Table of Contents
The natural gas industry is facing an unprecedented transformation toward sustainability and energy efficiency. In the midstream segment, compressor electrification is emerging as a key technological solution that combines emissions reduction, operational optimization, and environmental regulatory compliance.
This transition goes beyond simply replacing combustion engines with electric motors: it represents a comprehensive reengineering of systems that incorporates advanced technologies such as variable frequency drives (VFDs), robust electrical infrastructure, and smart control systems.
For engineers and specialists in rotating equipment, understanding the technical, economic, and operational implications of this transformation is critical to the successful design and implementation of modern midstream projects.
What is compressor electrification in midstream?
The electrification of midstream compressors involves the implementation of compression systems powered by electric motors, replacing traditional internal combustion engines that use natural gas or diesel as fuel.
This technology focuses specifically on primary compression equipment, differing from the general electrification of industrial plants.
Main components of the system
- High-efficiency electric motor (>90%)
- Variable frequency drive (VFD) for speed control
- Specialized electrical protection system
- Industrial power supply infrastructure
- Integrated SCADA monitoring and control systems
Where does compressor electrification apply?
The electrification of compressors involves installing compressors that use electric motors as their power source, which can be an alternative to traditional systems powered by combustion engines, especially in natural gas transportation and processing operations in the midstream segment.
Essential technical requirements
- Power capacity: The grid must be capable of supplying sufficient power to feed large-scale compressors, which usually operate with demands ranging from hundreds to thousands of kilowatts per unit.
- Industrial voltage: Facilities typically require industrial voltages, usually ranging from 4,000 V to 13,800 V, to minimize losses and facilitate distribution.
- Protective equipment: It is essential to have transformers, voltage regulators, overload protection systems, industrial circuit breakers, and certified electrical panels.
Regulatory and operational requirements
- Regulatory compliance: Industrial electrical standards such as NOM-001-SEDE-1999 must be observed, as well as other design standards that include calculation reports and certification of equipment for use in areas classified as hazardous due to the presence of gases.
- Redundancy and backup: It is advisable to install redundant power supply and backup systems to ensure operation in the event of interruptions, such as auxiliary generators or industrial UPS.
- Load management and monitoring: It is essential to implement SCADA or similar systems for remote monitoring, load control, and real-time electricity consumption management.
Midstream compressors with VFDs require transformers and electrical protections with strict technical specifications to ensure safe operation, efficiency, and regulatory compliance.
Specific applications in the sector
Electrified compressors are ideal for use in:
- Gas pipeline compression stations: To maintain transport pressure.
- Processing plants: In recompression and fractionation systems.
- Storage terminals: For loading/unloading products.
- LNG facilities: In liquefaction and regasification processes.
Technical advantages of electric compressors
Superior energy efficiency
- Electric compressors produce fewer emissions and can utilize renewable energy sources.
- They operate more quietly, efficiently, and with less maintenance compared to traditional compressors.
- They allow for the integration of technology such as VFDs (variable frequency drives), optimizing compressor control and efficiency according to network or system demand.
- Electric compressors offer operating efficiencies of 85-95%, significantly outperforming their thermal counterparts (30-40%). This improvement is due to:
- Direct energy conversion: Elimination of combustion losses
- Precise speed control: Exact adaptation to variable demand
- Reduction of mechanical losses: Fewer moving parts
VFD protections
- Overcurrent and short circuit: Use industrial circuit breakers and fuses sized according to the manufacturer’s recommendations for the VFD and compressor, following NFPA 70/NEC, Article 430 Part X and Section 430.122.
- Overload: It is not always necessary to add additional overload protection if the VFD includes it and is certified. If not, external overload protection must be installed according to the competent authority.
- Thermal and overheating protection: Sensors and thermal relays to prevent damage to the motor under out-of-range operating conditions, especially if the motor speed does not guarantee constant rated current.
- Separation and insulation: Correct installation of conductors with adequate insulation to withstand voltages, pulsating currents, and frequencies specific to VFD operation, recommending shielded cables and separate paths to minimize interference and induction.
Compliance with these specifications ensures safety, durability, and efficiency in the operation of midstream compressors with VFDs, and minimizes electrical and overpressure risks.
Disadvantages and limitations
- They require robust electrical infrastructure: their installation requires reliable and powerful access to the electrical grid, which can increase initial costs, especially in remote areas or areas with limited infrastructure.
- High initial investment: although they save on operating costs, the acquisition and modernization of electrical equipment can be more expensive than maintaining existing combustion technologies.
- Dependence on the electrical grid: in the event of failures or outages, operation may be compromised if there are no redundant systems or backup solutions.
- Technical limitations in high-power processes: where thermal compressors can sometimes handle higher loads in extremely demanding applications.
Transformer specifications
Midstream compressors with VFDs require transformers and electrical protections with strict technical specifications to ensure safe operation, efficiency, and regulatory compliance.
- Adequate power: The transformer must supply the rated power of the compressor motor, taking into account maximum demand and possible expansions, for example, transformers of more than 100 kVA in medium industrial applications.
- Short-circuit resistance: The design must comply with IEC 60076-5 or ANSI/IEEE C57.109 standards, withstanding the thermal and mechanical stresses of external short circuits, according to short-circuit calculations and tests.
- Overpressure protection: Incorporate relief valves set to release internal pressure due to sudden overpressure (example: 49 kPa).
- Noise and vibration: Compliance with NEMA TR-1 standards to minimize noise and vibration, with mechanisms for controlling and monitoring temperature, oil level, and tap position.
- Insulators and access: Includes heavy-duty insulators and inspection hatches, secure connections, and terminals for lightning arresters and reinforced grounding.
Relationship with industrial electrification
The electrification of compressors is a type of process electrification within a plant or industrial facility, but its focus is directly on the equipment that compresses the gas, not on the plant’s general power supply. Therefore, it is not just a matter of “having electricity in the plant,” but rather replacing the compressor’s primary motor with an electric one.
Table 1: Technical Comparison – Thermal vs. Electric Compressors (2000 HP)
| Parameter | Thermal Compressor (Natural Gas) | Electric Compressor + VFD | Improvement |
| Overall Efficiency | 32-38% | 85-92% | +150% |
| Power Consumption | 5,263 kW (fuel) | 1,492 kW (electric) | -72% |
| NOx emissions | 9-25 ppmvd | 0 ppmvd (direct) | -100% |
| CO₂ emissions | 845 tons/year | 0 ppmvd (direct) | -100% |
| CH₄ emissions | 845 tons/year | 0 ppmvd (direct) | -100% |
| Noise Level | 85-95 dBA | 70-80 dBA | -15 dBA |
| Startup Time | 5-10 minutes | 30-60 seconds | -90% |
| Capacity Control | Staggered (5 steps) | Continuous (0-100%) | Infinite |
| Power Factor | N/A | 0.95-0.98 | – |
| MTBF (Hours) | 25,000-35,000 | 50,000-80,000 | +128% |
| Operational Staff | 2-3 technicians per shift | 1 technician/shift | -67% |
| Availability | 94-96% | 98-99% | +3% |
| Response Time | 30-60 seconds | 2-5 seconds | -92% |
| Vibration | 12-25 mm/s | 2-6 mm/s | -75% |
Table 2: VFD Specifications by Power Range
| Engine Power | VFD voltage | Nominal Current | Rectifier Type | THD Current | THD Voltage | Efficiency | Weight (kg) | Approximate cost. |
| 500 HP (373 kW) | 4,160V | 65A | 6-pulse + Filter | <5% | <3% | 97.0% | 850 | $85,000 |
| 750 HP (560 kW) | 4,160V | 97A | 12-pulse | <3% | <2% | 97.2% | 1,200 | $125,000 |
| 1,000 HP (746 kW) | 4,160V | 127A | 12-pulse | <3% | <2% | 97.5% | 1,580 | $165,000 |
| 1,500 HP (1.1 MW) | 6,600V | 115A | 12-pulse | <3% | <2% | 97.8% | 2,100 | $220,000 |
| 2,000 HP (1.5 MW) | 6,600V | 154A | 18-pulse | <2% | <1.5% | 98.0% | 2,750 | $285,000 |
| 3,000 HP (2.2 MW) | 6,600V | 230A | 18-pulse | <2% | <1.5% | 98.2% | 3,850 | $415,000 |
| 4,000 HP (3.0 MW) | 13,800V | 154A | 24-pulse | <2% | <1% | 98.3% | 4,900 | $545,000 |
| 5,000 HP (3.7 MW) | 13,800V | 192A | 24-pulse | <2% | <1% | 98.5% | 6,200 | $675,000 |
Technical notes:
- Switching frequency: 2-5 kHz (optimized to minimize losses)
- Speed control range: 10:1 to 20:1
- Speed accuracy: ±0.1% of nominal speed
- Operating temperature: -10°C to +50°C
- Protection: IP54 for industrial applications
Economic analysis – 2000 HP compressor (8,760 hours/year)
Table 3A. Annual operating costs
| Concept | Thermal Engine (Gas) | Electric Motor + VFD | Annual Savings | % Reduction |
| Fuel/Energy | $425,000 | $179,000 | $246,000 | 58% |
| Scheduled Maintenance | $85,000 | $25,000 | $60,000 | 71% |
| Corrective Maintenance | $45,000 | $15,000 | $30,000 | 67% |
| Operational Staff | $180,000 | $90,000 | $90,000 | 50% |
| Consumables (oil, filters) | $25,000 | $8,000 | $17,000 | 68% |
| Emissions/Penalties | $35,000 | $0 | $35,000 | 100% |
| Insurance | $15,000 | $12,000 | $3,000 | 20% |
| ANNUAL OPERATING TOTAL | $810,000 | $329,000 | $481,000 | 59% |
Table 3B. Initial investment (CAPEX)
| Component | Internal Combustion Engine | Electric Motor | Difference |
| Base Compressor | $850,000 | $850,000 | $0 |
| Primary Motor | $320,000 | $180,000 | -$140,000 |
| VFD/Control System | $65,000 | $285,000 | +$220,000 |
| Infrastructure | $125,000 | $320,000 | +$195,000 |
| Installation/Commissioning | $140,000 | $195,000 | +$55,000 |
| TOTAL CAPEX | $1,500,000 | $1,830,000 | +$330,000 |
Table 3C. ROI analysis by scenario
| Setting | Electricity cost ($/kWh) | Gas cost ($/MMBTU) | Annual Savings | Simple ROI | VPN 10 years |
| Optimistic | $0.08 | $3.50 | $528,000 | 1.9 years | $3,450,000 |
| Base | $0.10 | $4.00 | $481,000 | 2.2 years | $2,980,000 |
| Conservative | $0.12 | $4.50 | $434,000 | 2.5 years | $2,510,000 |
| Pessimistic | $0.15 | $5.50 | $365,000 | 3.1 years | $1,890,000 |
3D table. Sensitivity factors
| Variable | Impact on ROI | Range of Variation |
| Electricity Price | High | ±25% of the base case |
| Natural Gas Price | Very High | ±30% of the base case |
| Load Factor | High | 70-95% utilization |
| Environmental Incentives | Medium | $0-50/ton CO₂ |
| Maintenance Costs | Medium | ±20% estimate |
Key benefits
- Annual operating savings: $481,000 (base case)
- Simple ROI: 2.2 years
- CO₂ emissions reduction: 845 tons/year
- Energy efficiency improvement: +150%
- Operating staff reduction: 50%
Note: Data updated – September 2025 Base prices: Natural Gas $4.00/MMBTU, Electricity $0.10/kWh
Advanced control capabilities
Integration with VFDs enables:
- Continuous capacity modulation: 0-100% without scaling
- Soft start: 70% reduction in mechanical stress
- Dynamic response: Response time <2 seconds
- Automatic optimization: Energy efficiency algorithms
Reduction of environmental emissions
Elimination of direct emissions
- Zero emissions of NOx (nitrogen oxides), CO₂, and particulates on site.
- 60-80% reduction in total carbon footprint.
- Possibility of integration with renewable energies.
Implementation of VFDs in compression systems
Technical operating principles
Frequency converters control the speed of electric motors by modulating frequency and voltage, providing:
Quantified operational benefits
- Energy savings: up to 35% in consumption
- Extended motor life: 20-30%
- Improved power factor: >0.95
- Noise reduction: 10-15 dB
Recommended technical configurations
For typical midstream applications (500-2000 HP):
- Converter topology: 6-pulse IGBT with filters
- Switching frequency: 2-5 kHz
- Speed control range: 10:1 minimum
- Speed accuracy: ±0.1% of nominal speed
Specific midstream infrastructure
Power and voltage specifications
The electrification of compressors in midstream involves installing electric compressors, often optimized using VFDs. This is a different technological trend from the mere electrification of the plant and responds to sustainability, efficiency, and emissions reduction objectives.
- The station requires high-voltage connections, its own electrical substations, specialized cabling, and reinforced grounding systems adapted to the industrial environment and the magnitude of compressor consumption.
- To meet operational continuity requirements, electrical availability must be guaranteed at over 98% annually, in line with the need for 24/7 operation of midstream systems.
Proper infrastructure design is key to the efficiency and safety of electrification in midstream stations, and requires expert planning aligned with regulations and the energy demand context.
Critical design parameters
- Operating voltage: 4,160V – 13,800V (industrial distribution)
- Power demand: 100 kVA – 5 MVA per unit
- Load factor: 0.8-0.95 for cost optimization
- Required availability: >98% annually (8,760 hours/year)
Specialized protection components
Comprehensive protection system
- Industrial circuit breakers with breaking capacity >25 kA
- Multifunction protection relays (50/51, 27/59, 81)
- Class 0.3 current and voltage transformers
- Low impedance grounding systems (<1Ω)
Regulatory compliance
Applicable standards:
- NOM-001-SEDE: Electrical installations in Mexico
- IEEE 519: Harmonic distortion in power systems
- IEC 61800-3: EMC for electric drives
- API 618: Reciprocating compressors for oil and gas services
Conclusions
The electrification of midstream compressors represents an inevitable technological evolution toward sustainability and operational efficiency. The technical and economic benefits are proven, but successful implementation depends on critical factors:
Installing VFDs on electric compressors amplifies the advantages: it allows for savings of up to 35% in energy consumption, extends the useful life of the motor, improves pressure stability, and reduces environmental noise.
These factors must be carefully considered in the transition to electrification in order to optimize benefits according to the operational and logistical context of the midstream.
Midstream stations that operate electric compressors require robust electrical infrastructure capable of delivering high power and continuous availability to meet technical and regulatory requirements.
The transition to electric compressors is not just a trend, but a strategic necessity to remain competitive in a changing energy market. Engineers and specialists who master these technologies will be positioned to lead the next generation of sustainable and efficient midstream projects.
