical connections including heat tracing on heated sample lines, calibration gas system solenoid wiring, the data acquisition system that records analyzer outputs and calculates emission rates, and the communication interface reporting data to the regulatory agency's database. CEMS commissioning includes a relative accuracy test audit in which the CEMS measurements are compared to reference method measurements to verify system accuracy.